title: Phosphorylation provides a negative mode of regulation for the yeast Rab GTPase Sec4p.
abstract: The Rab family of Ras-related GTPases are part of a complex signaling circuitry in eukaryotic cells, yet we understand little about the mechanisms that underlie Rab protein participation in such signal transduction networks, or how these networks are integrated at the physiological level. Reversible protein phosphorylation is widely used by cells as a signaling mechanism. Several phospho-Rabs have been identified, however the functional consequences of the modification appear to be diverse and need to be evaluated on an individual basis. In this study we demonstrate a role for phosphorylation as a negative regulatory event for the action of the yeast Rab GTPase Sec4p in regulating polarized growth. Our data suggest that the phosphorylation of the Rab Sec4p prevents interactions with its effector, the exocyst component Sec15p, and that the inhibition may be relieved by a PP2A phosphatase complex containing the regulatory subunit Cdc55p.
authors.affiliation: Graduate Program in Pharmacology, Cornell University, Ithaca, New York, United States of America.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Heger
authors.forename: Christiane D
authors.initials: CD
authors.lastname: Wrann
authors.forename: Ruth N
authors.initials: RN
authors.lastname: Collins
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism; D019295:Computational Biology; D004252:DNA Mutational Analysis; D005089:Exocytosis; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding; D054648:Protein Phosphatase 2 / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C071246:CDC55 protein, S cerevisiae; D018797:Cell Cycle Proteins; C060862:SEC15 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D010768:Phosphoserine; D054648:Protein Phosphatase 2; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins