Moonlight Function of Hexokinase 2 as a Protein Tyrosine Phosphatase to Dephosphorylate STAT3 in Macrophages and Suppress Renal Fibrosis

Background: Previous studies have shown that Hexokinase 2 (HK2), a rate-limiting enzyme in glycolysis, promotes macrophage M1 polarization and exacerbates metabolic dysfunction-related liver steatosis. However, the role and mechanisms of HK2 in macrophage activation and renal fibrosis remain largely unknown. Methods: Mouse models with HK2 deletion in myeloid monocyte-derived macrophages or residual macrophages were constructed using the Cre/LoxP system. Ischemia/reperfusion injury (IRI) and unilateral ureter obstruction (UUO) models were employed to induce renal fibrosis in mice. Results: We first observed that HK2 expression was upregulated in monocyte-derived macrophages in fibrotic kidneys. Further studies revealed that specific knockout of HK2 in monocyte-derived macrophages aggravated IRI or UUO-induced renal fibrosis, while knockout in residual macrophages did not affect renal fibrosis. We also found that HK2 influenced macrophage M2 polarization. RNA sequencing and KEGG enrichment analysis indicated that the JAK-STAT signaling pathway was enriched in BMDMs after HK2 knockout, accompanied by increased phosphorylation of STAT3 at Tyr705. Additionally, HK2 acted as a protein phosphatase, dephosphorylating STAT3 at Tyr705 and inhibiting its nuclear translocation. Further investigation showed that the Cys672 residue of HK2 is critical for its phosphatase activity; mutation at this site enhanced STAT3 phosphorylation at Tyr705. Moreover, HK2 ablation upregulated STAT3-associated gene expression, promoting infiltration of inflammatory cells and renal fibrosis. Conclusion: HK2 functions as a protein tyrosine phosphatase that dephosphorylates the Tyr705 site of STAT3, inhibiting STAT3-induced M2 polarization gene expression and renal fibrosis. Funding: Government Support – Non-U.S.