Modulation of brain Na+ channels by a G-protein-coupled pathway.
Na+ channels in acutely dissociated rat hippocampal neurons and in Chinese hamster ovary (CHO) cells transfected with a cDNA encoding the alpha subunit of rat brain type IIA Na+ channel (CNaIIA-1 cells) are modulated by guanine nucleotide binding protein (G protein)-coupled pathways under conditions of whole-cell voltage clamp. Activation of G proteins by 0.2-0.5 mM guanosine 5'-[gamma-thio]triphosphate (GTP[gamma S]), a nonhydrolyzable GTP analog, increased Na+ currents recorded in both cell types. The increase in current amplitude was caused by an 8- to 10-mV negative shift in the voltage dependence of both activation and inactivation. The effects of G-protein activators were blocked by treatment with pertussis toxin or guanosine 5'-[beta-thio]diphosphate (GDP[beta S]), a nonhydrolyzable GDP analog, but not by cholera toxin. GDP[beta S] (2 mM) alone had effects opposite those of GTP[gamma S], shifting Na(+)-channel gating 8-10 mV toward more-positive membrane potentials and suggesting that basal activation of G proteins in the absence of stimulation is sufficient to modulate Na+ channels. In CNaIIA-1 cells, thrombin, which activates pertussis toxin-sensitive G proteins in CHO cells, caused a further negative shift in the voltage dependence of Na(+)-channel activation and inactivation beyond that observed with GTP alone. The results in CNaIIA-1 cells indicate that the alpha subunit of the Na+ channel alone is sufficient to mediate G protein effects on gating. The modulation of Na+ channels via a G-protein-coupled pathway acting on Na(+)-channel alpha subunits may regulate electrical excitability through integration of different G-protein-coupled synaptic inputs.
Ma
J Y
JY
Department of Pharmacology, University of Washington, Seattle 98195.
Li
M
M
Catterall
W A
WA
Scheuer
T
T
D000818:Animals; D001921:Brain / Q000502:physiology*; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000502:physiology*; D037342:Pertussis Toxin; D051381:Rats; D017207:Rats, Sprague-Dawley; D018179:Receptors, Thrombin / Q000502:physiology; D015290:Second Messenger Systems; D015222:Sodium Channels / Q000096:biosynthesis / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D014162:Transfection; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D018179:Receptors, Thrombin; D015222:Sodium Channels; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D037342:Pertussis Toxin; D013917:Thrombin; D019204:GTP-Binding Proteins