Functional omics of ORP7 in primary endothelial cells.

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Oxysterol-binding protein-related protein 7 (ORP7) function remains largely unknown, despite its known localization to the endoplasmic reticulum and plasma membrane.
• ORP7 interacts with proteins involved in autophagy, suggesting a role in autophagosomal/lysosomal pathways.
• Previous studies implicated ORP7 in cholesterol efflux, hypercholesterolemia, and macroautophagy.

Purpose of the Study:

• To elucidate the functions of ORP7 in human umbilical vein endothelial cells (HUVECs) using a hypothesis-free multi-omics approach.
• To investigate the effects of ORP7 inhibition on lipid metabolism, inflammation, angiogenesis, and cell cycle.
• To identify novel interaction partners of ORP7.

Main Methods:

• Multi-omics analysis including transcriptomics, lipidomics, and proximity biotinylation interactomics.
• Chemical inhibition of ORP7 in primary HUVECs.
• Functional assays measuring angiogenesis, cholesterol efflux, and lipid droplet quantification.

Main Results:

• ORP7 inhibition upregulated genes involved in lipid metabolism and inflammation, while downregulating cell cycle and division genes.
• Lipidomic analysis showed increased ceramides, lysophosphatidylcholines, and triacylglycerols, with decreased cholesteryl esters.
• ORP7 inhibition reduced lipid droplet size, cholesterol efflux mediated by ABCG1, and angiogenesis, and revealed an interaction with AKT1.

Conclusions:

• ORP7 inhibition promotes prostanoid and oxysterol synthesis, potentially contributing to inflammation.
• Defective angiogenesis and reduced cell division in ORP7-inhibited HUVECs may stem from altered membrane lipid composition.
• ORP7 plays multifaceted roles in lipid homeostasis, angiogenesis, and the regulation of lipid metabolism, inflammation, and cell cycle genes in endothelial cells.