title: Sema4D/plexin-B1 activates GSK-3beta through R-Ras GAP activity, inducing growth cone collapse.
abstract: Plexins are receptors for the axonal guidance molecules known as semaphorins, and the semaphorin 4D (Sema4D) receptor plexin-B1 induces repulsive responses by functioning as an R-Ras GTPase-activating protein (GAP). Here we characterized the downstream signalling of plexin-B1-mediated R-Ras GAP activity, inducing growth cone collapse. Sema4D suppressed R-Ras activity in hippocampal neurons, in parallel with dephosphorylation of Akt and activation of glycogen synthase kinase (GSK)-3beta. Ectopic expression of the constitutively active mutant of Akt or treatment with GSK-3 inhibitors suppressed the Sema4D-induced growth cone collapse. Constitutive activation of phosphatidylinositol-3-OH kinase (PI(3)K), an upstream kinase of Akt and GSK-3beta, also blocked the growth cone collapse. The R-Ras GAP activity was necessary for plexin-B1-induced dephosphorylation of Akt and activation of GSK-3beta and was also required for phosphorylation of a downstream kinase of GSK-3beta, collapsin response mediator protein-2. Plexin-A1 also induced dephosphorylation of Akt and GSK-3beta through its R-Ras GAP activity. We conclude that plexin-B1 inactivates PI(3)K and dephosphorylates Akt and GSK-3beta through R-Ras GAP activity, inducing growth cone collapse.
authors.affiliation: Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Ito
authors.forename: Izumi
authors.initials: I
authors.lastname: Oinuma
authors.forename: Hironori
authors.initials: H
authors.lastname: Katoh
authors.forename: Kozo
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: Manabu
authors.initials: M
authors.lastname: Negishi
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D020439:Growth Cones / Q000378:metabolism* / Q000648:ultrastructure; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D039961:Semaphorins / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; C093224:CD100 antigen; D020690:GTPase-Activating Proteins; D036341:Intercellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; C488752:Plxnb1 protein, rat; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D039961:Semaphorins; C095114:collapsin response mediator protein-2; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D020558:GTP Phosphohydrolases; D018631:ras Proteins