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.
Field of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, NY 14853 Department of Molecular Medicine, Cornell University, Ithaca, NY 14853.
Dante
D
Lepore
Cornell Undergraduate Biology, Cornell University, Ithaca, NY 14853.
Olya
0000-0003-0115-4864
O
Spassibojko
Cornell Undergraduate Biology, Cornell University, Ithaca, NY 14853.
Gabrielle
G
Pinto
Department of Molecular Medicine, Cornell University, Ithaca, NY 14853 rnc8@cornell.edu.
Ruth N
RN
Collins
D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology*; D048749:Cytokinesis; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D033921:Vesicular Transport Proteins / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; C060862:SEC15 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D017346:Protein Serine-Threonine Kinases; C081927:CDC5 protein, S cerevisiae; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins