chemical-genetic approach to study G protein regulation of β cell function in vivo

• Published in: Proceedings of the National Academy of Sciences - PNAS 2009-11, Vol.106 (45), p.19197-19202
• Main Authors: Guettier, Jean-Marc, Gautam, Dinesh, Scarselli, Marco, de Azua, Inigo Ruiz, Li, Jian Hua, Rosemond, Erica, Ma, Xiaochao, Gonzalez, Frank J, Armbruster, Blaine N, Lu, Huiyan, Roth, Bryan L, Wess, Jürgen
• Format: Article
• Language: English
• Subjects: Animals; Beta cells; Biological Sciences; Blood glucose; Cercopithecus aethiops; Clozapine - analogs & derivatives; Clozapine - pharmacology; COS Cells; Diabetes Mellitus, Type 2 - metabolism; Female; Gene Expression Regulation - drug effects; Gene Expression Regulation - physiology; Glucose tolerance; Glucose Tolerance Test; GTP-Binding Proteins - metabolism; Insulin; Insulin - metabolism; Insulin Secretion; Insulin-Secreting Cells - metabolism; Islet cells; Islets of Langerhans - anatomy & histology; Islets of Langerhans - metabolism; Mice; Mice, Transgenic; Pancreatic cells; Radioligand Assay; Receptors; Receptors, G-Protein-Coupled - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction - drug effects; Signal Transduction - physiology; Transgenic animals; Type 2 diabetes mellitus
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0906593106

Impaired functioning of pancreatic β cells is a key hallmark of type 2 diabetes. β cell function is modulated by the actions of different classes of heterotrimeric G proteins. The functional consequences of activating specific β cell G protein signaling pathways in vivo are not well understood at present, primarily due to the fact that β cell G protein-coupled receptors (GPCRs) are also expressed by many other tissues. To circumvent these difficulties, we developed a chemical-genetic approach that allows for the conditional and selective activation of specific β cell G proteins in intact animals. Specifically, we created two lines of transgenic mice each of which expressed a specific designer GPCR in β cells only. Importantly, the two designer receptors differed in their G protein-coupling properties (Gq/₁₁ versus Gs). They were unable to bind endogenous ligand(s), but could be efficiently activated by an otherwise pharmacologically inert compound (clozapine-N-oxide), leading to the conditional activation of either β cell Gq/₁₁ or Gs G proteins. Here we report the findings that conditional and selective activation of β cell Gq/₁₁ signaling in vivo leads to striking increases in both first- and second-phase insulin release, greatly improved glucose tolerance in obese, insulin-resistant mice, and elevated β cell mass, associated with pathway-specific alterations in islet gene expression levels. Selective stimulation of β cell Gs triggered qualitatively similar in vivo metabolic effects. Thus, this developed chemical-genetic strategy represents a powerful approach to study G protein regulation of β cell function in vivo.