The Nuclear-Lipid-Droplet Proteome

TREJO, SEBASTIÁN A; LAGRUTTA, LUCÍA C.; VES LOSADA, ANA; LAYERENZA, JUAN P.

Paraná

Congreso; LIV Reunión Anual de SAIB; 2018

SAIB

Nuclear-lipid droplets (nLD) are a dynamic organelle that stores neutral lipids in a hydrophobic triacylglyceride-cholesterol-ester core enriched in oleic acid (OA) surrounded by a monolayer of polar lipids, cholesterol, and proteins. nLD are probably involved in lipid homeostasis as a buffer that provide or incorporate lipids and proteins in signaling pathways, as transcription factors and enzymes of lipid metabolism and nuclear processes. In nLD proteome analysis, we hypothesized that nLD-monolayer proteins could be involved in similar functions as cytosolic LD (cLD). We analyzed rat-liver-nLD proteome under physiological and nonpathological conditions by GeLC-MS2. Since isolated nLD are highly diluted, a protein-concentrating isolation protocol was designed. 35 proteins were identified within the functional categories: cytoskeleton and structural (31%), transcription and translation (23%), histones (20%), protein-folding and posttranslational modification (8.5%), cellular proliferation and/or cancer (8.5%), lipid metabolism (6%), and transport (3%). nLD contained an enzyme from lipid metabolism, carboxylesterase 1d (Ces1d/Ces3), whose intranuclear localization was confirmed by fluorescence microscopy in HepG2 cell line. Ces1d/Ces3 was observed to be involved in nLD- and cLD-population dynamics upon stimulation by external-OA. These results?the first describing nLD proteome?demonstrate that a tandem-GeLC-MS2-analysis protocol facilitates similar studies on rat-liver nuclei. A diversity of cellular-protein functions was identified indicating the direct or indirect nLD participation and involving Ces1d/Ces3 in LD-population dynamics.