Involvement of G protein-coupled receptor kinases and arrestins in desensitization to follicle-stimulating hormone action

FSH rapidly desensitizes the FSH-receptor (FSH-R) upon binding. Very little information is available concerning the regulatory proteins involved in th is process. In the present study, we investigated whether G protein-coupled receptor kinases (GRKs) and arrestins have a role in FSH-R desensitization , using a mouse Ltk 7/12 cell line stably overexpressing the rat FSH-R as a model. We found that these cells, which express GRK2, GRK3, GRK5, and GRK6 as well as beta-arrestins 1 and 2 as detected by RT-PCR and by Western blo tting, were rapidly desensitized in the presence of FSH. Overexpression of GRKs and/or beta-arrestins in Ltk 7/12 cells allowed us to demonstrate 1) t hat GRK2, -3, -5, -6a, and -6b inhibit the FSH-R-mediated signaling (from 7 1% to 96% of maximal inhibition depending on the kinase, P < 0.001); 2) tha t beta-arrestins 1 or 2 also decrease the FSH action when overexpressed (80 % of maximal inhibition, P < 0.01) whereas dominant negative beta-arrestin 2 [319-418] potentiates it 8-fold (P < 0.001); 3) that beta-arrestins and G RKs (except GRK6a) exert additive inhibition on FSH-induced response; and 4 ) that FSH-R desensitization depends upon the endogenous expression of GRKs , since there is potentiation of the FSH response (2- to 3-fold, P < 0.05) with antisenses cDNAs for GRK2, -5, and -6, but not GRK3. Our results show that the desensitization of the FSH-induced response involves the GRK/arres tin system.