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Med14 phosphorylation shapes genomic response to GLP-1 Agonist
Sam Van de Velde1, Jingting Yu2, K Garrett Evensen2
1Peptide Biology Laboratories, The Salk Institute for Biological Studies, La Jolla CA.
Biorxiv : the Preprint Server for Biology
|July 16, 2025
Summary
Glucagon-like peptide-1 (GLP-1) analogs promote insulin secretion and beta cell survival. Med14 phosphorylation by protein kinase A is crucial for sustained GLP-1 effects on beta cell gene expression and function.
Area of Science:
- Endocrinology
- Molecular Biology
- Diabetes Research
Background:
- Glucagon-like peptide-1 (GLP-1) enhances insulin secretion and beta cell viability under feeding conditions.
- GLP-1 signaling involves cAMP pathway activation, protein kinase A (PKA) mediated phosphorylation of CREB, and induction of CREB target genes.
Purpose of the Study:
- To identify transcriptional co-regulators mediating the long-term effects of GLP-1 analogs on beta cells.
- To elucidate the molecular mechanisms by which sustained GLP-1 receptor activation impacts beta cell gene expression.
Main Methods:
- Proteomic screening to identify key transcriptional co-regulators.
- Exposure of primary mouse beta cells to Exendin-4 (a stable GLP-1 receptor agonist).
- Analysis of Med14 phosphorylation at Ser983 and its functional consequences.
Main Results:
- Med14, a subunit of the Mediator complex, was identified as a key co-regulator.
- Exendin-4 stimulated Med14 phosphorylation at Ser983, a conserved PKA recognition site.
- Med14 phosphorylation by PKA is essential for maintaining enhancers driving beta cell-specific and diabetes-linked gene induction.
- Mutation of Med14 Ser983 to alanine impaired beta cell numbers and repressed Exendin-4-induced gene regulation.
Conclusions:
- Phosphorylation of the general transcription factor Med14 by PKA is a critical mechanism linking sustained GLP-1 signaling to a broad genomic response in beta cells.
- This phosphorylation event is essential for maintaining beta cell function and survival, offering potential therapeutic targets for diabetes.
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