title: Brevetoxin-induced phosphorylation of Pyk2 and Src in murine neocortical neurons involves distinct signaling pathways.
abstract: Brevetoxins (PbTx-1 to PbTx-10) are potent lipid soluble polyether neurotoxins produced by the marine dinoflagellate Karenia brevis. Brevetoxins bind to site 5 of the alpha-subunit of voltage-gated sodium channels (VGSCs) and augment Na(+) influx. In neocortical neurons brevetoxins elevate intracellular Ca(2+) and augment NMDA receptor signaling. In this study, we explored the effects of PbTx-2 on Pyk2 and Src activation in neocortical neurons. We found that both Pyk2 and Src were activated following PbTx-2 exposure. PbTx-2-induced Pyk2 Tyr402 phosphorylation was dependent on elevation of Ca(2+) influx through NMDA receptors. Moreover, Pyk2 Tyr402 phosphorylation was also found to require PKC activation inasmuch as RO-31-8425 and GF 109203x both attenuated the response. In contrast, PbTx-2-induced Src Tyr416 phosphorylation involved a Gq-coupled receptor inasmuch as U73122, a specific PLC inhibitor, abolished the response. This Gq-coupled receptor appears to be mGluR 5. The PKCdelta inhibitor rottlerin abolished PbTx-2-induced Src activation demonstrating that this isoform of PKC is involved in the activation of Src by PbTx-2. Considered together these data suggest that although activation of neuronal Pyk2 and Src result from PbTx-2 stimulation of VGSC, engagement of these two non-receptor tyrosine kinases involves distinct signaling pathways.
authors.affiliation: Creighton University, School of Medicine, Department of Pharmacology, Omaha, NE 68178, USA.
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Cao
authors.forename: Joju
authors.initials: J
authors.lastname: George
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Baden
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Murray
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism*; D008387:Marine Toxins / Q000494:pharmacology*; D051379:Mice; D019579:Neocortex / Q000166:cytology*; D009474:Neurons / Q000187:drug effects*; D009498:Neurotoxins / Q000494:pharmacology*; D035964:Oxocins / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D019061:src-Family Kinases / Q000378:metabolism*; D000095702:Polyether Toxins
chemical_list: D004791:Enzyme Inhibitors; D051418:Focal Adhesion Kinase 2; D008387:Marine Toxins; D009498:Neurotoxins; D035964:Oxocins; D019061:src-Family Kinases; C053342:brevetoxin; D000095702:Polyether Toxins; C496053:Ptk2b protein, mouse