The role of C-terminal binding protein 1 (CTBP1) in cellular energetics
Creators: name: Akdaş, Enes Yağız
Publisher: name: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Year: 2024

description: Kurzzusammenfassung/Abstract*: C-terminal Binding Protein 1 (CTBP1) is a ubiquitously expressed dual-function protein that acts as a transcriptional co-repressor and membrane trafficking regulator. It controls a broad range of cellular processes including apoptosis, cellular proliferation, and metabolism. In neurons, it can shuttle between the nucleus and the presynapse in a (nicotinamide adenine dinucleotide) NAD+/NADH, and neuronal activity-dependent manner. In the nucleus, CTBP1 regulates synaptic plasticity- and neurodevelopment-associated genes. In the presynapse, it controls synaptic vesicle recycling and maintains synaptic transmission. A recently identified de novo c.C991T mutation in the CTBP1 gene leads to the expression of p.R331W CTBP1 and causes hypotonia, ataxia, developmental delay, and tooth enamel defects syndrome (HADDTS). CTBP1 is a sensor of cellular metabolic state and was linked to cellular energetics in cancer. However, this aspect was not addressed for the function of CTBP1 in neurons and in connection to CTBP1R331W- linked HADDTS pathophysiology. This work aimed to elucidate the role of CTBP1 in hippocampal metabolic homeostasis, and HADDTS pathophysiology using CTBP1 knock-out mice and human embryonic stem cells (hESC) with the HADDTS-linked CTBP1R331W mutation that were generated using CRISPR/Cas9 genome editing in the frame of this thesis. Using electrophysiological recordings in acute hippocampal slices under different metabolic stress conditions we demonstrated that CTBP1 promotes the resilience of hippocampal neurotransmission to metabolic stress and identified the presynaptic compartment as the putative locus of this dysfunction. The HADDTS hESC showed reduced pluripotency, proliferation rate and changes in their differentiation potential to 3 germ layers. To understand the underlying mechanisms, we performed Seahorse metabolic flux assay, transcriptional profiling and specific enzymatic activity assays. These experiments revealed that lower glycolytic capacity and mitochondrial dysfunction drive the increased effect of metabolic stress on hippocampal neurotransmission in Ctbp1 KO animals. In HADDTS hESCs we performed seahorse metabolic flux assay, BrdU staining-based proliferation rate assay, gene expression profiling of pluripotency state and 3-germ line differentiation, pluripotency analysis following 2-DG treatment, expressional analysis of TP53 and its downstream pathways analysis. These experiments revealed decreased resilience to metabolic stresses, decreased glycolytic capacity and proliferation rate, mitotic phase prolongation, decreased pluripotency, and decreased ectodermal and mesodermal marker expression during differentiation but increased endodermal markers and attenuated neuronal maturation. Therefore we identified TP53-mediated metabolic dysregulation as a molecular mediator of HADDTS pathology These results provide new insight into the role of CTBP1 in the regulation of neuronal metabolism and reveal metabolic dysfunction as the key feature of cellular dysfunction in HADDTS. These results might contribute to the development of new therapeutic strategies in HADDTS and other CTBP1-linked pathological conditions.