Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Wednesday Speaker Abstracts

TRANSBILAYER PHOSPHOLIPID SCRAMBLING IS ESSENTIAL FOR EFFICIENT SYNAPTIC VESICLE ENDOCYTOSIS Margherita Caputo 1 ; Daniela Ivanova 2 ; Sylvette Chasserot-Golaz 1 ; Frédéric Doussau 1 ; Jason Ecard 1 ; Nicolas Vitale 1 ; Anne-Marie Haeberlé 1 ; Petra Tóth 1 ; Michael A Cousin 2 ; Stéphane Ory 1 ; Stéphane Gasman 1 ; 1 Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France 2 Centre for Discovery Brain Sciences, University of Edinburgh, Edingburgh, United Kingdom Structural phospholipids are asymmetrically distributed at the plasma membrane, with phosphatidylethanolamine and phosphatidylserine (PS) virtually absent from the outer leaflet. This asymmetric lipid distribution is transiently altered during specific biological processes including calcium-regulated exocytosis. We previously reported PS egress at the exocytic sites in both neuroendocrine cells and central neurons. However the impact of this transient membrane asymmetry remodeling to presynaptic function and its underlying mechanism remain unknown. An ideal candidate to mediate PS egress is PhosphoLipid SCRamblase 1 (PLSCR1), a protein that randomizes phospholipid distribution between the two leaflets of the plasma membrane in response to calcium activation. We therefore set out to determine the role of PLSCR1 in both synaptic vesicle recycling and neurotransmitter release, by combining electron microscopy, optical live cell imaging of pHluorin probes and electrophysiology in cultured cerebellar granule cells from PLSCR1 knock-out mice (PLSCR1-/-). We revealed that both PS egress and synaptic vesicle endocytosis are inhibited in PLSCR1-/- neurons demonstrating that PLSCR1 controls phospholipid remodeling and synaptic vesicle retrieval following neurotransmitter release. Rescue experiments with functional domain deletion mutants provide further molecular understanding of the function of PLSCR1 in phospholipid scrambling during exocytosis.Altogether, our data reveal a key role for PLSCR1 in synaptic vesicle recycling and provide the first evidence that phospholipid scrambling at the plasma membrane is a prerequisite for optimal presynaptic performance.

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