Chen, F.-J. | Search bioRxiv

bioRxiv2025

ORP2 regulates free cholesterol accumulation in hepatocytes during MASH

BackgroundCholesterol crystals in hepatocytes are known to strongly associate with human Metabolic Dysfunction-Associated Steatohepatitis (MASH). However, it remains unclear which molecular pathway(s) regulates free cholesterol accumulation, and therefore the formation of cholesterol crystals in hepatocytes. In cultured cell lines, oxysterol-binding protein-related protein 2 (ORP2) functions to deliver cholesterol to the plasma membrane from internal organelles. MethodsHere, we generated liver-specific ORP2 knockout (ORP2-LKO) mice and characterized their metabolic phenotypes on chow and high fat diet. ResultsThe ORP2-LKO mice developed much more severe hepatic steatosis than wild type mice after high-fat diet feeding. They also demonstrated more severe liver inflammation and damage. Notably, free but not esterified cholesterol, as well as cholesterol crystals accumulated in ORP2-LKO liver. The expression of Cyp7a1 was significantly upregulated in ORP2-LKO liver, accompanied with accumulation of taurocholic acid. Our results thus unveil an important in vivo function of ORP2 in preventing free cholesterol from accumulating in mouse liver. Conclusionsour results suggest that impaired cholesterol trafficking may enhance the deposition of cholesterol crystals in hepatocytes, promoting the development of MASH.

cell biology↗

bioRxiv2024

PI(4)P recruits CIDE proteins to promote the formation of unilocular lipids droplets

Lipid droplets (LDs) are evolutionarily conserved organelles that play important roles in metabolism. Each LD is enclosed by a monolayer of phospholipids, distinct from bilayer membranes. The composition of LD surface phospholipids and their impact on LD growth and function remain to be clearly defined. Phosphoinositides mark cellular organelles and regulate cell signalling and organellar function. Here, we demonstrate that PI(4)P decorates a subset of LDs to recruit and activate the CIDE proteins. Enhanced expression of ORP2 and ORP5, LD-associated lipid transfer proteins that remove PI(4)P from LDs, abolished the localization and function of CIDE proteins. Blocking the synthesis of PI(4)P on LD surface via knocking down PI4K2A also impaired the localization and function of CIDE proteins. In adipocytes, depleting PI(4)P dramatically reduced the size of LDs, as well as adipose tissue mass. In severe steatotic liver, depleting PI(4)P reduced LD accumulation. Our results thus identify a key function of LD surface PI(4)P under physiological conditions and unveil how CIDE proteins are recruited to LDs.

cell biology↗