Abstract
Potassium channels are important for K+ transport and cell volume regulation, which play important roles in many biological processes such as hormone secretion, ion homeostasis, excitability, and cell development. In mammals, a total of 15 potassium channels were identified and they were divided into six subfamilies, including TALK (TALK1, TALK2, TASK2), TASK (TASK1, TASK3, TASK5), TREK (TREK1, TREK2, TRAAK), TWIK (TWIK1, TWIK2, KCNK7), THIK (THIK1, THIK2) and TRESK. TASK1, also known as potassium channel subfamily k member 3 (KCNK3), is the first member identified in the TASK subfamily. This K2P channel has potential applications in fish breeding and aquaculture industry due to its important roles in various physiological processes. Despite its functional role has been well studied in mammals; however, it is less known in fishes. In this review, we systematically summarize recent research advances of this critical potassium channel in representative fishes, such as gene number variation, tissue distribution, phylogeny, and potential homeostasis regulation role. This paper provides novel insights into the functional properties of these fish kcnk3 genes (including osmoregulation, energy homeostasis maintenance and fatty acids metabolism regulation), and also expands our knowledge about their variations among diverse fishes.
Highlights
Potassium channels are the largest ion channel family with more than 78 genes encoding poreforming subunits in the human genome (Feliciangeli et al, 2015)
Our further studies showed that two kcnk3 genes were existed in many other fishes such as Northern snakehead (Wen et al, 2019), Nile tilapia (Wen et al, 2020b) and rabbitfish (Wen et al, 2020a) by a comparative genomics strategy (Figure 1). These findings suggest that two copies of kcnk3 genes might be widely existed in teleost, and this phenomenon may be caused by the specific whole genome duplication (WGD) event in teleost (Hughes et al, 2018; Xu et al, 2019; Wen et al, 2020c)
These findings suggest that the distribution patterns of kcnk3 genes are variable in various fishes, we found a common trait that these channels are primarily expressed in the excitable tissues including central nervous system (CNS) and heart
Summary
Potassium channels are the largest ion channel family with more than 78 genes encoding poreforming subunits in the human genome (Feliciangeli et al, 2015). Two paralogs of kcnk were identified in zebrafish, which were predicted to play important roles in regulation of reproduction (Loganathan et al, 2017) Another two paralogs of TWIK related potassium channels, Kcnk2a and Kcnk2b, were reported and they were proved to exhibit similar functional traits as their counterpart in human (Nasr et al, 2018). TASK1, known as potassium channel subfamily k member 3 (KCNK3) or K2P3.1, is the first member identified in the TASK subfamily to participate in regulation of resting membrane potential in several cell types (Olschewski et al, 2017; Lambert et al, 2018, 2019) This channel is characterized by four transmembrane domains and two pore domains per subunit (Ma et al, 2013; Feliciangeli et al, 2015). Our works will provide novel insights into the functional properties of these fish KCNK3 channels, and establish guidelines for related studies and applications in diverse fishes in the coming future
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