GH signalling in pancreatic beta-cells

Area of Science:

• Endocrinology
• Cell Biology
• Molecular Signaling

Background:

• Growth hormone (GH) and prolactin (PRL) are implicated in pancreatic beta-cell proliferation, insulin biosynthesis, and maturation.
• Understanding the precise signaling pathways activated by GH and PRL in beta-cells is essential for comprehending their role in glucose homeostasis.

Purpose of the Study:

• To investigate the signal transduction mechanisms of GH and PRL in insulin-secreting cells.
• To identify key signaling molecules and pathways involved in the mitogenic effects of GH and PRL on beta-cells.

Main Methods:

• Utilized the differentiated rat insulinoma cell line (INS-1) for experiments.
• Assessed hormone-stimulated proliferation, DNA synthesis, viability, and insulin content.
• Measured intracellular calcium ([Ca2+]i) levels, protein tyrosine phosphorylation (including JAK2), and nuclear protein DNA binding.
• Employed specific inhibitors (verapamil, lavendustin A, Rp-cAMPS) to elucidate signaling pathways.

Main Results:

• Both GH and PRL stimulated proliferation, DNA synthesis, viability, cellular metabolism, and insulin content in INS-1 cells.
• GH induced [Ca2+]i rises via voltage-gated Ca2+-channels and promoted JAK2 tyrosine kinase phosphorylation.
• The JAK-STAT pathway activation was identified as the primary signaling event for the mitogenic effects of GH and PRL, as MAP kinase was not activated.

Conclusions:

• GH and PRL activate the JAK-STAT signaling pathway in pancreatic beta-cells, mediating their mitogenic effects.
• The observed [Ca2+]i rise requires further investigation regarding its role in other hormone-mediated effects.
• This study highlights the JAK-STAT pathway as a key target for understanding and potentially modulating beta-cell function.