PT  - JOURNAL ARTICLE
AU  - Richard L. Hauger
AU  - J. Alberto Olivares-Reyes
AU  - Sandra Braun
AU  - Kevin J. Catt
AU  - Frank M. Dautzenberg
TI  - Mediation of Corticotropin Releasing Factor Type 1 Receptor Phosphorylation and Desensitization by Protein Kinase C: A Possible Role in Stress Adaptation
AID  - 10.1124/jpet.103.050088
DP  - 2003 Aug 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 794--803
VI  - 306
IP  - 2
4099  - http://jpet.aspetjournals.org/content/306/2/794.short
4100  - http://jpet.aspetjournals.org/content/306/2/794.full
SO  - J Pharmacol Exp Ther2003 Aug 01; 306
AB  - Protein kinase C (PKC)-mediated desensitization of the corticotropin releasing factor type 1 (CRF1) receptor was investigated in human retinoblastoma Y79 and transfected COS-7 cells. Because stimulation of Y79 cells with CRF resulted in large (∼30-fold) increases in intracellular cAMP accumulation without changing inositol phosphate levels, the CRF1 receptor expressed in retinoblastoma cells couples to Gs, but not to Gq, and predominantly signals via the protein kinase A cascade. Direct activation of PKC by treatment with the phorbol ester phorbol 12-myristate 13-acetate (PMA) or 1,2-dioctanoyl-sn-glycerol (DOG) desensitized CRF1 receptors in Y79 cells, reducing the maximum for CRF- (but not forskolin)-stimulated cAMP accumulation by 56.3 ± 1.2% and 40.4 ± 2.1%, respectively (p < 0.001). Pretreating Y79 cells with the PKC inhibitor bisindolylmaleimide I (BIM) markedly inhibited PMA's desensitizing action on CRF-stimulated cAMP accumulation, but did not affect homologous CRF1 receptor desensitization. Retinoblastoma cells were found to express PKCα, βI, βII, δ, λ, and RACK1. When α and β isoforms of PKC were down-regulated 80 to 90% by a 48-h PMA exposure, PMA-induced CRF1 receptor desensitization was abolished. In transfected COS-7 cells the magnitude of CRF1 receptor phosphorylation after a 5-min exposure to PMA was 2.32 ± 0.21-fold greater compared with the basal level. Pretreating COS-7 cells with BIM abolished PMA-induced CRF1 receptor phosphorylation. These studies demonstrate that protein kinase C (possibly α and β isoforms) has an important role in the phosphorylation and heterologous desensitization of the CRF1 receptor. The American Society for Pharmacology and Experimental Therapeutics