Structure and function of the beta 2 subunit of brain sodium channels, a transmembrane glycoprotein with a CAM motif.
Voltage-gated sodium channels in brain neurons are complexes of a pore-forming alpha subunit with smaller beta 1 and beta 2 subunits. cDNA cloning and sequencing showed that the beta 2 subunit is a 186 residue glycoprotein with an extracellular NH2-terminal domain containing an immunoglobulin-like fold with similarity to the neural cell adhesion molecule (CAM) contactin, a single transmembrane segment, and a small intracellular domain. Coexpression of beta 2 with alpha subunits in Xenopus oocytes increases functional expression, modulates gating, and causes up to a 4-fold increase in the capacitance of the oocyte, which results from an increase in the surface area of the plasma membrane microvilli. beta 2 subunits are unique among the auxiliary subunits of ion channels in combining channel modulation with a CAM motif and the ability to expand the cell membrane surface area. They may be important regulators of sodium channel expression and localization in neurons.
Department of Pharmacology, University of Washington Seattle 98195-7280, USA.
L L
LL
Isom
D S
DS
Ragsdale
K S
KS
De Jongh
R E
RE
Westenbroek
B F
BF
Reber
T
T
Scheuer
W A
WA
Catterall
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000196:embryology; D001923:Brain Chemistry / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000502:physiology*; D015816:Cell Adhesion Molecules, Neuronal; D002462:Cell Membrane / Q000502:physiology; D003001:Cloning, Molecular; D058966:Contactins; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression / Q000502:physiology; D007136:Immunoglobulins / Q000235:genetics; D008562:Membrane Glycoproteins / Q000502:physiology; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics; D009865:Oocytes / Q000502:physiology; D051381:Rats; D015222:Sodium Channels / Q000502:physiology* / Q000648:ultrastructure; D013116:Spinal Cord / Q000737:chemistry / Q000196:embryology; D014981:Xenopus
D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D058966:Contactins; D018076:DNA, Complementary; D007136:Immunoglobulins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D015222:Sodium Channels