title: The identification of novel proteins that interact with the GLP-1 receptor and restrain its activity.
abstract: Glucagon-like peptide 1 receptor (GLP-1R) controls diverse physiological functions in tissues including the pancreatic islets, brain, and heart. To understand the mechanisms that control glucagon-like peptide 1 (GLP-1) signaling better, we sought to identify proteins that interact with the GLP-1R using a membrane-based split ubiquitin yeast two-hybrid (MYTH) assay. A screen of a human fetal brain cDNA prey library with an unliganded human GLP-1R as bait in yeast revealed 38 novel interactor protein candidates. These interactions were confirmed in mammalian Chinese hamster ovarian cells by coimmunoprecipitation. Immunofluorescence was used to show subcellular colocalization of the interactors with GLP-1R. Cluster analysis revealed that the interactors were primarily associated with signal transduction, metabolism, and cell development. When coexpressed with the GLP-1R in Chinese hamster ovarian cells, 15 interactors significantly altered GLP-1-induced cAMP accumulation. Surprisingly, all 15 proteins inhibited GLP-1-activated cAMP. Given GLP-1's prominent role as an incretin, we then focused on 3 novel interactors, SLC15A4, APLP1, and AP2M1, because they are highly expressed and localized to the membrane in mouse insulinoma β-cells. Small interfering RNA-mediated knockdown of each candidate gene significantly enhanced GLP-1-induced insulin secretion. In conclusion, we have generated a novel GLP-1R-protein interactome, identifying several interactors that suppress GLP-1R signaling. We suggest that the inhibition of these interactors may serve as a novel strategy to enhance GLP-1R activity.
authors.affiliation: Department of Physiology and Medicine, Medical Sciences Building, 1 King's College Circle, University of Toronto, Ontario, Canada M5S 1A8.
authors.forename: X
authors.initials: X
authors.lastname: Huang
authors.forename: F F
authors.initials: FF
authors.lastname: Dai
authors.forename: G
authors.initials: G
authors.lastname: Gaisano
authors.forename: K
authors.initials: K
authors.lastname: Giglou
authors.forename: J
authors.initials: J
authors.lastname: Han
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: S
authors.initials: S
authors.lastname: Kittanakom
authors.forename: V
authors.initials: V
authors.lastname: Wong
authors.forename: L
authors.initials: L
authors.lastname: Wei
authors.forename: A D
authors.initials: AD
authors.lastname: Showalter
authors.forename: K W
authors.initials: KW
authors.lastname: Sloop
authors.forename: I
authors.initials: I
authors.lastname: Stagljar
authors.forename: M B
authors.initials: MB
authors.lastname: Wheeler
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000494:pharmacology; D000067757:Glucagon-Like Peptide-1 Receptor; D057809:HEK293 Cells; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D060066:Protein Interaction Maps / Q000187:drug effects; D018027:Receptors, Glucagon / Q000378:metabolism*; D015203:Reproducibility of Results; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism
chemical_list: C000593833:GLP1R protein, human; C000593834:Glp1r protein, mouse; D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin; D018027:Receptors, Glucagon; D025801:Ubiquitin; D052216:Glucagon-Like Peptide 1; D000242:Cyclic AMP