Title : O-glycosylation of the cardiac I(Ks) complex
Abstract :
- Post-translational modifications of the KCNQ1 – KCNE1 ( Kv7 ) K+ channel complex are vital for regulation of the cardiac IKs current and action potential duration
- Here, we show the KCNE1 regulatory subunit is O-glycosylated with mucin-type glycans in vivo
- As O-linked glycosylation sites are not recognizable by sequence gazing, we designed a novel set of glycosylation mutants and KCNE chimeras and analysed their glycan content using deglycosylation enzymes
- Our results show that KCNE1 is exclusively O-glycosylated at Thr-7 , which is also required for N-glycosylation at Asn-5
- For wild type KCNE1 , the overlapping N- and O-glycosylation sites are innocuous for subunit biogenesis; however, mutation of Thr-7 to a non-hydroxylated residue yielded mostly unglycosylated protein and a small fraction of mono-N-glycosylated protein
- The compounded hypoglycosylation was equally deleterious for KCNQ1 – KCNE1 cell surface expression, demonstrating that KCNE1 O-glycosylation is a post-translational modification that is integral for the proper biogenesis and anterograde trafficking of the cardiac IKs complex
- The enzymatic assays and panel of glycosylation mutants used here will be valuable for identifying the different KCNE1 glycoforms in native cells and determining the roles N- and O-glycosylation play in KCNQ1 – KCNE1 function and localization in cardiomyocytes