Functions of Vrp1p in cytokinesis and actin patches are distinct and neither requires a WH2/V domain

Abstract

Vrp1 (verprolin, End5) is a Saccharomyces cerevisiae actin-associated protein and is related to mammalian Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP). Vrp1-deficient (vrp1Δ) cells are inviable at high temperature, have partially depolarized cortical actin patches and have defects in both actomyosin ring-dependent and Hof1 (Cyk2)-dependent pathways of cytokinesis. We demonstrate here that N-Vrp11-364 and C-Vrp1364-817 are each sufficient to restore viability, actomyosin ring constriction and Hof1 localization at 37°C to vrp1Δ. C-Vrp1, like Vrp1, partially co-localizes with cortical actin patches and restores actin patch polarization to vrp1Δ. Cortical localization of C-Vrp1, but not Vrp1, requires Las17. N-Vrp1 exhibits diffuse cytoplasmic localization and functions in cytokinesis without efficiently restoring polarization of cortical actin patches. N-Vrp1 function is not abolished by mutations affecting the WASP homology 2 (WH2) [verprolin homology (V)] actin-binding domain. N-Vrp1 may function through the type I myosins and actin, while C-Vrp1 may function through both Las17 (Bee1) and type I myosins. The functions of Vrp1 in viability at 37°C and cytokinesis do not require efficient localization to, and function in, the cortical actin cytoskeleton.