title: Rit mutants confirm role of MEK/ERK signaling in neuronal differentiation and reveal novel Par6 interaction.
abstract: Rit is a novel member of the Ras superfamily of small GTP-binding proteins that regulates signaling pathways controlling cellular fate determination. Constitutively activated mutants of Rit induce terminal differentiation of pheochromocytoma (PC6) cells resulting in a sympathetic neuron-like phenotype characterized by the development of highly-branched neurites. Rit signaling has been found to activate several downstream pathways including MEK/ERK, p38 MAPK, Ral-specific guanine nucleotide exchange factors (GEFs), and Rit associates with the Par6 cell polarity machinery. In this study, a series of Rit effector loop mutants was generated to test the importance of these cellular targets to Rit-mediated neuronal differentiation. We find that Rit-mediated neuritogenesis is dependent upon MEK/ERK MAP kinase signaling but independent of RalGEF activation. In addition, in vivo binding studies identified a novel mechanism of Par6 interaction, suggesting that the cell polarity machinery may serve to spatially restrict Rit signaling.
authors.affiliation: Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, 741 South Limestone Street, Lexington, KY 40536-0509, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Rudolph
authors.forename: Geng-Xian
authors.initials: GX
authors.lastname: Shi
authors.forename: Eda
authors.initials: E
authors.lastname: Erdogan
authors.forename: Alan P
authors.initials: AP
authors.lastname: Fields
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Andres
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002454:Cell Differentiation; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005799:Genes, Dominant; D006801:Humans; D020935:MAP Kinase Signaling System; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D016501:Neurites / Q000201:enzymology; D009474:Neurons / Q000166:cytology* / Q000201:enzymology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D020726:ral Guanine Nucleotide Exchange Factor / Q000378:metabolism; D018631:ras Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D050505:Mutant Proteins; C499657:PARD6A protein, human; D020726:ral Guanine Nucleotide Exchange Factor; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins