Potassium voltage-gated channel, shaker-related subfamily, member 3, also known as KCNA3 or Kv1.3, is a protein that in humans is encoded by the KCNA3gene.[1][2][3]
Potassium channels represent the most complex class of voltage-gated ion channels from both functional and structural standpoints. Their diverse functions include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume. Four sequence-related potassium channel genes – shaker, shaw, shab, and shal – have been identified in Drosophila, and each has been shown to have human homolog(s).
This gene encodes a member of the potassium channel, voltage-gated, shaker-related subfamily. This member contains six membrane-spanning domains with a shaker-type repeat in the fourth segment. It belongs to the delayed rectifier class, members of which allow nerve cells to efficiently repolarize following an action potential. It plays an essential role in T cell proliferation and activation. This gene appears to be intronless and is clustered together with KCNA2 and KCNA10 genes on chromosome 1.[1]
KCNA3 encodes the voltage-gated Kv1.3 channel, which is expressed in T and B lymphocytes.[2][4][5][6][7][8][9] All human T cells express roughly 300 Kv1.3 channels per cell along with 10-20 calcium-activated KCa3.1 channels.[10][11] Upon activation, naive and central memory T cells increase expression of the KCa3.1 channel to approximately 500 channels per cell, while effector-memory T cells increase expression of the Kv1.3 channel.[10][11] Among human B cells, naive and early memory B cells express small numbers of Kv1.3 and KCa3.1 channels when they are quiescent, and augment KCa3.1 expression after activation.[12] In contrast, class-switched memory B cells express high numbers of Kv1.3 channels per cell (about 1500/cell) and this number increases after activation.[12]
Kv1.3 is physically coupled through a series of adaptor proteins to the T-cell receptor signaling complex and it traffics to the immunological synapse during antigen presentation.[13][14] However, blockade of the channel does not prevent immune synapse formation.[14] Kv1.3 and KCa3.1 regulate membrane potential and calcium signaling of T cells.[10] Calcium entry through the CRAC channel is promoted by potassium efflux through the Kv1.3 and KCa3.1 potassium channels.[14][15]
Blockade of Kv1.3 channels in effector-memory T cells suppresses calcium signaling, cytokine production (interferon-gamma, interleukin 2) and cell proliferation.[10][11][14] In vivo, Kv1.3 blockers paralyze effector-memory T cells at the sites of inflammation and prevent their reactivation in inflamed tissues.[15] In contrast, Kv1.3 blockers do not affect the homing to and motility within lymph nodes of naive and central memory T cells, most likely because these cells express the KCa3.1 channel and are, therefore, protected from the effect of Kv1.3 blockade.[15]
In patients with multiple sclerosis (MS), disease-associated myelin-specific T cells from the blood are predominantly co-stimulation-independent[21] effector-memory T cells that express high numbers of Kv1.3 channels.[11][14] T cells in MS lesions in postmortem brain lesions are also predominantly effector-memory T cells that express high levels of the Kv1.3 channel.[22] In children with type-1 diabetes mellitus, the disease-associated insulin- and GAD65-specific T cells isolated from the blood are effector-memory T cells that express high numbers of Kv1.3 channels, and the same is true of T cells from the synovial joint fluid of patients with rheumatoid arthritis.[14] T cells with other antigen specificities in these patients were naive or central memory T cells that upregulate the KCa3.1 channel upon activation.[14] Consequently, it should be possible to selectively suppress effector-memory T cells with a Kv1.3-specific blocker and thereby ameliorate many autoimmune diseases without compromising the protective immune response. In proof-of-concept studies, Kv1.3 blockers have prevented and treated disease in rat models of multiple sclerosis, type-1 diabetes mellitus, rheumatoid arthritis, contact dermatitis, and delayed-type hypersensitivity.[14][23][24][25][26]
At therapeutic concentrations, the blockers did not cause any clinically evident toxicity in rodents,[14][23] and it did not compromise the protective immune response to acute influenza viral infection and acute chlamydia bacterial infection.[15] Many groups are developing Kv1.3 blockers for the treatment of autoimmune diseases.[27]
Kv1.3 channels have been found to be highly expressed by activated and plaque-associated microglia in human Alzheimer’s disease (AD) post-mortem brains [33] as well as in mouse models of AD pathology.[34] Patch-clamp recordings and flow cytometric studies performed on acutely isolated mouse microglia have confirmed upregulation of Kv1.3 channels with disease progression in mouse AD models.[34][35] The Kv1.3 channel gene has also been found to be a regulator of pro-inflammatory microglial responses.[36] Selective blockade of Kv1.3 channels by the small molecule Pap1 as well as a peptide sea anemone toxin-based peptide ShK-223 have been found to limit amyloid beta plaque burden in mouse AD models, potentially via augmented clearance by microglia.[34][35]
↑Gutman GA, Chandy KG, Grissmer S, Lazdunski M, McKinnon D, Pardo LA, Robertson GA, Rudy B, Sanguinetti MC, Stühmer W, Wang X (December 2005). "International Union of Pharmacology. LIII. Nomenclature and molecular relationships of voltage-gated potassium channels". Pharmacological Reviews. 57 (4): 473–508. doi:10.1124/pr.57.4.10. PMID16382104.
↑DeCoursey TE, Chandy KG, Gupta S, Cahalan MD (1984). "Voltage-gated K + channels in human T lymphocytes: a role in mitogenesis?". Nature. 307 (5950): 465–8. doi:10.1038/307465a0. PMID6320007.
↑Matteson DR, Deutsch C (1984). "K channels in T lymphocytes: a patch clamp study using monoclonal antibody adhesion". Nature. 307 (5950): 468–71. doi:10.1038/307468a0. PMID6320008.
↑Chandy KG, Williams CB, Spencer RH, Aguilar BA, Ghanshani S, Tempel BL, Gutman GA (February 1990). "A family of three mouse potassium channel genes with intronless coding regions". Science. 247 (4945): 973–5. doi:10.1126/science.2305265. PMID2305265.
↑Cai YC, Osborne PB, North RA, Dooley DC, Douglass J (March 1992). "Characterization and functional expression of genomic DNA encoding the human lymphocyte type n potassium channel". DNA and Cell Biology. 11 (2): 163–72. doi:10.1089/dna.1992.11.163. PMID1547020.
↑ 12.012.1Wulff H, Knaus HG, Pennington M, Chandy KG (July 2004). "K + channel expression during B cell differentiation: implications for immunomodulation and autoimmunity". Journal of Immunology. 173 (2): 776–86. doi:10.4049/jimmunol.173.2.776. PMID15240664.
↑ 16.016.1Szabò I, Bock J, Jekle A, Soddemann M, Adams C, Lang F, Zoratti M, Gulbins E (April 2005). "A novel potassium channel in lymphocyte mitochondria". The Journal of Biological Chemistry. 280 (13): 12790–8. doi:10.1074/jbc.M413548200. PMID15632141.
↑Szabò I, Gulbins E, Apfel H, Zhang X, Barth P, Busch AE, Schlottmann K, Pongs O, Lang F (August 1996). "Tyrosine phosphorylation-dependent suppression of a voltage-gated K + channel in T lymphocytes upon Fas stimulation". The Journal of Biological Chemistry. 271 (34): 20465–9. doi:10.1074/jbc.271.34.20465. PMID8702786.
↑Storey NM, Gómez-Angelats M, Bortner CD, Armstrong DL, Cidlowski JA (August 2003). "Stimulation of Kv1.3 potassium channels by death receptors during apoptosis in Jurkat T lymphocytes". The Journal of Biological Chemistry. 278 (35): 33319–26. doi:10.1074/jbc.M300443200. PMID12807917.
↑Beeton C, Smith BJ, Sabo JK, Crossley G, Nugent D, Khaytin I, Chi V, Chandy KG, Pennington MW, Norton RS (January 2008). "The D-diastereomer of ShK toxin selectively blocks voltage-gated K + channels and inhibits T lymphocyte proliferation". The Journal of Biological Chemistry. 283 (2): 988–97. doi:10.1074/jbc.M706008200. PMID17984097.
↑Wulff H, Beeton C, Chandy KG (September 2003). "Potassium channels as therapeutic targets for autoimmune disorders". Current Opinion in Drug Discovery & Development. 6 (5): 640–7. PMID14579513.
↑Xu J, Koni PA, Wang P, Li G, Kaczmarek L, Wu Y, Li Y, Flavell RA, Desir GV (March 2003). "The voltage-gated potassium channel Kv1.3 regulates energy homeostasis and body weight". Human Molecular Genetics. 12 (5): 551–9. doi:10.1093/hmg/ddg049. PMID12588802.
↑ 31.031.1Valverde P, Kawai T, Taubman MA (June 2005). "Potassium channel-blockers as therapeutic agents to interfere with bone resorption of periodontal disease". Journal of Dental Research. 84 (6): 488–99. doi:10.1177/154405910508400603. PMID15914584.
↑Tschritter O, Machicao F, Stefan N, Schäfer S, Weigert C, Staiger H, Spieth C, Häring HU, Fritsche A (February 2006). "A new variant in the human Kv1.3 gene is associated with low insulin sensitivity and impaired glucose tolerance". The Journal of Clinical Endocrinology and Metabolism. 91 (2): 654–8. doi:10.1210/jc.2005-0725. PMID16317062.
↑Aiyar J, Withka JM, Rizzi JP, Singleton DH, Andrews GC, Lin W, Boyd J, Hanson DC, Simon M, Dethlefs B (November 1995). "Topology of the pore-region of a K + channel revealed by the NMR-derived structures of scorpion toxins". Neuron. 15 (5): 1169–81. doi:10.1016/0896-6273(95)90104-3. PMID7576659.
↑Bagdány M, Batista CV, Valdez-Cruz NA, Somodi S, Rodriguez de la Vega RC, Licea AF, Varga Z, Gáspár R, Possani LD, Panyi G (April 2005). "Anuroctoxin, a new scorpion toxin of the alpha-KTx 6 subfamily, is highly selective for Kv1.3 over IKCa1 ion channels of human T lymphocytes". Molecular Pharmacology. 67 (4): 1034–44. doi:10.1124/mol.104.007187. PMID15615696.
↑Pennington MW, Mahnir VM, Krafte DS, Zaydenberg I, Byrnes ME, Khaytin I, Crowley K, Kem WR (February 1996). "Identification of three separate binding sites on SHK toxin, a potent inhibitor of voltage-dependent potassium channels in human T-lymphocytes and rat brain". Biochemical and Biophysical Research Communications. 219 (3): 696–701. doi:10.1006/bbrc.1996.0297. PMID8645244.
↑Tudor JE, Pallaghy PK, Pennington MW, Norton RS (April 1996). "Solution structure of ShK toxin, a novel potassium channel inhibitor from a sea anemone". Nature Structural Biology. 3 (4): 317–20. doi:10.1038/nsb0496-317. PMID8599755.
↑Kalman K, Pennington MW, Lanigan MD, Nguyen A, Rauer H, Mahnir V, Paschetto K, Kem WR, Grissmer S, Gutman GA, Christian EP, Cahalan MD, Norton RS, Chandy KG (December 1998). "ShK-Dap22, a potent Kv1.3-specific immunosuppressive polypeptide". The Journal of Biological Chemistry. 273 (49): 32697–707. doi:10.1074/jbc.273.49.32697. PMID9830012.
↑Rauer H, Pennington M, Cahalan M, Chandy KG (July 1999). "Structural conservation of the pores of calcium-activated and voltage-gated potassium channels determined by a sea anemone toxin". The Journal of Biological Chemistry. 274 (31): 21885–92. doi:10.1074/jbc.274.31.21885. PMID10419508.
↑Han S, Yi H, Yin SJ, Chen ZY, Liu H, Cao ZJ, Wu YL, Li WX (July 2008). "Structural basis of a potent peptide inhibitor designed for Kv1.3 channel, a therapeutic target of autoimmune disease". The Journal of Biological Chemistry. 283 (27): 19058–65. doi:10.1074/jbc.M802054200. PMID18480054.
↑Cotton J, Crest M, Bouet F, Alessandri N, Gola M, Forest E, Karlsson E, Castañeda O, Harvey AL, Vita C, Ménez A (February 1997). "A potassium-channel toxin from the sea anemone Bunodosoma granulifera, an inhibitor for Kv1 channels. Revision of the amino acid sequence, disulfide-bridge assignment, chemical synthesis, and biological activity". European Journal of Biochemistry. 244 (1): 192–202. doi:10.1111/j.1432-1033.1997.00192.x. PMID9063464.
↑Schmitz A, Sankaranarayanan A, Azam P, Schmidt-Lassen K, Homerick D, Hänsel W, Wulff H (November 2005). "Design of PAP-1, a selective small molecule Kv1.3 blocker, for the suppression of effector memory T cells in autoimmune diseases". Molecular Pharmacology. 68 (5): 1254–70. doi:10.1124/mol.105.015669. PMID16099841.
↑Zhou YY, Hou GQ, He SW, Xiao Z, Xu HJ, Qiu YT, Jiang S, Zheng H, Li ZY (July 2015). "Psora-4, a Kv1.3 Blocker, Enhances Differentiation and Maturation in Neural Progenitor Cells". CNS Neuroscience & Therapeutics. 21 (7): 558–67. doi:10.1111/cns.12402. PMID25976092.
↑Koo GC, Blake JT, Shah K, Staruch MJ, Dumont F, Wunderler D, Sanchez M, McManus OB, Sirotina-Meisher A, Fischer P, Boltz RC, Goetz MA, Baker R, Bao J, Kayser F, Rupprecht KM, Parsons WH, Tong XC, Ita IE, Pivnichny J, Vincent S, Cunningham P, Hora D, Feeney W, Kaczorowski G (November 1999). "Correolide and derivatives are novel immunosuppressants blocking the lymphocyte Kv1.3 potassium channels". Cellular Immunology. 197 (2): 99–107. doi:10.1006/cimm.1999.1569. PMID10607427.
↑Miao S, Bao J, Garcia ML, Goulet JL, Hong XJ, Kaczorowski GJ, Kayser F, Koo GC, Kotliar A, Schmalhofer WA, Shah K, Sinclair PJ, Slaughter RS, Springer MS, Staruch MJ, Tsou NN, Wong F, Parsons WH, Rupprecht KM (March 2003). "Benzamide derivatives as blockers of Kv1.3 ion channel". Bioorganic & Medicinal Chemistry Letters. 13 (6): 1161–4. doi:10.1016/S0960-894X(03)00014-3. PMID12643934.
↑Nguyen A, Kath JC, Hanson DC, Biggers MS, Canniff PC, Donovan CB, Mather RJ, Bruns MJ, Rauer H, Aiyar J, Lepple-Wienhues A, Gutman GA, Grissmer S, Cahalan MD, Chandy KG (December 1996). "Novel nonpeptide agents potently block the C-type inactivated conformation of Kv1.3 and suppress T cell activation". Molecular Pharmacology. 50 (6): 1672–9. PMID8967992.
↑Bezerra EL, Vilar MJ, da Trindade Neto PB, Sato EI (October 2005). "Double-blind, randomized, controlled clinical trial of clofazimine compared with chloroquine in patients with systemic lupus erythematosus". Arthritis and Rheumatism. 52 (10): 3073–8. doi:10.1002/art.21358. PMID16200586.
↑Mackey JP, Barnes J (July 1974). "Clofazimine in the treatment of discoid lupus erythematosus". The British Journal of Dermatology. 91 (1): 93–6. doi:10.1111/j.1365-2133.1974.tb06723.x. PMID4851057.
↑Chuaprapaisilp T, Piamphongsant T (September 1978). "Treatment of pustular psoriasis with clofazimine". The British Journal of Dermatology. 99 (3): 303–5. doi:10.1111/j.1365-2133.1978.tb02001.x. PMID708598.
↑Arbiser JL, Moschella SL (February 1995). "Clofazimine: a review of its medical uses and mechanisms of action". Journal of the American Academy of Dermatology. 32 (2 Pt 1): 241–7. doi:10.1016/0190-9622(95)90134-5. PMID7829710.
↑Selby W, Pavli P, Crotty B, Florin T, Radford-Smith G, Gibson P, Mitchell B, Connell W, Read R, Merrett M, Ee H, Hetzel D (June 2007). "Two-year combination antibiotic therapy with clarithromycin, rifabutin, and clofazimine for Crohn's disease". Gastroenterology. 132 (7): 2313–9. doi:10.1053/j.gastro.2007.03.031. PMID17570206.