Inhibition of phosducin‐like protein–catalyzed G protein βγ dimer assembly impedes the translation of nascent Gβ and Gγ polypeptides

Abstract

Phosducin‐like protein, a ubiquitously expressed member of the phosducin gene family, is a positive regulator of G protein signaling by virtue of its ability to help assemble Gβ and Gγ subunits. Our lab has shown that PhLP mediates the release of nascent Gβ from the cytosolic chaperonin CCT and the subsequent interaction of Gβ with Gγ. Further work on the mechanism of Gβγ assembly has uncovered an intriguing observation. When PhLP is inhibited by RNA interference or a dominant negative variant, not only is Gβγ assembly blocked but de novo synthesis of both Gβ and Gγ is also decreased significantly. This decrease is not a result of changes in the mRNA levels of Gβ and Gγ, nor is it a result of increased degradation of their nascent polypeptides. Thus, it must come from a decrease in translation. The effect is specific because there is no change in actin translation when PhLP is inhibited. We are currently investigating the mechanism by which PhLP controls Gβ and Gγ translation. It is possible that a feedback mechanism exists so that when Gβγ assembly is blocked, the synthesis of the two subunits is reduced to avoid producing unstable free Gβ and Gγ polypeptides.