HRAS germline mutations impair LKB1/AMPK signaling and mitochondrial homeostasis in Costello syndrome models.

Germline mutations that activate genes in the canonical RAS/MAPK signaling pathway are responsible for rare human developmental disorders known as RASopathies. Here, we analyzed the molecular determinants of Costello syndrome (CS) using a mouse model expressing HRAS p.G12S, patient skin fibroblasts, hiPSC-derived human cardiomyocytes, a HRAS p.G12V zebrafish model, and human fibroblasts expressing lentiviral constructs carrying HRAS p.G12S or HRAS p.G12A mutations. The findings revealed alteration of mitochondrial proteostasis and defective oxidative phosphorylation in the heart and skeletal muscle of CS mice that were also found in the cell models of the disease. The underpinning mechanisms involved the inhibition of the AMPK signaling pathway by mutant forms of HRAS, leading to alteration of mitochondrial proteostasis and bioenergetics. Pharmacological activation of mitochondrial bioenergetics and quality control restored organelle function in HRAS p.G12A and p.G12S cell models, reduced left ventricle hypertrophy in CS mice, and diminished the occurrence of developmental defects in the CS zebrafish model. Collectively, these findings highlight the importance of mitochondrial proteostasis and bioenergetics in the pathophysiology of RASopathies and suggest that patients with CS may benefit from treatment with mitochondrial modulators.

Targeting Human Lung Adenocarcinoma with a Suppressor of Mitochondrial Superoxide Production.

Aims: REDOX signaling from reactive oxygen species (ROS) generated by the mitochondria (mitochondrial reactive oxygen species [mtROS]) has been implicated in cancer growth and survival. Here, we investigated the effect of 5-(4-methoxyphenyl)-3H-1,2-dithiole-3-thione (AOL), a recently characterized member of the new class of mtROS suppressors (S1QELs), on human lung adenocarcinoma proteome reprogramming, bioenergetics, and growth. Results: AOL reduced steady-state cellular ROS levels in human lung cancer cells without altering the catalytic activity of complex I. AOL treatment induced dose-dependent inhibition of lung cancer cell proliferation and triggered a reduction in tumor growth in vivo. Molecular investigations demonstrated that AOL reprogrammed the proteome of human lung cancer cells. In particular, AOL suppressed the determinants of the Warburg effect and increased the expression of the complex I subunit NDUFV1 which was also identified as AOL binding site using molecular modeling computer simulations. Comparison of the molecular changes induced by AOL and MitoTEMPO, an mtROS scavenger that is not an S1QEL, identified a core component of 217 proteins commonly altered by the two treatments, as well as drug-specific targets. Innovation: This study provides proof-of-concept data on the anticancer effect of AOL on mouse orthotopic human lung tumors. A unique dataset on proteomic reprogramming by AOL and MitoTEMPO is also provided. Lastly, our study revealed the repression of NDUFV1 by S1QEL AOL. Conclusion: Our findings demonstrate the preclinical anticancer properties of S1QEL AOL and delineate its mode of action on REDOX and cancer signaling.