Endophilin-A coordinates priming and fusion of neurosecretory vesicles via intersectin

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 and distribution of neurosecretory vesicles were not changed in chromaffin cells lacking endophilin-A, yet fast capacitance and amperometry measurements revealed reduced exocytosis, smaller vesicle pools and altered fusion kinetics. The levels and distributions of the main exocytic and endocytic factors were unchanged, and slow compensatory endocytosis was not robustly affected. Endophilin-A's role in exocytosis is mediated through its SH3domain, specifically via a direct interaction with intersectin-1, a coordinator of exocytic and endocytic traffic. Endophilin-A not able to bind intersectin-1, and intersectin-1 not able to bind endophilin-A, resulted in similar exocytic defects in chromaffin cells. Altogether, we report that two endocytic proteins, endophilin-A and intersectin-1, are enriched on neurosecretory vesicles and regulate exocytosis by coordinating neurosecretory vesicle priming and fusion.

Molecular mechanism of Fast Endophilin-Mediated Endocytosis

“…Endophilin A1 to A3 being simple proteins binding to membranes via their N-BAR domains and to PRM-containing proteins through their SH3 domains, they are unlikely to be only functioning in FEME. Consistently, they have been involved in other cellular processes such as CME, some type of autophagy [115][116][117], as well as exocytosis of neurosecretory vesicles [146][147][148]. There are also probably important functional differences between the A1, A2 and A3 subtypes, as suggested by the recent finding that Endophilin A3, but not A2, controls the Clathrin-independent and Dynamin-independent uptake of CD166, induced upon extracellular clustering by Galectin-8 [145].…”

Dependence of SARS-CoV-2 infection on cholesterol-rich lipid raft and endosomal acidification

“…FEME can be blocked by inhibitors of dynamin, Rac, phosphatidylinositol-3-OH kinase, PAK1 and actin polymerization, and be activated upon CDC42 inhibition [20] . Endophilin A2 has also been found to be associated with enterovirus 71 (EV71) entry [21] , exocytosis of neurosecretory vesicles [22] , and early uptake structures that are induced by the bacterial Shiga and cholera toxins [23] .…”

Tat-Endophilin A1 Fusion Protein Protects Neurons from Ischemic Damage in the Gerbil Hippocampus: A Possible Mechanism of Lipid Peroxidation and Neuroinflammation Mitigation as Well as Synaptic Plasticity

“…The C-terminal domain robustly binds to endocytic proteins such as dynamin, intersectin, and synaptojanin [ 19 , 20 , 21 , 22 , 23 ]. Endophilins are encoded by three genes in vertebrates of which endophilin A1 is exclusively expressed in the brain [ 24 , 25 , 26 ], while endophilin A2 is ubiquitously expressed and endophilin A3 is observed in the brain and testis [ 27 ]. In the hippocampus, endophilin A family proteins are expressed in the pre- and post-synaptic terminals [ 28 , 29 ], and knockout of the individual endophilin A family does not cause any problems in life span.…”