G protein-dependent signaling triggers a β-arrestin-scaffolded p70S6K/ rpS6 module that controls 5′TOP mRNA translation

Many interaction partners of β-arrestins intervene in the control of mRNA translation. However, how β-arrestins regulate this cellular process has been poorly explored. In this study, we show that β-arrestins constitutively assemble a p70S6K/ribosomal protein S6 (rpS6) complex inHEK293 cells and in primary Sertoli cells of the testis.We demonstrate that this interaction is direct, and experimentally validate the interaction interface between β-arrestin 1 and p70S6K predicted by our docking algorithm. Like most GPCRs, the biological function of folliclestimulating hormone receptor (FSHR) is transduced by G proteins and β-arrestins. Upon follicle-stimulating hormone (FSH) stimulation, activation of G protein-dependent signaling enhances p70S6K activity within the β-arrestin/p70S6K/rpS6 preassembled complex, which is not recruited to the FSHR. In agreement, FSH-induced rpS6 phosphorylation within the β-arrestin scaffold was decreased in cells depleted of Gα_s. Integration of the cooperative action of β-arrestin and G proteins led to the translation of 59 oligopyrimidine track mRNA with high efficacy within minutes of FSH input. Hence, this work highlights new relationships between G proteins and β-arrestins when acting cooperatively on a common signaling pathway, contrasting with their previously shown parallel action on the ERKMAP kinase pathway. In addition, this study provides insights into howGPCR can exert trophic effects in the cell.