alpha-Actinin is a potent regulator of G protein-coupled receptor kinase activity and substrate specificity in vitro.
G protein-coupled receptor kinases (GRKs) phosphorylate G protein-coupled receptors, thereby terminating receptor signaling. Herein we report that alpha-actinin potently inhibits all GRK family members. In addition, calcium-bound calmodulin and phosphatidylinositol 4,5-bisphosphate (PIP2), two regulators of GRK activity, coordinate with alpha-actinin to modulate substrate specificity of the GRKs. In the presence of calmodulin and alpha-actinin, GRK5 phosphorylates soluble, but not membrane-incorporated substrates. In contrast, in the presence of PIP2 and alpha-actinin, GRK5 phosphorylates membrane-incorporated, but not soluble substrates. Thus, modulation of alpha-actinin-mediated inhibition of GRKs by PIP2 and calmodulin has profound effects on both GRK activity and substrate specificity.
Freeman
J L
JL
Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA.
Pitcher
J A
JA
Li
X
X
Bennett
V
V
Lefkowitz
R J
RJ
D000185:Actinin / Q000378:metabolism*; D058672:Adrenergic beta-2 Receptor Antagonists; D000818:Animals; D002147:Calmodulin / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D002645:Chickens; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054774:G-Protein-Coupled Receptor Kinase 5; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism; D013379:Substrate Specificity; D051552:beta-Adrenergic Receptor Kinases
D058672:Adrenergic beta-2 Receptor Antagonists; D002147:Calmodulin; D002364:Caseins; D019269:Phosphatidylinositol 4,5-Diphosphate; D000185:Actinin; D012243:Rhodopsin; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D054774:G-Protein-Coupled Receptor Kinase 5