Two Nedd4-binding Motifs Underlie Modulation of Sodium Channel Nav1.6 by p38 MAPK |
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Authors: | Andreas Gasser Xiaoyang Cheng Elaine S Gilmore Lynda Tyrrell Stephen G Waxman Sulayman D Dib-Hajj |
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Institution: | From the ‡Department of Neurology and ;§Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut 06510.;the ¶Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516, and ;the ‖Department of Dermatology, Yale University School of Medicine, New Haven, Connecticut 06511 |
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Abstract: | Sodium channel Nav1.6 is essential for neuronal excitability in central and peripheral nervous systems. Loss-of-function mutations in Nav1.6 underlie motor disorders, with homozygous-null mutations causing juvenile lethality. Phosphorylation of Nav1.6 by the stress-induced p38 MAPK at a Pro-Gly-Ser553-Pro motif in its intracellular loop L1 reduces Nav1.6 current density in a dorsal root ganglion-derived cell line, without changing its gating properties. Phosphorylated Pro-Gly-Ser553-Pro motif is a putative binding site to Nedd4 ubiquitin ligases, and we hypothesized that Nedd4-like ubiquitin ligases may contribute to channel ubiquitination and internalization. We report here that p38 activation in hippocampal neurons from wild-type mice, but not from Scn8amedtg mice that lack Nav1.6, reduces tetrodotoxin-S sodium currents, suggesting isoform-specific modulation of Nav1.6 by p38 in these neurons. Pharmacological block of endocytosis completely abolishes p38-mediated Nav1.6 current reduction, supporting our hypothesis that channel internalization underlies current reduction. We also report that the ubiquitin ligase Nedd4-2 interacts with Nav1.6 via a Pro-Ser-Tyr1945 motif in the C terminus of the channel and reduces Nav1.6 current density, and we show that this regulation requires both the Pro-Gly-Ser-Pro motif in L1 and the Pro-Ser-Tyr motif in the C terminus. Similarly, both motifs are necessary for p38-mediated reduction of Nav1.6 current, whereas abrogating binding of the ubiquitin ligase Nedd4-2 to the Pro-Ser-Tyr motif results in stress-mediated increase in Nav1.6 current density. Thus, phosphorylation of the Pro-Gly-Ser-Pro motif within L1 of Nav1.6 is necessary for stress-induced current modulation, with positive or negative regulation depending upon the availability of the C-terminal Pro-Ser-Tyr motif to bind Nedd4-2. |
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Keywords: | Ion Channels MAPKs Membrane Proteins Sodium Channels Ubiquitin Ligase Hippocampal Neurons Stress Voltage-gated |
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