Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Monday Speaker Abstracts

A SYNERGY BETWEEN MECHANOSENSITIVE CALCIUM- AND MEMBRANE- BINDING MEDIATES TENSION-SENSING BY C2-LIKE DOMAINS Zhouyang Shen 1,2 ; Kalina T Belcheva 3 ; Mark Jelcic 1,2 ; King L Hui 1 ; Anushka Katikaneni 1 ; Philipp Niethammer 1 ; 1 Memorial Sloan Kettering Cancer Center, Cell Biology, New York, NY, USA 2 Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, NY, USA 3 Weill Cornell Graduate School of Medical Sciences, Biochemistry, Cellular and Molecular Biology Allied Program, New York, NY, USA To properly function in a complex physiological environment, a cell must be able to tell whether its surrounding lipid membranes are stretched. Currently, mechanosensitive ion channels (e.g. Piezo1) are the most well studied tension-sensors, but recent work on cytosolic phospholipase A2 (cPLA 2 ) suggests a peripheral enzyme that detects nuclear membrane stretch during cell migration or tissue damage constitutes the second class of mechano-sensors. When nuclear membranes are stretched, cPLA 2 binds through its calcium-dependent C2 domain and initiates the biosynthesis of eicosanoids, which participate in numerous physiological processes including immune defense and immune cell motility. However, precisely how membrane tension regulates cPLA 2 C2-domain sensing remains poorly understood. Although C2 and C2-like domains are commonly found in various peripheral enzymes involved in protein signal transduction and membrane trafficking, it remains largely unknown how many of them are mechano-sensors and the quantitative relationship between tension and membrane binding, leaving a large knowledge gap in the field of membrane mechano-transduction. In this study, we imaged the mechanosensitive adsorption of cPLA 2 and its C2 domains to intact nuclear membranes and artificial bilayers, comparing them to other related C2-like motifs. Membrane stretch enhances Ca 2+ sensitivity of all tested domains, promoting cPLA 2 half-maximal membrane binding at cytoplasmic-resting Ca 2+ concentrations. In contrast, increasing membrane tension selectively strengthens adsorption affinity of C2 domains that utilize prominent hydrophobic protrusions to insert into the bilayer core (e.g. cPLA 2 C2), but it produces no effect or even weakens the affinity of other C2 domains that electrostatically interact with membrane lipids (e.g. Protein Kinase C C2). Overall, our data suggests that a synergy of mechanosensitive Ca 2+ interactions and deep, hydrophobic membrane insertions contributes to the exceptional mechanosensitivity of cPLA 2 C2 domains, providing a quantitative basis for understanding C2 domain membrane mechanotransduction.

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