377-OR: Stabilizing 14-3-3 and ChREBP Cytoplasmic Interaction to Rescue ß-Cells from Glucolipotoxicity

Carbohydrate response element binding protein (ChREBP) is a glucose-responsive transcription factor with two splice isoforms (α and β). ChREBPα remains cytoplasmic by binding to 14-3-3. Increased glucose metabolism allows ChREBPα to enter the nucleus and induce ChREBPβ, a hyperactive isoform that is a key mediator of glucolipotoxicity. Using structure-guided stabilizer optimization, we have developed novel drugs that stabilize the protein-protein interaction between ChREBPα and 14-3-3, with a goal to prevent ChREBPα nuclear translocation, induction of ChREBPβ, and glucolipotoxicity. One hit compound, K391, has an EC50 of 0.3±0.1μM by fluorescent polarization assay and a Kd of 0.12μM by isotitration calorimetry. Using dual label analysis of the kinetics of cell growth and cell death, we found that K391 significantly reduced β-cell death by 31.8±3% and enabled proliferation in glucolipotoxic conditions in INS-1 cells (20mM glucose and 1mM palmitate). In response to glucose, 76.4±3.5 % of the cells stained for nuclear ChREBP. In the presence of K391, 39.75±5.3 % fewer cells displayed nuclear ChREBP in high glucose concentrations and 65.7±1.6% less in glucolipotoxic conditions, indicating that K391 retains ChREBPα in the cytoplasm and prevents transcription of ChREBPβ. Time course with an antibody against ChREBPα showed that ChREBPα transiently translocated to the nucleus at 30 min and then cleared out of the nucleus in high glucose, an effect blocked by K391 (N=3). In glucolipotoxic conditions, ChREBPα remained nuclear over time, an effect significantly attenuated by K391 (N=3). Txnip is an important mediator of glucose toxicity and a target gene of ChREBPβ. Importantly, K391 blocked the glucose response of the human Txnip promoter in a luciferase assay by 2±0.2 folds. We conclude that the K391 retains ChREBPα in the cytoplasm in high glucose and in glucolipotoxic conditions by stabilizing the ChREBPα and 14-3-3 interaction and thereby rescues β-cells from glucolipotoxicity. Disclosure L.S.Katz: None. I.L.Tse: None. E.Visser: None. S.Baumel-alterzon: None. M.Kaiser: None. L.M.Brunsveld: Consultant; Novartis, Ambagon Therapeutics, Research Support; Roche Diagnostics. M.Pennings: None. C.Ottmann: None. D.Scott: None. Funding National Institutes of Health (R01DK130300)