Substrate specificities of g protein-coupled receptor kinase-2 and -3 at cardiac myocyte receptors provide basis for distinct roles in regulation of myocardial function.
The closely related G protein-coupled receptor kinases GRK2 and GRK3 are both expressed in cardiac myocytes. Although GRK2 has been extensively investigated in terms of regulation of cardiac beta-adrenergic receptors, the substrate specificities of the two GRK isoforms at G protein-coupled receptors (GPCR) are poorly understood. In this study, the substrate specificities of GRK2 and GRK3 at GPCRs that control cardiac myocyte function were determined in fully differentiated adult cardiac myocytes. Concentration-effect relationships of GRK2, GRK3, and their respective competitive inhibitors, GRK2ct and GRK3ct, at endogenous endothelin, alpha(1)-adrenergic, and beta(1)-adrenergic receptor-generated responses in cardiac myocytes were achieved by adenovirus gene transduction. GRK3 and GRK3ct were highly potent and efficient at the endothelin receptors (IC(50) for GRK3, 5 +/- 0.7 pmol/mg of protein; EC(50) for GRK3ct, 2 +/- 0.2 pmol/mg of protein). The alpha(1)-adrenergic receptor was also a preferred substrate of GRK3 (IC(50),7 +/- 0.4 pmol/mg of protein). GRK2 lacked efficacy at both endothelin and alpha(1)-adrenergic receptors despite massive overexpression. On the contrary, both GRK2ct and GRK3ct enhanced beta(1)-adrenergic receptor-induced cAMP production with comparable potencies. However, the potency of GRK3ct at beta(1)-adrenergic receptors was at least 20-fold lower than that at endothelin receptors. In conclusion, this study demonstrates distinct substrate specificities of GRK2 and GRK3 at different GPCRs in fully differentiated adult cardiac myocytes. As inferred from the above findings, GRK2 may play its primary role in regulation of cardiac contractility and chronotropy by controlling beta(1)-adrenergic receptors, whereas GRK3 may play important roles in regulation of cardiac growth and hypertrophy by selectively controlling endothelin and alpha(1)-adrenergic receptors.
Vinge
Leif Erik
LE
Institute for Surgical Research, Rikshospitalet-Radiumhospitalet Medical Center, University of Oslo, Oslo, Norway.
Andressen
Kjetil W
KW
Attramadal
Toril
T
Andersen
Geir Øystein
GØ
Ahmed
Mohammed Shakil
MS
Peppel
Karsten
K
Koch
Walter J
WJ
Freedman
Neil J
NJ
Levy
Finn Olav
FO
Skomedal
Tor
T
Osnes
Jan-Bjørn
JB
Attramadal
Håvard
H
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D054769:G-Protein-Coupled Receptor Kinase 2; D054770:G-Protein-Coupled Receptor Kinase 3; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000201:enzymology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism; D018342:Receptors, Adrenergic, beta-1 / Q000235:genetics / Q000378:metabolism*; D017466:Receptors, Endothelin / Q000378:metabolism; D013379:Substrate Specificity; D014161:Transduction, Genetic; D051552:beta-Adrenergic Receptor Kinases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
D007527:Isoenzymes; D018340:Receptors, Adrenergic, alpha-1; D018342:Receptors, Adrenergic, beta-1; D017466:Receptors, Endothelin; D054770:G-Protein-Coupled Receptor Kinase 3; C496569:Grk2 protein, rat; C517851:Grk3 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2