Partially purified and reconstituted g-protein coupled receptors as substrates of specific receptor kinases
Most members of the G-protein-coupled receptor (GPCR) superfamily, which includes several hundred receptors, exhibit agonist-induced desensitization. Studies with rhodopsin and β2-adrenergic receptors indicate that a key biochemical event underlying the process of receptor desensitization is the stimulus-dependent phosphorylation of the receptor catalyzed by a family of specific receptor kinases (GRKs). That this paradigm of receptor desensitization may also apply to other GPCRs is indicated by recent findings that M2-muscarinic acetylcholine, α2-adrenergic, and substance P receptors also undergo stimulus-dependent phosphorylation by GRKs. Whether other GPCRs are regulated by GRKs remains to be evaluated. However, progress toward this goal has been slow, as demonstration of receptor phosphorylation has required substantially purified receptors and methods for purifying most GPCRs do not exist. To circumvent this problem, we have developed a general method for the partial purification and reconstitution of GPCRs expressed in Sf9 cells and find that these receptor preparations are suitable as substrates of various GRKs. Using this approach, we describe the agonist-dependent phosphorylation of human β2-AR and rat substance P receptors by GRKs. Furthermore, we show that partially purified and reconstituted GPCRs are also suitable for studying receptor/G-protein interactions. © 1994 Academic Press. All rights reserved.
Kwatra, MM; Lefkowitz, RJ; Caron, MG
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