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

Potential G protein-coupled receptor kinase (GRK) and protein kinase A (PKA ) mediation of homologous desensitization of corticotropin-releasing factor type 1 (CRF1) receptors was investigated in human retinoblastoma Y-79 cell s. Inhibition of PKA activity by PKI5-22 or H-89 failed to attenuate homolo gous desensitization of CRF1 receptors, and direct activation of PKA by for skolin or dibutyryl cAMP failed to desensitize CRF-induced cAMP accumulatio n. However, treatment of permeabilized Y-79 cells with heparin, a nonselect ive GRK inhibitor, reduced homologous desensitization of CRF1 receptors by similar to 35%. Furthermore, Y-79 cell uptake of a GRK3 antisense oligonucl eotide (ODN), but not of a random or mismatched ODN, reduced GRK3 mRNA expr ession by similar to 50% without altering GRK2 mRNA expression and inhibite d homologous desensitization of CRF1 receptors by similar to 55%. Finally, Y-79 cells transfected with a GRK3 antisense cDNA construct exhibited an si milar to 50% reduction in GRK3 protein expression and an similar to 65% red uction in homologous desensitization of CRF1 receptors. We conclude that GR K3 contributes importantly to the homologous desensitization of CRF1 recept ors in Y-79 cells, a brain-derived cell line.