RuvBL1 haploinsufficiency promotes hepatic lipid catabolism hampering NASH-HCC progression in mice. (March 2023)

• Record Type: Journal Article
• Authors: Guida, A.; Simeone, I.; Polvani, S.; Dragoni, G.; Ceni, E.; Picariello, L.; Galli, A.; Mello, T.
• Is Part Of: Digestive and liver disease. Volume 55(2023)Supplement 1
• Page Start: S55
• Page End: S56
• Publication Date: 2023-03
• Subjects: Digestive organs -- Diseases -- Periodicals; Liver -- Diseases -- Periodicals; 616.33005
• DOI: 10.1016/j.dld.2023.01.108
• Languages: English
• ISSNs: 1590-8658

Abstract

Abstract : RuvBL1 is a AAA + ATPase involved in several cellular processes including DNA repair, gene expression, telomerase complex assembly and mTOR pathway activity. It is deregulated in various human cancers and its expression correlates with a worse prognosis in HCC patients. We have previously demonstrated that RuvBL1 haploinsufficiency impairs insulin signalling affecting the PI3K/Akt/mTOR pathway. Given the relevance of mTOR pathway hyperactivation in HCC, we tested if RuvBL1 genetic targeting could reduce mTOR-driven hepatocarcinogenesis in Pten hep-/- mice. Pten hep-/- and Ruvbl1 hep+/- mice were crossed to generate Pten hep-/− Ruvbl1 hep+/- mice. Oil red, Sirius red and F4/80 staining revealed a significant reduction of steatosis, fibrosis, and inflammation in Pten hep-/− Ruvbl1 hep+/- compared to Pten hep-/- at 12 weeks of age. Similar mRNA expression of mTOR-driven lipogenic targets was found in the two mice models. However, expression of Ppara and its target CPT1 was increased in Pten hep-/− Ruvbl1 hep+/−, indicating a lipid-lowering action mediated by PPARalpha in this mouse model. Moreover, promoter reporter experiments revealed that inhibition of RuvBL1 activity by CB-6644 increases PPARalpha transcriptional activity in AML-12 hepatocytic cell line. Next, MS proteomics analysis of RuvBL1 immunoprecipitation in murine AML-12 and Hepa1-6 cells revealed that RuvBL1 interacts with several members of the lysosomal AMPK complex (V-ATPase, LAMTOR1, LAMTOR4, Rag C). Furthermore, p-AMPK and p-RAPTOR were increased in Pten hep-/− Ruvbl1 hep+/− compared to Pten hep-/− mice, suggesting a role of RuvBL1 at the interplay between mTOR and AMPK in hepatic lipid metabolism. Finally, Pten hep-/− Ruvbl1 hep+/− mice aged to 15 months showed better survival than Pten hep-/− which developed significantly more HCC and of higher grade. qPCR analysis showed a significant upregulation of key lipolytic genes, such as Cpt1a, Acadl, Acadvl and Ppara, in Pten hep-/− Ruvbl1 hep+/- at 15 months of age. In conclusion, RuvBL1 targeting mitigates the NASH metabolic and tumorigenic phenotype driven by mTOR hyperactivation in Pten hep-/- mice, likely promoting the switch from mTOR-driven lipogenesis to AMPK-induced fatty acid catabolism.