Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Wednesday Speaker Abstracts

MECHANISM OF ACTIN CAPPING PROTEIN RECRUITMENT AND TURN OVER DURING CLATHRIN MEDIATED ENDOCYTOSIS

Santiago Di Pietro ; 1 Colorado State University, Biochemistry and Molecular Biology, Fort Collins, CO, USA

Clathrin-mediated endocytosis depends on polymerization of a branched actin network to provide force for membrane invagination. A key regulator in branched actin network formation is actin capping protein (CP), which binds to the barbed end of actin filaments to prevent the addition or loss of actin subunits. CP was thought to stochastically bind actin filaments, but recent evidence shows CP is regulated by a group of proteins containing CP-interacting (CPI) motifs. Importantly, how CPI motif-proteins function together to regulate CP is poorly understood. Here, we show Aim21 and Bsp1 work synergistically to recruit CP to the endocytic actin network through their CPI motifs, which also allosterically modulate capping strength. In contrast, twinfilin works downstream CP recruitment, regulating the turnover of CP through its unconventional CPI motif and a non-allosteric mechanism. Collectively, our findings reveal how three CPI motif proteins work together to regulate CP in a stepwise fashion during endocytosis.

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