Regulation of GPCR expression through an interaction with CCT7, a subunit of the CCT/TRiC complex.

ABSTRACT: Mechanisms that prevent aggregation and promote folding of nascent G protein-coupled receptors (GPCRs) remain poorly understood. We identified chaperonin containing TCP-1 subunit eta (CCT7) as an interacting partner of the ?-isoform of thromboxane A2 receptor (TP?) by yeast two-hybrid screening. CCT7 coimmunoprecipitated with overexpressed TP? and ?2-adrenergic receptor (?2AR) in HEK 293 cells, but also with endogenous ?2AR. CCT7 depletion by small interfering RNA reduced total and cell-surface expression of both receptors and caused redistribution of the receptors to juxtanuclear aggresomes, significantly more so for TP? than ?2AR. Interestingly, Hsp90 coimmunoprecipitated with ?2AR but virtually not with TP?, indicating that nascent GPCRs can adopt alternative folding pathways. In vitro pull-down assays showed that both receptors can interact directly with CCT7 through their third intracellular loops and C-termini. We demonstrate that Trp334 in the TP? C-terminus is critical for the CCT7 interaction and plays an important role in TP? maturation and cell-surface expression. Of note, introducing a tryptophan in the corresponding position of the TP? isoform confers the CCT7-binding and maturation properties of TP?. We show that an interaction with a subunit of the CCT/TCP-1 ring complex (TRiC) chaperonin complex is involved in regulating aggregation of nascent GPCRs and in promoting their proper maturation and expression.

SUBMITTER: Genier S 

PROVIDER: S-EPMC5170604 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature