Regulation of glucose metabolism by telomerase in the health and disease

Zusammenfassung

Telomerase is a complex composed by a catalytic subunit (TERT) and an ARN component (TERC) whose main function is telomere synthesis in eukaryotic cells. For that reason, telomerase has been related directly to aging and cancer. Nevertheless, both TERT and TERC are known to perform extracurricular or non-canonical functions, that is, independently of telomere lengthening. The regulation of the energy metabolism is very important for the cell function, being the glucose metabolism one of the most studied in cancer cells and immune cells. In general terms, the regulation of both glycolysis and the Krebs cycle (TCA) is fundamental not only for cell proliferation but also, the generated metabolites in those pathways perform cell signaling functions, have immunomodulatory roles and even participate in the control of gene expression. In this doctoral thesis, we have described new extracurricular functions of TERT and TERC related to the regulation of glucose metabolism. In order to do that, we took advantage of zebrafish as an in vivo model, exploring these functions in two different disease models (chronic inflammation and cancer); moreover, we have used human cell lines for in vitro experimentation and in physiological conditions. The objectives of this doctoral thesis are the following: 1) Study the relationship between terc and the regulation of glucose metabolism in the context of chronic inflammation and the cancer immune response. 2) Validate and characterize the interaction between the pyruvate dehydrogenase complex and the telomerase components TERC and TERT. In the first chapter we performed a metabolic study and determined that terc expression was able to modify the glycolysis and TCA cycle metabolite composition. Likewise, we established that terc was playing a role as a long non-coding RNA, controlling the expression of the ldhbb gene, which encodes one isoform of the enzyme lactate dehydrogenase. Hence, we characterized this effect first in a chronic inflammation model by performing pharmacologic, transcriptomic, and functional studies; and second, in a cancer model, specifically studying the anti-tumor immune response in vivo by evaluating the tumor development and performing functional studies with several transgenic zebrafish lines. In the second chapter, we based our studies in a proteomic analysis performed in zebrafish and found that the E1 subunit of the pyruvate dehydrogenase complex (PDC) was a possible terc interactor. In our studies, we validated this interaction in human cell lines using molecular biology and imaging techniques. Moreover, we checked by immunofluorescence and enzymatic activity assays that TERC expression could modify the PDC cell location, but not its enzymatic activity. Lastly, we confirmed that the interaction with PDC-E1 was also taking place with TERT, and that both telomerase components were interacting with the E2 subunit of the PDC, stablishing a new extracurricular function for both complexes.