OSBPL3
Developmental stage
Expressed in several fetal tissues including kidney, thymus, spleen and lung.
Domain
The FFAT 2 motif is required for interaction with VAPA and regulation of the endoplasmic reticulum targeting of ORP3. The FFAT 1 motif may contribute to VAPA binding.
The PH domain binds phosphoinositides, with a preference for PI(3,4)P2 and PI(3,4,5)P3. The PH domain mediates targeting to the plasma membrane (PubMed:18270267).
Function
Phosphoinositide-binding protein which associates with both cell and endoplasmic reticulum (ER) membranes (PubMed:16143324). Can bind to the ER membrane protein VAPA and recruit VAPA to plasma membrane sites, thus linking these intracellular compartments (PubMed:25447204). The ORP3-VAPA complex stimulates RRAS signaling which in turn attenuates integrin beta-1 (ITGB1) activation at the cell surface (PubMed:18270267, PubMed:25447204). With VAPA, may regulate ER morphology (PubMed:16143324). Has a role in regulation of the actin cytoskeleton, cell polarity and cell adhesion (PubMed:18270267). Binds to phosphoinositides with preference for PI(3,4)P2 and PI(3,4,5)P3 (PubMed:16143324). Also binds 25-hydroxycholesterol and cholesterol (PubMed:17428193).
Post-translational modifications
Phosphorylation is enhanced in vitro by phorbol-12-myristate-13-acetate (PMA), forskolin and calcium ionophore A23187 (PubMed:25447204). Phosphorylation seems to be stimulated in conditions of low cell-cell (or cell-matrix) adhesion (PubMed:18270267).
Sequence Similarities
Belongs to the OSBP family.
Tissue Specificity
Expressed in a subset of small lymphocytes (at protein level). Expressed at high concentration in kidney, lymph node and thymus. Expressed at moderate concentration in stomach, jejunum, ileum, appendix, spleen, leukocytes, trachea, lung and thyroid gland. Expressed at low concentration in whole brain, esophagus, duodenum, ileocecum, colon, skeletal muscle, bone marrow, placenta and mammary gland (PubMed:14593528). Isoform 1a, isoform 1b, isoform 1c and isoform 1d are highly expressed in brain, bone marrow, colon, kidney, lung, skeletal muscle, spleen, thymus and thyroid. Not expressed in heart and liver. Isoform 2a, isoform 2b, isoform 2c and isoform 2d are expressed in brain, bone marrow, kidney, skeletal muscle, spleen, thymus and thyroid. Not expressed in heart, liver and lung (PubMed:12590732).
Cellular localization
- Endoplasmic reticulum membrane
- Peripheral membrane protein
- Cytoplasm
- Cytosol
- Cell membrane
- Peripheral membrane protein
- Cell projection
- Filopodium tip
- Nucleus membrane
- Peripheral membrane protein
- Co-localizes with OSBPL6 at contact sites between the plasma membrane and the endoplasmic reticulum.
Alternative names
KIAA0704, ORP3, OSBP3, OSBPL3, Oxysterol-binding protein-related protein 3, ORP-3, OSBP-related protein 3