Endophilin-A controls recruitment, priming and fusion of neurosecretory vesicles

Abstract

Endophilins-A are conserved endocytic adaptors with membrane curvature-sensing and - inducing properties. We show here that, independently of their role in endocytosis, endophilin-A1 and endophilin-A2 regulate exocytosis of neurosecretory vesicles. The number of neurosecretory vesicles was not altered in chromaffin cells without endophilin, yet fast capacitance and amperometry measurements revealed reduced exocytosis, smaller vesicle pools and changed fusion kinetics. Both endophilin-A1 (brain-enriched) and A2 (ubiquitous) rescued exocytic defects, but endophilin-A2 was more efficient. Distribution of neurosecretory vesicles was altered in the plasma membrane proximity, but levels and distributions of main exocytic and endocytic factors were unchanged, and slow compensatory endocytosis was not robustly affected. Endophilins role in exocytosis is mediated through its SH3-domain and, at least in part, interaction with intersectin, a coordinator of exocytic and endocytic traffic. Altogether, we report that endophilins-A, key endocytic proteins linked to neurodegeneration, directly regulate exocytosis by controlling vesicle recruitment, priming and fusion. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=72 SRC="FIGDIR/small/540864v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@b5cabeorg.highwire.dtl.DTLVardef@1119afborg.highwire.dtl.DTLVardef@d5da6aorg.highwire.dtl.DTLVardef@1f67e32_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIRecruitment, priming and fusion of secretory vesicles is controlled by endophilin C_LIO_LILack of endophilins alters the distribution of secretory vesicles near the PM C_LIO_LIEndophilins role in exocytosis is mediated through its SH3-domain C_LIO_LIEndophilin regulates intersectin localization by keeping it away from the PM C_LI