Cell polarity orients cytoskeletal filaments toward spatial landmarks, directing local cell growth. Protein kinases play key roles in cell polarity by translating spatial signals into regulation of cytoskeletal proteins including actin and myosin. At cell division, the actomyosin machinery dramatically reorganizes into a cytokinetic ring that constricts to separate the dividing cells. We hypothesize that cell polarity kinases act directly on the contractile actomyosin ring (CAR) to promote its assembly, organization, and function in cytokinesis. In this model, cell polarity signaling proteins regulate the CAR in cytokinesis analogous to their roles on other actomyosin structures in polarized growth. We study cell polarity and cytokinesis using the fission yeast S. pombe as a model system because it offers a well-defined parts list and a host of experimental advantages. Our preliminary data show that three conserved cell polarity protein kinases?Pak1, Kin1, and Pom1?directly phosphorylate CAR proteins and regulate specific steps in CAR assembly and constriction during cell division. In addition, regulators of the phosphatase PP2A are required to keep the CAR anchored in the correct place during cytokinesis. We propose to understand the molecular mechanisms by which these conserved protein kinases and phosphatases act on the CAR to promote cell division.
The specific aims of this grant are to: (1) determine how Pak1 regulates the cytoskeleton during cell division, (2) test the hypothesis that Pom1, Kin1, and Pak1 represent sequential regulatory inputs for cytokinesis proteins, and (3) investigate how regulation of PP2A phosphatase positions the CAR. Successful completion of these goals will define a signaling system that prevents defects in cell division, and will identify previously unknown connections between two fundamental cellular processes: cell polarity and cytokinesis.

Public Health Relevance

Defects in cytokinesis can lead to unequal distribution of duplicated DNA during cell division, important for the generation of cancer. In addition, loss of cell polarity is a common feature of cancer cells and contributes to multiple steps of tumorigenesis. We will use the model organism fission yeast to define how cell polarity signaling directly contributes to proper cytokinesis and cell division.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM133856-02
Application #
10017304
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Gindhart, Joseph G
Project Start
2019-09-15
Project End
2023-07-31
Budget Start
2020-08-01
Budget End
2021-07-31
Support Year
2
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Dartmouth College
Department
Biochemistry
Type
Schools of Medicine
DUNS #
041027822
City
Hanover
State
NH
Country
United States
Zip Code
03755