Oxidative regulation of cholesterol mobilization in C. elegans

VERÓNICA A. LOMBARDO; BERNABÉ BATTISTA; ANDRÉS BINOLFI; FRANCO A. BIGLIONE; DIEGO DE MENDOZA

Rosario

Congreso; Second Latin American Worm Meeting; 2020

The Latin American Worm Society

Cholesterol is an essential metabolite used by virtually all eukaryotic organisms. Its primary role as a structural component of cell membranes is to regulate membrane fluidity. However, cholesterol also serves as a scaffold for the synthesis of a plethora important biomolecules, such as steroid hormones and bile acids. Therefore, a proper cholesterol transport is crucial for cell viability and correct organism functioning. In the nematode Caenorhabditis elegans, cholesterol derivatives known as dafachronic acids (DAs) govern the entry of this animal into the diapause stage and their absence, leads worm to arrest as a dauer larva. Thus, accurate cholesterol transport to appropriate cellular locations is essential for DA biosynthesis. Furthermore, we have recently shown that endocannabinoids modulate sterol mobilization. Cholesterol vesicular transport is mediated by a multidomain membrane protein called STARD3 that binds cholesterol through its cytosolic domain (START). STARD3 co-localize with methionine sulfoxide reductase A, an enzyme that reduces methionine sulfoxide side-chains, and it was proposed that redox cycles of Met oxidation-reduction at the sterol binding site of START regulate cholesterol transport. We are interested in characterizing this interaction and the mechanistic basis of the process with atomic resolution using NMR spectroscopy in vitro and vivo. By applying novel in-cell NMR methodologies we characterized MSRA activity in tissue extracts of wt and MSRA-/- C. elegans in the presence and absence of cholesterol and monitored the effects of MSRA on worm lifespan. Combined with the structural characterization of the MSRA/START interaction and the enzymatic reduction of oxidized START, our work will shed light on novel signaling pathways mediating cholesterol mobilization.