Unspliced XBP1 Enhences Metabolic Reprogramming in Colorectal Cancer Cells by Interfering with the Mitochondrial Localization of MGME1

Tumor cells undergo metabolic reprogramming, which makes them tend to utilize anaerobic glycolysis rather than oxidation to rapidly produce energy and intermediate products required for proliferation. In this process, mitochondria inevitably undergo corresponding alterations; however, the specific alterations in mitochondria across different cancer types and the mechanisms governing these changes remain poorly understood. This study demonstrated that unspliced X-box binding protein 1 (XBP1-u) inhibits the translocation of mitochondrial genome maintenance exonuclease 1 (MGME1) into mitochondria by binding to the mitochondrial targeting sequence (MTS) of MGME1. This interaction results in the accumulation of mitochondrial 7sDNA, a reduction in mitochondrial DNA copy number, and a decrease in mitochondrial abundance. Consequently, this shift enhances the production of glycolysis and pentose phosphate pathway intermediates, thereby promoting the proliferation of colorectal cancer (CRC) cells. Our findings elucidated the critical mechanism by which XBP1-u enhances metabolic reprogramming by modulating mitochondrial biogenesis, and uncovered a novel role of MGME1 in the progression of CRC.