Advertisement

The Journal of Membrane Biology

, Volume 213, Issue 1, pp 19–29 | Cite as

Functional Expression of Inward Rectifier Potassium Channels in Cultured Human Pulmonary Smooth Muscle Cells: Evidence for a Major Role of Kir2.4 Subunits

  • Brian P. Tennant
  • Yi Cui
  • Andrew Tinker
  • Lucie H. Clapp
Article

Abstract

Strong inwardly rectifying K+ (KIR) channels that contribute to maintaining the resting membrane potential are encoded by the Kir2.0 family (Kir2.1–2.4). In smooth muscle, KIR currents reported so far have the characteristics of Kir2.1. However, Kir2.4, which exhibits unique characteristics of barium block, has been largely overlooked. Using patch-clamp techniques, we characterized KIR channels in cultured human pulmonary artery smooth muscle (HPASM) cells and compared them to cloned Kir2.1 and Kir2.4 channels. In a physiological K+ gradient, inwardly rectifying currents were observed in HPASM cells, the magnitude and reversal potential of which were sensitive to extracellular K+ concentration. Ba2+ (100 μM) significantly inhibited inward currents and depolarized HPASM cells by ∼10 mV. In 60 mM extracellular K+, Ba2+ blocked KIR currents in HPASM cells with a 50% inhibitory concentration of 39.1 μM at –100 mV compared to 3.9 μM and 65.6 μM for Kir2.1 and Kir2.4, respectively. Cloned Kir2.4 and KIR currents in HPASM cells showed little voltage dependence to Ba2+ inhibition, which blocked at a more superficial site than for Kir2.1. Single-channel recordings revealed strong inwardly rectifying channels with an average conductance of 21 pS in HPASM cells, not significantly different from either Kir2.1 (19.6 pS) or Kir2.4 (19.4 pS). Reverse-transcription polymerase chain reaction detected products corresponding to Kir2.1, Kir2.2 and Kir2.4 but not Kir2.3. We demonstrate that cultured HPASM cells express KIR channels and suggest both Kir2.1 and Kir2.4 subunits contribute to these channels, although the whole-cell current characteristics described share more similarity with Kir2.4.

Keywords

Inward rectifier potassium channel Pulmonary artery Human Kir2.4 Patch clamp 

Notes

Acknowledgment

This work was supported by the British Heart Foundation (PG 99176, PG/03/062). L. H. C. is a Medical Research Council Senior Fellow in Basic Science (G117/440).

References

  1. Alioua A., Conti L., Eghbali M., Mahajan A., Tanaka Y., Stefani E., Vandenberg C., Toro L. 2003. Inward rectifier K+ channels (Kir) control muscle tone of a rat conduit vessel: Role of Kir2.x. Biophys. J. 84:225AGoogle Scholar
  2. Bradley K.K., Jaggar J.H., Bonev A.D., Heppner T.J., Flynn E.R.M., Nelson M.T., Horowitz B. 1999. Kir2.1 encodes the inward rectifier potassium channel in rat arterial smooth muscle. J. Physiol. 515:639–651PubMedCrossRefGoogle Scholar
  3. Cui Y., Giblin J.P., Clapp L.H., Tinker A. 2001. A mechanism for ATP-sensitive potassium channel diversity: Functional coassembly of two pore forming subunits. Proc. Natl. Acad. Sci. USA 98:729–734PubMedCrossRefGoogle Scholar
  4. Cui Y., Tran S., Tinker A., Clapp L.H. 2002. The molecular composition of KATP channels in human pulmonary artery smooth muscle cells and their modulation by growth. Am. J. Respir. Cell. Mol. Biol. 26:135–143PubMedGoogle Scholar
  5. Edwards F.R., Hirst G.D.S., Silverberg G.D. 1988. Inward rectification in rat cerebral arterioles: Involvement of potassium ions in autoregulation. J. Physiol. 404:455–466PubMedGoogle Scholar
  6. Edwards G., Weston A.H. 2004. Potassium and potassium clouds in endothelium-dependent hyperpolarizations. Pharmacol. Res. 49:535–541PubMedCrossRefGoogle Scholar
  7. Fang Y., Schram G., Romanenko V.G., Shi C., Conti L., Vandenberg C.A., Davies P.F., Nattel S., Levitan I. 2005. Functional expression of Kir2.x in human aortic endothelial cells: The dominant role of Kir2.2. Am. J. Physiol. 289:C1134–C1144CrossRefGoogle Scholar
  8. Flynn E.R.M., McManus C.A., Bradley K.K., Koh S.D., Hegarty T.M., Horowitz B., Sanders K.M. 1999. Inward rectifier potassium conductance regulates membrane potential of canine smooth muscle. J. Physiol. 518:247–256PubMedCrossRefGoogle Scholar
  9. Giblin J.P., Leaney J.L., Tinker A. 1999. The molecular assembly of ATP-sensitive potassium channels: Determinants on the pore forming subunit. J. Biol. Chem. 274:22652–22659PubMedCrossRefGoogle Scholar
  10. Hoger J.H., Ilyin V.I., Forsyth S., Hoger A. 2002. Shear stress regulates the endothelial Kir2.1 ion channel. Proc. Natl. Acad. Sci. USA 99:7780–7785PubMedCrossRefGoogle Scholar
  11. Hogg D.S., McMurray G., Kozlowski R.Z. 2002. Endothelial cells freshly isolated from small pulmonary arteries of the rat possess multiple distinct K+ current profiles. Lung 180:203–214PubMedCrossRefGoogle Scholar
  12. Hughes B.A., Kumar G., Yuan Y., Swaminathan A., Yan D., Sharma A., Plumley L., Yang-Feng T.L., Swaroop A. 2000. Cloning and functional expression of human retinal Kir2.4, a pH-sensitive inwardly rectifying K+ channel. Am. J. Physiol. 279:C771–C784Google Scholar
  13. Kamouchi M., Van Den Bremt K., Eggermont J., Droogmans G., Nilius B. 1997. Modulation of inwardly rectifying potassium channels in cultured bovine pulmonary artery endothelial cells. J. Physiol. 504:545–556PubMedCrossRefGoogle Scholar
  14. Knot H.J., Zimmermann P.A., Nelson M.T. 1996. External K+ induced dilations of rat coronary and cerebral arteries involve inward rectifier K+ channels. J. Physiol. 492:419–430PubMedGoogle Scholar
  15. Liu G.X., Derst C., Schlichthorl G., Heinen S., Seebohm G., Bruggemann A., Kummer W., Veh R.W., Daut J., Preisig-Muller R. 2001. Comparison of cloned Kir2 channels with native inward rectifier K+ channels from guinea-pig cardiomyocytes. J. Physiol. 532:115–126PubMedCrossRefGoogle Scholar
  16. Michelakis E.D., Weir E.K., Wu X., Nsair A., Waite R., Hashimoto K., Puttagunta L., Knaus H.G., Archer S.L. 2001. Potassium channels regulate tone in rat pulmonary veins. Am. J. Physiol. 280:L1138–L1147Google Scholar
  17. Nakamura T.Y., Lee K., Artman M., Rudy B., Coetzee W.A. 1999. The role of Kir2.1 in the genesis of native cardiac inward-rectifier K+ currents during pre- and postnatal development. Ann. N. Y. Acad. Sci. 868:434–437PubMedCrossRefGoogle Scholar
  18. Nichols C.G., Lopatin A.N. 1997. Inward rectifier potassium channels. Annu. Rev. Physiol. 59:171–191PubMedCrossRefGoogle Scholar
  19. Nilius B. Droogmans G. 2001. Ion channels in the vascular endothelium. Physiol. Rev. 81:1415–1459PubMedGoogle Scholar
  20. Oonuma H., Iwasawa K., Iida H., Nagata T., Imuta H., Morita Y., Yamamoto K., Nagai R., Omata M., Nakajima T. 2002. Inward rectifier K+ current in human bronchial smooth muscle cells: Inhibition with antisense oligonucleotides targeted to Kir2.1 mRNA. Am. J. Respir. Cell Mol. Biol. 26:371–379PubMedGoogle Scholar
  21. Orie N.N., Fry C.H., Clapp L.H. 2006. Evidence that inward rectifier K+ channels mediate relaxation by the PGI2 receptor agonist cicaprost via a cyclic AMP-independent mechanism. Cardiovasc. Res. 69:107–115PubMedCrossRefGoogle Scholar
  22. Preisig-Muller R., Schlichthorl G., Goerge T., Heinen S., Bruggemann A., Rajan S., Derst C., Veh R.W., Daut J. 2002. Heteromerization of Kir2.x potassium channels contributes to the phenotype of the Andersen’s syndrome. Proc. Natl. Acad. Sci. USA 99:7774–7779PubMedCrossRefGoogle Scholar
  23. Quayle J.M., Dart C., Standen N.B. 1996. The properties and distribution of inward rectifier potassium currents in pig coronary arterial smooth muscle. J. Physiol. 494:715–726PubMedGoogle Scholar
  24. Quayle J.M., Mccarron J.G., Brayden J.E., Nelson M.T. 1993. Inward rectifier K+ currents in smooth muscle cells from rat resistance-sized cerebral arteries. Am. J. Physiol. 265:C1363–C1370PubMedGoogle Scholar
  25. Quayle J.M., Nelson M.T., Standen N.B. 1997. ATP-sensitive and inwardly rectifying potassium channels in smooth muscle. Physiol. Rev. 77:1166–1232Google Scholar
  26. Robertson B.E., Bonev A.D., Nelson M.T. 1996. Inward rectifier K+ currents in smooth muscle cells from rat coronary arteries: Block by Mg2+, Ca2+, and Ba2+. Am. J. Physiol. 40:H696–H705Google Scholar
  27. Sakai H., Shimizu T., Hori K., Ikari A., Asano S., Takeguchi N. 2002. Molecular and pharmacological properties of inwardly rectifying K+ channels of human lung cancer cells. Eur. J. Pharmacol. 435:125–133PubMedCrossRefGoogle Scholar
  28. Schram G., Melnyk P., Pourrier M., Wang Z., Nattel S. 2002. Kir2.4 and Kir2.1 K+ channel subunits co-assemble: A potential new contributor to inward rectifier current heterogeneity. J. Physiol 544:337–349PubMedCrossRefGoogle Scholar
  29. Shimoda L.A., Welsh L.E., Pearse D.B. 2002. Inhibition of inwardly rectifying K+ channels by cGMP in pulmonary vascular endothelial cells. Am. J. Physiol. 283:L297–L304Google Scholar
  30. Snetkov V.A., Ward J.P.T. 1999. Ion currents in smooth muscle cells from human small bronchioloes: Presence of an inward rectifier K+ current and three types of large conductance K+ channels. Exp. Physiol. 84:835–846PubMedCrossRefGoogle Scholar
  31. Stanfield P.R., Nakajima S., Nakajima Y. 2002. Constitutively active and G-protein coupled inward rectifier K+ channels: Kir2.0 and Kir3.0. Rev. Physiol. Biochem. Pharmacol. 145:47–179PubMedGoogle Scholar
  32. Stonehouse A.H., Pringle J.H., Norman R.I., Stanfield P.R., Conley E.C., Brammar W.J. 1999. Characterisation of Kir2.0 proteins in the rat cerebellum and hippocampus by polyclonal antibodies. Histochem. Cell Biol. 112:457–465PubMedCrossRefGoogle Scholar
  33. Topert C., Doring F., Wischmeyer E., Karschin C., Brockhaus J., Ballanyi K., Derst C., Karschin A. 1998. Kir2.4: A novel K+ inward rectifier channel associated with motoneurons of cranial nerve nuclei. J. Neurosci. 18:4096–4105PubMedGoogle Scholar
  34. Voets T., Droogmans G., Nilius B. 1996. Membrane currents and the resting membrane potential in cultured bovine pulmonary artery endothelial cells. J. Physiol. 497:95–107PubMedGoogle Scholar
  35. Woodhull A.M. 1973. Ionic blockage of sodium channels in nerve. J. Gen. Physiol 61:687–708PubMedCrossRefGoogle Scholar
  36. Zaritsky J.J., Eckman D.M., Wellman G.C., Nelson M.T., Schwarz T.L. 2000. Targeted disruption of Kir2.1 and Kir2.2 genes reveals the essential role of the inwardly rectifying K+ current in K+-mediated vasodilation. Circ. Res. 87:160–166PubMedGoogle Scholar
  37. Zaritsky J.J., Redell J.B., Tempel B.L., Schwarz T.L. 2001. The consequences of disrupting cardiac inwardly rectifying K+ current (IK1) as revealed by the targeted deletion of the murine Kir2.1 and Kir2.2 genes. J. Physiol. 533:697–710PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • Brian P. Tennant
    • 1
  • Yi Cui
    • 1
  • Andrew Tinker
    • 1
  • Lucie H. Clapp
    • 1
  1. 1.Department of MedicineBHF Laboratories, Rayne Institute, University College LondonLondonUnited Kingdom

Personalised recommendations