The crystal structure of ORP3 reveals the conservative PI4P binding pattern

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Oxysterol-binding protein (OSBP) and its related proteins (ORPs) form a conserved family of lipid transfer proteins (LTPs).
• ORPs function as intracellular lipid exchangers and sensors, regulating lipid homeostasis and signaling pathways.
• OSBP-related protein 3 (ORP3) is critical for cell adhesion and migration, presenting a potential drug target for cancer therapy.

Purpose of the Study:

• To determine the crystal structures of human ORP3 ORD and its complex with PI4P.
• To confirm the in vitro binding capability of ORP3 to PI4P.
• To validate PI4P as a common ligand for ORPs and their role as lipid exchangers at membrane contact sites (MCS).

Main Methods:

• X-ray crystallography to obtain high-resolution structures of human ORP3 ORD and the ORD-PI4P complex.
• In vitro binding assays to confirm the interaction between ORP3 and PI4P.

Main Results:

• Reported crystal structures of human ORP3 ORD at 2.1 Å and the ORD-PI4P complex at 3.2 Å.
• In vitro binding assays confirmed ORP3's ability to bind PI4P.
• Provided evidence that PI4P is a common ligand for all ORPs.

Conclusions:

• ORP3 plays a key role in lipid transfer and homeostasis.
• ORPs function as lipid exchangers at membrane contact sites.
• The findings support the development of ORP3 as a therapeutic target for cancer and other diseases involving lipid dysregulation.