Progesterone receptor membrane component 1 is a functional part of the glucagon-like peptide-1 (GLP-1) receptor complex in pancreatic β cells.
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.
Mesh Terms:
Adenylyl Cyclase Inhibitors, Animals, CHO Cells, Cell Line, Cricetinae, Cricetulus, Cyclic AMP, ErbB Receptors, Glucagon-Like Peptide 1, Glucagon-Like Peptide-1 Receptor, Guanine Nucleotide Exchange Factors, Humans, Insulin, Insulin Secretion, Insulin-Secreting Cells, Mass Spectrometry, Membrane Proteins, Mice, Phosphatidylinositol 3-Kinases, Rats, Receptors, Glucagon, Receptors, Progesterone, rab5 GTP-Binding Proteins
Adenylyl Cyclase Inhibitors, Animals, CHO Cells, Cell Line, Cricetinae, Cricetulus, Cyclic AMP, ErbB Receptors, Glucagon-Like Peptide 1, Glucagon-Like Peptide-1 Receptor, Guanine Nucleotide Exchange Factors, Humans, Insulin, Insulin Secretion, Insulin-Secreting Cells, Mass Spectrometry, Membrane Proteins, Mice, Phosphatidylinositol 3-Kinases, Rats, Receptors, Glucagon, Receptors, Progesterone, rab5 GTP-Binding Proteins
Mol. Cell Proteomics
Date: Nov. 01, 2014
PubMed ID: 25044020
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