title: Glycogen synthase kinase-3 is activated in neuronal cells by Galpha12 and Galpha13 by Rho-independent and Rho-dependent mechanisms.
abstract: Glycogen synthase kinase-3 (GSK-3) was generally considered a constitutively active enzyme, only regulated by inhibition. Here we describe that GSK-3 is activated by lysophosphatidic acid (LPA) during neurite retraction in rat cerebellar granule neurons. GSK-3 activation correlates with an increase in GSK-3 tyrosine phosphorylation. In addition, LPA induces a GSK-3-mediated hyperphosphorylation of the microtubule-associated protein tau. Inhibition of GSK-3 by lithium partially blocks neurite retraction, indicating that GSK-3 activation is important but not essential for the neurite retraction progress. GSK-3 activation by LPA in cerebellar granule neurons is neither downstream of Galpha(i) nor downstream of Galpha(q)/phospholipase C, suggesting that it is downstream of Galpha12/13. Overexpression of constitutively active Galpha12 (Galpha12QL) and Galpha13 (Galpha13QL) in Neuro2a cells induces upregulation of GSK-3 activity. Furthermore, overexpression of constitutively active RhoA (RhoAV14) also activates GSK-3 However, the activation of GSK-3 by Galpha13 is blocked by coexpression with C3 transferase, whereas C3 does not block GSK-3 activation by Galpha12. Thus, we demonstrate that GSK-3 is activated by both Galpha12 and Galpha13 in neuronal cells. However, GSK-3 activation by Galpha13 is Rho-mediated, whereas GSK-3 activation by Galpha12 is Rho-independent. The results presented here imply the existence of a previously unknown mechanism of GSK-3 activation by Galpha12/13 subunits.
authors.affiliation: Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: C Laura
authors.initials: CL
authors.lastname: Sayas
authors.forename: Jesús
authors.initials: J
authors.lastname: Avila
authors.forename: Francisco
authors.initials: F
authors.lastname: Wandosell
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D016501:Neurites / Q000187:drug effects / Q000502:physiology; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014157:Transcription Factors / Q000096:biosynthesis; D014162:Transfection; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D016875:tau Proteins / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D008246:Lysophospholipids; D009687:Nuclear Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D014157:Transcription Factors; D016875:tau Proteins; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020962:Heterotrimeric GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein