Alternative Splicing Modulates Inactivation of Type 1 Voltage-gated Sodium Channels by Toggling an Amino Acid in the First S3-S4 Linker

• Published in: The Journal of biological chemistry Vol. 286; no. 42; pp. 36700 - 36708
• Main Authors: Fletcher, Emily V., Kullmann, Dimitri M., Schorge, Stephanie
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 21.10.2011; American Society for Biochemistry and Molecular Biology
• Subjects: Alternative Splicing; Amino Acid Substitution; Epilepsy - genetics; Epilepsy - metabolism; Exons; HEK Cells; HEK293 Cells; Hot Temperature; Humans; Ion Channels; Membrane Proteins; Mutation, Missense; NAV1.1 Voltage-Gated Sodium Channel; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurobiology; Neurological Diseases; Patch Clamp; Protein Stability; Protein Structure, Secondary; Protein Structure, Tertiary; RNA Splicing; Sodium Channels; Sodium Channels - genetics; Sodium Channels - metabolism; Voltage-dependent; Membrane Proteins; HEK Cells; RNA Splicing; Ion Channels; Voltage-dependent; Neurobiology; Sodium Channels; Patch Clamp; Neurological Diseases
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M111.250225

Voltage-gated sodium channels underlie the upstroke of action potentials and are fundamental to neuronal excitability. Small changes in the behavior of these channels are sufficient to change neuronal firing and trigger seizures. These channels are subject to highly conserved alternative splicing, affecting the short linker between the third transmembrane segment (S3) and the voltage sensor (S4) in their first domain. The biophysical consequences of this alternative splicing are incompletely understood. Here we focus on type 1 sodium channels (Nav1.1) that are implicated in human epilepsy. We show that the functional consequences of alternative splicing are highly sensitive to recording conditions, including the identity of the major intracellular anion and the recording temperature. In particular, the inactivation kinetics of channels containing the alternate exon 5N are more sensitive to intracellular fluoride ions and to changing temperature than channels containing exon 5A. Moreover, Nav1.1 channels containing exon 5N recover from inactivation more rapidly at physiological temperatures. Three amino acids differ between exons 5A and 5N. However, the changes in sensitivity and stability of inactivation were reproduced by a single conserved change from aspartate to asparagine in channels containing exon 5A, which was sufficient to make them behave like channels containing the complete exon 5N sequence. These data suggest that splicing at this site can modify the inactivation of sodium channels and reveal a possible interaction between splicing and anti-epileptic drugs that stabilize sodium channel inactivation. Background: Small changes in voltage-gated sodium channel behavior can disrupt neuronal activity and cause severe neurological disorders. Results: By changing a single amino acid, a conserved alternative splicing event modifies the stability of channel inactivation. Conclusion: Splicing can regulate inactivation of sodium channels. Significance: Many commonly used drugs target sodium channel inactivation; consequently, splicing could affect treatment of several neurological disorders.