Function
Phosphoinositide-binding protein which associates with both cell and endoplasmic reticulum (ER) membranes. Can bind to the ER membrane protein VAPA and recruit VAPA to plasma membrane sites, thus linking these intracellular compartments. The ORP3-VAPA complex stimulates RRAS signaling which in turn attenuates integrin beta-1 (ITGB1) activation at the cell surface. With VAPA, may regulate ER morphology. Has a role in regulation of the actin cytoskeleton, cell polarity and cell adhesion. Binds to phosphoinositides with preference for PI(3,4)P2 and PI(3,4,5)P3. Also binds 25-hydroxycholesterol and cholesterol.
Subcellular Location
Endoplasmic reticulum membrane; Peripheral membrane protein. Cytoplasm, cytosol. Cell membrane; Peripheral membrane protein. Cell projection, filopodium tip. Nucleus membrane; Peripheral membrane protein.
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.