PP2A-Cdc55 phosphatase regulates actomyosin ring contraction and septum formation during cytokinesis

Abstract

Eukaryotic cells divide and separate all their components after chromosome segregation by a process called cytokinesis to complete cell division. Cytokinesis is highly regulated by the recruitment of the components to the division site and through post-translational modifications such as phosphorylations. The budding yeast mitotic kinases Cdc28-Clb2, Cdc5, and Dbf2-Mob1 phosphorylate several cytokinetic proteins contributing to the regulation of cytokinesis. The PP2A-Cdc55 phosphatase regulates mitosis counteracting Cdk1- and Cdc5-dependent phosphorylation. This prompted us to propose that PP2A-Cdc55 could also be counteracting the mitotic kinases during cytokinesis. Here we show that in the absence of Cdc55, AMR contraction and the primary septum formation occur asymmetrically to one side of the bud neck supporting a role for PP2A-Cdc55 in cytokinesis regulation. In addition, by in vivo and in vitro assays, we show that PP2A-Cdc55 dephosphorylates the chitin synthase II (Chs2 in budding yeast) a component of the Ingression Progression Complexes (IPCs) involved in cytokinesis. Interestingly, the non-phosphorylable version of Chs2 rescues the asymmetric AMR contraction and the defective septa formation observed in cdc55∆ mutant cells. Therefore, timely dephosphorylation of the Chs2 by PP2A-Cdc55 is crucial for proper actomyosin ring contraction. These findings reveal a new mechanism of cytokinesis regulation by the PP2A-Cdc55 phosphatase and extend our knowledge of the involvement of multiple phosphatases during cytokinesis.

Chitin Synthesis in Yeast: A Matter of Trafficking

“…Chs2 is synthesized in a cell cycle-regulated mode [ 23 , 103 ], but the coordination of its function with cell cycle progression is potentiated by a specific retention mechanism of the protein in the ER [ 104 ]. Chs2 is phosphorylated by the CDK1 activity at its N-terminal cytosolic domain, preventing its export from the ER [ 104 ].…”

PP2A-B56 regulates Mid1 protein levels for proper cytokinesis in fission yeast

“…While understudied relative to their kinase counterparts, protein phosphatases are increasingly appreciated as key regulators of cytokinesis (Bollen et al, 2009). For instance, the loss of PP2A and its regulators causes cytokinetic defects in both budding and fission yeast (Goyal & Simanis, 2012; Healy et al, 1991; Jiang & Hallberg, 2001; K. Kinoshita et al, 1996; Le Goff et al, 2001; Moyano-Rodríguez et al, 2022; Moyano-Rodriguez & Queralt, 2019; Schutt & Moseley, 2020). Budding yeast cells lacking Rts1, the B56 regulatory subunit of PP2A, are multinucleated and elongated at elevated temperatures, suggesting a failure to complete cytokinesis (Moyano-Rodriguez & Queralt, 2019).…”

“…Some protein phosphatases have been connected with regulation of cytokinesis (Barr et al, 2004; Burgess et al, 2010; Cundell et al, 2016; García-Blanco et al, 2019; Holder et al, 2019). For example, budding yeast PP2A-Cdc55 has been identified as a regulator of CR contraction and septum assembly during cytokinesis (Moyano-Rodríguez et al, 2022). In addition, Calcineurin/PP2B and Clp1 localize to the CAR in fission yeast and regulate cytokinesis (Martín-García et al, 2018; Mishra et al, 2004; Snider et al, 2020; Trautmann et al, 2001; Yoshida et al, 1994).…”