Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 281, Issue 42, Pages 31940-31949Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M602832200
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Clathrin is a major component of clathrin-coated pits and serves as a binding scaffold for endocytic machinery through the binding of a specific sequence known as the clathrin-binding motif. This motif is also found in cellular signaling proteins other than endocytic components, including G protein-coupled receptor kinase 2 (GRK2), which phosphorylates G protein-coupled receptors and promotes uncoupling of receptor-G protein interaction. However, the functions of clathrin in the regulation of GRK2 are unknown. Here we demonstrated that overexpression of GRK2 mutated at the clathrin-binding motif with alanine (GRK2-5A) results in inhibition of phosphorylation and internalization of the beta(2)-adrenergic receptor (beta(2)AR). However, the interaction of beta(2)AR with GRK2-5A is the same as that of wild type GRK2 as determined by bioluminescence resonance energy transfer. Furthermore, GRK2-5A phosphorylates rhodopsin essentially to the same extent as wild type GRK2 in vitro. Depletion of the clathrin heavy chain using small interference RNA inhibits agonist-induced phosphorylation and internalization of beta(2)AR. Thus, clathrin works as a regulator of GRK2 in cells. These results indicate that clathrin is a novel player in cellular functions in addition to being a component of endocytosis.
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