**2.5 OSBPL3 (ORP3)**

**Structure, Tissue distribution and Intracellular localization:** ORP3 belongs to the subfamily III of OSBP/ORP homologues. ORP3 has an ORD, a PH domain and an FFAT motif. A total of eight isoforms of ORP3 were demonstrated with alternative splicing (Collier, Gregorio-King et al. 2003). In human tissues there was specific isoform distribution, with most tissues expressing varied levels of isoforms with the complete ORD; while only whole brain, kidney, spleen, thymus, and thyroid expressed high levels of the isoforms associated with the truncated ORD. The expression in cerebellum, heart, and liver of most isoforms was negligible. Lehto et al described that ORP3 was expressed at high levels in kidney tubule epithelia and in the human embryonic kidney cell line HEK293 (Lehto, Mayranpaa et al. 2008).

They also described that the endogenous ORP3 protein in HEK293 cells localized at the ER and the PM, especially thin filopodial cell-surface projections.

**Molecular functions related to dyslipidemia:** The direct evidence that ORP3 functions to regulate Dyslipidemia is yet to be reported.

ORP3 interacts with R-Ras, a small GTPase regulating cell adhesion, spreading and migration (Lehto, Mayranpaa et al. 2008). Gene silencing of ORP3 and overexpression of ORP3 in HEK293 cells or primary macrophages demonstrate the function of ORP3 as part of the machinery that controls the actin cytoskeleton, cell polarity and cell adhesion. These functional evidences, together with the abundant expression of ORP3 in polarized cell types, suggest that ORP3 may play an important role in efficient directed membrane trafficking. **Epidemiological study:** Epidemiological study of ORP3 is not reported yet.
