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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., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

We have characterized the DBF2 gene, encoding a protein kinase of the NDR family in Candida albicans, and demonstrate that this gene is essential for cell viability. Conditional mutants were constructed by using the MET3 promoter to analyse the phenotype of cells lacking this kinase. The absence of Dbf2 resulted in cells arrested as large-budded pairs that failed to contract the actomyosin ring, a function similar to that described for its Saccharomyces cerevisiae orthologue. In addition to its role in cytokinesis, Dbf2 regulates mitotic spindle organization and nuclear segregation as Dbf2-depleted cells have abnormal microtubules and severe defects in nuclear migration to the daughter cell, which results in a cell cycle block during mitosis. Taken together, these results imply that Dbf2 performs several functions during exit from mitosis and cytokinesis. Consistent with a role in spindle organization, the protein localizes to the mitotic spindle during anaphase, and it interacts physically with tubulin, as indicated by immunoprecipitation experiments. Finally, DBF2 depletion also resulted in impaired true hyphal growth.