Restoring Beta-cell Integrity through Targeted SPOP Inhibition and PDX-1 Preservation

• Applicant: Professor Dr. Oliver Plettenburg
• Subject Area: Pharmacy
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544918080

Diabetes is an enormous threat to global health. It has been long known it manifests itself among others by impaired functions of β-cells, but regeneration of β-cell mass has not been achieved. Here, we plan to investigate a therapeutic strategy to normalize the levels of Pancreatic and duodenal homeobox factor-1 (PDX-1), a critical protein for insulin production and for β-cell differentiation and survival. PDX-1 is degraded by SPOP, linking of Pdx1 to a Cullin-3 E3 ubiquitin-protein ligase. It is known, that disrupting this process leads to improved glucose homeostasis by normalization of β-cell function, survival and mass. Therefore, targeting the turnover of PDX-1 appears as a promising therapeutic option to improve glucose homeostasis in diabetic patients. Recently, first inhibitors of SPOP were reported as potential kidney cancer therapeutics. However, no research has been conducted yet on the effects of these compounds on β-cells. In our preliminary work we used these published inhibitors to test SPOP-PDX-1 protein-protein interaction (PPI) as a target for diabetes treatment. Prof. Plettenburg's team at LUH synthesized both, reported and novel molecules that produce enhanced effects. These were then examined by dr Czarna's group at MCB in biological assays. The results of our experiments indicated a substantial increase of insulin levels in isolated pancreatic islets, highlighting the promise of this approach. In this multidisciplinary project, we aim to extend our preliminary results by validating PDX-1-SPOP inhibitors as a promising mechanism leading to the observed, highly desired functions of pancreatic islets. First, we aim to enhance the potency of our compounds using insights from structural biology and molecular modelling. We will then validate the compounds in cellular models and human organoids in the MCB lab through chemoproteomics. Additionally, we will develop another peptidomimetic series of inhibitors. This will be done using structural data on the Pdx1-SPOP interaction in dr Dawidowski labs at WUM. Another key focus of this project is the targeted delivery of SPOP inhibitors to β-cells, using GLP-1 receptor-mediated internalization to ensure specificity and overcome possible cell penetration challenges. This approach, involving carefully designed peptides, will be conducted at LUH. The biological studies planned in this proposal will utilize β-cell lines, dispersed islets and human islet organoids, progressively increasing in complexity. Finally, we intend to conduct exploratory in vivo studies in rodent models of diabetes. Our ultimate goal is to establish SPOP inhibition as a novel target for diabetes treatment, which can pave the way for innovative strategies in developing regenerative antidiabetic drugs. Ultimately, our research aims to demonstrate whether safeguarding PDX-1 protein levels can effectively prevent β-cell apoptosis and loss, a crucial milestone in the journey towards a therapy against diabetes.

• DFG Programme: Research Grants
• International Connection: Poland
• Cooperation Partners: Dr. Anna Czarna; Dr. Maciej Dawidowski