Referenced in: none

Automatically associated channels: Kir2.1 , Kir3.1 , Slo1

Title: Functional expression of an epitope-tagged G protein-coupled K+ channel (GIRK1).

Authors: L H Philipson, A Kuznetsov, P T Tóth, J F Murphy, G Szabó, G H Ma, R J Miller

Journal, date & volume: J. Biol. Chem., 1995 Jun 16 , 270, 14604-10

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/7540174

Abstract
An epitope-tagged form of an inwardly rectifying and G protein-coupled K+ channel (GIRK1-cp) was expressed at high levels in transfected mammalian cells. Immunoblot analysis of transfected human embryonic kidney cells (HEK293) and mouse insulinoma cells (beta TC3) revealed several GIRK1-cp polypeptides, including the major 59-kDa band, corresponding to the predicted mass of the GIRK1 polypeptide plus the epitope tag. Immunohistochemical staining using two anti-tag antibodies showed abundant immunoreactive material, which was predominantly concentrated in the perinuclear area in both transfected cell types. While functional GIRK1-cp message was present in poly(A)+ RNA prepared from HEK293 cells expressing GIRK1-cp protein, appropriate K+ currents could not be detected. In contrast, whole cell recordings made directly from transfected beta TC3 cells expressing GIRK1-cp revealed inwardly rectifying, pertussis toxin-sensitive currents activated by norepinephrine and galanin. Single channel recordings in excised patches of beta TC3 cells expressing GIRK1-cp showed rectifying K+ currents when activated by 50 microM guanosine 5'-O-(thiotriphosphate), with a slope conductance of 39.1 +/- 1.0 picosiemens. This is the first report of stable heterologous expression of a functional G protein-coupled K+ channel in mammalian cells. The activity of an epitope-tagged channel in insulinoma cells demonstrates the utility of this system for further biochemical and biophysical analyses of G protein-K+ channel interactions.