Mouse ERG K+ channel clones reveal differences in protein trafficking and function

Background: the mouse ether-a-go-go-related gene 1a (merg1a,mkcnh2) encodes merg k+ channels in mouse cardiomyocytes. the merg channels and their human analogue,herg channels,conduct ikr. mutations in herg channels reduce ikr to cause congenital long-qt syndrome type 2,mostly by decreasing surface membrane expression of trafficking-deficient channels. three cdna sequences were originally reported for merg channels that differ by 1 to 4 amino acid residues (merg-london,mergwaterston,and merg-nie). we characterized these merg channels to test the postulation that they would differ in their protein trafficking and biophysical function,based on previous findings in long-qt syndrome type 2. methods and results: the 3 merg and herg channels were expressed in hek293 cells and neonatal mouse cardiomyocytes and were studied using western blot and whole-cell patch clamp. we then compared our findings with the recent sequencing results in the welcome trust sanger institute mouse genomes project (wtsimgp). conclusions: first,the merg-london channel with amino acid substitutions in regions of highly ordered structure is trafficking deficient and undergoes temperature-dependent and pharmacological correction of its trafficking deficiency. second,the voltage dependence of channel gating would be different for the 3 merg channels. third,compared with the wtsimgp data set,the mergnie clone is likely to represent the wild-type mouse sequence and physiology. fourth,the wtsimgp analysis suggests that substrain-specific sequence differences in merg are a common finding in mice. these findings with merg channels support previous findings with herg channel structure-function analyses in long-qt syndrome type 2,in which sequence changes in regions of highly ordered structure are likely to result in abnormal protein trafficking. © 2014 the authors.