title: Characterization of specific allosteric effects of the Na+channel β1 subunit on the Nav1.4 isoform.
abstract: The mechanism of inactivation of mammalian voltage-gated Na+channels involves transient interactions between intracellular domains resulting in direct pore occlusion by the IFM motif and concomitant extracellular interactions with the β1 subunit. Navβ1 subunits constitute single-pass transmembrane proteins that form protein-protein associations with pore-forming α subunits to allosterically modulate the Na+influx into the cell during the action potential of every excitable cell in vertebrates. Here, we explored the role of the intracellular IFM motif of rNav1.4 (skeletal muscle isoform of the rat Na+channel) on the α-β1 functional interaction and showed for the first time that the modulation of β1 is independent of the IFM motif. We found that: (1) Nav1.4 channels that lack the IFM inactivation particle can undergo a "C-type-like inactivation" albeit in an ultraslow gating mode; (2) β1 can significantly accelerate the inactivation of Nav1.4 channels in the absence of the IFM motif. Previously, we identified two residues (T109 and N110) on the β1 subunit that disrupt the α-β1 allosteric modulation. We further characterized the electrophysiological effects of the double alanine substitution of these residues demonstrating that it decelerates inactivation and recovery from inactivation, abolishes the modulation of steady-state inactivation and induces a current rundown upon repetitive stimulation, thus causing a general loss of function. Our results contribute to delineating the process of the mammalian Na+channel inactivation. These findings may be relevant to the design of pharmacological strategies, targeting β subunits to treat pathologies associated to Na+current dysfunction.
authors.affiliation: Laboratorio de Biofísica, Instituto de Fisiología, Universidad Autónoma de Puebla, 14 Sur No. 6301 C.U., 72570, Puebla, Pue, Mexico.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Sánchez-Solano
authors.affiliation: Laboratorio de Biofísica, Instituto de Fisiología, Universidad Autónoma de Puebla, 14 Sur No. 6301 C.U., 72570, Puebla, Pue, Mexico.|Facultad de Ciencias Químicas, Universidad Autónoma de Puebla, Puebla, Mexico.
authors.forename: Angel A
authors.initials: AA
authors.lastname: Islas
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Puebla, Puebla, Mexico.
authors.forename: Thomas
authors.initials: T
authors.lastname: Scior
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Puebla, Puebla, Mexico.
authors.forename: Bertin
authors.initials: B
authors.lastname: Paiz-Candia
authors.affiliation: Centro de Química, Instituto de Ciencias, Universidad Autónoma de Puebla, Puebla, Mexico.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Millan-PerezPeña
authors.affiliation: Laboratorio de Biofísica, Instituto de Fisiología, Universidad Autónoma de Puebla, 14 Sur No. 6301 C.U., 72570, Puebla, Pue, Mexico. eduardo.salinas@correo.buap.mx.
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Salinas-Stefanon
mesh_terms: D000494:Allosteric Regulation; D020816:Amino Acid Motifs; D000818:Animals; D055724:Electrophysiological Phenomena; D042541:Intracellular Space / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D062553:NAV1.4 Voltage-Gated Sodium Channel / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D062547:Voltage-Gated Sodium Channel beta-1 Subunit / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D062553:NAV1.4 Voltage-Gated Sodium Channel; D062547:Voltage-Gated Sodium Channel beta-1 Subunit
keywords: Allosteric; C-type; IFM; Inactivation; Loss of function; Mutant; Nav1.4; Oocyte; Sodium