Oxysterol-binding protein 1

Oxysterol-binding protein 1 (OSBP) is a lipid transporter that mediates cholesterol and phosphatidylinositol 4-phosphate (PI4P) exchange between the Golgi complex and endoplasmic reticulum membranes (UniProt: P22059). The protein binds cholesterol and oxysterols, including 25-hydroxycholesterol, and regulates cholesterol homeostasis by modulating ABCA1 stability and controlling cholesterol efflux activity. OSBP also regulates intracellular signaling through interactions with phosphatase complexes that dephosphorylate ERK1/2 in response to sterol binding.

OSBP functions in lipid metabolism and intracellular cholesterol trafficking, processes essential for normal cellular function and membrane organization. While UniProt lists no curated disease associations for this protein, its role in sterol metabolism and signaling implicates it in pathways relevant to neurodegenerative conditions.

In Alzheimer's disease, OSBP is down-regulated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics: mean log2FC = −0.54). This reduction was detected in one subcellular fraction of a TMT-labeled tandem mass spectrometry study examining four fractions from AD brain, suggesting compromised lipid transport capacity in AD pathology.