The Ca2+-activate Cl− channel Ano1 controls microvilli length and membrane surface area in the oocyte

Abstract

Ca2+-activated Cl− channels (CaCC) play important physiological functions in epithelia and other tissues. In frog oocytes the CaCC Ano1 regulates resting membrane potential and the block to polyspermy. Here we show that Ano1 expression increases the oocyte surface, revealing a novel function for Ano1 in regulating cell morphology. Confocal imaging shows that Ano1 increases microvilli length, which requires ERM protein-dependent linkage to the cytoskeleton. A dominant negative form of the ERM protein moesin, precludes the Ano1-dependent increase in membrane area. Furthermore, both full-length and the truncated dominant-negative forms of moesin co-localize with Ano1 to the microvilli, and the two proteins co-immunoprecipitate. The Ano1-moesin interaction limits Ano1 lateral membrane mobility, and contributes to microvilli scaffolding therefore stabilizing larger membrane structures. Collectively these results reveal a novel role for Ano1 in shaping the plasma membrane during oogenesis, with broad implications on the regulation of microvilli in epithelia.