Voltage-gated sodium channel Nav1.6 is modulated by p38 mitogen-activated protein kinase.
Nav1.6 is the major sodium channel isoform at nodes of Ranvier in myelinated axons and, additionally, is distributed along unmyelinated C-fibers of sensory neurons. Thus, modulation of the sodium current produced by Nav1.6 might significantly impact axonal conduction. Mitogen-activated protein kinases (MAPKs) are expressed in neurons and are activated after injury, for example, after sciatic nerve transection and hypoxia. Although the role of MAPK in signal transduction and in injury-induced regulation of gene expression is well established, the ability of these kinases to phosphorylate and modulate voltage-gated sodium channels has not been reported. Sequence analysis shows that Nav1.6 contains a putative MAP kinase-recognition module in the cytoplasmic loop (L1), which joins domains 1 and 2. We show in this study that sodium channels and p38 MAP kinase colocalize in rat brain tissue and that activated p38alpha phosphorylates L1 of Nav1.6, specifically at serine 553 (S553), in vitro. None of the other cytoplasmic loops and termini of the channel are phosphorylated by activated p38alpha in these assays. Activation of p38 in the neuronal ND7/23 cell line transfected with Nav1.6 leads to a significant reduction in the peak Nav1.6 current amplitude, without a detectable effect on gating properties. The substitution of S553 with alanine within L1 of the Nav1.6 channel prevents p38-mediated reduction of Nav1.6 current density. This is the first demonstration of MAPK phosphorylation and modulation of a voltage-gated sodium channel, and this modulation may represent an additional role for MAPK in regulating the neuronal response to injury.
Wittmack
Ellen K
EK
Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Rush
Anthony M
AM
Hudmon
Andy
A
Waxman
Stephen G
SG
Dib-Hajj
Sulayman D
SD
D019943:Amino Acid Substitution; D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D001923:Brain Chemistry; D002460:Cell Line; D004789:Enzyme Activation; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D007668:Kidney; D008297:Male; D051379:Mice; D016297:Mutagenesis, Site-Directed; D062557:NAV1.6 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D025941:Protein Interaction Mapping; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D011689:Purkinje Cells / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D007093:Imidazoles; D062557:NAV1.6 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D011993:Recombinant Fusion Proteins; C465539:SB202494; C491046:Scn8a protein, mouse; C507811:Scn8a protein, rat; D015222:Sodium Channels; D010768:Phosphoserine; D013779:Tetrodotoxin; D000841:Anisomycin; D012964:Sodium; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580