12560 RIMOC1, A Novel Regulator Of Mitochondrial Function, And Its Role In Pancreatic Beta-cell Survival, Mitophagy, And Diabetogenesis

Abstract Disclosure: D. Filingeri: None. R. Liu: None. V. Negi: None. J. Lee: None. A. Kumar: None. V. Mandi: None. M. Moulik: None. V. Yechoor: None. Background: Literature supports preserving beta-cell function as an approach to slowing diabetes progression. Mitochondria emerge as an interesting area of focus, driving cellular respiration and glucose-stimulated insulin secretion (GSIS) within beta-cells in physiologic conditions, and leading to increased intracellular ROS generation when damaged. Damaged mitochondria are recycled via lysosomes by mitophagy, and defects in mitophagy have been linked to numerous disease states, with more recent data implicating impaired mitophagy with beta-cell death. Our previous work on the Hippo-TEAD pathway and beta-cell survival led to the isolation of the TEAD binding partner RIMOC1 (RAB7A-Interacting MON1-CCZ1 Complex Subunit 1), a protein highly expressed in pancreatic beta-cells, though its role in beta-cells remains unknown. The overarching hypothesis is that RIMOC1 is protective against the development of diabetes by preserving beta-cell mitophagy and mitochondrial function, and that impaired RIMOC1 function would lead to beta-cell failure and diabetes.Methods: We have generated both a stable INS2 RIMOC1 KO (knockout) cell line and an INS1-Cre RIMOC1 KO mouse model, that are beta-cell specific knockouts of RIMOC1. Mitochondrial membrane potentials were measured using TMRE and JC1 stains, and mitophagy was quantified using the mtKeima probe via flow cytometry. Protein expression was quantified via western blotting. Ongoing studies involving our mouse model include in vivo GTTs (glucose tolerance testing), ex vitro GSIS experiments to assess beta-cell function from mouse islets, and seahorse assays to quantify mitochondrial function. Results: Published GEO datasets show RIMOC1 expression is positively correlated with beta-cell maturity and negatively correlated with glucose load and HgbA1c. Our in vitro data demonstrates RIMOC1 knockout leads to decreased insulin mRNA expression, decreased insulin content, and increased beta-cell cycle inhibition. Early in vivo data shows worsened hyperglycemia with oral refeeding after fasting. In vitro mitophagy experiments demonstrate significantly diminished mitochondrial membrane potential in RIMOC1 KO INS2 cells. Conclusions: RIMOC1 is highly expressed in beta-cells and has a significant role in maintaining euglycemia through mitochondrial functioning, insulin processing, and altered mitophagy. This research highlights RIMOC1 as a promising target of further diabetes research. Presentation: 6/2/2024