Expression of GIRK (Kir3.1/Kir3.4) channels in mouse fibroblast cells with and without β1 integrins

G protein-activated K+ channel (GIRK) subunits possess a conserved extracellular integrin-binding motif (RGD) and bind directly to beta 1 integrins, We expressed GIRK1/GIRK4 channels labeled with green fluorescent protein in fibroblast cell lines expressing or lacking beta 1 integrins, Neither plasma membrane localization nor agonist-evoked GIRK currents were affected by the absence of beta 1 integrins or by incubation with externally applied RGD-containing peptide. Mutation of the aspartate (D) of RGD impaired currents, GIRK glycosylation, and membrane localization, but the interaction with beta 1 integrins remained intact. Thus, beta 1 integrins are not essential for functional GIRK expression; and the GIRK-integrin interactions involve structural elements other than the RGD motif. (C) 2000 Federation of European Biochemical Societies.