Xenopus laevis oocytes showed no electrophysiological responses to acetylcholine (ACh) and had no significant cholinergic receptor sites when prepared under our conditions. However, they were found to acquire robust electrophysiological responsiveness to ACh when bovine G(L2)α which is a member of the G(q)α family and is highly homologous to mouse G11α, was expressed by mRNA injection. Further analyses indicated that G(L2)α amplified the activity of endogenous muscarinic ACh receptors that are expressed at an otherwise undetectable level, and thus made their detection possible. Thus, G(L2)α may prove to be an effective method for detecting the activities of phospholipase C-linked receptors which are only marginally expressed. The usefulness of this method was confirmed in the analyses of a chimeric receptor constructed from metabotropic glutamate receptor subtype la and muscarinic ACh receptor subtype M1. The chimeric receptor showed no electrophysiological responses to ACh when expressed alone in oocytes, but became responsive to ACh when co-expressed with G(L2)α.
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