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Mol Cell Proteomics. 2014 Nov;13(11):3049-62. doi: 10.1074/mcp.M114.040196. Epub 2014 Jul 20.

Progesterone receptor membrane component 1 is a functional part of the glucagon-like peptide-1 (GLP-1) receptor complex in pancreatic β cells.

Author information

1
From the ‡Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Canada, M5S 1A8; §Division of Advanced Diagnosis, Toronto General Research Institute, Toronto, Canada, M5G 1C7;
2
¶Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, and Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto, Canada, M5S 3M2;
3
‖Endocrine Discovery, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, 46285;
4
From the ‡Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Canada, M5S 1A8;
5
‖‖Quantitative Biology, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, 46285;
6
**Department of Endocrinology and Metabolism, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai, China 200233;
7
‡‡Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Canada, M5S 1A8.
8
From the ‡Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Canada, M5S 1A8; michael.wheeler@utoronto.ca f.dai@utoronto.ca.
9
From the ‡Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Canada, M5S 1A8; §Division of Advanced Diagnosis, Toronto General Research Institute, Toronto, Canada, M5G 1C7; michael.wheeler@utoronto.ca f.dai@utoronto.ca.

Abstract

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that regulates glucose homeostasis. Because of their direct stimulation of insulin secretion from pancreatic β cells, GLP-1 receptor (GLP-1R) agonists are now important therapeutic options for the treatment of type 2 diabetes. To better understand the mechanisms that control the insulinotropic actions of GLP-1, affinity purification and mass spectrometry (AP-MS) were employed to uncover potential proteins that functionally interact with the GLP-1R. AP-MS performed on Chinese hamster ovary cells or MIN6 β cells, both expressing the human GLP-1R, revealed 99 proteins potentially associated with the GLP-1R. Three novel GLP-1R interactors (PGRMC1, Rab5b, and Rab5c) were further validated through co-immunoprecipitation/immunoblotting, fluorescence resonance energy transfer, and immunofluorescence. Functional studies revealed that overexpression of PGRMC1, a novel cell surface receptor that associated with liganded GLP-1R, enhanced GLP-1-induced insulin secretion (GIIS) with the most robust effect. Knockdown of PGRMC1 in β cells decreased GIIS, indicative of positive interaction with GLP-1R. To gain insight mechanistically, we demonstrated that the cell surface PGRMC1 ligand P4-BSA increased GIIS, whereas its antagonist AG-205 decreased GIIS. It was then found that PGRMC1 increased GLP-1-induced cAMP accumulation. PGRMC1 activation and GIIS induced by P4-BSA could be blocked by inhibition of adenylyl cyclase/EPAC signaling or the EGF receptor-PI3K signal transduction pathway. These data reveal a dual mechanism for PGRMC1-increased GIIS mediated through cAMP and EGF receptor signaling. In conclusion, we identified several novel GLP-1R interacting proteins. PGRMC1 expressed on the cell surface of β cells was shown to interact with the activated GLP-1R to enhance the insulinotropic actions of GLP-1.

PMID:
25044020
PMCID:
PMC4223491
DOI:
10.1074/mcp.M114.040196
[Indexed for MEDLINE]
Free PMC Article

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