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Cyclic nucleotide-regulated channels
Unless otherwise stated all data on this page refer to the human proteins. Gene information is provided for human (Hs), mouse (Mm) and rat (Rn).
Overview
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Cyclic nucleotide-gated (CNG) channels are responsible for signalling in the primary sensory cells of the vertebrate visual and olfactory systems. A standardised nomenclature for CNG channels has been proposed by the NC-IUPHAR subcommittee on voltage-gated ion channels [7].
CNG channels are voltage-independent cation channels formed as tetramers. Each subunit has 6TM, with the pore-forming domain between TM5 and TM6. CNG channels were first found in rod photoreceptors [6,8], where light signals through rhodopsin and transducin to stimulate phosphodiesterase and reduce intracellular cGMP level. This results in a closure of CNG channels and a reduced ‘dark current’. Similar channels were found in the cilia of olfactory neurons [9] and the pineal gland [5]. The cyclic nucleotides bind to a domain in the C terminus of the subunit protein: other channels directly binding cyclic nucleotides include HCN, eag and certain plant potassium channels.
Hyperpolarisation-activated, cyclic nucleotide-gated (HCN)
The hyperpolarisation-activated, cyclic nucleotide-gated (HCN) channels are cation channels that are activated by hyperpolarisation at voltages negative to ~-50 mV. The cyclic nucleotides cAMP and cGMP directly activate the channels and shift the activation curves of HCN channels to more positive voltages, thereby enhancing channel activity. HCN channels underlie pacemaker currents found in many excitable cells including cardiac cells and neurons [4,10]. In native cells, these currents have a variety of names, such as Ih, Iq and If. The four known HCN channels have six transmembrane domains and form tetramers. It is believed that the channels can form heteromers with each other, as has been shown for HCN1 and HCN4 [1]. A standardised nomenclature for HCN channels has been proposed by the NC-IUPHAR subcommittee on voltage-gated ion channels [7].
Subunits
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CNGA1
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CNGA2
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CNGA3
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CNGA4
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CNGB1
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CNGB3
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HCN1
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HCN2
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HCN3
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HCN4
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Further reading
* Key recommended reading is highlighted with an asterisk
* Baruscotti M, Bottelli G, Milanesi R, DiFrancesco JC, DiFrancesco D. (2010) HCN-related channelopathies. Pflugers Arch., 460 (2): 405-15. [PMID:20213494]
* Baruscotti M, Bucchi A, Difrancesco D. (2005) Physiology and pharmacology of the cardiac pacemaker ("funny") current. Pharmacol. Ther., 107 (1): 59-79. [PMID:15963351]
Biel M, Ludwig A, Zong X, Hofmann F. (1999) Hyperpolarization-activated cation channels: a multi-gene family. Rev. Physiol. Biochem. Pharmacol., 136: 165-81. [PMID:9932486]
* Biel M, Michalakis S. (2009) Cyclic nucleotide-gated channels. Handb Exp Pharmacol, (191): 111-36. [PMID:19089328]
Biel M, Schneider A, Wahl C. (2002) Cardiac HCN channels: structure, function, and modulation. Trends Cardiovasc. Med., 12 (5): 206-12. [PMID:12161074]
* Biel M, Wahl-Schott C, Michalakis S, Zong X. (2009) Hyperpolarization-activated cation channels: from genes to function. Physiol. Rev., 89 (3): 847-85. [PMID:19584315]
* Bois P, Guinamard R, Chemaly AE, Faivre JF, Bescond J. (2007) Molecular regulation and pharmacology of pacemaker channels. Curr. Pharm. Des., 13 (23): 2338-49. [PMID:17692005]
* Bradley J, Reisert J, Frings S. (2005) Regulation of cyclic nucleotide-gated channels. Curr. Opin. Neurobiol., 15 (3): 343-9. [PMID:15922582]
* Brown RL, Strassmaier T, Brady JD, Karpen JW. (2006) The pharmacology of cyclic nucleotide-gated channels: emerging from the darkness. Curr. Pharm. Des., 12 (28): 3597-613. [PMID:17073662]
* Craven KB, Zagotta WN. (2006) CNG and HCN channels: two peas, one pod. Annu. Rev. Physiol., 68: 375-401. [PMID:16460277]
* Cukkemane A, Seifert R, Kaupp UB. (2011) Cooperative and uncooperative cyclic-nucleotide-gated ion channels. Trends Biochem. Sci., 36 (1): 55-64. [PMID:20729090]
DiFrancesco D. (1993) Pacemaker mechanisms in cardiac tissue. Annu. Rev. Physiol., 55: 455-72. [PMID:7682045]
* DiFrancesco D. (2010) The role of the funny current in pacemaker activity. Circ. Res., 106 (3): 434-46. [PMID:20167941]
DiFrancesco D, Camm JA. (2004) Heart rate lowering by specific and selective I(f) current inhibition with ivabradine: a new therapeutic perspective in cardiovascular disease. Drugs, 64 (16): 1757-65. [PMID:15301560]
* Dunlop J, Vasilyev D, Lu P, Cummons T, Bowlby MR. (2009) Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and pain. Curr. Pharm. Des., 15 (15): 1767-72. [PMID:19442189]
* Hofmann F, Biel M, Kaupp UB. (2005) International Union of Pharmacology. LI. Nomenclature and structure-function relationships of cyclic nucleotide-regulated channels. Pharmacol. Rev., 57 (4): 455-62. [PMID:16382102]
Kaupp UB, Seifert R. (2001) Molecular diversity of pacemaker ion channels. Annu. Rev. Physiol., 63: 235-57. [PMID:11181956]
Kaupp UB, Seifert R. (2002) Cyclic nucleotide-gated ion channels. Physiol. Rev., 82 (3): 769-824. [PMID:12087135]
* Maher MP, Wu NT, Guo HQ, Dubin AE, Chaplan SR, Wickenden AD. (2009) HCN channels as targets for drug discovery. Comb. Chem. High Throughput Screen., 12 (1): 64-72. [PMID:19149492]
Matulef K, Zagotta WN. (2003) Cyclic nucleotide-gated ion channels. Annu. Rev. Cell Dev. Biol., 19: 23-44. [PMID:14570562]
* Mazzolini M, Marchesi A, Giorgetti A, Torre V. (2010) Gating in CNGA1 channels. Pflugers Arch., 459 (4): 547-55. [PMID:19898862]
* Meldrum BS, Rogawski MA. (2007) Molecular targets for antiepileptic drug development. Neurotherapeutics, 4 (1): 18-61. [PMID:17199015]
Pape HC. (1996) Queer current and pacemaker: the hyperpolarization-activated cation current in neurons. Annu. Rev. Physiol., 58: 299-327. [PMID:8815797]
* Tardif JC. (2008) Ivabradine: I(f) inhibition in the management of stable angina pectoris and other cardiovascular diseases. Drugs Today, 44 (3): 171-81. [PMID:18536779]
* Wahl-Schott C, Biel M. (2009) HCN channels: structure, cellular regulation and physiological function. Cell. Mol. Life Sci., 66 (3): 470-94. [PMID:18953682]
Yu FH, Catterall WA. (2004) The VGL-chanome: a protein superfamily specialized for electrical signaling and ionic homeostasis. Sci. STKE, 2004 (253): re15. [PMID:15467096]
References
1. Altomare C, Terragni B, Brioschi C, Milanesi R, Pagliuca C, Viscomi C, Moroni A, Baruscotti M, DiFrancesco D. (2003) Heteromeric HCN1-HCN4 channels: a comparison with native pacemaker channels from the rabbit sinoatrial node. J. Physiol. (Lond.), 549 (Pt 2): 347-59. [PMID:12702747]
2. BoSmith RE, Briggs I, Sturgess NC. (1993) Inhibitory actions of ZENECA ZD7288 on whole-cell hyperpolarization activated inward current (If) in guinea-pig dissociated sinoatrial node cells. Br. J. Pharmacol., 110 (1): 343-9. [PMID:7693281]
3. Bucchi A, Baruscotti M, DiFrancesco D. (2002) Current-dependent block of rabbit sino-atrial node I(f) channels by ivabradine. J. Gen. Physiol., 120 (1): 1-13. [PMID:12084770]
4. DiFrancesco D. (1993) Pacemaker mechanisms in cardiac tissue. Annu. Rev. Physiol., 55: 455-72. [PMID:7682045]
5. Dryer SE, Henderson D. (1991) A cyclic GMP-activated channel in dissociated cells of the chick pineal gland. Nature, 353 (6346): 756-8. [PMID:1719422]
6. Fesenko EE, Kolesnikov SS, Lyubarsky AL. (1985) Induction by cyclic GMP of cationic conductance in plasma membrane of retinal rod outer segment. Nature, 313 (6000): 310-3. [PMID:2578616]
7. Hofmann F, Biel M, Kaupp UB. (2005) International Union of Pharmacology. LI. Nomenclature and structure-function relationships of cyclic nucleotide-regulated channels. Pharmacol. Rev., 57 (4): 455-62. [PMID:16382102]
8. Kaupp UB, Niidome T, Tanabe T, Terada S, Bönigk W, Stühmer W, Cook NJ, Kangawa K, Matsuo H, Hirose T. (1989) Primary structure and functional expression from complementary DNA of the rod photoreceptor cyclic GMP-gated channel. Nature, 342 (6251): 762-6. [PMID:2481236]
9. Nakamura T, Gold GH. (1987) A cyclic nucleotide-gated conductance in olfactory receptor cilia. Nature, 325 (6103): 442-4. [PMID:3027574]
10. Pape HC. (1996) Queer current and pacemaker: the hyperpolarization-activated cation current in neurons. Annu. Rev. Physiol., 58: 299-327. [PMID:8815797]
11. Peng C, Rich ED, Varnum MD. (2004) Subunit configuration of heteromeric cone cyclic nucleotide-gated channels. Neuron, 42 (3): 401-10. [PMID:15134637]
12. Weitz D, Ficek N, Kremmer E, Bauer PJ, Kaupp UB. (2002) Subunit stoichiometry of the CNG channel of rod photoreceptors. Neuron, 36 (5): 881-9. [PMID:12467591]
13. Zheng J, Trudeau MC, Zagotta WN. (2002) Rod cyclic nucleotide-gated channels have a stoichiometry of three CNGA1 subunits and one CNGB1 subunit. Neuron, 36 (5): 891-6. [PMID:12467592]
14. Zheng J, Zagotta WN. (2004) Stoichiometry and assembly of olfactory cyclic nucleotide-gated channels. Neuron, 42 (3): 411-21. [PMID:15134638]
15. Zhong H, Molday LL, Molday RS, Yau KW. (2002) The heteromeric cyclic nucleotide-gated channel adopts a 3A:1B stoichiometry. Nature, 420 (6912): 193-8. [PMID:12432397]
NC-IUPHAR subcommittee and family contributors
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Martin Biel
Verena Hammelmann
Franz Hofmann (Past contributor)
U. Benjamin Kaupp (Past contributor) |
How to cite this family page
Database page citation:
Cyclic nucleotide-regulated channels. Accessed on 02/08/2014. IUPHAR/BPS Guide to PHARMACOLOGY, http://www.guidetopharmacology.org/GRAC/FamilyDisplayForward?familyId=71.
Concise Guide to PHARMACOLOGY citation:
Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Catterall WA, Spedding M, Peters JA and Harmar AJ, CGTP Collaborators. (2013) The Concise Guide to PHARMACOLOGY 2013/14: Ion Channels. Br J Pharmacol. 170: 1607–1651.
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CNGA1, CNGA2 and CNGA3 express functional channels as homomers. Three additional subunits CNGA4 (Q8IV77 ), CNGB1 (Q14028) and CNGB3 (Q9NQW8) do not, and are referred to as auxiliary subunits. The subunit composition of the native channels is believed to be as follows. Rod: CNGA13/CNGB1a; Cone: CNGA32/CNGB32; Olfactory neurons: CNGA22/CNGA4/CNGB1b [11-15].
Hyperpolarisation-activated, cyclic nucleotide-gated (HCN)
HCN channels are permeable to both Na+ and K+ ions, with a Na+/K+ permeability ratio of about 0.2. Functionally, they differ from each other in terms of time constant of activation with HCN1 the fastest, HCN4 the slowest and HCN2 and HCN3 intermediate. The compounds ZD7288 [2] and ivabradine [3] have proven useful in identifying and studying functional HCN channels in native cells. zatebradine and cilobradine are also useful blocking agents.