title: Post-translational N-glycosylation of type I transmembrane KCNE1 peptides: implications for membrane protein biogenesis and disease.
abstract: N-Glycosylation of membrane proteins is critical for their proper folding, co-assembly and subsequent matriculation through the secretory pathway. Here, we examine the kinetics of N-glycan addition to type I transmembrane KCNE1 K(+) channel β-subunits, where point mutations that prevent N-glycosylation at one consensus site give rise to disorders of the cardiac rhythm and congenital deafness. We show that KCNE1 has two distinct N-glycosylation sites: a typical co-translational site and a consensus site ∼20 residues away that unexpectedly acquires N-glycans after protein synthesis (post-translational). Mutations that ablate the co-translational site concomitantly reduce glycosylation at the post-translational site, resulting in unglycosylated KCNE1 subunits that cannot reach the cell surface with their cognate K(+) channel. This long range inhibition is highly specific for post-translational N-glycosylation because mutagenic conversion of the KCNE1 post-translational site into a co-translational site restored both monoglycosylation and anterograde trafficking. These results directly explain how a single point mutation can prevent N-glycan attachment at multiple sites, providing a new biogenic mechanism for human disease.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605-2324, USA.
authors.forename: Tuba
authors.initials: T
authors.lastname: Bas
authors.forename: Grace Y
authors.initials: GY
authors.lastname: Gao
authors.forename: Anatoli
authors.initials: A
authors.lastname: Lvov
authors.forename: Kshama D
authors.initials: KD
authors.lastname: Chandrasekhar
authors.forename: Reid
authors.initials: R
authors.lastname: Gilmore
authors.forename: William R
authors.initials: WR
authors.lastname: Kobertz
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006031:Glycosylation; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology*
chemical_list: C489622:KCNE1 protein, human; D010455:Peptides; D024642:Potassium Channels, Voltage-Gated