N-glycosylation-dependent control of functional expression of background potassium channels K2P3.1 and K2P9.1

Abstract

Two-pore domain potassium (K2P) channels play fundamental roles in cellular processes by enabling a constitutive leak of potassium from cells in which they are expressed, thus influencing cellular membrane potential and activity. Hence, regulation of these channels is of critical importance to cellular function. A key regulatory mechanism of K2Pchannels is the control of their cell surface expression. Membrane protein delivery to and retrieval from the cell surface is controlled by their passage through the secretory and endocytic pathways, and post-translational modifications regulate their progression through these pathways. All but one of the K 2Pchannels possess consensus N-linked glycosylation sites, and here we demonstrate that the conserved putative N-glycosylation site in K 2P3.1 and K2P9.1 isa glycan acceptor site. Patch clamp analysis revealed that disruption of channel glycosylation reduced K 2P3.1 current, and flow cytometry was instrumental in attributing this to a decreased number of channels on the cell surface. Similar findings were observed when cells were cultured in reduced glucose concentrations. Disruption of N-linked glycosylation has less of an effect on K2P9.1, with a small reduction in number of channels on the surface observed, but no functional implications detected. Because nonglycosylated channels appear to pass through the secretory pathway in a manner comparable with glycosylated channels, theevidence presented here suggests that the decreased number of nonglycosylated K2P3.1 channels on the cell surface may be due to their decreased stability. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.