KCNJ15

Potassium inwardly-rectifying channel, subfamily J, member 15, also known as KCNJ15 is a human gene, which encodes the gene product Kir4.2.cite web | title = Entrez Gene: KCNJ15 potassium inwardly-rectifying channel, subfamily J, member 15| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=3772| accessdate = ]

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summary_text = 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. The encoded protein has a greater tendency to allow potassium to flow into a cell rather than out of a cell. Three transcript variants encoding the same protein have been found for this gene.cite web | title = Entrez Gene: KCNJ15 potassium inwardly-rectifying channel, subfamily J, member 15| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=3772| accessdate = ]

The existing literature describing KCNJ15 and kir4.2 is sparse. In spite of some initial channel nomenclature confusion, in which the gene was referred to as kir1.3cite journal |author=Pearson WL, Dourado M, Schreiber M, Salkoff L, Nichols CG |title=Expression of a functional Kir4 family inward rectifier K+ channel from a gene cloned from mouse liver |journal=J. Physiol. (Lond.) |volume=514 ( Pt 3) |issue= |pages=639–53 |year=1999 |pmid=9882736 |doi=10.1111/j.1469-7793.1999.639ad.x] the channel was first cloned from human kidney by Shuck and coworkers in 1997cite journal |author=Shuck ME, Piser TM, Bock JH, Slightom JL, Lee KS, Bienkowski MJ |title=Cloning and characterization of two K+ inward rectifier (Kir) 1.1 potassium channel homologs from human kidney (Kir1.2 and Kir1.3) |journal=J. Biol. Chem. |volume=272 |issue=1 |pages=586–93 |year=1997 |pmid=8995301 |doi=10.1074/jbc.272.1.586] . Shortly thereafter it was shown that mutation of an extracellular lysine residue resulted in 6-fold increase in K⁺ currentcite journal |author=Derst C, Wischmeyer E, Preisig-Müller R, "et al" |title=A hyperprostaglandin E syndrome mutation in Kir1.1 (renal outer medullary potassium) channels reveals a crucial residue for channel function in Kir1.3 channels |journal=J. Biol. Chem. |volume=273 |issue=37 |pages=23884–91 |year=1998 |pmid=9727001 |doi=10.1074/jbc.273.37.23884] . Two years later, in 1999, voltage clamp measurements in xenopus oocytes found that intracellular acidification decreased the potassium current of Kir4.2. Also activation of protein kinase C decreased the current although in a non-reversible fashion. Furthermore it was found that coexpression with related potassium channel kir5.1, changed these results somewhat, which the authors concluded was likely to be a result of heterodimerization. Further voltage clamp investigations found the exact pH sensitivity (pK_a = 7.1), open probability (high) and conductance of ~25 pScite journal |author=Pessia M, Imbrici P, D'Adamo MC, Salvatore L, Tucker SJ |title=Differential pH sensitivity of Kir4.1 and Kir4.2 potassium channels and their modulation by heteropolymerisation with Kir5.1 |journal=J. Physiol. (Lond.) |volume=532 |issue=Pt 2 |pages=359–67 |year=2001 |pmid=11306656 |doi=] . In 2007 the channel was found to interact with the Calcium-sensing receptor in human kidney, using a yeast-two-hybrid system. This co-localization was verified at the protein level using both immunofluorescence techniques and coimmunoprecipitation of kir4.2 and the Calcium-sensing receptorcite journal |author=Huang C, Sindic A, Hill CE, "et al" |title=Interaction of the Ca2+-sensing receptor with the inwardly rectifying potassium channels Kir4.1 and Kir4.2 results in inhibition of channel function |journal=Am. J. Physiol. Renal Physiol. |volume=292 |issue=3 |pages=F1073–81 |year=2007 |pmid=17122384 |doi=10.1152/ajprenal.00269.2006] . Also a mutational study of kir4.2 has demonstrated that removal of a c-terminal tyrosine increased the K⁺ current more than 10-foldcite journal |author=Pearson WL, Skatchkov SN, Eaton MJ, Nichols CG |title=C-terminal determinants of Kir4.2 channel expression |journal=J. Membr. Biol. |volume=213 |issue=3 |pages=187–93 |year=2006 |pmid=17468958 |doi=10.1007/s00232-006-0058-6] . Because the channel has a very high open probability, the authors of this last article conclude that this increase is mediated by increased trafficking of the protein to the membrane and not increased single-channel conductance. This same line of reasoning is applicable to the initial work of Derst and coworkers.

ee also

* Inward-rectifier potassium ion channel

References

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