ROMK

The renal outer medullary potassium channel (ROMK) is an ATP-dependent potassium channel (Kir1.1) that transports potassium out of cells. It plays an important role in potassium recycling in the thick ascending limb (TAL) and potassium secretion in the cortical collecting duct (CCD) of the nephron. In humans, ROMK is encoded by the KCNJ1 (potassium inwardly-rectifying channel, subfamily J, member 1) gene.[5][6][7] Multiple transcript variants encoding different isoforms have been found for this gene.[8]

KCNJ1
Identifiers
AliasesKCNJ1, KIR1.1, ROMK, ROMK1, potassium voltage-gated channel subfamily J member 1, potassium inwardly rectifying channel subfamily J member 1
External IDsOMIM: 600359 MGI: 1927248 HomoloGene: 56764 GeneCards: KCNJ1
Orthologs
SpeciesHumanMouse
Entrez

3758

56379

Ensembl

ENSG00000151704

ENSMUSG00000041248

UniProt

P48048

O88335

RefSeq (mRNA)

NM_153767
NM_000220
NM_153764
NM_153765
NM_153766

NM_001168354
NM_019659

RefSeq (protein)

NP_000211
NP_722448
NP_722449
NP_722450
NP_722451

NP_001161826
NP_062633

Location (UCSC)Chr 11: 128.84 – 128.87 MbChr 9: 32.28 – 32.31 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Function

Potassium channels are present in most mammalian cells, where they participate in a wide range of physiologic responses. The protein encoded by this gene is an integral membrane protein and inward-rectifier type potassium channel. It is inhibited by internal ATP and probably plays an important role in potassium homeostasis. The encoded protein has a greater tendency to allow potassium to flow into a cell rather than out of a cell, which has (hence the term "inwardly rectifying" referring to corresponding currents in electrophysiology, but has limited physiological relevance).[8] ROMK was identified as the pore-forming component of the mitochondrial ATP-sensitive potassium (mitoKATP) channel, known to play a critical role in cardioprotection against ischemic-reperfusion injury in the heart[9] as well as in the protection against hypoxia-induced brain injury from stroke or other ischemic attacks.

Klotho is a beta-glucuronidase-like enzyme that activates ROMK by removal of sialic acid.[10][11]

Clinical significance

Mutations in this gene have been associated with antenatal Bartter syndrome, which is characterized by salt wasting, hypokalemic alkalosis, hypercalciuria, and low blood pressure.[8]

Role in hypokalemia and magnesium deficiency

The ROMK channels are inhibited by magnesium in the nephron's normal physiologic state. In states of hypokalemia (a state of potassium deficiency), concurrent magnesium deficiency results in a state of hypokalemia that may be more difficult to correct with potassium replacement alone. This may be directly due to decreased inhibition of the outward potassium current in states where magnesium is low. Conversely, magnesium deficiency alone is not likely to cause a state of hypokalemia.[12] Sgk1 kinase has also been reported to phosphorylate ROMK, resulting in an increase of channels on the apical surface of the distal tubule.[13] Sgk1 is in turn regulated by the mineralocorticoid receptor such an effect may contribute to the kaliuretic action of aldosterone.

References
  1. GRCh38: Ensembl release 89: ENSG00000151704 - Ensembl, May 2017
  2. GRCm38: Ensembl release 89: ENSMUSG00000041248 - Ensembl, May 2017
  3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. Ho K, Nichols CG, Lederer WJ, Lytton J, Vassilev PM, Kanazirska MV, Hebert SC (March 1993). "Cloning and expression of an inwardly rectifying ATP-regulated potassium channel". Nature. 362 (6415): 31–8. Bibcode:1993Natur.362...31H. doi:10.1038/362031a0. PMID 7680431. S2CID 4332298.
  6. Yano H, Philipson LH, Kugler JL, Tokuyama Y, Davis EM, Le Beau MM, Nelson DJ, Bell GI, Takeda J (May 1994). "Alternative splicing of human inwardly rectifying K+ channel ROMK1 mRNA". Molecular Pharmacology. 45 (5): 854–60. PMID 8190102.
  7. Kubo Y, Adelman JP, Clapham DE, Jan LY, Karschin A, Kurachi Y, Lazdunski M, Nichols CG, Seino S, Vandenberg CA (December 2005). "International Union of Pharmacology. LIV. Nomenclature and molecular relationships of inwardly rectifying potassium channels". Pharmacological Reviews. 57 (4): 509–26. doi:10.1124/pr.57.4.11. PMID 16382105. S2CID 11588492.
  8. "Entrez Gene: potassium inwardly-rectifying channel".
  9. Foster DB, Ho AS, Rucker J, Garlid AO, Chen L, Sidor A, Garlid KD, O'Rourke B (August 2012). "Mitochondrial ROMK channel is a molecular component of mitoK(ATP)". Circulation Research. 111 (4): 446–54. doi:10.1161/circresaha.112.266445. PMC 3560389. PMID 22811560.
  10. Cha SK, Ortega B, Kurosu H, Rosenblatt KP, Kuro-O M, Huang CL (2008). "Removal of sialic acid involving Klotho causes cell-surface retention of TRPV5 channel via binding to galectin-1". Proceedings of the National Academy of Sciences of the United States of America. 105 (28): 9805–9810. Bibcode:2008PNAS..105.9805C. doi:10.1073/pnas.0803223105. PMC 2474477. PMID 18606998.
  11. Huang CL (2010). "Regulation of ion channels by secreted Klotho: mechanisms and implications". Kidney International. 77 (10): 855–860. doi:10.1038/ki.2010.73. PMID 20375979.
  12. Huang CL, Kuo E (October 2007). "Mechanism of hypokalemia in magnesium deficiency". Journal of the American Society of Nephrology. 18 (10): 2649–2652. doi:10.1681/asn.2007070792. PMID 17804670.
  13. Yoo D, Kim BY, Campo C, Nance L, King A, Maouyo D, Welling PA (June 2003). "Cell surface expression of the ROMK (Kir 1.1) channel is regulated by the aldosterone-induced kinase, SGK-1, and protein kinase A". The Journal of Biological Chemistry. 278 (25): 23066–23075. doi:10.1074/jbc.M212301200. PMID 12684516.

Further reading


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