G protein-coupled receptor kinase 2 and β-arrestins are recruited to FSH receptor in stimulated rat primary Sertoli cells

Abstract

FSH-receptor (FSH-R) signaling is regulated by agonist-induced desensitization and internalization. It has been shown, in a variety of overexpression systems, that G protein-coupled receptor kinases (GRKs) phosphorylate the activated FSH-R, promote β-arrestin recruitment and ultimately lead to internalization. The accuracy of this mechanism has not yet been demonstrated in cells expressing these different molecules at physiological levels. Using sucrose gradient fractionation, we show that FSH induces the recruitment of the endogenous GRK 2 and β-arrestin 1/2 from the cytoplasm to the plasma membrane of rat primary Sertoli cells. As assessed by ligand binding, the FSH-R was found expressed in the fractions where GRK 2 and β-arrestins were recruited upon FSH treatment. In addition, the endogenous β-arrestin 1 was found dephosphorylated in an agonist-dependent manner. Finally, a significant FSH-binding activity was co-immunoprecipitated with the endogenous β-arrestins from agonist-stimulated but not from untreated Sertoli cell extracts. This FSH-R interaction with β-arrestins was sustained for up to 30 min. In conclusion, our data strongly suggest that the GRK/β-arrestin machinery plays a physiologically relevant role in the regulation of the FSH signaling.