Sodium channel beta4, a new disulfide-linked auxiliary subunit with similarity to beta2.
The principal alpha subunit of voltage-gated sodium channels is associated with auxiliary beta subunits that modify channel function and mediate protein-protein interactions. We have identified a new beta subunit termed beta4. Like the beta1-beta3 subunits, beta4 contains a cleaved signal sequence, an extracellular Ig-like fold, a transmembrane segment, and a short intracellular C-terminal tail. Using TaqMan reverse transcription-PCR analysis, in situ hybridization, and immunocytochemistry, we show that beta4 is widely distributed in neurons in the brain, spinal cord, and some sensory neurons.beta4 is most similar to the beta2 subunit (35% identity), and, like the beta2 subunit, the Ig-like fold of beta4 contains an unpaired cysteine that may interact with the alpha subunit. Under nonreducing conditions, beta4 has a molecular mass exceeding 250 kDa because of its covalent linkage to Nav1.2a, whereas on reduction, it migrates with a molecular mass of 38 kDa, similar to the mature glycosylated forms of the other beta subunits. Coexpression of beta4 with brain Nav1.2a and skeletal muscle Nav1.4 alpha subunits in tsA-201 cells resulted in a negative shift in the voltage dependence of channel activation, which overrode the opposite effects of beta1 and beta3 subunits when they were present. This novel, disulfide-linked beta subunit is likely to affect both protein-protein interactions and physiological function of multiple sodium channel alpha subunits.
Yu
Frank H
FH
Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280, USA.
Westenbroek
Ruth E
RE
Silos-Santiago
Inmaculada
I
McCormick
Kimberly A
KA
Lawson
Deborah
D
Ge
Pei
P
Ferriera
Holly
H
Lilly
Jeremiah
J
DiStefano
Peter S
PS
Catterall
William A
WA
Scheuer
Todd
T
Curtis
Rory
R
D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D003001:Cloning, Molecular; D004220:Disulfides / Q000737:chemistry; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014018:Tissue Distribution; D062548:Voltage-Gated Sodium Channel beta-2 Subunit; D062585:Voltage-Gated Sodium Channel beta-4 Subunit
D004220:Disulfides; D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; C568251:SCN2A protein, human; C117620:SCN2B protein, human; C477263:SCN4B protein, human; C568253:Scn2A protein, rat; C000654500:Scn2a protein, mouse; D015222:Sodium Channels; D062548:Voltage-Gated Sodium Channel beta-2 Subunit; D062585:Voltage-Gated Sodium Channel beta-4 Subunit