Phosphatidylcholine transfer protein

Phosphatidylcholine transfer protein (PCTP) also known as StAR-related lipid transfer domain protein 2 (STARD2) is a specific intracellular is_associated_with::phospholipid binding is_associated_with::protein that can transfer is_associated_with::phosphatidylcholine between different membranes in the is_associated_with::cytosol.

In humans, phosphatidylcholine transfer protein is encoded by the PCTP is_associated_with::gene.

Function
PCTP transfers phosphatidylcholine molecules between membranes is_associated_with::in vitro. Further studies found that sensitivity to phosphatidylcholine levels causes PCTP to interact with select is_associated_with::enzymes, promoting their activation. PCTP stimulates the acyl-CoA is_associated_with::thioesterase activity of thioesterase superfamily member 2 (Them2)/acyl-CoA thioesterase 13 (ACOT13) and the activity of homeodomain transcription factor paired box gene 3 (is_associated_with::PAX3). Protein kinase C phosphorylation promotes localization of PCTP to the mitochondrion where it may activate Them2.

Structure
This soluble protein is 214 is_associated_with::amino acids long. It is almost entirely composed of a is_associated_with::StAR-related transfer domain (START). is_associated_with::X-ray crystallography shows that this domain forms a pocket that can bind a single is_associated_with::molecule of phosphatidylcholine.

This protein also founds the StarD2 subfamily of proteins. This subfamily consists of PCTP, StarD7, StarD10 and collagen type IV alpha-3-binding protein or StarD11, all of which bind phosphatidylcholine except for StarD11 which prefers is_associated_with::ceramide.

Tissue distribution and pathology
PCTP is produced in all tissues in the body at various levels. The protein is expressed at high levels in tissues engaged in high metabolism, notably including the liver and macrophages.

No human patients with defects in PCTP have been described to date. Mice lacking PCTP exhibit a resistance to is_associated_with::atherosclerosis linked to changes in plasma lipid levels and changes in body weight linked to the level of brown fat use of fatty acids and Them2 activity. Loss of PCTP in fasting mice alters the sensitivity of the liver to insulin, reducing is_associated_with::glucose and is_associated_with::free fatty acid levels.