RRC ID 50389
Author Klein O, Roded A, Zur N, Azouz NP, Pasternak O, Hirschberg K, Hammel I, Roche PA, Yatsu A, Fukuda M, Galli SJ, Sagi-Eisenberg R.
Title Rab5 is critical for SNAP23 regulated granule-granule fusion during compound exocytosis.
Journal Sci Rep
Abstract Compound exocytosis is considered the most massive mode of exocytosis, during which the membranes of secretory granules (SGs) fuse with each other to form a channel through which the entire contents of their granules is released. The underlying mechanisms of compound exocytosis remain largely unresolved. Here we show that the small GTPase Rab5, a known regulator of endocytosis, is pivotal for compound exocytosis in mast cells. Silencing of Rab5 shifts receptor-triggered secretion from a compound to a full exocytosis mode, in which SGs individually fuse with the plasma membrane. Moreover, we show that Rab5 is essential for FcεRI-triggered association of the SNARE protein SNAP23 with the SGs. Direct evidence is provided for SNAP23 involvement in homotypic SG fusion that occurs in the activated cells. Finally, we show that this fusion event is prevented by inhibition of the IKKβ2 kinase, however, neither a phosphorylation-deficient nor a phosphomimetic mutant of SNAP23 can mediate homotypic SG fusion in triggered cells. Taken together our findings identify Rab5 as a heretofore-unrecognized regulator of compound exocytosis that is essential for SNAP23-mediated granule-granule fusion. Our results also implicate phosphorylation cycles in controlling SNAP23 SNARE function in homotypic SG fusion.
Volume 7(1)
Pages 15315
Published 2017-11-10
DOI 10.1038/s41598-017-15047-8
PII 10.1038/s41598-017-15047-8
PMID 29127297
PMC PMC5681557
MeSH Cell Line Cell Membrane / genetics Cell Membrane / metabolism* Exocytosis / physiology* Humans Membrane Fusion / physiology* Phosphorylation / physiology Qb-SNARE Proteins / genetics Qb-SNARE Proteins / metabolism* Qc-SNARE Proteins / genetics Qc-SNARE Proteins / metabolism* Secretory Vesicles / genetics Secretory Vesicles / metabolism* rab5 GTP-Binding Proteins / genetics rab5 GTP-Binding Proteins / metabolism*
IF 3.998
Times Cited 7
DNA material pEF-HA-SNAP23-S95E/S120E (RDB15724) pEF-HA-SNAP23-S95A/S120A (RDB15725).