title: Palmitoylation influences the function and pharmacology of sodium channels.
abstract: Palmitoylation is a common lipid modification known to regulate the functional properties of various proteins and is a vital step in the biosynthesis of voltage-activated sodium (Nav) channels. We discovered a mutation in an intracellular loop of rNav1.2a (G1079C), which results in a higher apparent affinity for externally applied PaurTx3 and ProTx-II, two voltage sensor toxins isolated from tarantula venom. To explore whether palmitoylation of the introduced cysteine underlies this observation, we compared channel susceptibility to a range of animal toxins in the absence and presence of 2-Br-palmitate, a palmitate analog that prevents palmitate incorporation into proteins, and found that palmitoylation contributes to the increased affinity of PaurTx3 and ProTx-II for G1079C. Further investigations with 2-Br-palmitate revealed that palmitoylation can regulate the gating and pharmacology of wild-type (wt) rNav1.2a. To identify rNav1.2a palmitoylation sites contributing to these phenomena, we substituted three endogenous cysteines predicted to be palmitoylated and found that the gating behavior of this triple cysteine mutant is similar to wt rNav1.2a treated with 2-Br-palmitate. As with chemically depalmitoylated rNav1.2a channels, this mutant also exhibits an increased susceptibility for PaurTx3. Additional mutagenesis experiments showed that palmitoylation of one cysteine in particular (C1182) primarily influences PaurTx3 sensitivity and may enhance the inactivation process of wt rNav1.2a. Overall, our results demonstrate that lipid modifications are capable of altering the gating and pharmacological properties of rNav1.2a.
authors: Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA. bosmansf@ninds.nih.gov
authors: Frank
authors: F
authors: Bosmans
authors: Mirela
authors: M
authors: Milescu
authors: Kenton J
authors: KJ
authors: Swartz
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000494:pharmacology; D003545:Cysteine / Q000378:metabolism; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D054878:Lipoylation / Q000187:drug effects; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology*; D051381:Rats; D015222:Sodium Channels / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology*; D013111:Spider Venoms / Q000633:toxicity; D014981:Xenopus
chemical_list: D050505:Mutant Proteins; D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; C568253:Scn2A protein, rat; D015222:Sodium Channels; D013111:Spider Venoms; D002784:Cholesterol; D003545:Cysteine