title: Phosphorylation by protein kinase Cα regulates RalB small GTPase protein activation, subcellular localization, and effector utilization.
abstract: Ras-like (Ral) small GTPases are regulated downstream of Ras and the noncanonical Ral guanine nucleotide exchange factor (RalGEF) effector pathway. Despite RalA and RalB sharing 82% sequence identity and utilization of shared effector proteins, their roles in normal and neoplastic cell growth have been shown to be highly distinct. Here, we determined that RalB function is regulated by protein kinase Cα (PKCα) phosphorylation. We found that RalB phosphorylation on Ser-198 in the C-terminal membrane targeting sequence resulted in enhanced RalB endomembrane accumulation and decreased RalB association with its effector, the exocyst component Sec5. Additionally, RalB phosphorylation regulated vesicular trafficking and membrane fusion by regulating v- and t-SNARE interactions. RalB phosphorylation regulated vesicular traffic of α5-integrin to the cell surface and cell attachment to fibronectin. In summary, our data suggest that phosphorylation by PKCα is critical for RalB-mediated vesicle trafficking and exocytosis.
authors.affiliation: Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Martin
authors.forename: Natalia
authors.initials: N
authors.lastname: Mitin
authors.forename: Adrienne D
authors.initials: AD
authors.lastname: Cox
authors.forename: Jen Jen
authors.initials: JJ
authors.lastname: Yeh
authors.forename: Channing J
authors.initials: CJ
authors.lastname: Der
mesh_terms: D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D005089:Exocytosis / Q000502:physiology*; D006801:Humans; D010766:Phosphorylation / Q000502:physiology; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism; D020725:ral GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C470182:EXOC2 protein, human; C483163:Ralb protein, human; C082190:Ralb protein, rat; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; C496628:PRKCA protein, human; D051571:Protein Kinase C-alpha; D020725:ral GTP-Binding Proteins