Cell Biology

Getting Back What You've Put In

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Science  10 Mar 2000:
Vol. 287, Issue 5459, pp. 1713
DOI: 10.1126/science.287.5459.1713d

During stimulated secretion, intracellular vesicles fuse at the cell surface and release their contents. Cells have developed efficient mechanisms to retrieve the vesicular membrane components for reuse; in sea urchin eggs, fertilization triggers a wave of secretory granule exocytosis that is followed rapidly by a compensatory wave of endocytosis.

Smith et al. have examined the mechanism controlling the endocytic burst by direct observation in a confocal microscope. Granule membranes contain a P-type voltage-sensitive calcium channel, which is incorporated into the plasma membrane during exocytosis. This generates localized entry of calcium, which in turn stimulates a localized burst of endocytosis that specifically retrieves granule membrane components. Thus, sites of endocytosis are restricted to sites of exocytosis, and plasma membrane proteins are excluded from the endocytic vesicles. Similar mechanisms marrying sites of exocytosis to sites of compensatory endocytosis may occur generally.—SMH

J. Cell Biol.148, 755 (2000).

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