Exploring G Protein-Coupled Receptor Signaling in Primary Pancreatic Islets

Doreen Thor,Robert Kraft,Torsten Schöneberg,Juliane Röthe

doi:10.1186/s12575-019-0116-y

Doreen Thor, Robert Kraft

Open Access

https://doi.org/10.1186/s12575-019-0116-y

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Abstract

BackgroundTargeting G protein-coupled receptors (GPCRs) in pancreatic cells is feasible to modulate glucose-induced insulin secretion. Because pancreatic islets consist of several cell types and GPCRs can couple to more than one G-protein family, results obtained in pancreatic cell lines do not always match the response in primary cells or intact islets. Therefore, we set out to establish a protocol to analyze second messenger activation in mouse pancreatic islets.ResultsActivation of Gq/11-coupled receptor expressed in primary β cells increased the second messenger IP1 in an accumulation assay. Applying a Gq/11 protein inhibitor completely abolished this signal. Activation of the V1 vasopressin and ghrelin receptors, predominantly expressed in the less abundant alpha and delta cells, was not sufficient to induce a significant IP1 increase in this assay. However, fura-2-based fluorescence imaging showed calcium signals upon application of arginine vasopressin or ghrelin within intact pancreatic islets. Using the here established protocol we were also able to determine changes in intracellular cAMP levels induced by receptors coupling to Gs and Gi/o proteins.ConclusionsDetection of the second messengers IP1, cAMP, and calcium, can be used to reliably analyze GPCR activation in intact islets.

Highlights

Targeting G protein-coupled receptors (GPCRs) in pancreatic cells is feasible to modulate glucoseinduced insulin secretion
Diabetes mellitus is a major metabolic disorder characterized by high glucose levels in the blood which can lead to secondary diseases
The main signal for secretion of insulin, glucagon, and somatostatin is the changing blood glucose level. It is well-established that secretion of all pancreatic islet hormones can be modified by intracellular cyclic AMP and calcium ion levels [3, 4]

Summary

Introduction

Targeting G protein-coupled receptors (GPCRs) in pancreatic cells is feasible to modulate glucoseinduced insulin secretion. Diabetes mellitus is a major metabolic disorder characterized by high glucose levels in the blood which can lead to secondary diseases. Type 2 diabetes (T2D), accounting for more than 90% of the patients [1], results from insulin resistance of peripheral tissues and impaired βcell function including altered hormone secretion [2]. The main signal for secretion of insulin, glucagon, and somatostatin is the changing blood glucose level. It is well-established that secretion of all pancreatic islet hormones can be modified by intracellular cyclic AMP (cAMP) and calcium ion levels [3, 4]. G protein-coupled receptors (GPCRs), a superfamily of transmembrane receptors, are the main modulators of these signal

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