Cell cycle-dependent phosphorylation of Sec4p controls membrane deposition during cytokinesis.

Intracellular trafficking is an essential and conserved eukaryotic process. Rab GTPases are a family of proteins that regulate and provide specificity for discrete membrane trafficking steps by harnessing a nucleotide-bound cycle. Global proteomic screens have revealed many Rab GTPases as phosphoproteins, but the effects of this modification are not well ...
understood. Using the Saccharomyces cerevisiae Rab GTPase Sec4p as a model, we have found that phosphorylation negatively regulates Sec4p function by disrupting the interaction with the exocyst complex via Sec15p. We demonstrate that phosphorylation of Sec4p is a cell cycle-dependent process associated with cytokinesis. Through a genomic kinase screen, we have also identified the polo-like kinase Cdc5p as a positive regulator of Sec4p phosphorylation. Sec4p spatially and temporally localizes with Cdc5p exclusively when Sec4p phosphorylation levels peak during the cell cycle, indicating Sec4p is a direct Cdc5p substrate. Our data suggest the physiological relevance of Sec4p phosphorylation is to facilitate the coordination of membrane-trafficking events during cytokinesis.
Mesh Terms:
Cell Cycle Proteins, Cell Membrane, Cytokinesis, Gene Expression Regulation, Enzymologic, Gene Expression Regulation, Fungal, Mutation, Phosphorylation, Protein Transport, Protein-Serine-Threonine Kinases, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Signal Transduction, Time Factors, Vesicular Transport Proteins, rab GTP-Binding Proteins
J. Cell Biol.
Date: Sep. 12, 2016
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