Dance of the podosomes

杨柳

Macrophages crawl across a substrate using podosomes, focal complex-like adhesions that form and disappear rapidly at the cell's leading edge. Beginning on page 697, Evans et al. provide a high-resolution view of the dynamic turnover of these structures, revealing some surprising behavior and suggesting a novel mechanism of cell migration.
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Using fluorescently labeled podosome components and quantitative 4-D microscopy, the authors show that the majority of leading edge podosomes either assemble from older podosomes or form through the dramatic fragmentation of a large podosome cluster precursor (PCP). In the first pathway, simple podosomes undergo both fission and fusion events. This often produces a sort of forward stepping movement, when a trailing podosome fuses with one closer to the leading edge. The other pathway begins with a podosome that grows to several times normal size to form a PCP. The PCP then fragments rapidly into a cluster of four to six individual podosomes.
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3 g& K5 |& j$ kIn contrast to focal adhesions, which stick to a substrate and allow a cell to pull itself forward, podosomes appear to step forward more or less continuously. This dynamic crawl may allow macrophages to adapt quickly while moving through complex tissues.(A PCP (arrowhead) turns into four podoso)