Skip to main content
NCBI home page
The Journal of General Physiology logoLink to The Journal of General Physiology
. 1991 Jun 1;97(6):1279–1293. doi: 10.1085/jgp.97.6.1279

The nature and origin of spontaneous noise in G protein-gated ion channels

PMCID: PMC2216511  PMID: 1651979

Abstract

Arrival of agonist is generally thought to initiate the signal transduction process in G protein-receptor coupled systems. However, the muscarinic atrial K+ (K+[ACh]) channel opens spontaneously in the absence of applied agonist, giving a noisy appearance to the current records. We investigated the nature and origin of the noise by measuring single channel currents in cell-attached or excised, inside- out membrane patches. Guanosine triphosphate (GTP) produced identical single channel currents in a concentration- and Mg(2+)-dependent manner in the presence or absence of carbachol, but the requirements for GTP were greater in the absence of agonist. Hence the agonist-independent currents appeared to be produced by an endogenous G protein, Gk. This prediction was confirmed when an affinity-purified, sequence-specific Gi-3 alpha antibody or pertussis toxin (PTX) blocked the agonist- independent currents. Candidate endogenous agonists were ruled out by the lack of effect of their corresponding antagonists. Thus agonist- independent currents had the same nature as agonist-dependent K+[ACh] currents and seemed to originate in the same way. We have developed a hypothesis in which agonist-free, empty receptors prime Gk with GTP and Gk activates atrial K+ [ACh] channels producing basal currents or noise. Agonist-independent activation by G proteins of effectors including ion channels appears to be a common occurrence.

Full Text

The Full Text of this article is available as a PDF (968.6 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Akaike N., Inoue M., Krishtal O. A. 'Concentration-clamp' study of gamma-aminobutyric-acid-induced chloride current kinetics in frog sensory neurones. J Physiol. 1986 Oct;379:171–185. doi: 10.1113/jphysiol.1986.sp016246. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Breitwieser G. E., Szabo G. Mechanism of muscarinic receptor-induced K+ channel activation as revealed by hydrolysis-resistant GTP analogues. J Gen Physiol. 1988 Apr;91(4):469–493. doi: 10.1085/jgp.91.4.469. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Breitwieser G. E., Szabo G. Uncoupling of cardiac muscarinic and beta-adrenergic receptors from ion channels by a guanine nucleotide analogue. Nature. 1985 Oct 10;317(6037):538–540. doi: 10.1038/317538a0. [DOI] [PubMed] [Google Scholar]
  4. Brown A. M., Birnbaumer L. Direct G protein gating of ion channels. Am J Physiol. 1988 Mar;254(3 Pt 2):H401–H410. doi: 10.1152/ajpheart.1988.254.3.H401. [DOI] [PubMed] [Google Scholar]
  5. Brown A. M., Kunze D. L., Yatani A. The agonist effect of dihydropyridines on Ca channels. Nature. 1984 Oct 11;311(5986):570–572. doi: 10.1038/311570a0. [DOI] [PubMed] [Google Scholar]
  6. Buhmann J., Schulten K. Influence of noise on the function of a "physiological" neural network. Biol Cybern. 1987;56(5-6):313–327. doi: 10.1007/BF00319512. [DOI] [PubMed] [Google Scholar]
  7. Cantiello H. F., Patenaude C. R., Ausiello D. A. G protein subunit, alpha i-3, activates a pertussis toxin-sensitive Na+ channel from the epithelial cell line, A6. J Biol Chem. 1989 Dec 15;264(35):20867–20870. [PubMed] [Google Scholar]
  8. Cassel D., Selinger Z. Catecholamine-stimulated GTPase activity in turkey erythrocyte membranes. Biochim Biophys Acta. 1976 Dec 8;452(2):538–551. doi: 10.1016/0005-2744(76)90206-0. [DOI] [PubMed] [Google Scholar]
  9. Cerione R. A., Codina J., Benovic J. L., Lefkowitz R. J., Birnbaumer L., Caron M. G. The mammalian beta 2-adrenergic receptor: reconstitution of functional interactions between pure receptor and pure stimulatory nucleotide binding protein of the adenylate cyclase system. Biochemistry. 1984 Sep 25;23(20):4519–4525. doi: 10.1021/bi00315a003. [DOI] [PubMed] [Google Scholar]
  10. Codina J., Yatani A., Grenet D., Brown A. M., Birnbaumer L. The alpha subunit of the GTP binding protein Gk opens atrial potassium channels. Science. 1987 Apr 24;236(4800):442–445. doi: 10.1126/science.2436299. [DOI] [PubMed] [Google Scholar]
  11. Costa T., Herz A. Antagonists with negative intrinsic activity at delta opioid receptors coupled to GTP-binding proteins. Proc Natl Acad Sci U S A. 1989 Oct;86(19):7321–7325. doi: 10.1073/pnas.86.19.7321. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Ferguson K. M., Higashijima T., Smigel M. D., Gilman A. G. The influence of bound GDP on the kinetics of guanine nucleotide binding to G proteins. J Biol Chem. 1986 Jun 5;261(16):7393–7399. [PubMed] [Google Scholar]
  13. Gilman A. G. G proteins: transducers of receptor-generated signals. Annu Rev Biochem. 1987;56:615–649. doi: 10.1146/annurev.bi.56.070187.003151. [DOI] [PubMed] [Google Scholar]
  14. Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
  15. Hohl C. M., Rösen P. The role of arachidonic acid in rat heart cell metabolism. Biochim Biophys Acta. 1987 Sep 25;921(2):356–363. doi: 10.1016/0005-2760(87)90037-3. [DOI] [PubMed] [Google Scholar]
  16. Isenberg G., Klockner U. Calcium tolerant ventricular myocytes prepared by preincubation in a "KB medium". Pflugers Arch. 1982 Oct;395(1):6–18. doi: 10.1007/BF00584963. [DOI] [PubMed] [Google Scholar]
  17. Kim D., Lewis D. L., Graziadei L., Neer E. J., Bar-Sagi D., Clapham D. E. G-protein beta gamma-subunits activate the cardiac muscarinic K+-channel via phospholipase A2. Nature. 1989 Feb 9;337(6207):557–560. doi: 10.1038/337557a0. [DOI] [PubMed] [Google Scholar]
  18. Kurachi Y., Ito H., Sugimoto T., Shimizu T., Miki I., Ui M. Alpha-adrenergic activation of the muscarinic K+ channel is mediated by arachidonic acid metabolites. Pflugers Arch. 1989 May;414(1):102–104. doi: 10.1007/BF00585635. [DOI] [PubMed] [Google Scholar]
  19. Kurachi Y., Ito H., Sugimoto T., Shimizu T., Miki I., Ui M. Arachidonic acid metabolites as intracellular modulators of the G protein-gated cardiac K+ channel. Nature. 1989 Feb 9;337(6207):555–557. doi: 10.1038/337555a0. [DOI] [PubMed] [Google Scholar]
  20. Kurachi Y., Nakajima T., Sugimoto T. On the mechanism of activation of muscarinic K+ channels by adenosine in isolated atrial cells: involvement of GTP-binding proteins. Pflugers Arch. 1986 Sep;407(3):264–274. doi: 10.1007/BF00585301. [DOI] [PubMed] [Google Scholar]
  21. Kurachi Y., Nakajima T., Sugimoto T. Role of intracellular Mg2+ in the activation of muscarinic K+ channel in cardiac atrial cell membrane. Pflugers Arch. 1986 Nov;407(5):572–574. doi: 10.1007/BF00657521. [DOI] [PubMed] [Google Scholar]
  22. Light D. B., Ausiello D. A., Stanton B. A. Guanine nucleotide-binding protein, alpha i-3, directly activates a cation channel in rat renal inner medullary collecting duct cells. J Clin Invest. 1989 Jul;84(1):352–356. doi: 10.1172/JCI114162. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Logothetis D. E., Kim D. H., Northup J. K., Neer E. J., Clapham D. E. Specificity of action of guanine nucleotide-binding regulatory protein subunits on the cardiac muscarinic K+ channel. Proc Natl Acad Sci U S A. 1988 Aug;85(16):5814–5818. doi: 10.1073/pnas.85.16.5814. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Logothetis D. E., Kurachi Y., Galper J., Neer E. J., Clapham D. E. The beta gamma subunits of GTP-binding proteins activate the muscarinic K+ channel in heart. Nature. 1987 Jan 22;325(6102):321–326. doi: 10.1038/325321a0. [DOI] [PubMed] [Google Scholar]
  25. Lux H. D., Brown A. M. Patch and whole cell calcium currents recorded simultaneously in snail neurons. J Gen Physiol. 1984 May;83(5):727–750. doi: 10.1085/jgp.83.5.727. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. May D. C., Ross E. M., Gilman A. G., Smigel M. D. Reconstitution of catecholamine-stimulated adenylate cyclase activity using three purified proteins. J Biol Chem. 1985 Dec 15;260(29):15829–15833. [PubMed] [Google Scholar]
  27. Noma A. ATP-regulated K+ channels in cardiac muscle. Nature. 1983 Sep 8;305(5930):147–148. doi: 10.1038/305147a0. [DOI] [PubMed] [Google Scholar]
  28. Okabe K., Yatani A., Evans T., Ho Y. K., Codina J., Birnbaumer L., Brown A. M. Beta gamma dimers of G proteins inhibit atrial muscarinic K+ channels. J Biol Chem. 1990 Aug 5;265(22):12854–12858. [PubMed] [Google Scholar]
  29. Sakmann B., Trube G. Conductance properties of single inwardly rectifying potassium channels in ventricular cells from guinea-pig heart. J Physiol. 1984 Feb;347:641–657. doi: 10.1113/jphysiol.1984.sp015088. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Simonds W. F., Goldsmith P. K., Codina J., Unson C. G., Spiegel A. M. Gi2 mediates alpha 2-adrenergic inhibition of adenylyl cyclase in platelet membranes: in situ identification with G alpha C-terminal antibodies. Proc Natl Acad Sci U S A. 1989 Oct;86(20):7809–7813. doi: 10.1073/pnas.86.20.7809. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Soejima M., Noma A. Mode of regulation of the ACh-sensitive K-channel by the muscarinic receptor in rabbit atrial cells. Pflugers Arch. 1984 Apr;400(4):424–431. doi: 10.1007/BF00587544. [DOI] [PubMed] [Google Scholar]
  32. Sullivan K. A., Miller R. T., Masters S. B., Beiderman B., Heideman W., Bourne H. R. Identification of receptor contact site involved in receptor-G protein coupling. Nature. 1987 Dec 24;330(6150):758–760. doi: 10.1038/330758a0. [DOI] [PubMed] [Google Scholar]
  33. Sunyer T., Monastirsky B., Codina J., Birnbaumer L. Studies on nucleotide and receptor regulation of Gi proteins: effects of pertussis toxin. Mol Endocrinol. 1989 Jul;3(7):1115–1124. doi: 10.1210/mend-3-7-1115. [DOI] [PubMed] [Google Scholar]
  34. Van Dop C., Yamanaka G., Steinberg F., Sekura R. D., Manclark C. R., Stryer L., Bourne H. R. ADP-ribosylation of transducin by pertussis toxin blocks the light-stimulated hydrolysis of GTP and cGMP in retinal photoreceptors. J Biol Chem. 1984 Jan 10;259(1):23–26. [PubMed] [Google Scholar]
  35. VanDongen A. M., Codina J., Olate J., Mattera R., Joho R., Birnbaumer L., Brown A. M. Newly identified brain potassium channels gated by the guanine nucleotide binding protein Go. Science. 1988 Dec 9;242(4884):1433–1437. doi: 10.1126/science.3144040. [DOI] [PubMed] [Google Scholar]
  36. Yatani A., Brown A. M. Rapid beta-adrenergic modulation of cardiac calcium channel currents by a fast G protein pathway. Science. 1989 Jul 7;245(4913):71–74. doi: 10.1126/science.2544999. [DOI] [PubMed] [Google Scholar]
  37. Yatani A., Codina J., Brown A. M., Birnbaumer L. Direct activation of mammalian atrial muscarinic potassium channels by GTP regulatory protein Gk. Science. 1987 Jan 9;235(4785):207–211. doi: 10.1126/science.2432660. [DOI] [PubMed] [Google Scholar]
  38. Yatani A., Codina J., Sekura R. D., Birnbaumer L., Brown A. M. Reconstitution of somatostatin and muscarinic receptor mediated stimulation of K+ channels by isolated GK protein in clonal rat anterior pituitary cell membranes. Mol Endocrinol. 1987 Apr;1(4):283–289. doi: 10.1210/mend-1-4-283. [DOI] [PubMed] [Google Scholar]
  39. Yatani A., Mattera R., Codina J., Graf R., Okabe K., Padrell E., Iyengar R., Brown A. M., Birnbaumer L. The G protein-gated atrial K+ channel is stimulated by three distinct Gi alpha-subunits. Nature. 1988 Dec 15;336(6200):680–682. doi: 10.1038/336680a0. [DOI] [PubMed] [Google Scholar]
  40. Yatani A., Okabe K., Birnbaumer L., Brown A. M. Detergents, dimeric G beta gamma, and eicosanoid pathways to muscarinic atrial K+ channels. Am J Physiol. 1990 May;258(5 Pt 2):H1507–H1514. doi: 10.1152/ajpheart.1990.258.5.H1507. [DOI] [PubMed] [Google Scholar]
  41. Yatani A., Okabe K., Polakis P., Halenbeck R., McCormick F., Brown A. M. ras p21 and GAP inhibit coupling of muscarinic receptors to atrial K+ channels. Cell. 1990 Jun 1;61(5):769–776. doi: 10.1016/0092-8674(90)90187-j. [DOI] [PubMed] [Google Scholar]

Articles from The Journal of General Physiology are provided here courtesy of The Rockefeller University Press

RESOURCES