title: Protein kinase C regulation of neuronal zinc signaling mediates survival during preconditioning.
abstract: Sub-lethal activation of cell death processes initiate pro-survival signaling cascades. As intracellular Zn(2+) liberation mediates neuronal death pathways, we tested whether a sub-lethal increase in free Zn(2+) could also trigger neuroprotection. Neuronal free Zn(2+) transiently increased following preconditioning, and was both necessary and sufficient for conferring excitotoxic tolerance. Lethal exposure to NMDA led to a delayed increase in Zn(2+) that contributed significantly to excitotoxicity in non-preconditioned neurons, but not in tolerant neurons, unless preconditioning-induced free Zn(2+) was chelated. Thus, preconditioning may trigger the expression of Zn(2+)-regulating processes, which, in turn, prevent subsequent Zn(2+)-mediated toxicity. Indeed, preconditioning increased Zn(2+)-regulated gene expression in neurons. Examination of the molecular signaling mechanism leading to this early Zn(2+) signal revealed a critical role for protein kinase C (PKC) activity, suggesting that PKC may act directly on the intracellular source of Zn(2+). We identified a conserved PKC phosphorylation site at serine-32 (S32) of metallothionein (MT) that was important in modulating Zn(2+)-regulated gene expression and conferring excitotoxic tolerance. Importantly, we observed increased PKC-induced serine phosphorylation in immunopurified MT1, but not in mutant MT1(S32A). These results indicate that neuronal Zn(2+) serves as an important, highly regulated signaling component responsible for the initiation of a neuroprotective pathway.
authors.affiliation: Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Mandar A
authors.initials: MA
authors.lastname: Aras
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Hara
authors.forename: Karen A
authors.initials: KA
authors.lastname: Hartnett
authors.forename: Karl
authors.initials: K
authors.lastname: Kandler
authors.forename: Elias
authors.initials: E
authors.lastname: Aizenman
mesh_terms: D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D020520:Brain Infarction / Q000378:metabolism / Q000503:physiopathology; D016923:Cell Death / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D019610:Cytoprotection / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism* / Q000503:physiopathology; D007424:Intracellular Fluid / Q000378:metabolism; D019194:Ischemic Preconditioning / Q000379:methods*; D008668:Metallothionein / Q000378:metabolism; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009474:Neurons / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015032:Zinc / Q000378:metabolism*
chemical_list: C491055:Mt2A protein, rat; D012694:Serine; D008668:Metallothionein; D011493:Protein Kinase C; D015032:Zinc