Understanding Periperal Membrane Protein Interactions | BPS Thematic Meeting

Understanding Peripheral Membrane Protein Interactions: Structure, Dynamics, Function and Therapy

Poster Abstracts

22-POS Board 22 CURVATURE IN COMMAND: HOW MEMBRANES ORCHESTRATE PROTEIN FUNCTION IN AUTOPHAGOSOME FORMATION Fang Tian 1 ; Yansheng Ye 1 ; Guifang Wang 1 ; HongGang Wang 2 ; 1 Pennsylvania State University College of Medicine, Department of Molecular and Precision Medicine, Hershey, PA, USA 2 Pennsylvania State University College of Medicine, Department of Pediatrics, Hershey, PA, USA Macroautophagy is a fundamental cellular process that degrades and recycles damaged organelles, invasive microbes, and cytosolic proteins. A key step in this pathway is autophagosome formation, which requires the covalent conjugation of LC3 proteins to the amino headgroup of phosphatidylethanolamine (PE). The E2-like enzyme Atg3 catalyzes this reaction by transferring LC3 from an LC3–Atg3 intermediate to PE in autophagic membranes. We previously showed that membrane association of human Atg3 (hAtg3) through its N-terminal amphipathic helix (NAH) in a curvature-sensitive manner is necessary, but not sufficient, to drive LC3–PE conjugation (1). Instead, a conserved region following the NAH couples membrane geometry recognition with catalytic activity. However, how the C-terminal catalytic center is positioned at the membrane surface to enable conjugation has remained unresolved. Here, we demonstrate that the C-terminal catalytic region of hAtg3 is conformationally dynamic and directly engages membranes in concert with NAH-mediated curvature sensing (2). We further identify functional contributions of two conserved histidine residues, which help orient the catalytic center at the membrane interface. The functional relevance of these interactions is confirmed by both in vitro lipidation assays and in vivo cellular studies. Together, our findings reveal a histidine- and curvature-mediated mechanism by which Atg3 couples membrane geometry to enzymatic activation, providing new mechanistic insight into the spatial regulation of autophagosome biogenesis (3). Reference 1. Yansheng Ye, Erin R. Tyndall, Van Bui, Maria C. Bewley, Guifang Wang, Xupeng Hong, Yang Shen, John M. Flanagan, Hong-Gang Wang, Fang Tian. Translating membrane geometry into protein function: Multifaceted membrane interactions of human Atg3 promote LC3-phosphatidylethanolamine conjugation during autophagy. Nat. Commun. 2023, 14: 5503.2. Yansheng Ye, Erin R Tyndall, Van Bui, Zhenyuan Tang, Yan Shen, Xuejun Jiang, John M Flanagan, Hong-Gang Wang, Fang Tian. An N-terminal conserved region in human Atg3 couples membrane curvature sensitivity to conjugase activity during autophagy, Nat. Commun. 2021, 12(1):374.3. Sangeeta Nath, Julia Dancourt, Vladimir Shteyn, Gabriella Puente, Wendy M. Fong, Shanta Nag, Joerg Bewersdorf, Ai Yamamoto, Bruno Antonny & Thomas J. Melia. Lipidation of the LC3/GABARAP family of autophagy proteins relies on a membrane-curvature-sensing domain in Atg3. Nat. Cell Biol. 2014, 16: 821-821.

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