title: Ca2+/calmodulin-dependent protein kinases II and IV both promote survival but differ in their effects on axon growth in spiral ganglion neurons.
abstract: Spiral ganglion neuron (SGN) survival in vitro can be maintained by neurotrophins, permeant cAMP analogs, and depolarization in an additive manner, with depolarization being the most efficacious. Therefore, we used cultured SGNs to determine the mechanism by which depolarization promotes neuronal survival. Our data implicate Ca(2+)/calmodulin-dependent protein kinase (CaMK) activity by showing that it is induced by depolarization, that CaMK activity is necessary for at least part of the survival-promoting effect of depolarization, and that CaMKII or CamKIV activity suffices to support neuronal survival in the absence of other trophic stimuli. First, that depolarization of SGNs activates CaMKs is evidenced by observation of increased CaMKII phosphorylation and of CaMK-dependent CREB phosphorylation. Second, the requirement for CaMKs is shown by a reduction of SGN survival under depolarizing conditions in the presence of CaMK inhibitors. Third, transfection of COOH-terminal-truncated (lacking regulatory domain), constitutively active CaMKII or CaMKIV, but not of normal, full-length CAMKs, promotes SGN survival in the absence of other trophic stimuli, indicating that CaMK activity is sufficient to promote survival. The survival-promoting effect of truncated CaMKs is additive with that of depolarization, neurotrophins, or cyclic AMP. Although both CaMKII and CaMKIV activities converge in promoting survival, their actions on axon growth are markedly different: Transfection of truncated CaMKII, but not of truncated CaMKIV, into SGNs prevents axon outgrowth.
authors.affiliation: Department of Biological Sciences, University of Iowa, Iowa City 52242-1324, USA.
authors.forename: Marlan R
authors.initials: MR
authors.lastname: Hansen
authors.forename: Jinwoong
authors.initials: J
authors.lastname: Bok
authors.forename: Anand K
authors.initials: AK
authors.lastname: Devaiah
authors.forename: Xiang-Ming
authors.initials: XM
authors.lastname: Zha
authors.forename: Steven H
authors.initials: SH
authors.lastname: Green
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000201:enzymology; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017384:Sequence Deletion; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013136:Spiral Ganglion / Q000166:cytology* / Q000201:enzymology*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D007093:Imidazoles; D010446:Peptide Fragments; D020033:Protein Isoforms; C031938:calmidazolium; C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases