Loss of CtBP2 may be a mechanistic link between metabolic derangements and progressive impairment of pancreatic β cell function

C-terminal binding protein 2 interacts with JUNB to control macrophage inflammation

Although acute inflammatory responses are critical for survival, chronic inflammation is a leading cause of disease and mortality worldwide. Nevertheless, our mechanistic understanding of pathogenesis is still limited and precise treatment options are lacking. Here, we investigate the role of the transcriptional co-repressors C-terminal binding protein (CTBP) 1 and 2 in murine and human macrophage activation using loss-of-function models to show that CTBP2 but not CTBP1 controls inflammatory gene expression. We find that CTBP2 occupies cis-regulatory elements of inflammatory genes together with the transcription factors NF-κB and AP-1 and forms a co-repressor complex. Rescue of Ctbp1/2 double knockout cells with WT, oligomeric CTBP2 attenuates inflammatory responses, whereas a monomeric mutant does not. Differential profiling of CTBP2's WT and monomeric interactome confirms oligomer-specific interactions with multiple repressors. Conversely, monomers retain the ability to interact with AP-1 and RNA polymerase II, boosting gene expression. Our findings point to an important function for CTBP2 in fine-tuning inflammatory gene expression, potentially unveiling novel therapeutic targets for the treatment of inflammatory diseases.

Genetic and functional analyses of CTBP2 in anorexia nervosa and body weight regulation

The C-terminal binding protein 2 (CTBP2) gene (translational isoforms: CTBP2-L/S, RIBEYE) had been identified by a cross-trait analysis of genome-wide association studies for anorexia nervosa (AN) and body mass index (BMI). Here, we did a mutation analysis in CTBP2 by performing polymerase chain reactions with subsequent Sanger-sequencing to identify variants relevant for AN and body weight regulation and ensued functional studies. Analysis of the coding regions of CTBP2 in 462 female patients with AN (acute or recovered), 490 children and adolescents with severe obesity, 445 healthy-lean adult individuals and 168 healthy adult individuals with normal body weight detected 24 variants located in the specific exon of RIBEYE. In the initial analysis, three of these were rare non-synonymous variants (NSVs) detected heterozygously in patients with AN (p.Arg72Trp - rs146900874; p.Val289Met -rs375685611 and p.Gly362Arg - rs202010294). Four NSVs and one heterozygous frameshift variant were exclusively detected in children and adolescents with severe obesity (p.Pro53Ser - rs150867595; p.Gln175ArgfsTer45 - rs141864737; p.Leu310Val - rs769811964; p.Pro397Ala - rs76134089 and p.Pro402Ser - rs113477585). Ribeye mRNA was detected in mouse hypothalamus. No effect of fasting or overfeeding on murine hypothalamic Ribeye expression was determined. Yet, increased Ribeye expression was detected in hypothalami of leptin-treated Lepob/ob mice. This increase was not related to reduced food intake and leptin-induced weight loss. We detected rare and frequent variants in the RIBEYE specific exon in both patients with AN and in children and adolescents with severe obesity. Our data suggest RIBEYE as a relevant gene for weight regulation.

C-Terminal Binding Protein 2 Emerges as a Critical Player Linking Metabolic Imbalance to the Pathogenesis of Obesity

Metabolism is one of the vital functions of cells and living organisms, and the systems to sense and respond to the metabolic alterations play pivotal roles in a plethora of biological processes, including cell proliferative activities, immune cell functions, aging processes, and neuronal functions. Recently, we have reported that a transcriptional cofactor, C-terminal binding protein 2 (CtBP2), serves as a critical metabolite sensor in this context. CtBP2 has a structural pocket called Rossmann fold to accommodate metabolites, and it has been reported to be activated upon binding to NADH/NAD＋. Owing to its preferential binding affinity for NADH compared with NAD＋, increased glycolysis activates CtBP2 by regenerating NADH from NAD＋. Furthermore, we recently reported that fatty acyl-CoAs, metabolites accumulated under the condition of lipid overload, as represented by obesity, can inactivate CtBP2. These observations suggest that CtBP2 monitors not only redox state but also energy substrate preference in the maintenance of metabolic homeostasis. In line with these metabolite-sensing capabilities, CtBP2 is activated in healthy subjects to protect against metabolic disturbances, whereas inactivation of CtBP2 in obesity contributes to the pathogeneses of obesity.This metabolic system orchestrated by CtBP2 can provide a novel framework for understanding how cells maintain their homeostasis through coordination of metabolism, and CtBP2 incapacitation can be a critical point of the obesogenic cascade.