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First published online May 10, 2006

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Exocytosis: removing the PIPs

Despite their low abundance in biological membranes, phosphoinositides are important cellular regulators. Phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P₂] regulates both endocytosis and exocytosis, but its role in the latter process is unclear. On p. 2084, Giampietro Schiavo and co-workers report that elimination of PtdIns(4,5)P₂ from the plasma membrane is required for regulated exocytosis in activated mast cells. These cells release pro-inflammatory mediators by exocytosis of pre-formed granules, a process that involves granule-plasma-membrane fusion and granule-granule fusion but no compensatory endocytosis. Using quantitative immunofluorescence, the authors show that PtdIns(4,5)P₂ is present in the plasma membrane of mast cells but not their granule membranes. Upon activation of exocytosis, they report, PtdIns(4,5)P₂ is transiently depleted from the plasma membrane by phosphatidylinositol-specific phospholipase C; both removal of PtdIns(4,5)P₂ and production of its metabolite diacylglycerol (but not activation of Ca²⁺ signalling,) are required for exocytosis. The authors conclude that a cycle of PtdIns(4,5)P₂ synthesis and breakdown regulates exocytosis in mast cells and speculate that a similar cycle functions in other secretory cells.

Related articles in JCS:

Elimination of plasma membrane phosphatidylinositol (4,5)-bisphosphate is required for exocytosis from mast cells

Gerald R. V. Hammond, Stephen K. Dove, Alastair Nicol, Jef A. Pinxteren, Daniel Zicha, and Giampietro Schiavo
JCS 2006 119: 2084-2094. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JCS Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content