Dominant negative effects of a Gβ mutant on G-protein coupled inward rectifier K+ channel

HEK293 cells were transfected with cDNAs for Gβ1(W332A) [a mutant Gβ1], Gγ2, and inward rectifier K+ channels (Kir3.1/Kir3.2). Application of Gβ1γ2 protein to these cells activated the K+ channels only slightly. When mu-opioid receptors and Kir3.1/Kir3.2 were transfected, application of a mu-opioid agonist induced a Kir3 current. However, co-expression of Gβ1(W332A) suppressed this current. Most likely, Gβ1(W332A) inhibited the action of the endogenous Gβ. Such a dominant negative effect of Gβ1(W332A) was also observed in neuronal Kir3 channels in locus coeruleus. The mutant, Gβ1(W332A) protein, although inactive, retains its ability to bind Kir3 and prevents the wild type Gβ from activating the channel.