Functional Expression Profile of Voltage-Gated K+ Channel Subunits in Rat Small Mesenteric Arteries

• Published in: Cell biochemistry and biophysics 2016-06, Vol.74 (2), p.263-276
• Main Authors: Cox, Robert H., Fromme, Samantha
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biophysics; Biotechnology; Cell Biology; Gene Expression Regulation; HEK293 Cells; Humans; Life Sciences; Male; Mesenteric Arteries - anatomy & histology; Mesenteric Arteries - metabolism; Organ Size; Organ Specificity; Original Paper; Pharmacology/Toxicology; Potassium Channels, Voltage-Gated - genetics; Protein Subunits - genetics; Rats; Rats, Wistar
• ISSN: 1085-9195; 1559-0283
• DOI: 10.1007/s12013-015-0715-4

Multiple K v channel complexes contribute to total K v current in numerous cell types and usually subserve different physiological functions. Identifying the complete compliment of functional K v channel subunits in cells is a prerequisite to understanding regulatory function. It was the goal of this work to determine the complete K v subunit compliment that contribute to functional K v currents in rat small mesenteric artery (SMA) myocytes as a prelude to studying channel regulation. Using RNA prepared from freshly dispersed myocytes, high levels of K v 1.2, 1.5, and 2.1 and lower levels of K v 7.4 α-subunit expressions were demonstrated by quantitative PCR and confirmed by Western blotting. Selective inhibitors correolide ( K v 1; COR), stromatoxin ( K v 2.1; ScTx), and linopirdine ( K v 7.4; LINO) decreased K v current at +40 mV in SMA by 46 ± 4, 48 ± 4, and 6.5 ± 2 %, respectively, and K v current in SMA was insensitive to α-dendrotoxin. Contractions of SMA segments pretreated with 100 nmol/L phenylephrine were enhanced by 27 ± 3, 30 ± 8, and 7 ± 3 % of the response to 120 mmol/L KCl by COR, ScTX, and LINO, respectively. The presence of K v 6.1, 9.3, β1.1, and β1.2 was demonstrated by RT-PCR using myocyte RNA with expressions of K v β1.2 and K v 9.3 about tenfold higher than K v β1.1 and K v 6.1, respectively. Selective inhibitors of K v 1.3, 3.4, 4.1, and 4.3 channels also found at the RNA and/or protein level had no significant effect on K v current or contraction. These results suggest that K v current in rat SMA myocytes are dominated equally by two major components consisting of K v 1.2–1.5–β1.2 and K v 2.1–9.3 channels along with a smaller contribution from K v 7.4 channels but differences in voltage dependence of activation allows all three to provide significant contributions to SMA function at physiological voltages.