FAT10 localises in dendritic cell aggresome-like induced structures and contributes to their disassembly

Landscape of Immune Microenvironment in Epithelial Ovarian Cancer and Establishing Risk Model by Machine Learning

Background

Epithelial ovarian cancer (EOC) is an extremely lethal gynecological malignancy and has the potential to benefit from the immune checkpoint blockade (ICB) therapy, whose efficacy highly depends on the complex tumor microenvironment (TME).

Method and Result

We comprehensively analyze the landscape of TME and its prognostic value through immune infiltration analysis, somatic mutation analysis, and survival analysis. The results showed that high infiltration of immune cells predicts favorable clinical outcomes in EOC. Then, the detailed TME landscape of the EOC had been investigated through “xCell” algorithm, Gene set variation analysis (GSVA), cytokines expression analysis, and correlation analysis. It is observed that EOC patients with high infiltrating immune cells have an antitumor phenotype and are highly correlated with immune checkpoints. We further found that dendritic cells (DCs) may play a dominant role in promoting the infiltration of immune cells into TME and forming an antitumor immune phenotype. Finally, we conducted machine-learning Lasso regression, support vector machines (SVMs), and random forest, identifying six DC-related prognostic genes (CXCL9, VSIG4, ALOX5AP, TGFBI, UBD, and CXCL11). And DC-related risk stratify model had been well established and validated.

Conclusion

High infiltration of immune cells predicted a better outcome and an antitumor phenotype in EOC, and the DCs might play a dominant role in the initiation of antitumor immune cells. The well-established risk model can be used for prognostic prediction in EOC.

Parkin is an E3 ligase for the ubiquitin-like modifier FAT10, which inhibits Parkin activation and mitophagy

Parkin is an E3 ubiquitin ligase belonging to the RING-between-RING family. Mutations in the Parkin-encoding gene PARK2 are associated with familial Parkinson's disease. Here, we investigate the interplay between Parkin and the inflammatory cytokine-induced ubiquitin-like modifier FAT10. FAT10 targets hundreds of proteins for degradation by the 26S proteasome. We show that FAT10 gets conjugated to Parkin and mediates its degradation in a proteasome-dependent manner. Parkin binds to the E2 enzyme of FAT10 (USE1), auto-FAT10ylates itself, and facilitates FAT10ylation of the Parkin substrate Mitofusin2 in vitro and in cells, thus identifying Parkin as a FAT10 E3 ligase. On mitochondrial depolarization, FAT10ylation of Parkin inhibits its activation and ubiquitin-ligase activity causing impairment of mitophagy progression and aggravation of rotenone-mediated death of dopaminergic neuronal cells. In conclusion, FAT10ylation inhibits Parkin and mitophagy rendering FAT10 a likely inflammation-induced exacerbating factor and potential drug target for Parkinson's disease.