Paxillin-Mediated Recruitment of Calcineurin to the Contractile Ring Is Required for the Correct Progression of Cytokinesis in Fission Yeast

Abstract

Summary: Paxillin is a scaffold protein that participates in focal adhesion signaling in mammalian cells. Fission yeast paxillin ortholog, Pxl1, is required for contractile actomyosin ring (CAR) integrity and collaborates with the β-glucan synthase Bgs1 in septum formation. We show here that Pxl1’s main function is to recruit calcineurin (CN) phosphatase to the actomyosin ring; and thus the absence of either Pxl1 or calcineurin causes similar cytokinesis defects. In turn, CN participates in the dephosphorylation of the Cdc15 F-BAR protein, which recruits and concentrates Pxl1 at the CAR. Our findings suggest the existence of a positive feedback loop between Pxl1 and CN and establish that Pxl1 is a crucial component of the CN signaling pathway during cytokinesis. : Martín-García et al. show that fission yeast paxillin binds and recruits calcineurin (CN) phosphatase to the cytokinetic actomyosin ring (CAR). There, CN collaborates with Bgs1 in septum ingression and promotes the concentration of Pxl1 at the CAR in a feedback loop likely mediated through CN dephosphorylation of the Cdc15 F-BAR protein, essential for cytokinesis. Keywords: Schizosaccharomyces pombe, cytokinesis, calcineurin, paxillin, septum, actomyosin ring, Bgs1, Cdc15