ORP10/OSBPL10 is a member of the
oxysterol-binding protein family, and genetic variation in OSBPL10 is associated with
dyslipidemias and
peripheral artery disease. In this study we investigated the
ligand binding properties of ORP10 in vitro as well as its localization and function in human HuH7 hepatocytes. The
pleckstrin homology (PH) domain of ORP10 selectively interacts with
phosphatidylinositol-4-phosphate, while the C-terminal
ligand binding domain binds
cholesterol and several acidic
phospholipids. Full-length ORP10 decorates microtubules (MT), while the ORP10 N-terminal fragment (aa 1-318) localizes at Golgi membranes. Removal of the C-terminal aa 712-764 of ORP10 containing a predicted coiled-coil segment abolishes the MT association, but allows partial Golgi targeting. A PH domain-GFP fusion
protein is distributed mainly in the cytosol and the plasma membrane, indicating that the Golgi affinity of ORP10 involves other determinants in addition to the PH domain. HuH7 cells expressing ORP10-specific
shRNA display increased accumulation of
apolipoprotein B-100 (apoB-100), but not of
albumin, in culture medium, and contain reduced levels of intracellular
apoB-100. Pulse-chase analysis of cellular [(35)S]
apoB-100 demonstrates enhanced
apoB-100 secretion by cells expressing ORP10-specific
shRNA. The
apoB-100 secretion phenotype is replicated in HepG2 cells transduced with the ORP10
shRNA lentiviruses. As a conclusion, the present study dissects the determinants of ORP10 association with MT and the Golgi complex and provides evidence for a specific role of this
protein in β-
lipoprotein secretion by human hepatocytes.