Introduction of KCNK13
Potassium channel subfamily K member 13 (KCNK13), also known as tandem pore domain halothane-inhibited potassium channel THIK-1 and K2P13.1, is encoded by gene KCNK13. KCNK13 is assigned to chromosomal region 14q24.1-14q24.3. Sharing 58% sequence homology with KCNK12 (THIK-2), KCNK13 also belongs to the family of tandem pore domain potassium (K2P) channels, characterized with four transmembrane segments (M1-M4) and two typical pore-forming regions (P1 and P2) including the K+ selectivity filter consensus sequence and a large extracellular loop between M1 and P1. In human kidney, KCNK13 is mainly expressed in the proximal tubule (PT), thick ascending limb (TAL), and cortical collecting duct (CCD). It is compelling that KCNK13 carries a caspase recognition sequence in its cytoplasmic region.
|Basic Information of KCNK13|
|Protein Name||Potassium channel subfamily K member 13|
|Organism||Homo sapiens (Human)|
Function of KCNK13 Membrane Protein
Unlike KCNK12, a ‘silent’ channel of K2P family, KCNK13 can produce background K+ currents by itself, and that is inhibited by halothane and insensitive to extracellular pH variations. Beyond the function of setting the resting membrane potential and thus regulating cell excitability, the background K+ channels can regulate cell function under various physiological and pathophysiological conditions, via targeting to multiple intracellular and extracellular biological signals. KCNK13 combines with KCNK12 to form active heteromeric channels and tandem-KCNK13-KCNK12 distributes at the plasma membrane, whereas tandem-KCNK12-KCNK12 is mainly detected in the endoplasmic reticulum, indicating that KCNK13 can mask the endoplasmic reticulum retention/retrieval motif of KCNK12. It is documented that whole-cell KCNK13 current can be inhibited by halothane and activated by arachidonic acid. It has been identified that KCNK13 is a novel substrate of caspase-8, which can cleave an evolutionarily conserved sequence in the intracellular region of KCNK13. Overexpression of KCNK13 will accelerate cell shrinkage in response to apoptotic stimuli. Furthermore, a truncated KCNK13 mutant lacking the intracellular region will decrease cell volume without apoptotic stimulation and excessively promote the irregular development of Xenopus embryos.
Fig.1 The transmembrane topology, crystal structure and dendrogram of human K2P channels. (Feliciangeli, 2015)
Application of KCNK13 Membrane Protein in Literature
In this article, the authors identified that THIK-1 was a novel caspase-8 substrate, which could cleave an evolutionarily conserved sequence in the intracellular region of THIK-1. Fluctuating expression of THIK-1 would affect cell volume during apoptosis and underexpression of THIK-1 resulted in the delay of K+ efflux in dying cells.
This article revealed that THIK1 and THIK2 could assemble to form active channels. Moreover, Tandem-THIK1-THIK2 could induce K+ currents of amplitude similar to Tandem-THIK1-THIK1 but with a noticeable difference in the current kinetics.
This article demonstrated that THIK-1 was functionally expressed in trigeminal ganglion (TG) neurons and could produce a small conductance (~5-pS) channel contributing to the background K+ conductance.
The authors demonstrated that isoflurane caused activation of RTN neurons, which was CO2/pH-sensitive and located in the retrotrapezoid nucleus (RTN) of the rodent brainstem. In this process, inhibition of THIK-1-like background K+ current was essential, which may contribute to maintaining respiratory motor activity under immobilizing anesthetic conditions.
The authors described the cloning of the first two members of a novel subfamily of 2P K+ channels (THIK-1 and THIK-2) from rat brain, and they studied the distribution of these channels. In rats, THIK-1 was expressed ubiquitously, while THIK-2 expression was found in several tissues including brain and kidney.
The review gathered massive data and gave a synthetic view of the most noticeable features of the K2P channels which were central players in many processes, including ion homeostasis, hormone secretion, cell development, and excitability.
KCNK13 Preparation Options
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