INVITED REVIEWTGF- signal transduction and mesangial cellfibrogenesis - 《American Journal of Physiology》美国生理学杂志干细胞之家



免疫细胞治疗专区	欢迎关注干细胞微信公众号

12 3 4 5 6 7 8 9 10 ... 28 下一页

返回列表

查看: 529618\|回复: 279	go INVITED REVIEWTGF- signal transduction and mesangial cellfibrogenesis [复制链接]

轻羽

新手上路

Rank: 1

积分: 0
威望: 0
包包: 0

楼主

发表于 2009-4-21 13:32 |只看该作者 |倒序浏览 |打印

作者：H. WilliamSchnaper, TomokoHayashida, Susan C.Hubchak,  Anne-ChristinePoncelet作者单位：Division of Kidney Diseases, Department of Pediatrics, TheFeinberg School of Medicine of Northwestern University, andChildren‘s Memorial Institute for Education and Research, Chicago,Illinois 60611-3008
   3 E; N& y# W+ J7 m) o+ W1 v






         3 y% V# k9 _8 e7 {. ~3 i

      ; P9 ~8 j( D+ U' i

      ! P: w4 x; L: z" h) ^; W; D& s
      【摘要】
   Transforming growth factor- (TGF- )is closely associated with progressive renal fibrosis. Significantprogress has been accomplished in determining the cellular signalingpathways that are activated by TGF-. This knowledge is being appliedto glomerular mesangial cell models of extracellular matrix (ECM)accumulation. A central component of TGF- -stimulated mesangial cellfibrogenesis is the TGF- family-specific Smad signal transductionpathway. However, while Smads play an important role in collagenaccumulation, recent findings indicate that cross talk among a varietyof pathways is necessary for maximal stimulation of collagenexpression. Further investigation of these multiple interactions willprovide insight into possible ways to interrupt cellular mechanisms ofglomerular fibrogenesis. * {( z* Q, I9 P. ?0 V# A! K3 d
      【关键词】 transforming growth factor glomerulosclerosis Smads. U  k( F. L  }0 J) M
   INTRODUCTION
5 s7 ~2 A' B* |# j6 q7 Y' P
GLOMERULOSCLEROSIS IS A PROCESS bywhich normal, functional glomerular tissue is replaced by accumulateddeposits of extracellular matrix (ECM). It represents a common pathwayfor the loss of functioning glomeruli associated with primary diseasesas disparate as chronic glomerulonephritis, obstructive uropathy, andretroviral infection ( 88, 90 ). In addition, it representseither the cause or the outcome of many cases of steroid-unresponsivenephrotic syndrome. Idiopathic focal segmental glomerulosclerosis is aleading cause of chronic progressive kidney disease and appears to beincreasing in incidence in both children ( 8, 95 ) andadults ( 47 )." m' J+ s  Z. f( C* g- `
  e& C1 |2 j3 j$ o+ e
The pathogenesis of glomerulosclerosis is uncertain. It is likelythat all three major cells of the glomerulus participate in thefibrotic process. Recently published genetic data ( 11, 44, 75 ) and the finding of podocyte abnormalities in transgenic models of glomerulosclerosis ( 93 ) or in patients( 94 ) suggest that the visceral epithelial cell plays asignificant role. This assertion is supported by earlier dataimplicating potential epithelial cell stressors such as glomerularhypertension, hyperfiltration, or hypertrophy in sclerosis( 12 ). Some models implicate the endothelial cell in thesclerotic process ( 4, 53 ). Still others suggest a role forthe mesangial cell ( 25 ). This last possibility isattractive because, in many models of glomerulosclerosis (as well as inidiopathic focal segmental glomerulosclerosis, clinically), ECMaccumulation often appears to begin in the mesangium. In addition,filtered macromolecules may be trapped in the mesangium, initiating aninflammatory response that could play a role in stimulating ECMsynthesis. A unifying hypothesis can be constructed that includesparticipation by all of the cellular elements of the glomerulus.Glomerular capillary hypertension, or a genetic or acquired abnormalityof podocyte adhesion or structure, permits hyperfiltration ofmacromolecules. Paracrine signals from the injured podocyte stimulateendothelial cell expression of leukocyte adhesion molecules and impairendothelial cell fibrinolytic activity. Signals from epithelial orendothelial cells to the mesangium, or direct delivery ofproinflammatory substances through the glomerular filtrate, initiates aprocess that culminates in the accumulation of ECM ( 89 ).Mesangial expansion infringes on the capillary spaces, decreasingfiltration surface area in the glomerular tuft.

One aspect of this unfortunate series of events is mesangialaccumulation of ECM. The critical determinant of matrix accumulation isthe balance between ECM synthesis and dissolution ( 19, 87 ). This net matrix turnover reflects rates of matrixproduction (affected by transcription and translation) or degradation(determined by synthesis and activity of ECM proteases and theirinhibitors) and factors that affect the susceptibility of the ECMproteins to degradation, such as glycosylation ( 102 ) orthe stability with which these proteins have been incorporated into thematrix. Recently, efforts have been directed toward modeling thecellular events regulating glomerular ECM turnover. A variety ofphysiological, pharmacological, and molecular approaches has been usedto study how various mediators initiate or modify intracellularsignaling pathways to cause mesangial cell matrix accumulation. Thesefactors include transforming growth factor (TGF)- ( 9 ),basic fibroblast growth factor ( 28 ), platelet-derivedgrowth factor ( 28 ), ANG II ( 64 ), connectivetissue growth factor ( 24 ), and various eicosanoids( 52 ). This review will focus primarily on TGF-., `  J* j' z3 g, N  l

TGF- IN PROGRESSIVE RENAL DISEASE

A significant body of literature supports a role for TGF- inglomerular ECM accumulation. This growth factor is present in humanglomeruli and has been associated with increased mesangial matrix inseveral glomerular diseases ( 109 ), including diabetic nephropathy ( 105 ). Intrarenal infusion of antisenseoligonucleotides to decrease the expression of TGF- decreasessclerosis in experimental nephropathy ( 3 ). Conversely,infusion of the TGF- gene causes sclerosis in rats( 40 ). Mice transgenic for increased expression of TGF- develop renal fibrosis ( 66 ). These data suggest that TGF- could play a role in glomerular ECM accumulation in human disease.( k  a# @  B& b0 n% y
) _- v' X/ k7 U2 s4 ]- t+ s
However, not all studies have detected elevated levels of TGF- inthe glomerulus in human disease or animal models of glomerulosclerosis. Sclerosis represents the final outcome of a number of initiating eventsthat could affect the balance in ECM turnover. In addition to diseaseheterogeneity, varied data also could reflect the duration of illness.Thus patients studied late in disease progression could be at a stagewhere a TGF- -mediated process has been supplanted by one mediated byanother factor such as connective tissue growth factor. Nonetheless,the evidence is strong, albeit circumstantial, that TGF- plays asignificant role in many cases of glomerulosclerosis.

TGF- SIGNAL TRANSDUCTION

TGF- is a pleiotrophic cytokine that originally wasdescribed as permitting anchorage-independent growth in soft agar(a model of neoplastic transformation). It was subsequently found to decrease cell division, suppress certain immune responses, andinduce differentiation in some cell types. The mammalian TGF- s belong to a larger family of similar molecules that includes activin and the bone morphogenetic proteins (BMPs) ( 59 ). The mostbroadly studied TGF-, TGF- 1, is secreted as an inactive, 25-kDahomodimer that is noncovalently associated with a latency-associatedprotein (Fig. 1 ). In some cases, thiscomplex may be bound to a 125- to 160-kDa latent TGF- -bindingprotein. The latency-associated protein inhibits binding of TGF- toits receptor. Dissociation of the potentially active molecule from thecomplex may be accomplished by a number of environmental triggers,including heat, shear force, pH extremes, and proteolysis( 67 ). The concepts of latency and activation are importantand often overlooked in studies of TGF- production, secretion, andeffects ( 68 ). In addition, the local availability ofTGF- is not usually taken into consideration. It binds to the ECM(perhaps facilitated by the latent TGF- -binding protein) with a K D of ~10 8 M, while the K D for the receptor is at least an order ofmagnitude lower ( 22 ). These affinity differences permitthe ECM to function as a reservoir, releasing the growth factor whenthe local concentration falls below the ECM K D while maintaining an ambient level sufficient to bind to the cellreceptors. This modulation of local concentration is a criticaldeterminant of the effects of TGF- in a given system.5 Y0 |: B' T' E4 K* s2 ]

Fig. 1. Schematic structure of transforming growth factor(TGF)-. The active protein is shown in 2 forms: with the smalllatent complex including the latency-associated protein (LAP; A ) and in the large latent complex associated with thelatent TGF- -binding protein (LTBP; B ).! Q9 `8 z6 m, e" ]/ h
  [9 s8 V; r+ k5 S! G# @
TGF- -family ligands bind to a corresponding family of receptors thatis comprised of seven type I receptors (T R-I) and five type IIreceptors (T R-II) ( 5 ). T R-I and T R-II may form a variety of heterodimers; several of these have been described in renalcells ( 55 ). There are some unique aspects ofTGF- -family signal transduction. First, whereas most growth factorreceptors are tyrosine kinases, the TGF- -family receptors functionas membrane-bound serine/threonine kinases. Second, most receptorssignal by activating a cascade of second messengers that transmitsignals toward the nucleus, culminating in the activation of atranscription factor; or, in the case of the steroid hormone receptorfamily, the ligand binds to a cytoplasmic receptor that itself servesas a transcription factor. The TGF- -family receptors are unique inthat they are integral membrane receptors which bind to and activateproteins that translocate to the nucleus to regulate transcriptionrather than initiate a cascade. Viewed in terms of function andcomplexity, these attributes suggest that the mechanism of action ofthis family of receptors is an evolutionary intermediate between those of the nuclear hormone receptors and the receptor tyrosine kinases.: U4 N/ o& G1 V& t  r3 [9 d8 S
9 L6 _0 A; a# u( p6 Y
The proteins that are activated by the TGF- -family receptors arecalled "Smad" proteins. The Smads were originally described simultaneously by the fly and worm scientific communities. In Drosophila melanogaster, a gene product was determined toplay a role in embryological patterning regulated by a BMP homologue called decapentaplegic and was termed "MAD" (for "mothers against decapentaplegic") ( 91 ). Researchers investigating thedevelopmental genetics of Caenorhabditis elegans identifieda series of proteins that, when mutated, produced an identical, smallphenotype in the worms (indicating a common effector pathway for thesemolecules). They termed this family the "Sma" proteins( 84 ). Eventually, a consensus name, Smad, was agreed on.

The Smads have a general structure of two MAD homology (MH) domainsconnected by a linker region (Fig. 2 ).The protein-amino acid sequence includes a number of serines andthreonines that represent potential phosphoacceptor sites. On ligandbinding, T R-II transphosphorylates T R-I (Fig. 3 ). Two receptor heterodimers combine toform a tetramer that binds to a subfamily of Smads termed the R-Smads,which are receptor activated and also pathway restricted (Smad2 andSmad3 for TGF- and activin; Smad1, -5, and -8 for the BMPs)( 60 ). Smad2 and Smad3 are recruited to the cell membranereceptor through their affinity for the Smad anchor for receptoractivation, a protein that has a binding domain specific forTGF- -family receptors ( 100 ). The quiescent R-Smads maintain a hairpin configuration until becoming phosphorylated at aCOOH-terminal SSXS motif, whereupon they spring open and become active.The activated R-Smads form heteromultimers with a second type of Smad,the common-pathway Smad called Smad4. This complex is translocated tothe nucleus, where it participates in transcriptional regulation( 76 ). Initially, it was uncertain whether Smads bounddirectly to DNA or attached through an intermediary protein complex( 14, 113 ). Subsequently, however, a Smad-binding element,including the sequence CAGA, has been characterized ( 43, 110 ). Nonetheless, in most cases transcriptional activation, even when demonstrably Smad dependent, requires the binding of additional transcription factors. Transcriptional cooperation has beendemonstrated with proteins such as AP-1 transcription factors( 113 ), Fast-1 ( 14 ), Fast-2 ( 50 ),TFE3 ( 35 ), and Sp1 ( 18, 51, 112 ). R-Smads andSmad4 have also been shown to interact with the binding protein forcAMP-response element binding protein/p300 coactivators ( 92, 104 ). Inhibiting factors include TRIP-1 ( 16 ), SnoN( 96 ), Ski ( 56 ), and SNIP ( 46 ).$ ^: Y+ l- M! ~5 g. u6 E% b9 a
6 q/ N+ ^( G5 `9 U6 ^/ C; [
Fig. 2. Domain structure of Smad2. * Potential phosphoacceptorsites; MH, MAD homology domain.
( F' U" X: ?( v" d
Fig. 3. Schematic diagram of Smad signal transduction. R-Smads in thecytoplasm ( A ) are recruited to the TGF- receptors(T Rs; B ), where they are phosphorylated (P; C ). A complex with the common Smad, Smad4, is formed( D ) and translocated to the nucleus, where it regulates genetranscription ( E ). SARA, Smad anchor for receptoractivation.

A third category of Smad proteins, the inhibitory Smads (I-Smads),includes Smad6 ( 38 ) and Smad7 ( 30, 73 ), whichhave been identified in the kidney ( 101 ). The I-Smads areable to bind to T R-I but lack critical phosphoacceptor sites andtherefore prevent phosphorylation of R-Smads. In addition, Smad6 hasbeen shown to inhibit the binding of Smad4 with R-Smads, decreasing signal in that way as well ( 29 ). Smad7 expression isstimulated by TGF- in an apparent negative-feedback loop( 69 ).$ E1 M$ q! Z) O: O+ ^4 i
( d4 v4 X$ S" ]. }8 |  j3 d4 T. N' L
The definition of this pathway, and of its unique attributes describedabove, has represented a major advance in our understanding of howTGF- -family ligands and their receptors function to transmit signalsinto the cell. A caveat regarding this progress is that it wasaccomplished primarily utilizing ectopic molecular expression systemsand/or transformed cell lines. Thus much of the initial data focused onthe role of Smads in regulating developmentally expressed genes or cellproliferation and differentiation in cancer. The first human Smadmutations were identified in colon ( 98 ), pancreatic( 26 ), and lung ( 70 ) cancers, and many morehave been described. However, transformed cells may not have a full complement of signal-regulating proteins. In addition, when signaling proteins are overexpressed in cells, the requirements for specific activation steps and specific subcellular localization, as well as thepotential need for interaction with additional proteins and signalingpathways, may be freed from subtle physiological regulatory constraints( 65 ). Thus it has been important that these pathwaysshould be studied for their function in ligand-activated, nontransformed cells.
% B  z: W- _" X. H1 y' n
TGF- -STIMULATED ECM COLLAGEN PRODUCTION' t3 p  M7 C% k( h
& a) A. o9 V$ ?; J; `" O9 {
Several reports have indicated that TGF- stimulates mesangialcell ECM production. In cultured mouse mesangial cells, TGF- 1 stimulates production of types I and -IV collagen and fibronectin ( 57 ). In rat mesangial cells, TGF- 1 has been shown tohave variable effects. In one report, it increased proteoglycansynthesis without any changes in collagen and fibronectin synthesis( 10, 72 ), while another group described increasedexpression of 1 (I) collagen and 1 (IV)collagen and fibronectin genes ( 97 ). TGF- 1 alsoinhibits plasminogen activator production while stimulating plasminogenactivator inhibitor synthesis by normal rat glomeruli ( 99 ). In various assays examining cultured human mesangialcells or isolated perfused kidneys, TGF- 1 stimulates expression of types I, -III, and -IV collagen, laminin, fibronectin, and heparan sulfate proteoglycans ( 21, 27, 63, 80 ).
- g# h/ E" y  D  }. E
To define more precisely the nature and timing of changes in matrixturnover that are stimulated by TGF-, our laboratory evaluated humanmesangial cells. TGF- 1 increases expression of mRNA for the ECMprotease matrix metalloproteinase (MMP)-2, which is paralleled by anincrease in its antagonist, tissue inhibitor of metalloproteinases(TIMP)-2. There is no change in TIMP-1 or membrane-type MMP mRNAexpression, while the level of MMP-1 mRNA is decreased. At the proteinlevel, TGF- 1 increases types I and -IV collagen in both themesangial cell layer and conditioned media. Many of these changes occurrapidly, with increased expression of collagen mRNAs beginning within1-4 h of TGF- 1 treatment. In contrast to the mRNA studies,MMP-2 and TIMP-1 activity showed little change while MMP-1 did decreaseand TIMP-2 was not detected. Together, the net protease activity didnot appear to change significantly, suggesting that, for regulatingcollagen turnover in this short-term cellular model, changes inprotease activity are less significant than those in ECM synthesis( 80 ). In other model systems, the regulation of ECMdegradation by TGF- may be at least as important as ECM synthesis( 6 ).
( h! T% }% N7 L( C5 O5 }
In addition to the rapid changes in mRNA expression, collagen proteinturnover was faster than anticipated. Treatment of near-confluent cellswith cycloheximide to inhibit protein synthesis for only 4 hvirtually eliminated detectable collagens from the cell layers andconditioned media. While this result could reflect the scorbutic culture conditions (ascorbate, which facilitates the stabilization ofcollagen fibrils in a matrix, was omitted from the culture mediumbecause it also stimulates collagen synthesis), the results suggestedthat mesangial cell collagen protein expression in vitro represents asteady-state phenomenon rather than simply ongoing accumulation ofsynthesized protein. Interestingly, cycloheximide did not affect earlyTGF- 1-induced changes in mRNA expression but reversed increases in 1 (I) collagen mRNA at 24 h, suggesting that earlychanges in expression represent direct effects whereas later changesare mediated by the synthesis of additional proteins. In contrast, 1 (IV) collagen mRNA expression did not requireintermediate protein synthesis at any time point but was superinducedby cycloheximide treatment. These data indicate that, in humanmesangial cells, early changes in net collagen accumulation areregulated primarily at the level of protein synthesis rather thandegradation and that the mechanisms of type I collagen and type IVcollagen mRNA expression differ significantly ( 80 ).

SMAD SIGNALING IN MESANGIAL CELL ECM ACCUMULATION

These data suggested that the most appropriate avenue for theinvestigation of immediate profibrotic cellular events inTGF- -stimulated mesangial cells is the examination of ECM synthesis.Toward this goal, we determined whether Smad activity could be linkedto mesangial cell collagen expression. Mesangial cells express at leastSmad1, -2, -3, -4, and -7. Stimulation of human mesangial cells with TGF- 1 induces phosphorylation of Smad2 and Smad3, beginning within 5 min of exposure. Phosphorylation peaks at 30 min but remains presentfor as long as 24 h ( 79, 83 ). The phosphorylation event is paralleled by association among Smad2, -3, and -4. Phosphorylation and association are followed within minutes byincreased nuclear localization of this complex. Activity of theTGF- /Smad-responsive p3TP-Lux promoter-reporter construct isstimulated by TGF- 1 treatment. These data are consistent with themodel that ligand-stimulated Smad activation in mesangial cells leadsto transcriptional activity in the nucleus, in parallel with previousresults derived from the study of transformed cells or overexpressedSmads. The 1 (I) collagen and 2 (I)collagen promoters are also activated ( 31, 79 ); andactivation of a collagen promoter-luciferase reporter construct isinhibited by Smad3A, a mutated Smad3 expression construct that lackscritical COOH-terminal serine phosphoacceptor sites and functions as adominant-negative mutant in this assay ( 79 ). Together,these results demonstrate that the Smad pathway is present andfunctional in mesangial cells and that it can mediateTGF- -stimulated collagen I expression. Further support for typicalSmad pathway interactions regulating collagen production is provided bythe finding of other groups that Smad7 decreases TGF- -stimulated mesangial cell collagen production ( 13, 54 ). Another wayin which Smad7 signaling can affect the sclerosing process is by inducing podocyte apoptosis ( 85 ).
4 v' m/ n9 s! x  T7 A
It is noteworthy that, while the dominant-negative mutant Smad3A blocksTGF- stimulation of COL1A2 promoter-luciferase reporter activity,simply expressing either wild-type Smad3 or Smad3A leads to a largeincrease (15- and 8-fold, respectively) in basal responses ( 79 ). Thus, although the Smad3A construct does nottransduce the receptor-activated signal, its overexpression appears toat least partly bypass the requirement for activation. This observation illustrates the concern raised previously about the impact of overexpressing specific proteins on the geometry or the stoichiometry of the cellular signaling response.
/ W+ G( i! x. |- R
CROSS TALK BETWEEN SMAD SIGNALING AND MAP KINASE PATHWAYS

Thus the interpretation of these studies can be complicated bytechnical as well as biological factors. Moreover, investigators examining the response of different cells to an identical stimulus havereported varied and contradictory findings. This outcome has beenattributed to myriad differences in experimental conditions, includingthe culture media used, the question of whether the cells aretransformed, the timing and conditions of treatment, etc. However, itis increasingly accepted that such differences may be real and maydefine tissue specificity in an organism. For example, an endothelialcell will respond differently from a smooth muscle cell, even thoughthe basic signaling pathways in the two cell types are similar. Thelikely source of this heterogeneity is cross talk among differentsignal transduction pathways that are present and active to varyingdegrees in different cells ( 86 ). While the paradigm ofSmad activation described above is likely to exist in most cells,interaction of Smads with other signals may significantly alter theirfunction. For example, TGF- 1 may stimulate a variety of kinases inmesangial cells, including protein kinase A ( 103 ) andcasein kinase II ( 111 ). In rat mesangial cells, TGF- has been shown to activate ERK and p38 MAP kinase ( 15, 36 ). Activation of p38 has been implicated inTGF- 1-stimulated 1 (I) collagen mRNA expression( 15 ), whereas ERK has been associated with fibronectinaccumulation ( 39 ). In human mesangial cell studies fromour laboratory, TGF- 1 stimulates phosphorylation of both the ERK-and JNK-MAP kinase pathways, but not p38 ( 31 ). Biochemicalinhibition of ERK reduces TGF- 1-stimulated human mesangial cellcollagen mRNA expression. Moreover, a dominant-negative ERK construct,but not dominant-negative inhibition of JNK activation, decreasesactivation of the TGF- -specific p3TP-Lux construct as well as acollagen promoter-luciferase reporter construct ( 31 ). These results indicate that the ERK-MAP kinase pathway enhances oramplifies Smad-mediated mesangial cell responses.9 j# o* Q3 p8 ]0 x
  i- o- d( }7 S. c. \! _9 M
The interaction of ERK with TGF- signaling in mesangial cells isunder investigation. Our preliminary data suggest that ERK enhancesSmad phosphorylation ( 32 ). This finding may contribute further to the controversy in the literature regarding the effect ofERK on Smad activity. Initially, it was felt that ERK activation inhibited Smad signaling ( 48 ). More recent studies havesupported both the enhancing ( 20 ) and inhibitory( 49 ) effects of ERK on Smad activation. Inhibiting ERKdecreases Smad-mediated transcriptional activity ( 31, 32 ).These differences could reflect the developmental origin of the tissueunder study, the nature and intensity of the stimulating and inhibitorysignals, the question of whether endogenous or ectopically expressedproteins were studied, or the specific downstream target of Smads thatis being evaluated. In renal tubular epithelial cells, TGF- stimulates epithelial-to-mesenchymal transdifferentiation (EMT), apivotal event in some models of fibrogenesis ( 107 ) (seebelow). EMT is inhibited by stimuli of ERK activity ( 106 )or by mediators that have been associated with ERK activation( 17 ). The role of ERK in antagonizing the effects ofTGF- in renal tubular EMT remains to be fully established.
# n0 C9 o/ `0 D2 b/ E& N
The non-Smad signaling pathways that are activated after TGF- stimulation have been reviewed recently ( 77 ). Althoughthey clearly play a role in regulating a number of processes inaddition to fibrogenesis ( 7 ), the mechanisms by which theTGF- receptor mediates these alternative pathways are not wellunderstood. This is an important area for further investigation.) a) J! q9 q7 l4 D* u% @; V% T
6 g$ ^- W7 w% Y/ x! p' @' i
INTERACTIONS IN TRANSCRIPTIONAL REGULATION9 C+ |3 W! K; b9 g+ s, b/ K

Another potential site of interaction between Smads and otherfactors is in the nucleus. As described above, Smad activity likelyrequires other transcription factors, including an interaction with Sp1that has been described in several systems ( 18, 51, 112 ).In human mesangial cells, TGF- 1-induced collagen mRNA expression isinhibited by mithramycin, a blocker of Sp1 DNA binding, but not bycurcumin, which inhibits AP-1 transcriptional activity. TGF- 1stimulates interaction of Smad3 and Sp1, and the resulting complexbinds to promoter sequences in the COL1A2 gene. Deletion from the promoter of GC boxes that bind to Sp1, or mutation of the CAGAsequence in the Smad-binding element (SBE), abrogates promoteractivation by TGF- 1. Additional studies showed that thetranscriptional activity of the Sp1 transactivation domain B was not induced directly by TGF- 1 but instead that this domain became responsive when Smad3 was coexpressed. Thus Smad3 activity iscritical to the response, but Sp1 plays a key role in supporting thatresponse ( 81 ).! c! f, `& i* Y2 Q

Further insight into these events is provided by elegant studies oflaminin- 1 gene regulation by Bomsztyk and colleagues ( 33, 45 ). The LAMC1 promoter contains ahighly conserved transcriptional element, termed bcn-1. With the use ofa yeast one-hybrid approach, the TFE3 transcription factor was clonedfrom a rat mesangial cell cDNA library, indicating that this basichelix-loop-helix/leucine zipper transcription factor bindsto bcn-1. Stimulation of bcn-1 by TGF- to activate the LAMC1 promoter was enhanced by overexpression of Smad3 andwas dependent on the Smad-binding element in the LAMC1 promoter ( 45 ). In addition, a similar strategy identified binding of the gut-enriched Kruppel-like factor (GKLF) to bcn-1. GKLFactivity was dependent on synergy with Sp1 ( 33 ). Although this second study did not address the role of TGF-, the involvement of Sp1 in these events and the responsiveness of GKLFs toTGF- -family ligands in other experimental systems ( 1 )suggest that multiple transcription factors, binding to multiple sites,cooperate to induce ECM protein gene expression in response to TGF- stimulation. Additional protein-protein interactions at the level ofgene transcription include those of Smad with p300, shown in severalsystems ( 23, 104 ), and with estrogen receptor( 61 ).
" E8 p8 m- _: S: c- Q4 E- K5 s
EFFECTS OF TGF- ON THE ACTIN CYTOSKELETON

The paradigm of TGF- signaling through Smads involves atranscriptional mechanism of action and, by extension, delayedresponses. However, other responses may be more immediate in somecircumstances, suggesting nontranscriptional actions. For example,TGF- 1 rapidly stimulates Ca 2  influx, without promotingCa 2  release, in SV-40-transformed murine mesangial cells.This response is inhibited by pharmacological inhibitors ofinositol-1,4,5-trisphosphate (IP 3 ) receptors and by anantibody to the type III IP 3 receptor. Whereas untreatedmesangial cells had numerous, spike-like projections on their cellsurface, TGF- 1 treatment reduced these projections in aCa 2  -dependent manner within 15 min ( 62 ).
* x/ c& a4 n; }# ~  \4 k
In preliminary studies, we have found that treatment of human mesangialcells with TGF- 1 not only stimulates cytoskeletal rearrangementbut also increases incorporation of -smooth muscle actin( -SMA) into stress fibers. Our evidence suggests that these cytoskeletal changes could play a role in collagen expression (Hubchakand Schnaper, unpublished observations). One mechanism for thisrole could relate to a theory of fibrogenesis that has gainedincreasing attention: that fibrosis requires resident tissue cells todifferentiate into fibroblasts. In atherosclerosis, this has beencharacterized as vascular smooth muscle cells assuming a"myofibroblastoid phenotype." In mesangial cells, altered collagen expression after TGF- treatment has been associated with increased expression of -SMA ( 37 ). The phenomenon has been morefully described in the tubular epithelium, where the tubular celltransdifferentiates from an epithelial cell phenotype to afibroblastoid cell that produces and secretes ECM ( 107 ),in a process that also is associated with increased -SMAincorporation into stress fibers ( 107 ).+ F# N% I( i' w/ r7 p% S, b

IMPLICATIONS OF TGF- SIGNALING MECHANISMS FORDISEASE PATHOGENESIS AND TREATMENT

Taken together, the data presented here suggest that TGF- stimulates several pathways in mesangial cells (Fig. 4 ). In addition to the Smad pathway,Ca 2  influx and MAP kinases are activated; there may be anas yet undetermined hierarchy to these signals. These pathways in turn synergize, perhaps through effects on each other or through parallel tracks into the nucleus, where a variety of transcription factors interact to modulate the transcription of ECM genes. Other events inthe glomerulus that may be mediated by Smads, such as endothelial nitric oxide synthase gene expression ( 108 ) or cellapoptosis ( 41, 78, 85 ), also could affectglomerular function and sclerosis.0 G! Z( f1 u$ O  ]4 n+ p# [  N' a2 i. k

Fig. 4. Signaling events activated in TGF- -stimulated mesangial cellfibrogenesis. Much remains to be determined, such as themechanism by which the cytoskeleton influences ECM geneexpression and the identity of specific inhibitors of ECM genetranscription. IP 3, inositol-1,4,5-trisphosphate. Forsimplicity, the IP 3 receptor is shown at the cell membrane,whereas the mechanism by which it increases intracellular calcium isuncertain.
% n- d+ ]' H+ a+ a$ U0 O$ Z
While we have emphasized transcriptional effects of these pathways,posttranslational effects such as alterations in the activity of ECMproteases also could modulate the accumulation of ECM. For example,TGF- has been reported to decrease ( 74 ) or increase ( 58 ) the expression or activity of the MMPs that degradeECM or the tissue inhibitors of MMPs that slow matrix degradation. Cytochalasin D, a pharmacological agent that disrupts the cytoskeleton, stimulates the activation of MMP-2, increasing collagen degradation ( 2 ). Thus the effects of TGF- on other biologicalevents that affect ECM turnover, and potential nontranscriptionalmechanisms of TGF- signaling, are areas of importance that presentlyare under-studied.

An even more important area of potential investigation is the role ofthese newly defined pathways in fibrogenesis in vivo. It is clear thatincreasing TGF- expression either locally or systemically( 66 ) causes glomerular or renal fibrosis. Inhibition ofTGF- binding to its receptor can lessen the degree of experimental renal fibrosis ( 42 ). Hong and colleagues ( 34 )have associated the TGF- /Smad signaling pathway with an animal modelof diabetic renal disease. However, studies of the effects ofinterrupting Smad signaling on renal fibrogenesis have not beenperformed. The lack of pharmacological inhibitors of Smad signaling hasprevented all but the most rudimentary studies of how Smad signalingmight be regulated in vivo. A possible approach might involve newtechniques of local gene expression ( 71, 82 ) to increaseintracellular levels of I-Smads. Significant technical advances will berequired for such approaches to be feasible. Thus our expandedunderstanding of this field over the past several years offers greatpromise but one that requires considerable additional investment before it will reach fruition.

NOTE ADDED IN PROOF
2 \  x; S1 O* [+ f: @
Further evidence of a role for inhibitory Smads in glomerulardisease is found in an article by Schiffer and colleagues (Schiffer M,Schiffer LE, Gupta A, Shaw AS, Roberts ISD, Mundel P, andBöttinger EP. Inhibitory Smads and TGF- signaling inglomerular cells. J Am Soc Nephrol 13: 2657-2666,2002), reporting altered podocyte I-Smad expression in human disease.
# ^7 w& @4 W" q8 U$ l( ^
ACKNOWLEDGEMENTS

This work was supported in part by National Institute of Diabetesand Digestive and Kidney Diseases Grant DK-49362 and a grant to Dr.A.-C. Poncelet from the National Kidney Foundation of Illinois.
      【参考文献】% X" z  {; ]8 k- d, j" x
1. Adam, PJ,Regan CP,Hautmann MB,andOwens GK. Positive- and negative-acting Kruppel-like transcription factors bind a transforming growth factor control element required for expression of the smooth muscle cell differentiation marker SM22alpha in vivo. J Biol Chem 275:37798-37806,2000 .$ R! z* d! L5 S: {! D
3 |8 @- K4 e' f! G  t6 A
) D# i  ^& H3 D) [# ]2 P

2. Ailenberg, M,andSilverman M. Cellular activation of mesangial gelatinase A by cytochalasin D is accompanied by enhanced mRNA expression of both gelatinase A and its membrane-associated gelatinase A activator (MT-MMP). Biochem J 313:879-884,1996  .
4 y$ G$ u; b" R, d8 ]/ m
, `. J# X, f! J8 M3 z

3. Akagi, Y,Isaka Y,Arai M,Kaneko T,Takenaka M,Moriyama T,Kaneda Y,Ando A,Orita Y,Kamada T,Ueda N,andImai E. Inhibition of TGF- 1 expression by antisense oligonucleotides suppressed extracellular matrix accumulation in experimental glomerulonephritis. Kidney Int 50:148-155,1996  ., L8 o8 I% {! o6 s: `
- b8 d6 O8 I* N- A9 a  v6 R* o& C/ g4 _

/ y3 J, [% i' n' e: v6 z' ~
4. Akaoka, K,White RHR,andRaafat F. Glomerular morphometry in childhood reflux nephropathy, emphasizing the capillary changes. Kidney Int 47:1108-1114,1995  ., y1 b! y- J5 x3 ~

/ N0 D/ V; N3 P% Z$ I4 P0 x; L$ x3 V
5. Attisano, L,andWrana JL. Signal transduction by the TGF- superfamily. Science 296:1646-1647,2002 .
( c2 V6 H. E- h2 G5 l& `7 L
1 Z: i  K6 K1 X$ x# }4 K# J- M1 o
; J( Z' r5 x! n" u9 K3 o; H! k
6. Baricos, WH,Cortez SL,Deboisblanc M,andXin S. Transforming growth factor- is a potent inhibitor of extracellular matrix degradation by cultured human mesangial cells. J Am Soc Nephrol 10:790-795,1999 .

8 j. w% ?+ i  B9 H- n0 _6 Q- T6 g
! i2 f" o( v/ G0 q( ^* `
7. Bhowmick, NA,Ghiassi M,Bakin A,Aakre M,Lundquist CA,Engel ME,Arteaga CL,andMoses HL. Transforming growth factor- 1 mediates epithelial to mesenchymal transdifferentiation through a RhoA-dependent mechanism. Mol Biol Cell 12:27-36,2001 .# A( N* L3 C; `6 y
2 d2 z$ b* g( E" j0 r3 _7 M7 r

6 s2 k, k% C, }, D1 ?
8. Bonilla-Felix, M,Parra C,Dajani T,Ferris M,Swinford RD,Portman RJ,andVerani R. Changing patterns in the histopathology of idiopathic nephrotic syndrome in children. Kidney Int 55:1885-1890,1999  .  z& i+ A& I* H) @
/ D% g, q# a/ Q: B; l5 G4 @

9. Border, WA,andNoble NA. TGF- in kidney fibrosis: a target for gene therapy. Kidney Int 51:1388-1396,1997  .

3 I7 P6 S/ G: I( @, s1 k
10. Border, WA,Okuda S,Languino LR,andRuoslahti E. Transforming growth factor- regulates production of proteoglycans by mesangial cells. Kidney Int 37:689-695,1990  .

. h# y% G3 {& s% I
* c: e& d  l& Z
11. Boute, N,Gribouval O,Roselli S,Benessy F,Lee H,Fuchshuber A,Dahan K,Gubler MC,Niaudet P,andAntignac C. NPHS2, encoding the glomerular protein podocin, is mutated in autosomal recessive steroid-resistant nephrotic syndrome. Nat Genet 24:349-354,2000  .
& a, \, Z. N) e, s: m
( I+ L- w* p% Y  a: |

12. Brenner, BM. Nephron adaptation to renal injury or ablation. Am J Physiol Renal Fluid Electrolyte Physiol 249:F324-F337,1985 .

13. Chen, R,Huang C,Morinelli TA,Trojanowska M,andPaul RV. Blockade of the effects of transforming growth factor- 1 on mesangial cells by over-expression of Smad7. J Am Soc Nephrol 13:887-893,2002 .: l: S- S1 V/ x3 B5 ^
9 z$ _2 Y% T5 c7 B' B/ t: a  ?/ b4 ^9 c

) d; P( Y- ~7 k1 \7 E1 c
14. Chen, X,Weisberg E,Fridmacher V,Watanabe M,Naco G,andWhitman M. Smad4 and FAST-1 in the assembly of activin-responsive factor. Nature 389:85-89,1997 .

15. Chin, BY,Mohsenin A,Li SX,Choi AM,andChoi ME. Stimulation of pro- 1 (I) collagen by TGF- 1 in mesangial cells: role of the p38 MAPK pathway. Am J Physiol Renal Physiol 280:F495-F504,2001 .+ V- x. W: j3 w# N( y
9 \1 f$ E( ~( f+ x- @% \
& g" F/ c: g4 u) L) B7 Z
4 ?1 Z$ m7 \/ Q) I: K) x
16. Choy, L,andDerynck R. The type II transforming growth factor (TGF)- receptor-interacting protein TRIP-1 acts as a modulator of the TGF- response. J Biol Chem 273:31455-31462,1998 .! g0 Y; a. N3 F! m& n' [/ K

, U) ~$ g5 P0 o% R
, f# y- O  O5 }  f
17. Dai, C,Yang J,andLiu Y. Single injection of naked plasmid encoding hepatocyte growth factor prevents cell death and ameliorates acute renal failure in mice. J Am Soc Nephrol 13:411-422,2002 .
! Z8 D5 c5 m( ?5 w7 c+ X
" B$ Z, g4 Q3 p1 s2 v! B4 _5 V

18. Datta, PK,Blake MC,andMoses HL. Regulation of plasminogen activator inhibitor-1 expression by transforming growth factor- -induced physical and functional interactions between Smads and Sp1. J Biol Chem 275:40014-40019,2000 .

9 ~1 ]: g' N: T& u" V
* H3 V( H7 M+ O0 l8 x: `- [
19. Davies, M,Martin J,Thomas GT,andLovett DH. Proteinases and glomerular matrix turnover. Kidney Int 41:671-678,1992  .
) e  ?; R7 L; {  C$ A0 Z
3 S1 D( ~) U! W3 G

20. De Caestecker, MP,Parks WT,Frank CJ,Castagnino P,Bottaro DP,Roberts AB,andLechleider RJ. Smad2 transduces common signals from receptor serine-threonine and tyrosine kinase. Genes Dev 12:1587-1592,1998 .
) `: r% l0 R, R% r% I
' p$ j! a4 G( m
7 |, Z, J( ^! W: a! J
21. Douthwaite, JA,Johnson TS,Haylor JL,Watson P,andEl Nahas AM. Effects of transforming growth factor- on renal extracellular matrix components and their regulating proteins. J Am Soc Nephrol 10:2109-2119,1999 .

22. Flaumenhaft, R,Moscatelli D,andRifkin DB. Heparin and heparan sulfate increase the radius of diffusion and action of basic fibroblast growth factor. J Cell Biol 111:1651-1659,1990 .; z' p( h; m+ ?6 V3 A7 @2 _
3 P9 J/ E$ h+ d1 P( U+ @- C: G# I

" d1 v2 F4 O6 o7 ^" S, \8 \  c
23. Ghosh, AK,Yuan W,Mori Y,Chen SJ,andVarga J. Antagonistic regulation of type I collagen gene expression by interferon- and transforming growth factor-. Integration at the level of p300/CBP transcriptional coactivators. J Biol Chem 276:11041-11048,2001 .
/ c  {8 X! \  p! P

5 \6 ]8 Z6 c! Z* V6 \; l+ w" A9 g
24. Gupta, S,Clarkson MR,Duggan J,andBrady HR. Connective tissue growth factor: potential role in glomerulosclerosis and tubulointerstitial fibrosis. Kidney Int 58:1389-1399,2000  .- K# p- `: q2 m+ l6 Q

2 A  |, P& W- M  _/ k
. }# z6 p1 }- H$ e
25. Habib, R. Focal glomerulosclerosis. Kidney Int 4:355-361,1973  .' q9 M5 C2 f& I. I+ O8 ?
! s9 k' w* g, d5 y- Y0 h

26. Hahn, SA,Schutte M,Hoque ATMS,Moskaluk CA,da Costa LT,Rozenblum E,Weisnstein CL,Fisher Y,Yeo CJ,andHruban RH. DPC4, a candidate tumor suppressor gene at human chromosome 18q21.1 Science 271:350-353,1996 .
4 q* }& I( h1 b& s; |

27. Hansch, GM,Wagner C,Burger A,Dong W,Staehler G,andStoek M. Matrix protein synthesis by glomerular mesangial cells in culture: effects of transforming growth factor (TGF ) and platelet-derived growth factor (PDGF) on fibronectin and collagen type IV mRNA. J Cell Physiol 163:451-457,1995  .5 ~2 q, h  [2 _9 V

5 U8 s4 L" W3 ]: R( }9 |4 j

28. Haseley, LA,Hugo C,Reidy MA,andJohnson RJ. Dissociation of mesangial cell migration and proliferation in experimental glomerulonephritis. Kidney Int 56:964-972,1999  .# p9 B3 [1 O$ [* U% L
/ P6 V+ B' V1 {; c5 r: Q% u! h; w" _

1 ~8 o+ L9 v  h% j( p8 U
29. Hata, A,Lagna G,Massague J,andHemmati-Brivanlou A. Smad6 inhibits BMP/Smad1 signaling by specifically competing with the Smad4 tumor suppressor. Genes Dev 12:186-197,1998 .

30. Hayashi, H,Abdollah S,Qui Y,Cai J,Xu YY,Grinnell BW,Richardson MA,Topper JN,Gimbrone MA, Jr,Wrana JL,andFalb D. The MAD-related protein Smad7 associates with the TGF receptor and functions as an antagonist of TGF signaling. Cell 89:1165-1173,1997  .+ [0 B. }, A1 G$ }! {) P

31. Hayashida, T,Poncelet AC,Hubchak SC,andSchnaper HW. TGF- 1 activates MAP kinases in human mesangial cells: a possible role in collagen expression. Kidney Int 56:1710-1720,1999  ." M; f9 r3 ?# c- Q- K
" r! u0 @/ d7 v9 Q' \& q# e8 j

32. Hayashida T and Schnaper HW. A Smad/ERK amplification loop forTGF- -stimulated collagen expression in human mesangial cells(Abstract). J Am Soc Nephrol. In press.

. Y/ C; L# u% }

33. Higaki, Y,Schullery D,Kawata Y,Shnyreva M,Abrass CK,andBomsztyk K. Synergistic activation of the rat laminin 1 chain promoter by the gut-enriched Kruppel-like factor (GKLF/KLF4) and Sp1. Nucl Acids Res 30:2270-2279,2002 .
2 F! u1 K7 P  s5 ]1 B2 m  h5 z, e

; k: ^, y5 G/ s. u" z  y$ W
34. Hong, SW,Isono M,Chen S,Iglesias-de la Cruz MC,Han DC,andZiyadeh FN. Increased glomerular and tubular expression of transforming growth factor- 1, its type II receptor, and activation of the Smad signaling pathway in the db/db mouse. Am J Pathol 158:1653-1663,2001 .* j# @$ Q+ D0 W% q+ D

3 g; O( f7 H+ {# i2 c
( y0 q& [' H% l, F% Y* i
35. Hua, X,Miller ZA,Benchabane H,Wrana JL,andLodish HF. Synergism between transcription factors TFE3 and Smad3 in transforming growth factor- -induced transcription of the Smad7 gene. J Biol Chem 275:33205-33208,2000 .. D& p5 z+ ?3 E. [" I9 z% |- m" P
! f5 \' ]  C2 A

36. Huwiler, A,andPfeilschifter J. Transforming growth factor 2 stimulates acute and chronic activation of the mitogen-activated protein kinase cascade in rat renal mesangial cells. FEBS Lett 354:255-258,1994  .

" J3 p: R4 ^; B" Y# p3 {) t
+ M( d/ M" \$ O. @( E5 M8 O
37. Iehara, N,Takeoka H,Ysuji H,Imabayashi T,Foster DN,Strauch AR,Yamada Y,Kita T,andDoi T. Differentiation of smooth muscle phenotypes in mouse mesangial cells. Kidney Int 49:1330-1341,1996  .
% h! ~6 n0 v( l$ ^
/ X# L4 d; [0 y0 Q1 P" {1 ?# P

38. Imamura, T,Takase M,Nishihara A,Oeda E,Hanai JI,Kawabata M,andMiyazono K. Smad6 inhibits signaling by the TGF superfamily. Nature 389:622-626,1997 .' ?% p- z0 o, t( u" o

: X) S; Z1 C  ~+ A5 ^
) A4 T: f8 ~% j, S1 q, W
39. Inoki, K,Haneda M,Ishida T,Mori H,Maeda S,Koya D,Sugimoto T,andKikkawa R. Role of mitogen-activated protein kinases as downstream effectors of transforming growth factor- in mesangial cells. Kidney Int Suppl 77:S76-S80,2000 .) K( F9 d* C+ ~# @

40. Isaka, Y,Fujiwara Y,Ueda N,Kaneda Y,Kamada T,andImai E. Glomerulosclerosis induced by in vivo transfection of transforming growth factor- or platelet-derived growth factor gene into the rat kidney. J Clin Invest 92:2597-2601,1993  .
* e# r7 R7 f! q, s0 h

41. Jang, CW,Chen CH,Chen CC,Chen JY,Su YH,andChen RH. TGF- induces apoptosis through Smad-mediated expression of DAP-kinase. Nat Cell Biol 4:51-58,2002  .
* y2 `1 |) H# n
) Z" b: ^1 L$ f" Q! J% s

42. Jernigan, S,Wing D,Schnaper HW,Poncelet AC,López-Guisa J,Ueno H,andEddy A. Effects of chronic blockade with soluble TGF receptor II in rats with overload proteinuria (Abstract). J Am Soc Nephrol 10:573A,1999., t- Q5 j1 w0 q1 r7 @0 ^) a$ H

1 p; n2 N3 [7 D& N- D6 S' ^, j

43. Jonk, LJC,Itoh S,Heldin CH,ten Dijke P,andKruijer W. Identification and functional characterization of a Smad binding element (SBE) in the JunB promoter that acts as a transforming growth factor-, activin, and bone morphogenetic protein-inducible enhancer. J Biol Chem 273:21145-21152,1998 .$ t; W. ~$ l+ h: A6 E
5 L: n8 G7 y; `3 w/ K
/ B* L+ ?* O# o) j6 h: b+ q
& K2 Q8 w" b1 |- g" F6 r
44. Kaplan, JM,Kim SH,North KN,Rennke H,Correia LA,Tong HQ,Mathis BJ,Rodriguez-Perez JC,Allen PG,Beggs AH,andPollak MR. Mutations in ACTN4, encoding -actinin-4, cause familial focal segmental glomerulosclerosis. Nat Genet 24:251-256,2000  .8 q5 }/ J3 `, i3 E) {
& w# U' g+ b6 h& p$ K3 U
  [$ l" N# H! j5 k* M, Y8 s( B- q
7 B  Y( A) T. p+ S9 I$ N5 Q
45. Kawata, Y,Suzuki H,Higaki Y,Denisenko O,Schullery D,Abrass CK,andBomsztyk K. Bcn-1 element-dependent activation of the laminin 1 chain gene by the cooperative action of transcription factor E2 (TFE3) and Smad proteins. J Biol Chem 277:11375-11384,2002 .

6 m* A0 j9 `4 D! m$ U3 j
46. Kim, RH,Wang D,Tsang M,Martin J,Huff C,de Caestecker MP,Parks WT,Meng X,Lechleider RJ,Wang T,andRoberts AB. A novel smad nuclear binding protein, SNIP1, suppresses p300-dependent TGF- signal transduction. Genes Dev 14:1605-1616,2000 ." t, f5 E0 j. M" {

* e4 p' I6 Q. H9 {3 k
47. Korbet, SM,Genchi RM,Borok RZ,andSchwartz MM. The racial prevalence of glomerular lesions in nephrotic adults. Am J Kidney Dis 27:647-651,1996  .

48. Kretzschmar, M,Doody J,andMassague J. Opposing BMP and EGF signaling pathways converge on the TGF- family mediator Smad1. Nature 389:618-622,1997 .
; A9 r, |3 r) \' W/ \2 l
7 y: _# w0 O$ A# i9 G, g

49. Kretzschmar, M,Doody J,Timokhina I,andMassague J. A mechanism of repression of TGF / Smad signaling by oncogenic Ras. Genes Dev 13:804-816,1999 .
: {) b( R. Y3 ]; ^, A

' t. q# v% E5 m8 ]
50. Labbé, E,Silvestri C,Hoodless PA,Wrana JL,andAttisano L. Smad2 andSmad3 positively and negatively regulate TGF -dependent transcription through the forkhead DNA-binding protein FAST2. Mol Cell 2:109-120,1998  .5 F+ l# D+ |, V+ S. C
9 w$ V5 L- a: \  }( z- i: s& e$ R

' A% N1 X8 @5 B
51. Lai, CF,Feng X,Nishimura R,Teitelbaum SL,Avioli LV,Ross FP,andCheng SL. TGF- upregulates 5 integrin subunit expression via Sp1 and Smad signaling. J Biol Chem 275:36400-36406,2000 .

! X. A* `/ m9 {3 ^& \

52. Ledbetter, SE,Copeland EJ,Noonan D,Vogelli G,andHassell JR. Altered steady-state mRNA levels of basement membrane proteins in diabetic mouse kidneys and thromboxane synthase inhibition. Diabetes 39:196-203,1990 .% a* w( K; q9 P% c+ J" r
9 s  ?, \0 \; u; }: ^# p

8 Q( V- }. t  }# y9 L* o# v) T! S
53. Lee, LK,Meyer TM,Pollock AS,andLovett DH. Endothelial cell injury initiates glomerular sclerosis in the rat remnant kidney. J Clin Invest 96:953-964,1995  .

( Q( @! x, h, s9 m4 A0 _& Z
  @' e0 O; \9 p# W4 `, [& ]
54. Li, JH,Zhu HJ,Huang XR,Lai KN,Johnson RJ,andLan HY. Smad7 inhibits fibrotic effects of TGF- on renal tubular epithelial cells by blocking Smad2 activation. J Am Soc Nephrol 13:1464-1472,2002 .

55. Liu, A,andBallermann BJ. TGF- type II receptor in rat renal vascular development: localization to juxtaglomerular cells. Kidney Int 53:716-725,1998  .

1 ]- `1 d! D) ~  Y' w3 A3 L+ I
56. Luo, K,Stroschein SL,Wang W,Chen D,Martens E,Zhou S,andZhou Q. The Ski oncoprotein interacts with the Smad proteins to repress TGF signaling. Genes Dev 13:2196-2206,1999 .: Z: Z5 y& l# Z

57. MacKay, K,Striker LJ,Stauffer JW,Doi T,Agodoa LY,andStriker GE. Transforming growth factor-. Murine glomerular receptors and responses of isolated glomerular cells. J Clin Invest 83:1160-1167,1989  .  |6 |# Y3 A  X
$ E6 ~6 ]  {/ e
+ ]* o8 `! t- k5 E% x3 K
6 a6 h9 |/ T8 n9 q! K
58. Marti, HP,Lee L,Kashgarian M,andLovett DH. Transforming growth factor- 1 stimulates glomerular mesangial cell synthesis of the 72-kd type IV collagenase. Am J Pathol 144:82-94,1994 .
- l# P2 J! N" b; e& c$ v/ b: s3 @

59. Massague, J. TGF signaling: receptors, transducers and Mad proteins. Cell 85:947-950,1996  .
+ {- b8 ^  p- {) E9 ~

. z  R9 V" c: I  Y
60. Massague, J,andChen YE. Controlling TGF signaling. Genes Dev 14:627-644,2000 .( F* ^  j! {1 d9 j: s+ g. c  C8 q
9 h! Y) M" C; y
4 d0 E' w( z  g- ~' o
) P  x( _8 m7 \3 }  L1 J# J7 h. |3 W
61. Matsuda, T,Yamamoto T,Muraguchi A,andSaatcioglu F. Cross-talk between TGF- and estrogen receptor signaling through Smad3. J Biol Chem 276:42908-42914,2001 .3 @" D# q$ F( Z6 d
4 W: D$ ^1 G1 P; i6 T
. S" a0 j4 p1 O

62. McGowan, TA,Madesh M,Zhu Y,Wang L,Russo M,Deelman L,Henning R,Joseph S,Hajnoczky G,andSharma K. TGF- -induced Ca 2  influx involves the type III IP 3 receptor and regulates actin cytskeleton. Am J Physiol Renal Physiol 282:F910-F920,2002 .
( Q6 p! e7 ~2 v1 J+ }
, R# g/ i7 Z% ?' H7 z

63. McKay, NG,Khong TF,Haites NE,andPower DA. The effect of transforming growth factor 1 on mesangial cell fibronectin synthesis: increased incorporation into the extracellular matrix and reduced pI but no effect on alternative splicing. Exp Mol Pathol 59:211-224,1993  .- E/ q# \+ Z  I1 o7 D3 E" \
& B/ q/ a  Q8 f. Y) H% B3 @! p
6 l5 b6 a- z5 b8 f
+ |0 k" A" q0 m/ r0 S9 C
64. Mezzano, SA,Ruiz-Ortega M,andEgido J. Angiotensin II and renal fibrosis. Hypertension 36:635-638,2001.% m  i" k( P3 e( q0 ~

# c0 r6 t; y; B  g) `9 |
65. Moustakas, A,andHeldin CH. From mono- to oligo-Smads: the heart of the matter in TGF- signal transduction. Genes Dev 16:1867-1871,2002 .+ _  v/ ~- B( l  G2 Y9 r/ v
' l- h/ z0 @8 z2 L
7 a7 Y2 A) O( f  {4 \$ P8 C' d/ u

66. Mozes, MM,Bottinger EP,Jacot TA,andKopp JB. Renal expression of fibrotic matrix proteins and of transforming growth factor- (TGF- ) isoforms in TGF- transgenic mice. J Am Soc Nephrol 10:271-280,1999 .

% U1 H# i1 Q5 X+ m( ]( e' Z2 p: ^6 A

67. Munger, JS,Harpel J,Gleizes PE,Mazzieri R,Nunes I,andRifkin DB. Latent transforming growth factor- : structural features and mechanism of activation. Kidney Int 51:1376-1382,1997  .3 x+ ?) q: |' I) n; }$ I. @
3 V; O3 ^' |3 ?% h  c% c

. f# m6 Z3 m3 X( U5 @7 e; M6 {6 c# {; U
68. Munger, JS,Huang X,Kawakatsu H,Griffiths MJ,Dalton SL,Wu J,Pittet JF,Kaminski N,Garat C,Matthay MA,Rifkin DB,andSheppard D. The integrin v 6 binds and activates latent TGF 1: a mechanism for regulating pulmonary inflammation and fibrosis. Cell 96:319-328,1999  ., V* t5 h6 V. y) u

69. Nagarajan, RP,Zhang J,Li W,andChen Y. Regulation of Smad7 promoter by direct association with Smad3 and Smad4. J Biol Chem 274:33412-33418,1999 .- x6 I4 J- {8 A: l
8 v% S7 O' a3 x5 U0 C

  [& X9 u% S; Y- ~/ a6 E
70. Nagatake, M,Takagi Y,Osada H,Uchida K,Mitsudomi T,Saji S,Shimokata K,Takahashi T,andTakahashi T. Somatic in vivo alterations of the DPC4 gene at 18q21 in human lung cancers. Cancer Res 56:2718-2720,1996 .! A' x- c+ i; i' ~9 R- V9 z, B! J
) ^  X6 Y# {8 n4 N' K) \

% ^% L4 l. H/ u; E
71. Nakamura, H,Isaka Y,Tsujie M,Rupprecht HD,Akagi Y,Ueda N,Imai E,andHori M. Introduction of DNA enzyme for Egr-1 into tubulointerstitial fibroblasts by electroporation reduced interstitial alpha-smooth muscle actin expression and fibrosis in unilateral ureteral obstruction (UUO) rats. Gene Ther 9:495-502,2002  .

3 D, G9 T+ L7 D8 u
72. Nakamura, T,Ebihara I,Tomino Y,Koide H,Kikuchi K,andKoiso K. Gene expression of growth-related proteins and ECM constituents in response to unilateral nephrectomy. Am J Physiol Renal Fluid Electrolyte Physiol 262:F389-F396,1992 .: j: W. X5 I, B; G# p9 E$ P+ N
' F( h/ L5 [; Y4 e, o$ d5 W$ n8 z' j
* o# K& G" |: b! ^" {. H" T8 ?
* s- B6 x3 R" F
73. Nakao, A,Afrakhte M,Moren A,Nakayama T,Christian JL,Heuchel R,Itoh S,Kawabata M,Heldin NE,Heldin CH,andten Dijke P. Identification of Smad7, a TGF -inducible antagonist of TGF- signalling. Nature 389:631-635,1997 .
, N1 h: M9 [# w$ l& F$ D2 G6 x

74. Overall, CM,Wrana JL,andSodek J. Independent regulation of collagenase, 72-kDa progelatinase, and metalloendoproteinase inhibitors expression in human fibroblasts by transforming growth factor-. J Biol Chem 264:1860-1869,1989 .
- v# ]7 N$ k1 r9 M: E

. L8 x% ]  c3 ^! \( c) e
75. Patrakka, J,Kestila M,Wartiovaara J,Ruotsalainen V,Tissari P,Lenkkeri U,Mannikko M,Visapaa I,Holmberg C,Rapola J,Tryggvason K,andJalanko H. Congenital nephrotic syndrome (NPHS1): features resulting from different mutations in Finnish patients. Kidney Int. 58:972-980,2000  .
, v  F4 l) V4 E$ I, f' r

76. Piek, E,Heldin CH,andten Dijke P. Specificity, diversity and regulation in TGF- superfamily signaling. FASEB J 13:2105-2124,1999 .! d0 l9 l; y3 G, k  `) s* z# v
" @& W; o3 N7 P' H$ O

* Q( e+ j% S6 e5 N3 h3 X
77. Piek, E,andRoberts AB. Suppressor and oncogenic roles of transforming growth factor- and its signaling pathways in tumorigenesis. Adv Cancer Res 83:1-54,2001  .
8 P# Q  X  X5 F4 Q# X1 E% t/ A
% ?! Q: z$ a: w
: n% Q0 A$ Y; G9 e3 }
78. Piscone, TD,Phan T,andRosenblum ND. BMP7 controls collecting tubule cell proliferation and apoptosis via Smad1-dependent and -independent pathways. Am J Physiol Renal Physiol 280:F19-F33,2001 .5 o$ s; I6 y  q" p2 J* J
% }% y/ C; N  c; I; k
" p  E' b, l% Y$ e3 N

79. Poncelet, AC,de Caestecker MP,andSchnaper HW. The TGF- /SMAD signaling pathway is present and functional in human mesangial cells. Kidney Int 56:1354-1365,1999  .

8 G1 ]2 R/ f* J& I1 O& r
80. Poncelet, AC,andSchnaper HW. Regulation of mesangial cell collagen turnover by transforming growth factor- 1. Am J Physiol Renal Physiol 275:F458-F466,1998 .
6 `- f4 _/ V& r& T4 W7 K* m; o4 o! H
7 o3 O& P! }" }% t$ e: u$ h

81. Poncelet, AC,andSchnaper HW. Sp1 and Smad proteins cooperate to mediate TGF- 1-induced 2(I) collagen expression in human glomerular mesangial cells. J Biol Chem 276:6983-6992,2001 .8 D1 {+ M$ P3 t6 c

' R" q3 W! H' C. |7 R/ m3 k# _

82. Rini, BI,Selk LM,andVogelzang NJ. Phase I study of direct intralesional gene transfer of HLA-B7 into metastatic renal carcinoma lesions. Clin Cancer Res 5:2766-2772,1999 .

83. Runyan, CE,Schnaper HW,andPoncelet AC. Smad, PI3K and PKC interactions mediate TGF- 1-induced collagen I expression (Abstract). J Am Soc Nephrol. 13:502A,2002.

$ S+ f  i: t5 P7 b: U, ?
7 u6 o( ~0 A9 e8 A
84. Savage, C,Das P,Finelli A,Townsend SR,Sun CY,Baird SE,andPadgett RW. Caenorhabditis elegans genes sma-2, sma-3 and sma-4 define a conserved family of transforming growth factor pathway components. Proc Natl Acad Sci USA 93:790-794,1996 .

85. Schiffer, M,Bitzer M,Roberts IS,Kopp JB,ten Dijke P,Mundel P,andBottinger EP. Apoptosis in podocytes induced by TGF- and Smad7. J Clin Invest 108:807-816,2001  .

  v5 T* i3 ^& a% Y% s. a' N4 e

86. Schiffer, M,von Gersdorff G,Bitzer M,Susztak K,andBottinger EP. Smad proteins and transforming growth factor-beta signaling. Kidney Int Suppl 77:S45-S52,2000 .

. c( x% \3 d% w8 M  s1 c1 r% M

87. Schnaper, HW. Balance between matrix synthesis and degradation: a determinant of glomerulosclerosis. Pediatr Nephrol 9:104-111,1995  .
* _' J* R! p9 v# V. I
- Z* g& u) q- q3 x/ Q$ ^- M! y/ Q6 d

88. Schnaper, HW. Focal segmental glomerulosclerosis.In: Immunologic Renal Disease (2nd ed.), edited by Neilson EG,and Couser WG.. Philadelphia, PA: Lippincott Williams & Willkins, 2001, p. 1001-1027.

4 z  e+ r+ H  c* c4 J

89. Schnaper HW and Kopp JB. Renal fibrosis. Front Biosci.In press.
3 I  \+ r4 H- E
: \/ n& n, V! @. G0 F) k& h

90. Schnaper, HW,andRobson AM. Nephrotic syndrome: minimal change disease, focal glomerulosclerosis, and related disorders.In: Diseases of the Kidney and Urinary Tract (7th ed.), edited by Schrier RW,and Gottschalk CW.. Philadelphia, PA: Lippincott Williams & Wilkins, 2001, p. 1773-1831.! e, D) P2 T9 E- \5 C4 i

' X, M) H/ F- j8 l4 y7 }0 }; y" M

91. Sekelsky, JJ,Newfeld SJ,Raferty LA,Chartoff EF,andGelbart WM. Genetic characterization and cloning of Mothers against dpp, a gene required for decapentaplegic function in Drosophila melanogaster. Genetics 139:1347-1358,1995 ./ E3 m- i) `- o

, }# U" K9 W$ Z2 N' D' B7 l. S

92. Shen, X,Hu PP,Liberati NT,Datto MB,Frederick JP,andWang XF. TGF- -induced phosphorylation of Smad3 regulates its interaction with coactivator p300/CREB-binding protein. Mol Biol Cell 9:3309-3319,1998 .
5 c: Z9 z* r/ L9 [

93. Shih, NY,Li J,Karpitskii V,Nguyen A,Dustin ML,Kanagawa O,Miner JH,andShaw AS. Congenital nephrotic syndrome in mice lacking CD2-associated protein. Science 286:312-315,1999 .

8 a& B2 m4 W; B8 d; d  ?$ p9 L
, \7 t% d; j) p/ J1 Y2 }' P
94. Srivastava, T,Garola RE,Whiting JM,andAlon US. Synaptopodin expression in idiopathic nephrotic syndrome of childhood. Kidney Int 59:118-125,2001  .

95. Srivastava, T,Simon SD,andAlon US. High incidence of focal segmental glomerulosclerosis in nephrotic syndrome of childhood. Pediatr Nephrol 13:13-18,1999  ., S$ S* d5 t4 Z. ?9 b5 O; ^
2 c, s1 B, R3 I" A: F$ o1 X
& F9 x1 F' m3 v( R, s) M

96. Stroschein, SL,Wang W,Zhou S,Zhou Q,andLuo K. Negative feedback regulation of TGF- signaling by the SnoN oncoprotein. Science 286:771-774,1999 .
: \7 b. U9 h2 e' |

% v. J! q! J4 U6 i
97. Suzuki, S,Ebihara I,Tomino Y,andKoide H. Transcriptional activation of matrix genes by transforming growth factor 1 in mesangial cells. Exp Nephrol 1:229-237,1993  .
0 T; E  ~1 q. l6 L
, F. ]4 R) \: k% e7 S) I8 I2 a' e

98. Thiagalingam, S,Lengauer C,Leach FS,Schutte M,Hahn SA,Overhauser J,Willson JK,Markowitz S,Hamilton SR,Kern SE,Kinzler KW,andVogelstein B. Evaluation of candidate tumour suppressor genes on chromosome 18 in colorectal cancers. Nat Genet 13:343-346,1996  .
" G: B2 A: A9 Q  \+ F
9 O# x/ s+ X& }. X9 S7 @$ S
7 ^. ^+ l3 J3 _$ |$ V$ V& R
99. Tomooka, S,Border WA,Marshall BC,andNoble NA. Glomerular matrix accumulation is linked to inhibition of the plasmin protease system. Kidney Int 42:1462-1469,1992  ., u2 u, s8 }9 ~1 z, }7 g
: t% _4 E8 x; s' ]- S) H

+ H/ e: t- F* i; x
100. Tsukazaki, T,Chiang TA,Davison AF,Attisano L,andWrana JL. SARA, a FYVE domain protein that recruits Smad2 to the TGF receptor. Cell 95:779-791,1998  .
2 f8 J0 @( i2 u% G! \3 `) q
+ O1 r$ y, [% {7 B, M$ w* N2 N

101. Uchida, K,Nitta K,Kobayashi H,Kawachi H,Shimizu F,Yumura W,andNihei H. Localization of Smad6 and Smad7 in the rat kidney and their regulated expression in the anti-Thy-1 nephritis. Mol Cell Biol Res Commun 4:98-105,2000 .

102. Van den Steen, PE,Opdenakker G,Wormald MR,Dwek RA,andRudd PM. Matrix remodelling enzymes, the protease cascade and glycosylation. Biochim Biophys Acta 1528:61-73,2001 .
" E- d/ `5 Q7 C1 f+ D& u( v- @

' p# j0 R5 g. z1 r1 A$ o/ [
103. Wang, L,Zhu Y,andSharma K. Transforming growth factor- 1 sitmulates protein kinase A in mesangial cells. J Biol Chem 273:8522-8527,1998 .

5 k5 |9 E- J6 f8 f
. ^: @' n! ~: V# d" n3 _. U  ]
104. Yahata, T,de Caestecker MP,Lechleider RJ,Andriole S,Roberts AB,Isselbacher KJ,andShioda T. The MSG1 non-DNA-binding transactivator binds to the p300/CBP coactivators, enhancing their functional link to the Smad transcription factors. J Biol Chem 275:8825-8834,2000 .

) V  C! M( s$ j8 T8 e! U

105. Yamamoto, T,Noble NA,Cohen AH,Nast CC,Hishida A,Gold LI,andBorder WA. Expression of transforming growth factor-beta isoforms in human glomerular disease. Kidney Int 49:461-469,1996  .

# C6 M5 {" x; V$ a5 v

106. Yang, J,andLiu Y. Blockage of tubular epithelial to myofibroblast transition by hepatocyte growth factor prevents renal interstitial fibrosis. J Am Soc Nephrol 13:96-107,2002 .
# L/ l# z! @# |7 x4 z
3 r) t* _- O# a
- |2 o1 g! B! p9 ?1 f0 C
107. Yang, J,andLiu Y. Dissection of key events in tubular epithelial to myofibroblast transition and its implications in renal interstitial fibrosis. Am J Pathol 159:1465-1475,2002.

108. Ying, WZ,andSanders PW. Dietary salt enhances glomerular endothelial nitric oxide synthase through TGF- 1. Am J Physiol Renal Physiol 275:F18-F24,1998 .
1 n6 m, ^# D' a$ W
' L  D  A& g' e- s' }# C+ P( t. ~4 j

109. Yoshioka, K,Takemura T,Murakami K,Okada M,Hino S,Miyamoto H,andMaki S. Transforming growth factor- protein and mRNA in glomeruli in normal and diseased human kidneys. Lab Invest 68:154-163,1993  .

8 ?+ E) W9 D+ n* z
110. Zawel, L,Le Dai J,Buckhaults P,Zhou S,Kinzler KW,Volgelstein B,andKern SE. Human Smad3 and Smad4 are sequence-specific transcription activators. Mol Cell 1:611-617,1998  .
4 L! U5 P8 Y: X+ e( }

111. Zdunek, M,Silbiger S,Lei J,andNeugarten J. Protein kinase CK2 mediates TGF- 1-stimulated type IV collagen gene transcription and its reversal by estradiol. Kidney Int 60:2097-2108,2001  .
) Q; ^  D: s; _- V, W: V

4 Y  `1 b8 x, u: _! t4 w7 V7 j
112. Zhang, W,Ou J,Inagaki Y,Greenwel P,andRamirez F. Synergistic cooperation between Sp1 and Smad3/Smad4 mediates TGF 1 stimulation of 2(I) collagen (COL1A2) transcription. J Biol Chem 275:39237-39245,2000 .) k3 V* B& J  s7 ^- I

& h8 v: B  B  y
113. Zhang, Y,Feng XH,andDerynck R. Smad3 and Smad4 cooperate with c-Jun/c-Fos to mediate TGF- -induced transcription. Nature 394:909-913,1998 .

收藏0 分享0 顶0 踩0