ERN1 KNOCKDOWN AFFECTS THE EXPRESSION OF PDHA1, PDHB, PDHX, DLD, AND DLAT GENES AND MODIFIES THEIR HYPOXIC REGULATION

Hypoxia and endoplasmic reticulum stress are critical factors affecting tumor growth. Inhibition of ERN1 protein has the ability to suppress glioma cell proliferation and growth. Pyruvate dehydrogenase complex is a important factor for glioma cell growth because they have an increased rate of glucose consumption. Aim. The purpose of this study was to investigate the role of ERN1 in the regulation of the expression of pyruvate dehydrogenase complex genes in U87MG glioma cells. Methods. We used qPCR analysis to study the role of hypoxia, caused by incubating cells in 0.5 mM dimethyloxalylglycine for 4 hours, in the expression of pyruvate dehydrogenase complex genes as well as its interaction with the ERN1 endoplasmic reticulum stress signaling pathway in U87 glioma cell culture. Three glioma cell culture lines were used in the study (control glioma cells, cells with complete blockade of the enzymatic activity of ERN1 protein, and cells with inactivation of endoribonuclease only). Results. It has been demonstrated that the expression level of most PHD genes decreases under hypoxic conditions in control glioma cells and cells with ERN1 blockade. Conclusions. It is important to note that the effect of hypoxia is gene-specific and dependent on the activity of ERN1 protein for some genes. It has also been demonstrated that different genes are regulated by different enzymatic activities of the ERN1 signaling protein. The PDHX and DLD genes are regulated by the protein kinase activity of ERN1, PDHA1 and PDHB proteins by the endoribonuclease of ERN1, and the DLAT gene is regulated by both enzymatic activities.