title: Calcium-dependent regulation of the voltage-gated sodium channel hH1: intrinsic and extrinsic sensors use a common molecular switch.
abstract: The function of the human cardiac voltage-gated sodium channel Na(V)1.5 (hH1) is regulated in part by binding of calcium to an EF hand in the C-terminal cytoplasmic domain. hH1 is also regulated via an extrinsic calcium-sensing pathway mediated by calmodulin (CaM) via binding to an IQ motif immediately adjacent to the EF-hand domain. The intrinsic EF-hand domain is shown here to interact with the IQ motif, which controls calcium affinity. Remarkably, mutation of the IQ residues has only a minor effect on CaM affinity but drastically reduces calcium affinity of the EF-hand domain, whereas the Brugada mutation A1924T significantly reduces CaM affinity but has no effect on calcium affinity of the EF-hand domain. Moreover, the differences in the biochemical effects of the mutations directly correlate with contrasting effects on channel electrophysiology. A comprehensive model is proposed in which the hH1 IQ motif serves as a molecular switch, coupling the intrinsic and extrinsic calcium sensors.
authors.affiliation: Department of Anesthesiology, Vanderbilt University, Nashville, TN 37232, USA.
authors.forename: Vikas N
authors.initials: VN
authors.lastname: Shah
authors.forename: Tammy L
authors.initials: TL
authors.lastname: Wingo
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Weiss
authors.forename: Christina K
authors.initials: CK
authors.lastname: Williams
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Balser
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Chazin
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009206:Myocardium / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D015222:Sodium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C568320:SCN5A protein, human; D015222:Sodium Channels; D002118:Calcium