RRC ID 50387
Author Azouz NP, Zur N, Efergan A, Ohbayashi N, Fukuda M, Amihai D, Hammel I, Rothenberg ME, Sagi-Eisenberg R.
Title Rab5 is a novel regulator of mast cell secretory granules: impact on size, cargo, and exocytosis.
Journal J. Immunol.
Abstract Secretion of inflammatory mediators prestored in mast cells secretory granules (SGs) enhances immune responses such as in allergy and host defense. However, the mechanisms underlying the biogenesis of the SGs remain largely unresolved. By combining high-resolution live cell imaging and quantitative morphometric analyses, we show that the small GTPase Rab5 controls the SG size and cargo composition by a VAMP8-dependent fusion mechanism. Knockdown of the endogenous Rab5, or expression of constitutively negative mutants, significantly reduces the size of SGs and increases their number. Conversely, expression of constitutively active Rab5 mutants induces few, but giant, SGs. Both the small and giant SGs maintain their exocytosis competence. Finally, we show that Rab5-mediated fusion between Golgi-derived SGs and early endosomes precedes the maturation of the SGs, as reflected by the recruitment of Rab27B, and allows the incorporation of cargo, such as CD63, that traffics through endosomes. Collectively, our results assign Rab5 a key role in mediating mast cell SG fusion during biogenesis, thereby controlling the amount and composition of the SGs content and maintaining the communication between new and pre-existing SGs.
Volume 192(9)
Pages 4043-53
Published 2014-5-1
DOI 10.4049/jimmunol.1302196
PII jimmunol.1302196
PMID 24696234
MeSH Animals Cell Degranulation / immunology* Exocytosis* Flow Cytometry Gene Knockdown Techniques Immunohistochemistry Mast Cells / immunology* Mast Cells / metabolism Mice Mice, Inbred BALB C Microscopy, Confocal Rats Reverse Transcriptase Polymerase Chain Reaction Secretory Vesicles / immunology* Secretory Vesicles / metabolism Transfection rab5 GTP-Binding Proteins / immunology* rab5 GTP-Binding Proteins / metabolism
IF 4.539
Resource
DNA material pSilencer-neo-Rab5A (RDB15727) pSilencer-neo-Rab5B/C (RDB15728).