Genomic Organization, Chromosomal Localization, Tissue Distribution, and Biophysical Characterization of a Novel MammalianShaker-related Voltage-gated Potassium Channel, Kv1.7

Abstract

We report the isolation of a novel mouse voltage-gated Shaker-related K ؉ channel gene, Kv1.7 (Kcna7/KCNA7). Unlike other known Kv1 family genes that have intronless coding regions, the protein-coding region of Kv1.7 is interrupted by a 1.9-kilobase pair intron. The Kv1.7 gene and the related Kv3.3 (Kcnc3/KCNC3) gene map to mouse chromosome 7 and human chromosome 19q13.3, a region that has been suggested to contain a diabetic susceptibility locus. The mouse Kv1.7 channel is voltage-dependent and rapidly inactivating, exhibits cumulative inactivation, and has a single channel conductance of 21 pS. It is potently blocked by noxiustoxin and stichodactylatoxin, and is insensitive to tetraethylammonium, kaliotoxin, and charybdotoxin. Northern blot analysis reveals ϳ3-kilobase pair Kv1.7 transcripts in mouse heart and skeletal muscle. In situ hybridization demonstrates the presence of Kv1.7 in mouse pancreatic islet cells. Kv1.7 was also isolated from mouse brain and hamster insulinoma cells by polymerase chain reaction.Ion channels that exhibit a variety of gating patterns and ion selectivity are critical elements that transduce signals in diverse cell types (1). Voltage-gated potassium-selective (Kv) 1 channels represent the largest family within this class of proteins (2), and perform many vital functions in both electrically excitable and nonexcitable cells. Following initiation of an action potential in nerve and muscle cells, Kv channels play the important role of repolarizing the cell membrane (1). Kv channels can also modulate hormone secretion, for example insulin release from pancreatic islet cells (3-6), and regulate calcium signaling during mitogen-stimulated activation of lymphocytes (7).Kv channels in mammalian cells are encoded by an extended family of at least nineteen genes (2). The largest subfamily, Kv1, is related to the fly Shaker gene and contains six members, Kv1.1-Kv1.6 (2). The Shaker gene has 21 exons, which can be alternatively spliced to generate at least five functionally distinct transcripts (8, 9). In contrast, the protein-coding regions of each of the six known mammalian Kv1 genes and the three known Xenopus homologues are contained in a single exon (2, 10), precluding alternative splicing as a means of generating functionally different proteins. The evolutionary significance of this pattern of organization remains a puzzle.Here we report the identification of a novel mammalian gene, Kv1.7 (Kcna7/KCNA7), that has a genomic organization distinct from the other members of the vertebrate Kv1 subfamily. We have defined the chromosomal location of this gene in the mouse and human genome, determined its tissue distribution, and characterized the biophysical and pharmacological properties of the cloned channel. mKv1.7, hKv1.7, hKv3.3, and hKv3.4 DNA Clones-Three overlapping genomic clones (KC225, KC254, and KC256) were isolated from an AKR/J mouse genomic library screened with a mixture of mKv1.1 and rKv1.5 cDNA probes, as described previously (10), and mapped by multiple and partial restrict...

Characterisation of the human voltage-gated potassium channel gene, KCNA7, a candidate gene for inherited cardiac disorders, and its exclusion as cause of progressive familial heart block I (PFHBI)

“…7 Upon investigation, we detected an error in the published kcna7 cDNA sequence; the`G' (GCCCTGCGGCTGCTGCG) at position 29 in the coding region (Figure 1a) is absent in the published sequence (position 264) resulting in a frame-shift. This nucleotide is present in the human and mouse genomic sequences, as well as in three mouse ESTs (AA021711, AI322534, AI324179), which supports the observation that the published AF032099 sequence is incorrect.…”

A paired-sibling analysis of the XbaI polymorphism in the muscle glycogen synthase gene

“…More than 30 genes have been mapped to the 19q13.3 region [37,38], including genes for vasodilator stimulated phosphoprotein (VASP), protein phosphatase 5 catalytic subunit (PPP5C), dystrophia myotonica associated homeodomain protein (DMAHP), calmodulin 3 (CALM3), histidine rich calcium binding protein (HRC) and two Shaker related potassium voltage gated channels (KCNA7 and KCNC3). The KCNA7 gene was recently located between GYS1 and HRC, within 50 kb from GYS1 [39]. In addition, we have recently found an association between the hormone Observed sum of differences is the sum of differences calculated as the value in sibling with the A2 variant minus the value in sibling with the A1 variant.…”

Voltage-dependent K + channels in pancreatic beta cells: Role, regulation and potential as therapeutic targets

“…Although these channels are thought to facilitate action potential repolarisation and perhaps modulate glucose-dependent bursting, the hERG antagonist WAY123 398 did not enhance glucose-stimulated insulin secretion in that study making the true role of these channels unclear. [95], although the incidence of Kv channel polymorphism in a diabetic cohort has not been investigated. Mutations in Kv and related channels are known to play important roles in disorders such as familial long QT syndrome, episodic ataxia type 1, benign familial neonatal convulsion, familial and thyrotoxic hypokalemic periodic paralysis, and autosomal dominant deafness [96].…”