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Oxysterol-binding protein (OSBP)-related protein 4 (ORP4) is essential for cell proliferation and survival.

ABSTRACT: Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) comprise a large gene family with sterol/lipid transport and regulatory activities. ORP4 (OSBP2) is a closely related paralogue of OSBP, but its function is unknown. Here we show that ORP4 binds similar sterol and lipid ligands as OSBP and other ORPs but is uniquely required for the proliferation and survival of cultured cells. Recombinant ORP4L and a variant without a pleckstrin homology (PH) domain (ORP4S) bind 25-hydroxycholesterol and extract and transfer cholesterol between liposomes. Two conserved histidine residues in the OSBP homology domain ORP4 are essential for binding phosphatidylinositol 4-phosphate but not sterols. The PH domain of ORP4L also binds phosphatidylinositol 4-phosphate in the Golgi apparatus. However, in the context of ORP4L, the PH domain is required for normal organization of the vimentin network. Unlike OSBP, RNAi silencing of all ORP4 variants (including a partial PH domain truncation termed ORP4M) in HEK293 and HeLa cells resulted in growth arrest but not cell death. ORP4 silencing in non-transformed intestinal epithelial cells (IEC)-18 caused apoptosis characterized by caspase 3 and poly(ADP-ribose) polymerase processing, DNA cleavage, and JNK phosphorylation. IEC-18 transformed with oncogenic H-Ras have increased expression of ORP4L and ORP4S proteins and are resistant to the growth-inhibitory effects of ORP4 silencing. Results suggest that ORP4 promotes the survival of rapidly proliferating cells.

SUBMITTER: Charman M

PROVIDER: S-EPMC4140924 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Oxysterol-binding protein (OSBP)-related protein 4 (ORP4) is essential for cell proliferation and survival.

Charman Mark M Colbourne Terry R TR Pietrangelo Antonietta A Kreplak Laurent L Ridgway Neale D ND

The Journal of biological chemistry 20140416 22

Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) comprise a large gene family with sterol/lipid transport and regulatory activities. ORP4 (OSBP2) is a closely related paralogue of OSBP, but its function is unknown. Here we show that ORP4 binds similar sterol and lipid ligands as OSBP and other ORPs but is uniquely required for the proliferation and survival of cultured cells. Recombinant ORP4L and a variant without a pleckstrin homology (PH) domain (ORP4S) bind 25-hydroxycholest ...[more]

PMID: 24742681

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Project description:Oxysterol-binding Protein (OSBP) is a human lipid-transport protein required for the cellular replication of many types of viruses, including several human pathogens. The structurally-diverse small molecule compounds OSW-1, itraconazole (ITZ), T-00127-HEV2 (THEV) and TTP-8307 (TTP) inhibit viral replication through interaction with the OSBP protein. The OSW-1 compound reduces intracellular OSBP, and the reduction of OSBP protein levels persists multiple days after the OSW-1-compound treatment is stopped. The OSW-1-induced reduction of OSBP levels inhibited Enterovirus replication prophylactically in cells. In this report, the OSBP-interacting compounds ITZ, THEV, and TTP are shown not to reduce OSBP levels in cells, unlike the OSW-1-compound, and the OSW-1 compound is determined to be the only compound capable of providing prophylactic antiviral activity in cells. Furthermore, OSW-1 and THEV inhibit the binding of 25-hydroxycholesterol (25-OHC) to OSBP indicating that these compounds bind at the conserved sterol ligand binding site. The ITZ and TTP compounds do not inhibit 25-hydroxycholesterol binding to OSBP, and therefore ITZ and TTP interact with OSBP through other, unidentified binding sites. Co-administration of the THEV compound partially blocks the cellular activity of OSW-1, including the reduction of cellular OSBP protein levels; co-administration of the ITZ and TTP compounds have minimal effect on OSW-1 cellular activity further supporting different modes of interaction with these compounds to OSBP. OSW-1, ITZ, THEV, and TTP treatment alter OSBP cellular localization and levels, but in four distinct ways. Co-administration of OSW-1 and ITZ induced OSBP cellular localization patterns with features similar to the effects of ITZ and OSW-1 treatment alone. Based on these results, OSBP is capable of interacting with multiple structural classes of antiviral small molecule compounds at different binding sites, and the different compounds have distinct effects on OSBP cellular activity.

Dataset Information

Oxysterol-binding protein (OSBP)-related protein 4 (ORP4) is essential for cell proliferation and survival.

Publications

Oxysterol-binding protein (OSBP)-related protein 4 (ORP4) is essential for cell proliferation and survival.

Similar Datasets

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