Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Poster Abstracts

17-POS Board 5 TETRASPANIN SELF-ASSEMBLY GENERATES MEMBRANE CURVATURE IN VERTEBRATE PHOTORECEPTORS Andrew F. Goldberg 1 ; Michelle L Milstein 1 ; Breyanna Cavanaugh 1 ; Stefanie Volland 2 ; David S Williams 2 ; Membrane curvature is an essential aspect of cellular structure; it functions in a broad range of processes including endocytosis, exocytosis, vesicular trafficking, protein localization and others. Highly curved (< 40 nm diameter) biological membranes can be generated and stabilized in multiple ways. Several different protein-based mechanisms have been identified to date, and multiple mechanisms often participate in particular instances. The elegant architecture of vertebrate rod and cone photoreceptor outer segment (OS) organelles is characterized by abundant (negative) membrane curvature, but the molecular mechanisms responsible for its generation and stabilization have remained obscure. OS organelle biogenesis includes the production of many hundreds of pita bread-shaped membranous disks that are bounded by high- curvature (~26 nm diameter) rims. Disruption of disk rim membrane curvature generation in vertebrate photoreceptors causes dysmorphic OSs, vision loss, and a variety of progressive retinal diseases.Our studies utilize in vitro, in cellulo, and vertebrate expression systems, in conjunction with biochemical, biophysical, molecular genetic, and imaging approaches to investigate how OS disk rim membrane curvature is generated and propagated. Our findings demonstrate that the photoreceptor-specific tetraspanin, peripherin-2 (prph2; TSPAN22), can directly generate membrane curvature in cellulo and in vivo. Further, they suggest a mechanistic model in which V-shaped transmembrane tetramers create an initial membrane deformation (dimple), followed by disulfide-mediated tetramer polymerization, which organizes that deformation into extended high curvature bends. This work advances understanding of peripherin-2 function for OS biogenesis and architecture, and clarifies how pathogenic PRPH2 mutations trigger progressive retinal degenerations. It also introduces the possibility that other tetraspanins may generate or sense membrane curvature in support of their diverse biological functions. 1 Oakland University, Eye Research Institute, Rochester, MI, USA 2 UCLA School of Medicine, Stein Eye Institute, Los Angeles, MI, USA

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