GRK3 mediates desensitization of CRF1 receptors: a potential mechanism regulating stress adaptation

1 Pharma Division, Preclinical Research, F-Hoffmann-La Roche Ltd., CH-4070 Basel, Switzerland; 2 Department of Molecular Neuroendocrinology, Max-Planck-Institute for Experimental Medicine, 37075 Goettingen, Germany; and 3 Veterans Affairs Medical Center and Department of Psychiatry, University of California, San Diego, La Jolla, California 92093-0603 Potential G protein-coupled receptor kinase (GRK) and protein kinase A (PKA) mediation of homologous desensitization of corticotropin-releasing factor type 1 (CRF 1 ) receptors was investigated in human retinoblastoma Y-79 cells. Inhibition of PKA activity by PKI 5-22 or H-89 failed to attenuate homologous desensitization of CRF 1 receptors, and direct activation of PKA by forskolin or dibutyryl cAMP failed to desensitize CRF-induced cAMP accumulation. However, treatment of permeabilized Y-79 cells with heparin, a nonselective GRK inhibitor, reduced homologous desensitization of CRF 1 receptors by ~35%. Furthermore, Y-79 cell uptake of a GRK3 antisense oligonucleotide (ODN), but not of a random or mismatched ODN, reduced GRK3 mRNA expression by ~50% without altering GRK2 mRNA expression and inhibited homologous desensitization of CRF 1 receptors by ~55%. Finally, Y-79 cells transfected with a GRK3 antisense cDNA construct exhibited an ~50% reduction in GRK3 protein expression and an ~65% reduction in homologous desensitization of CRF 1 receptors. We conclude that GRK3 contributes importantly to the homologous desensitization of CRF 1 receptors in Y-79 cells, a brain-derived cell line. antisense; G protein-coupled receptor kinase; corticotropin-releasing factor type 1 receptor regulation; homologous and heterologous desensitization of the CRF 1 receptor