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Expression of insulin receptor mRNA and insulin receptor substrate 1 in pancreatic islet beta-cells
M C Harbeck1, D C Louie, J Howland
1Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, 19104, USA.
Abstract:
The expression of insulin receptor mRNA was examined in rat pancreatic islet cells by single-cell reverse transcriptase (RT)-polymerase chain reaction (PCR). Single cells from disaggregated islets were individually isolated in a microcapillary pipet, and the beta-cells were identified by amplification of the mRNA for insulin. We found that in single beta-cells, the mRNA for the insulin receptor was also expressed. The fraction of single islet cells expressing both insulin receptor and insulin mRNAs corresponds closely to the fraction of beta-cells in the disaggregated islet cell preparation. These results indicate that normal beta-cells have the potential to express authentic insulin receptors. Immunohistochemical analysis was insufficiently sensitive for assaying insulin receptor protein; however, insulin receptor substrate 1 (IRS-1) was readily immunolocalized in islet beta-cells. Since IRS-1 links several cell surface receptors, including those for insulin and IGF-I, to distal signal transduction pathways, our observations indicate that hormonal regulation of islet beta-cells potentially involves the same signal transduction pathway that mediates insulin and growth factor signaling in peripheral insulin target tissue cell types.
Insights
Normal pancreatic beta-cells express insulin receptor mRNA, indicating their potential to respond to insulin. This suggests shared signaling pathways between islet cells and peripheral tissues.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Biology
Background:
- Pancreatic beta-cells regulate blood glucose.
- Insulin signaling is crucial in peripheral tissues.
- The role of insulin receptors in beta-cells was unclear.
Purpose of the Study:
- To investigate insulin receptor mRNA expression in rat pancreatic islet beta-cells.
- To determine if beta-cells possess the machinery for insulin signaling.
Main Methods:
- Single-cell reverse transcriptase (RT)-polymerase chain reaction (PCR) on isolated islet cells.
- Identification of beta-cells via insulin mRNA amplification.
- Immunohistochemistry for insulin receptor substrate 1 (IRS-1).
Main Results:
- Insulin receptor mRNA was detected in single beta-cells.
- The proportion of cells expressing insulin receptor mRNA matched beta-cell fractions.
- Insulin receptor substrate 1 (IRS-1) was localized in beta-cells.
Conclusions:
- Normal pancreatic beta-cells can express authentic insulin receptors.
- Beta-cells likely utilize similar insulin/IGF-I signaling pathways as peripheral tissues.
- Hormonal regulation of beta-cells may involve common signal transduction mechanisms.