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Ischemia induces regulator of G protein signaling 2 (RGS2) protein& n6 |/ m% t" f8 V
upregulation and enhances apoptosis in astrocytes' d9 Z3 A" C# }! e% }
Mehari Endale,1* Sung Dae Kim,1* Whi Min Lee,1 Sangseop Kim,2 Kyoungho Suk,2 Jae Youl Cho,3
9 o0 O8 |3 [8 J; L6 qHwa Jin Park,4 Yadav Wagley,5 Suk Kim,6 Jae-Wook Oh,5 and Man Hee Rhee1
8 O' ?. v8 L/ [
) R3 F0 O* `" n& N6 }, K7 aEndale M, Kim SD, Lee WM, Kim S, Suk K, Cho JY, Park HJ,) U, C( Q) X4 r |3 `, D
Wagley Y, Kim S, Oh JW, Rhee MH. Ischemia induces regulator of G8 O% a# ~, M) h, P4 }
protein signaling 2 (RGS2) protein upregulation and enhances apoptosis1 |. k! X# |1 ?5 F+ o0 ?3 J% q# ]
in astrocytes. Am J Physiol Cell Physiol 298: C611–C623, 2010. First
! S* H8 k2 B! Z; r4 ?published December 23, 2009; doi:10.1152/ajpcell.00517.2008.—Regulator2 O/ A! G* C) j2 x
of G protein signaling (RGS) family members, such as RGS2,- w$ @1 Q* g' ^! z) r9 p, m
interact with G subunits of heterotrimeric G proteins, accelerating' r1 m) ^) s$ m# a* W) k5 M8 F! E/ D
the rate of GTP hydrolysis and attenuating the intracellular signaling
q; W3 R( u% Ttriggered by the G protein-coupled receptor-ligand interaction.
+ Z% f* U# W7 V# {They are also reported to regulate G protein-effector interactions
P" E$ [& X& F8 Y; fand form multiprotein signaling complexes. Ischemic stress-induced9 j/ j+ O3 T, p ]1 p% B
changes in RGS2 expression have been described in astrocytes, T j" g4 Z) o" K9 l- F; S
and these changes are associated with intracellular signaling0 a+ g' L! `, ?, X. Q8 u! _% c
cascades, suggesting that RGS2 upregulation may be an important
7 |& o5 h: ?/ A1 w+ g2 pmechanism by which astrocytes may regulate RGS2 function in' K) k J1 _$ V3 E- y0 j' _( ^5 R/ s
response to physiological stress. However, information on the
. R9 r q$ N: {) j; U B3 y( sfunctional roles of stress-induced modulation of RGS2 protein; E! K% l3 F& `; F/ G
expression in astrocyte function is limited. We report the role of
4 u# e: L0 X6 X' Lischemic stress in RGS2 protein expression in rat C6 astrocytoma
* C$ m6 D6 g$ f) U8 P: R: |1 Hcells and primary mouse astrocytes. A marked increase in RGS2- X: Q0 @% k$ j' [; t" B* R7 e
occurred after ischemic stress induced by chemicals (sodium azide! M( V$ H6 d5 n# A t6 A1 N3 {
and 2-deoxyglucose) or oxygen-glucose deprivation (OGD, real
$ @* {0 J. X- Z4 T4 |( R$ [ischemia). RGS2 mRNA expression was markedly enhanced by 1: z0 g4 c) @3 w8 P
h of exposure to chemical ischemia or 6 h of OGD followed by 2
3 A9 R" k+ `9 f7 n$ \7 H0 o+ x1 ior 6 h of recovery, respectively. This enhanced expression in
1 t6 V6 c% x& F' kprimary astrocytes and C6 cells was restored to baseline levels
1 y# o1 @6 I9 T& @2 m: Yafter 12 h of recovery from chemically induced ischemic stress or
: }+ [4 h! X; \- w5 V" y: D5 m i6 I4 – 6 h of recovery from OGD. RGS2 protein was also significantly% F- J* k4 ~: W
expressed at 12–24 h of recovery from ischemic insult. Ischemiainduced
+ M5 u) Q6 J; q5 @RGS2 upregulation was associated with enhanced apoptosis.- e6 a3 v& v# j e |) m$ ?& ]3 q( a
It significantly increased annexin V-positive cells, cleaved
! [8 }7 k7 N8 ocaspase-3, and enhanced DNA ladder formation and cell cycle3 r9 Z/ m, o3 f' I3 v( B
arrest. However, a small interfering RNA (siRNA)-mediated RGS2% E& W* d L d+ Q7 e
knockdown reversed the apoptotic cell death associated with ischemia- n( P( u0 B/ i3 |: z" y
induced RGS2 upregulation. Upregulated RGS2 was significantly
0 B0 V2 k; {5 O1 A# m, Iinhibited by SB-203580, a p38 MAPK inhibitor. Rottlerin,8 |) \. W( M5 l( T, @
a potent inhibitor of PKC, completely abrogated the increased* }$ i" Q( V# E3 {, L' @- c, H
RGS2 expression. We also examine whether ischemia-induced0 F5 l6 [ J3 Y2 X/ {7 q
RGS2-mediated apoptosis is affected by siRNA-targeted endogenous" }5 \9 I |, R- H7 Z" Z+ x
PKC downregulation or its phosphorylation. Although
) ^7 P% s& E3 ^2 ?% q* V( A' {7 b h/ `RGS2 upregulation was not affected, siRNA transfection significantly
8 P' q8 l3 b' Vsuppressed endogenous PKC mRNA and protein expresexpressions.
p# v5 L& o4 |. X0 g# NIschemia-induced PKC phosphorylation and caspase-3
" J1 R" M% J) h1 m- ]cleavage were dose dependently inhibited by PKC knockdown,6 K1 A& _* P2 q* f$ D1 V
and this endogenous PKC suppression reversed ischemia-induced
5 m4 \ J/ [& [annexin V-positive cells. This study suggests that ischemic stress! t' |% T- @2 Q8 G
increases RGS2 expression and that this condition contributes to2 B0 A$ E: x7 `7 Q+ G! V0 X
enhanced apoptosis in C6 cells and primary astrocytes. The signaling
, ^0 g7 g0 `& E8 m% H; Pit follows may involve PKC and p38 MAPK pathways.
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发表于 2011-8-24 05:41
