D-ribose-induced cytotoxicity in K562 cells: RBKS-dependent disruption of copper homeostasis and mitochondrial function.

BACKGROUND: D-ribose, a highly reducing pentose sugar, can be phosphorylated by ribokinase (RBKS) to form ribose-5-phosphate (R-5-P). Elevated urinary D-ribose levels have been reported in patients with type 2 diabetes mellitus (T2DM) and Alzheimer's disease, implicating its potential role in disease pathogenesis. Previous investigations into D-ribose cytotoxicity have primarily focused on its non-enzymatic glycation activity, while alternative mechanisms remain underexplored. Since hemoglobin is a major in vivo target of glycation, this study utilized K562 cells-which retain inducible hemoglobin expression-to explore additional cytotoxic mechanisms of D-ribose. METHODS AND RESULTS: CCK-8 assays demonstrated that D-ribose inhibited K562 cell proliferation in a concentration- and time-dependent manner, and this inhibitory effect was significantly enhanced in both hemin-induced differentiated and RBKS knockout K562 cells. Conversely, RBKS overexpression promoted proliferation and alleviated oxidative stress in K562 cells. Transcriptomic analysis revealed that differentially expressed genes in D-ribose-treated cells were enriched in mineral absorption and oxidative phosphorylation pathways (KEGG), as well as in biological processes related to copper ion homeostasis (GO). RT-qPCR confirmed that both D-ribose treatment and RBKS knockout downregulated key copper homeostasis genes (e.g., SLC31A1, MT1F, ATOX1) and mitochondrial respiratory chain genes (e.g., COX17, COX11, MTATP8, MTND6), and were accompanied by a significant reduction in intracellular free copper levels. CONCLUSIONS: These findings reveal a novel cytotoxic mechanism mediated by the RBKS-copper-oxidative phosphorylation axis in D-ribose-treated K562 cells, providing key insights into the intracellular role of D-ribose.