Connecting cell polarity signals to the cytokinetic machinery in yeast and metazoan cells

Abstract

Polarized growth and cytokinesis are two fundamental cellular processes that exist in virtually all cell types. Mechanisms for asymmetric distribution of materials allow for cells to grow in a polarized manner. This gives rise to a variety of cell shapes seen throughout all cell types. Following polarized growth during interphase, dividing cells assemble a cytokinetic ring containing the protein machinery to constrict and separate daughter cells. Here, we discuss how cell polarity signaling pathways act on cytokinesis, with a focus on direct regulation of the contractile actomyosin ring (CAR). Recent studies have exploited phosphoproteomics to identify new connections between cell polarity kinases and CAR proteins. Existing evidence suggests that some polarity kinases guide the local organization of CAR proteins and structures while also contributing to global organization of the division plane within a cell. We provide several examples of this regulation from budding yeast, fission yeast, and metazoan cells. In some cases, kinase-substrate connections point to conserved processes in these different organisms. We point to several examples where future work can indicate the degree of conservation and divergence in the cell division process of these different organisms.

Keywords: Cytokinesis; actomyosin; cerevisiae; polarity; pombe; yeast.

Figure 1.

Schematic cartoon of key cytokinesis structures. (A) Fission yeast cells assemble cortical multi-protein structuresin the cell middle termed “nodes,” which are precursors of the CAR. Polarity proteins at cell tips promote node formation in the cell middle. (B) Budding yeast septin rings recruit proteins essential for cytokinesis. The CAR assembles between the split septin rings. (C) Metazoan cells assemble the CAR at a position defined by the spindle midzone and by astral microtubuleinteractions with the cell cortex

Figure 2.

The conserved Cdc15/Hof1 network in cytokinesis. (A) Pom1, Kin1, and Pak1 kinases phosphorylate distinct residues in the linker domain of fission yeast Cdc15. (B) Cartoon of the Cdc15 interaction network that contributes to linking the CAR to the plasma membrane in fission yeast; not all ligands and interactions are shown. (C) Conserved components of the fission yeast Cdc15 and the budding yeast Hof1 interaction networks

Figure 3.

Schematic of protein kinases and substrates discussed in the text. In each case, kinase-substrate interactions drive specific steps in spatial and temporal control of cytokinesis. Question marks denote that the kinase or substrate is currently unknown