USP17L2 Regulates SphK1 Ubiquitination and Stability during Autophagy and Pyroptosis in Mycoplasma Pneumoniae Pneumonia.

This study explored the role of ubiquitin-specific peptidase 17-like family member 2 (USP17L2) and sphingosine kinase 1 (SphK1) in regulating macrophage autophagy and pyroptosis via the TRAF6-ULK1-NLRP3 signaling axis during Mp lipid exposure. Using in vitro and in vivo models, the study examines protein expression, cytokine levels, and cellular processes. Mechanistic explorations were performed on the mycoplasma pneumoniae pneumonia (MPP) models. Mp lipid treatment significantly upregulated SphK1 and USP17L2 expression in MH-S cells while promoting proinflammatory cytokine secretion, ROS production, and activation of pyroptosis and autophagy. Silencing SphK1 suppressed Mp lipid-induced macrophage autophagy, pyroptosis, and activation of the TRAF6-ULK1 signaling axis. Co-IP confirmed direct interaction between SphK1 and TRAF6, with SphK1 inducing ULK1 ubiquitination. USP17L2 was a specific deubiquitinating enzyme for SphK1, and the two proteins interacted. Silencing USP17L2 significantly reduced inflammatory infiltration in lung tissue, neutrophil recruitment in bronchoalveolar lavage fluid, and bacterial load in MPP mice. Concurrently, it suppressed the expression of autophagy-related molecules, pyroptosis-related molecules, and proinflammatory factors in lung tissue. In conclusion, USP17L2 stabilizes SphK1 through deubiquitination modification and activates the TRAF6-ULK1-NLRP3 signaling axis, thereby promoting macrophage autophagy and pyroptosis and exacerbating MPP damage. Silencing USP17L2 blocks this regulatory pathway, inhibiting excessive inflammatory responses and cell death.