title: Comparison of Voltage Gated K+Currents in Arterial Myocytes with Heterologously Expressed KvSubunits.
abstract: We have shown that three components contribute to functional voltage gated K+(Kv) currents in rat small mesenteric artery myocytes: (1) Kv1.2 plus Kv1.5 with Kvβ1.2 subunits, (2) Kv2.1 probably associated with Kv9.3 subunits, and (3) Kv7.4 subunits. To confirm and address subunit stoichiometry of the first two, we have compared the biophysical properties of Kvcurrents in small mesenteric artery myocytes with those of Kvsubunits heterologously expressed in HEK293 cells using whole cell voltage clamp methods. Selective inhibitors of Kv1 (correolide, COR) and Kv2 (stromatoxin, ScTx) channels were used to separate these Kvcurrent components. Conductance-voltage and steady state inactivation data along with time constants of activation, inactivation, and deactivation of native Kvcomponents were generally well represented by those of Kv1.2-1.5-β1.2 and Kv2.1-9.3 channels. The slope of the steady state inactivation-voltage curve (availability slope) proved to be the most sensitive measure of accessory subunit presence. The availability slope curves exhibited a single peak for both native Kvcomponents. Availability slope curves for Kv1.2-1.5-β1.2 and Kv2.1-9.3 channels expressed in human embryonic kidney cells also exhibited a single peak that shifted to more depolarized voltages with increasing accessory to α subunit transfection ratio. Availability slope curves for SxTc-insensitive currents were similar to those of Kv1.2-1.5 expressed with Kvβ1.2 at a 1:5 molar ratio while curves for COR-insensitive currents closely resembled those of Kv2.1 expressed with Kv9.3 at a 1:1 molar ratio. These results support the suggested Kvsubunit combinations in small mesenteric artery, and further suggest that Kv1 α and Kvβ1.2 but not Kv2.1 and Kv9.3 subunits are present in a saturated (4:4) stoichiometry.
authors.affiliation: Program in Cardiovascular Disease, Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA, 19096, USA. coxr@mlhs.org.
authors.forename: Robert H
authors.identifier: http://orcid.org/0000-0001-8884-9540
authors.initials: RH
authors.lastname: Cox
authors.affiliation: Program in Cardiovascular Disease, Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA, 19096, USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: Fromme
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits
keywords: Biophysical properties; Small mesenteric artery; Steady state inactivation; Subunit combinations; Voltage gated K+ channels