Probing cell type–specific functions of Gi in vivo identifies GPCR regulators of insulin secretion
Jean B. Regard, … , Matthias Hebrok, Shaun R. Coughlin
Jean B. Regard, … , Matthias Hebrok, Shaun R. Coughlin
Published November 8, 2007
Citation Information: J Clin Invest. 2007;117(12):4034-4043. https://doi.org/10.1172/JCI32994.
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Probing cell type–specific functions of Gi in vivo identifies GPCR regulators of insulin secretion

Abstract

The in vivo roles of the hundreds of mammalian G protein–coupled receptors (GPCRs) are incompletely understood. To explore these roles, we generated mice expressing the S1 subunit of pertussis toxin, a known inhibitor of Gi/o signaling, under the control of the ROSA26 locus in a Cre recombinase–dependent manner (ROSA26PTX). Crossing ROSA26PTX mice to mice expressing Cre in pancreatic β cells produced offspring with constitutive hyperinsulinemia, increased insulin secretion in response to glucose, and resistance to diet-induced hyperglycemia. This phenotype underscored the known importance of Gi/o and hence of GPCRs for regulating insulin secretion. Accordingly, we quantified mRNA for each of the approximately 373 nonodorant GPCRs in mouse to identify receptors highly expressed in islets and examined the role of several. We report that 3-iodothyronamine, a thyroid hormone metabolite, could negatively and positively regulate insulin secretion via the Gi-coupled α2A-adrenergic receptor and the Gs-coupled receptor Taar1, respectively, and protease-activated receptor–2 could negatively regulate insulin secretion and may contribute to physiological regulation of glucose metabolism. The ROSA26PTX system used in this study represents a new genetic tool to achieve tissue-specific signaling pathway modulation in vivo that can be applied to investigate the role of Gi/o-coupled GPCRs in multiple cell types and processes.

Authors

Jean B. Regard, Hiroshi Kataoka, David A. Cano, Eric Camerer, Liya Yin, Yao-Wu Zheng, Thomas S. Scanlan, Matthias Hebrok, Shaun R. Coughlin

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Figure 4

GPCR expression in isolated mouse pancreatic islets.

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GPCR expression in isolated mouse pancreatic islets. (A) RNA from freshl...
(A) RNA from freshly isolated mouse pancreatic islets was reversed transcribed and subjected to qRT-PCR analysis for each of 373 nonodorant GPCRs annotated in the mouse genome. Abundance of each GPCR mRNA relative to 3 internal controls (β-actin, cyclophilin, GAPDH) in islets [Abundance (ΔCt)] and abundance of each GPCR in islets relative to abundance in a mixed tissue pool [Enrichment (2ΔΔCt)] are shown. Open squares indicate receptors known to be physiologically important regulators of insulin secretion. (B) Identity of the 28 receptors most highly expressed and enriched in islets as demarcated by the dashed line in A (see also Table 1). Open squares indicate GPCRs known to be important regulators of insulin secretion; filled triangles indicate GPCRs with ligands that have been implicated in regulating insulin secretion without identification of the precise receptor or the physiologic importance; filled squares indicate orphan receptors; open circles indicate GPCRs with known ligands not previously implicated in the regulation of islet function. These data represent the average of 5 independent experiments.