Expression of the long and amino-terminal deleted (Kv1-5 delta 5') isoforms in Xenopus oocytes elicited similar K+ currents, but with drastically decreased efficacy for the short isoform.
Identification and characterization of multiple mRNA isoforms of the mouse cardiac Kv1-5 channel reveals differential functional properties and regulatory interactions.
The mouse Kv1-5 K+ channel cDNA has been cloned from heart. This channel was highly expressed in heart and, to a lesser extent, in other tissues, including brain and thymus. Two alternatively spliced isoforms were found. The longer form encoded a 602-amino acid protein, while in the short form (Kv1-5 delta 5'), the first 200 amino acids lying upstream the transmembrane segment S1 were deleted. RNase protection experiments showed that both Kv1-5 mRNA isoforms are present in the mouse tissues examined, the longer form being predominant. The short mRNA (Kv1-5 delta 5') arose by an unusual splicing event within the exonic sequence. An additional short cDNA clone (Kv1-5 delta 3') that codes for a carboxyl-terminal truncated protein has been isolated. The gene coding sequence contained a single exon and has been mapped on human chromosome 12 (p13) and on mouse chromosome 6 (band F). Expression in Xenopus oocytes revealed that the long (Kv1-5) and the amino-terminal deleted (Kv1-5 delta 5') isoforms elicited similar K+ currents with a drastically decreased efficacy for Kv1-5 delta 5'. The carboxyl-terminal truncated Kv1-5 delta 3' clone was not functional but inhibited the expression of the long isoform.
Attali et al. (Mon,) conducted a other in Mouse cardiac Kv1-5 delayed rectifier K+ channel. Expression of Kv1-5 isoforms in Xenopus oocytes was evaluated. Expression of the long and amino-terminal deleted (Kv1-5 delta 5') isoforms in Xenopus oocytes elicited similar K+ currents, but with drastically decreased efficacy for the short isoform.
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