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Decreased insulin content and secretion in RIN 1046-38 cells overexpressing alpha 2-adrenergic receptors
M S Rodriguez-Pena1, R Collins, C Woodard
1Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
Several Gi-protein-coupled receptors normally expressed in islet beta-cells inhibit insulin secretion on binding of their respective agonists. To study the effect of supraphysiologic expression of such a receptor in insulin-secreting beta-cells, we stably transfected cDNA encoding the mouse alpha 2a-adrenergic receptor into RIN 1046-38 cells. Four different cell lines were selected, each overexpressing the alpha 2a-adrenergic receptor to varying degrees. Cell lines showing the highest level of receptor expression showed significantly reduced insulin content, and reduced basal and stimulated insulin secretion. Pertussis toxin (PTX) treatment of cells was able to reverse partially the reduced insulin secretory response. Our results suggest that overexpression of a Gi-protein-coupled receptor in beta-cells causes tonic inhibition of both insulin synthesis and secretion. Abnormalities in expression or function of such receptors could be a contributory factor in the impaired insulin secretion present in type II diabetes.
Insights
Overexpressing Gi-protein-coupled receptors in beta-cells inhibits insulin synthesis and secretion. This suggests receptor dysfunction may contribute to impaired insulin secretion in type II diabetes.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Biology
Background:
- Gi-protein-coupled receptors (GPCRs) in islet beta-cells normally inhibit insulin secretion.
- Supraphysiologic expression of these receptors can alter cellular function.
Purpose of the Study:
- To investigate the impact of supraphysiologic alpha 2a-adrenergic receptor expression on insulin-secreting beta-cells.
- To determine if overexpression of Gi-protein-coupled receptors affects insulin synthesis and secretion.
Main Methods:
- Stable transfection of mouse alpha 2a-adrenergic receptor cDNA into RIN 1046-38 cells.
- Selection and characterization of cell lines with varying receptor expression levels.
- Assessment of insulin content and secretion, with and without Pertussis toxin (PTX) treatment.
Main Results:
- Cell lines with high alpha 2a-adrenergic receptor expression exhibited significantly reduced insulin content.
- Basal and stimulated insulin secretion were diminished in cells overexpressing the receptor.
- Pertussis toxin (PTX) partially reversed the reduced insulin secretory response.
Conclusions:
- Overexpression of Gi-protein-coupled receptors in beta-cells leads to tonic inhibition of insulin synthesis and secretion.
- Dysregulation of these receptors may play a role in the impaired insulin secretion observed in type II diabetes.
- Further research into GPCR function is warranted for understanding diabetes pathophysiology.