Phosphatidylcholine transfer protein (PCTP) also known as StAR-related lipid transfer domain protein 2 (STARD2) is a specific intracellular phospholipid binding protein that can transfer phosphatidylcholine between different membranes in the cytosol.
In humans, phosphatidylcholine transfer protein is encoded by the PCTPgene.
PCTP transfers phosphatidylcholine molecules between membranes in vitro. Further studies found that sensitivity to phosphatidylcholine levels causes PCTP to interact with select enzymes, promoting their activation. PCTP stimulates the acyl-CoA thioesterase activity of thioesterase superfamily member 2 (Them2)/acyl-CoA thioesterase 13 (ACOT13) and the activity of homeodomain transcription factor paired box gene 3 (PAX3). Protein kinase C phosphorylation promotes localization of PCTP to the mitochondrion where it may activate Them2.
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 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 glucose and free fatty acid levels.
^van Golde LM, Oldenborg V, Post M, Batenburg JJ, Poorthuis BJ, Wirtz KW (July 1980). "Phospholipid transfer proteins in rat lung. Identification of a protein specific for phosphatidylglycerol". J. Biol. Chem. 255 (13): 6011–3. PMID7391000.
^Kanno K, Wu MK, Agate DA, Fanelli BK, Wagle N, Scapa EF, Ukomadu C, Cohen DE (October 2007). "Interacting proteins dictate function of the minimal START domain phosphatidylcholine transfer protein/StarD2". J. Biol. Chem. 282 (42): 30728–36. PMID17704541. doi:10.1074/jbc.M703745200.
^de Brouwer AP, Westerman J, Kleinnijenhuis A, Bevers LE, Roelofsen B, Wirtz KW (March 2002). "Clofibrate-induced relocation of phosphatidylcholine transfer protein to mitochondria in endothelial cells". Exp. Cell Res. 274 (1): 100–11. PMID11855861. doi:10.1006/excr.2001.5460.
^Roderick SL, Chan WW, Agate DS, Olsen LR, Vetting MW, Rajashankar KR, Cohen DE (July 2002). "Structure of human phosphatidylcholine transfer protein in complex with its ligand". Nature Structural & Molecular Biology. 9 (7): 507–11. PMID12055623. doi:10.1038/nsb812.
^Scapa EF, Pocai A, Wu MK, Gutierrez-Juarez R, Glenz L, Kanno K, Li H, Biddinger S, Jelicks LA, Rossetti L, Cohen DE (July 2008). "Regulation of energy substrate utilization and hepatic insulin sensitivity by phosphatidylcholine transfer protein/StarD2". FASEB J. 22 (7): 2579–90. PMID18347010. doi:10.1096/fj.07-105395.