<scp>CBL</scp>/Cbl‐b mediates Fas degradation to reduce neuronal damage in experimental autoimmune encephalomyelitis

Fas has been shown to positively regulate the differentiation of T helper 17 (Th17) cells in mouse models of experimental autoimmune encephalomyelitis (EAE). Fas protein expression is regulated by ubiquitination but has not been further studied. In this study, we investigated the role of the Fas ubiquitin ligase in Th17 cell differentiation and highlighted its potential as a therapeutic target for EAE. The E3 ubiquitin ligase CBL of Fas was predicted using the online prediction software ubibrowser. Overexpression of CBL significantly reduced Fas protein levels but did not affect mRNA levels. The decrease in Fas protein mediated by CBL overexpression was rescued by the proteasome inhibitor MG132. Co-IP analysis revealed that CBL interacted with Fas. Further results suggested that CBL regulated Fas expression through ubiquitination, thereby affecting Th17 cell differentiation. Cbl-b, a homologue of CBL, significantly promoted the degradation of Fas protein and increased its ubiquitination modification. Furthermore, CBL and Cbl-b could synergistically regulate Fas to influence Th17 cell differentiation. The same conclusion was also reached in animal models. Luxol Fast Blue staining showed that myelinated fibres in the spinal cord were significantly increased after CBL/Cbl-b overexpression in EAE. Finally, flow cytometry and immunofluorescence staining showed that overexpression of CBL or Cbl-b decreased the proportion of Th17 cells in the spinal cord of EAE mice, ultimately reducing neuronal damage. Taken together, these data demonstrate that CBL and Cbl-b can synergistically regulate Fas to inhibit Th17 cell differentiation, thereby alleviating spinal cord nerve injury in the EAE model.