| Summary: | G-protein coupled receptors (GPCRs) have been shown to interact with an array of accessory proteins that modulate their function. I hypothesize that the GLP-1R, a B-class GPCR, similarly has interacting proteins that regulate its signaling. An unliganded human GLP-1R was screened using a membrane-based split ubiquitin yeast two-hybrid (MYTH) assay and a human fetal brain cDNA prey library to reveal 38 novel interactor proteins. These interactions were confirmed by co-immunoprecipitation and immunofluorescence. When co-expressed with the GLP-1R in cell lines, 15 interactors significantly attenuated GLP-1-induced cAMP accumulation. Interestingly, SiRNA-mediated knock down of three selected novel interactors, SLC15A4, APLP1 and AP2M1, significantly enhanced GLP-1-stimulated insulin secretion from the MIN6 beta cells. In conclusion, this present work generated a novel GLP-1R-protein interactome, identifying several interactors that suppress GLP-1R signaling; and the inhibition of these interactors may serve as a novel strategy to enhance GLP-1R activity.
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