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Control of local actin assembly during exocytosis by compartment mixing
Author(s) -
Bement William
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.628.2
Subject(s) - exocytosis , microbiology and biotechnology , granule (geology) , actin , secretory pathway , membrane , secretory vesicle , chemistry , secretion , biophysics , biology , biochemistry , golgi apparatus , endoplasmic reticulum , paleontology
Localized actin assembly is an essential feature of many fundamental cell processes, but how it is controlled is poorly understood. Here we have investigated the trigger for assembly of actin “coats” around exocytosing secretory granules in Xenopus eggs. We show that the trigger is fusion of the secretory granule with the plasma membrane, and the resultant mixing of the membrane contents of these two compartments. Specifically, diacylyglcerol from the plasma membrane incorporates into the membrane of the exocytosing secretory granules after fusion with the plasma membrane, and directs sustained recruitment of protein kinase C beta which, in turn, promotes local activation of Cdc42 which then directs actin assembly. The secretory granule membrane contributes Cdc42, which is localized (in the inactive, GDP‐bound form) to the secretory granule surface prior to exocytosis. Thus, actin assembly is limited to the surface of exocytosing secretory granules by virtue of compartment mixing. This mechanism provides a broadly useful means for cells to precisely limit actin assembly at the plasma membrane and other areas where membrane fusion occurs.