The Deubiquitinating Enzyme Otub2 Modulates Pancreatic Beta-Cells Function and Survival

Background: We have previously demonstrated that ovarian tumor (Otu) domain-containing ubiquitin aldehyde-binding protein 2 (Otub2), a deubiquitinating enzyme, exerts anti-apoptotic effects in primary human islets. The present study aims to further elucidate the molecular mechanisms underlying the role of Otub2 as a regulator of insulin secretion and β-cell function. Methods: Otub2 overexpression or silencing was employed to study its effects on cultured MIN6 cells and dispersed human islets. To evaluate its in vivo effects, Otub2 knockout (KO) mice were employed, as well as a pancreata-specific Otub2 overexpression model. RNA sequencing was performed on pancreatic tissue from Otub2-KO and control mice to study its effects on gene expression patterns. Co-immunoprecipitation followed by mass spectrometry identified Otub2-interacting proteins. Results: Overexpression of Otub2 inhibited NF-κB activity and enhanced glucose-stimulated insulin secretion (GSIS) in cultured MIN6 cells and primary human islets. Otub2 KO mice exhibited impaired glucose tolerance and upregulation of NF-κB target genes. Conversely, selective in vivo overexpression of Otub2 in pancreata of C57BL wild-type mice resulted in significantly lower (~30%) blood glucose levels, post glucose injection, compared to control mice. Transcriptomic analysis of KO pancreata revealed downregulation of K+ transporter-related genes and upregulation of oxidative phosphorylation genes, consistent with defective insulin secretion. Mass spectrometry identified the voltage-gated potassium channel subunit Kv9.3 as a major Otub2 binding partner, along with paternally expressed 3 (Peg3) and calcium/calmodulin dependent protein kinase II delta (Camk2d) proteins known to promote NF-κB signaling and β-cell apoptosis. Conclusions: Otub2 is a critical regulator of β-cell function, acting through modulation of NF-κB signaling and K+ channel-associated complexes. By deubiquitinating components such as Peg3 and Camk2d, Otub2 may protect β-cells from cytokine-induced apoptosis and sustain insulin secretory capacity. These findings position Otub2 as a potential therapeutic target for preserving β-cell function in diabetes.