Phosphatidylinositol 4,5-bisphosphate (PIP2)-enhanced G protein-coupled receptor kinase (GRK) activity. Location, structure, and regulation of the PIP2 binding site distinguishes the GRK subfamilies.
The G protein-coupled receptor kinases (GRKs) phosphorylate agonist occupied G protein-coupled receptors and play an important role in mediating receptor desensitization. The localization of these enzymes to their membrane incorporated substrates is required for their efficient function and appears to be a highly regulated process. In this study we demonstrate that phosphatidylinositol 4, 5-bisphosphate (PIP2) enhances GRK5-mediated beta-adrenergic receptor (betaAR) phosphorylation by directly interacting with this enzyme and facilitating its membrane association. GRK5-mediated phosphorylation of a soluble peptide substrate is unaffected by PIP2, suggesting that the PIP2-enhanced receptor kinase activity arises as a consequence of this membrane localization. The lipid binding site of GRK5 exhibits a high degree of specificity and appears to reside in the amino terminus of this enzyme. Mutation of six basic residues at positions 22, 23, 24, 26, 28, and 29 of GRK5 ablates the ability of this kinase to bind PIP2. This region of the GRK5, which has a similar distribution of basic amino acids to the PIP2 binding site of gelsolin, is highly conserved between members of the GRK4 subfamily (GRK4, GRK5, and GRK6). Indeed, all the members of the GRK4 subfamily exhibit PIP2-dependent receptor kinase activity. We have shown previously that the membrane association of betaARK (beta-adrenergic receptor kinase) (GRK2) is mediated, in vitro, by the simultaneous binding of PIP2 and the betagamma subunits of heterotrimeric G proteins to the carboxyl-terminal pleckstrin homology domain of this enzyme (Pitcher, J. A., Touhara, K., Payne, E. S., and Lefkowitz, R. J. (1995) J. Biol. Chem. 270, 11707-11710). Thus, five members of the GRK family bind PIP2, betaARK (GRK2), betaARK2 (GRK3), GRK4, GRK5, and GRK6. However, the structure, location, and regulation of the PIP2 binding site distinguishes the betaARK (GRK2 and GRK3) and GRK4 (GRK4, GRK5, and GRK6) subfamilies.
Pitcher
J A
JA
Departments of Medicine and Biochemistry, Howard Hughes Medical Research Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
Fredericks
Z L
ZL
Stone
W C
WC
Premont
R T
RT
Stoffel
R H
RH
Koch
W J
WJ
Lefkowitz
R J
RJ
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D054774:G-Protein-Coupled Receptor Kinase 5; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D018411:Spodoptera; D051552:beta-Adrenergic Receptor Kinases
D019269:Phosphatidylinositol 4,5-Diphosphate; D011943:Receptors, Adrenergic, beta; D011994:Recombinant Proteins; D020794:Receptor Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D054774:G-Protein-Coupled Receptor Kinase 5; D019204:GTP-Binding Proteins