A P-loop Mutation in Gα Subunits Prevents Transition to the Active State: Implications for G-protein Signaling in Fungal Pathogenesis
Figure 5
Gαq G48R is not constitutively active in a cellular context.
The analogous P-loop mutation in human Gαq, G48R, did not yield constitutive activity in contrast to the GTPase-deficient Gαq(Q209L) (A,B). Transfection of increasing amounts of Gαq(Q209L) markedly stimulated phospholipase C (PLC) activity in COS-7 cells, indicated by increased inositol phosphates (IPx) accumulation. Like wild type Gαq, G48R overexpression did not alter PLC activity. (C,D) Endogenous and overexpressed KT3 epitope-tagged wild type Gαq stimulated PLC activity upon treatment with AlF4−. The response of cells expressing Gαq(G42R) was blunted relative to wild type Gαq.