Rab1 recruits WHAMM during membrane remodeling but limits actin nucleation |
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Authors: | Ashley J Russo Alyssa J Mathiowetz Steven Hong Matthew D Welch Kenneth G Campellone |
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Institution: | CEA Grenoble;aDepartment of Molecular and Cell Biology, Institute for Systems Genomics, University of Connecticut, Storrs, CT 06269;bDepartment of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 |
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Abstract: | Small G-proteins are key regulatory molecules that activate the actin nucleation machinery to drive cytoskeletal rearrangements during plasma membrane remodeling. However, the ability of small G-proteins to interact with nucleation factors on internal membranes to control trafficking processes has not been well characterized. Here we investigated roles for members of the Rho, Arf, and Rab G-protein families in regulating WASP homologue associated with actin, membranes, and microtubules (WHAMM), an activator of Arp2/3 complex–mediated actin nucleation. We found that Rab1 stimulated the formation and elongation of WHAMM-associated membrane tubules in cells. Active Rab1 recruited WHAMM to dynamic tubulovesicular structures in fibroblasts, and an active prenylated version of Rab1 bound directly to an N-terminal domain of WHAMM in vitro. In contrast to other G-protein–nucleation factor interactions, Rab1 binding inhibited WHAMM-mediated actin assembly. This ability of Rab1 to regulate WHAMM and the Arp2/3 complex represents a distinct strategy for membrane remodeling in which a Rab G-protein recruits the actin nucleation machinery but dampens its activity. |
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