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Published on: January 26, 2024
FK506-Binding Protein 2 Participates in Proinsulin Folding.
Carolin Hoefner1, Tenna Holgersen Bryde1,2, Celina Pihl1
1Inflammation, Metabolism and Oxidation Section, Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark.
FK506-binding protein 2 (FKBP2) is crucial for correct proinsulin folding by catalyzing proline isomerization. Its absence leads to misfolded proteins, reduced insulin, and increased pancreatic cell death, suggesting a role in type 2 diabetes.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Biology
Background:
- Proinsulin folding is complex and not fully understood, requiring proline isomerization for accuracy.
- FK506-binding protein 2 (FKBP2) is an endoplasmic reticulum-resident enzyme with proline isomerase activity.
Purpose of the Study:
- To investigate the role of FKBP2 in proinsulin folding and its potential contribution to type 2 diabetes (T2D).
Main Methods:
- Co-immunoprecipitation assays to detect protein interactions.
- FKBP2 inhibition and knockout studies in pancreatic beta-cells.
- Analysis of proinsulin and insulin levels, protein complex formation, and apoptosis.
- FKBP2 mRNA expression analysis in T2D patient islets.
- Molecular modeling and in vitro enzymatic assays.
Main Results:
- FKBP2 interacts with proinsulin and its chaperone GRP94.
- FKBP2 inhibition causes increased proinsulin turnover, reduced intracellular insulin, and formation of misfolded proinsulin complexes.
- FKBP2 knockout in beta-cells increases apoptosis.
- FKBP2 mRNA is overexpressed in T2D patient islets.
- Proline at position 28 in the proinsulin B-chain (P28) is identified as a substrate for FKBP2.
Conclusions:
- FKBP2-mediated proline isomerization at P28 is essential for correct proinsulin folding.
- Dysfunctional FKBP2 may contribute to beta-cell dysfunction and T2D pathogenesis.
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