title: Antillatoxin, a novel lipopeptide, enhances neurite outgrowth in immature cerebrocortical neurons through activation of voltage-gated sodium channels.
abstract: Antillatoxin (ATX) is a structurally novel lipopeptide that activates voltage-gated sodium channels (VGSC) leading to sodium influx in cerebellar granule neurons and cerebrocortical neurons 8 to 9 days in vitro (Li et al., 2001; Cao et al., 2008). However, the precise recognition site for ATX on the VGSC remains to be defined. Inasmuch as elevation of intracellular sodium ([Na(+)](i)) may increase N-methyl-d-aspartate receptor (NMDAR)-mediated Ca(2+) influx, Na(+) may function as a signaling molecule. We hypothesized that ATX may enhance neurite outgrowth in cerebrocortical neurons by elevating [Na(+)](i) and augmenting NMDAR function. ATX (30-100 nM) robustly stimulated neurite outgrowth, and this enhancement was sensitive to the VGSC antagonist, tetrodotoxin. To unambiguously demonstrate the enhancement of NMDA receptor function by ATX, we recorded single-channel currents from cell-attached patches. ATX was found to increase the open probability of NMDA receptors. Na(+)-dependent up-regulation of NMDAR function has been shown to be regulated by Src family kinase (SFK) (Yu and Salter, 1998). The Src kinase inhibitor PP2 abrogated ATX-enhanced neurite outgrowth, suggesting a SFK involvement in this response. ATX-enhanced neurite outgrowth was also inhibited by the NMDAR antagonist, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), and the calmodulin-dependent kinase kinase (CaMKK) inhibitor, 1,8-naphthoylene benzimidazole-3-carboxylic acid (STO-609), demonstrating the requirement for NMDAR activation with subsequent downstream engagement of the Ca(2+)-dependent CaMKK pathway. These results with the structurally and mechanistically novel natural product, ATX, confirm and generalize our earlier results with a neurotoxin site 5 ligand. These data suggest that VGSC activators may represent a novel pharmacological strategy to regulate neuronal plasticity through NMDAR-dependent mechanisms.
authors.affiliation: Creighton University School of Medicine, Department of Pharmacology, Omaha, NE 68178, USA.
authors.forename: S V
authors.initials: SV
authors.lastname: Jabba
authors.forename: A
authors.initials: A
authors.lastname: Prakash
authors.forename: S M
authors.initials: SM
authors.lastname: Dravid
authors.forename: W H
authors.initials: WH
authors.lastname: Gerwick
authors.forename: T F
authors.initials: TF
authors.lastname: Murray
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D004622:Embryo, Mammalian; D042541:Intracellular Space / Q000378:metabolism; D015640:Ion Channel Gating; D055666:Lipopeptides / Q000494:pharmacology*; D008564:Membrane Potentials; D051379:Mice; D016501:Neurites / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010456:Peptides, Cyclic / Q000494:pharmacology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D015398:Signal Transduction; D012964:Sodium / Q000502:physiology; D062687:Sodium Channel Agonists; D015222:Sodium Channels / Q000502:physiology*; D019061:src-Family Kinases / Q000502:physiology
chemical_list: D055666:Lipopeptides; D010456:Peptides, Cyclic; D016194:Receptors, N-Methyl-D-Aspartate; D062687:Sodium Channel Agonists; D015222:Sodium Channels; C121886:antillatoxin; D012964:Sodium; D019061:src-Family Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D002118:Calcium