CMPK2 promotes microglial activation through the cGAS-STING pathway in the neuroinflammatory mechanism

The activation of microglia and the resulting neuroinflammation play crucial regulatory roles in the pathogenesis and progression of neurological diseases, although the specific mechanisms remain incompletely understood. Cytidine monophosphate kinase 2 (CMPK2) is a key mitochondrial nucleotide kinase involved in cellular energy metabolism and nucleotide synthesis. Recent studies suggest that CMPK2 plays a role in microglial-mediated neuroinflammation; however, its specific impact on microglial activation remains unclear. In this study, we hypothesize that CMPK2 promotes microglial-mediated neuroinflammation by activating the cGAS-STING signaling pathway. To investigate this mechanism, we employed lipopolysaccharide (LPS)-treated microglial cells to investigate the detailed mechanisms by which CMPK2 regulates neuroinflammation. Our experimental results indicate that in the BV2 and mouse primary microglial neuroinflammation model, both CMPK2 protein and transcript levels were significantly elevated, accompanied by microglial activation phenotypes such as increased cell size, shortened processes, transformation to round or rod-like shapes, and elevated CD40 expression. Concurrently, there was an increase in pro-inflammatory cytokine levels and a decrease in anti-inflammatory cytokine levels. Further investigation revealed that in the microglial, the expression of cGAS and STING was elevated, along with an increase in oxidative products and inflammatory responses. CMA stimulation further intensified these changes, while cGAS knockdown mitigated them. Finally, we demonstrated that cGAS knockdown inhibited the oxidative stress, cell activation-related changes, and neuroinflammatory responses induced by CMPK2 overexpression in the BV2 neuroinflammation model. Molecular docking experiments showed that CMPK2 stably binds to cGAS at the protein level. These findings suggest that the cGAS-STING pathway mediates CMPK2-induced microglial activation. In summary, our study demonstrates that LPS-induced CMPK2 overactivity promotes microglial activation and neuroinflammatory through the cGAS-STING pathway.