title: Apoptotic pathway and MAPKs differentially regulate chemotropic responses of retinal growth cones.
abstract: Previous work has shown that guidance cues trigger rapid changes in protein dynamics in retinal growth cones: netrin-1 stimulates both protein synthesis and degradation, while Sema3A elicits synthesis, and LPA induces degradation. What signaling pathways are involved? Our studies confirm that p42/44 MAPK mediates netrin-1 responses and further show that inhibiting its activity blocks cue-induced protein synthesis. Unexpectedly, p38 MAPK is also activated by netrin-1 in retinal growth cones and is required for chemotropic responses and translation. Sema3A- and LPA-induced responses, by contrast, require a single MAPK, p42/p44 and p38, respectively. In addition, we report that caspase-3, an apoptotic protease, is rapidly activated by netrin-1 and LPA in a proteasome- and p38-dependent manner and is required for chemotropic responses. These findings suggest that the apoptotic pathway may be used locally to control protein levels in growth cones and that the differential activation of MAPK pathways may underlie cue-directed migration.
authors.affiliation: Department of Anatomy, University of Cambridge, Downing Street, Cambridge, CB2 3DY United Kingdom. campbell@neuro.utah.edu
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Campbell
authors.forename: Christine E
authors.initials: CE
authors.lastname: Holt
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D020439:Growth Cones / Q000187:drug effects* / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D009414:Nerve Growth Factors / Q000494:pharmacology; D000075388:Netrin-1; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012160:Retina / Q000196:embryology* / Q000378:metabolism; D040121:Semaphorin-3A / Q000494:pharmacology; D025521:Tumor Suppressor Proteins; D014982:Xenopus laevis / Q000196:embryology; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D039561:Eukaryotic Initiation Factor-4E; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids; C000617351:NTN1 protein, human; D009414:Nerve Growth Factors; D010750:Phosphoproteins; D011506:Proteins; D040121:Semaphorin-3A; D025521:Tumor Suppressor Proteins; D000075388:Netrin-1; C491395:MKNK1 protein, human; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases