Phosphatidylinositol transfer proteins couple lipid transport to phosphoinositide synthesis

Phosphatidylinositol transfer proteins (PITPs) are lipid binding proteins that can catalyse the transfer of phosphatidylinositol (PI) from membranes enriched in PI fo PI-deficient membranes. Three soluble forms of PITP of 35-38 kDa (PITP alpha, PITP beta and rdgB beta) and two larger,integral proteins of 160 kDa (rdgB alphaI and II), which contain a PITP domain, arp Sound in mammalian cells. PITPs are intimately associated with the compartmentalised synthesis of different phosphorylated inositol lipids. PI is the primary inositol lipid that is synthesised at the endo-plasmic reticulum and is further phosphorylated in distinct membrane compartments by many specific lipid kinases to generate seven phosphorylated inositol lipids which are required for both signalling and for membrane traffic. PITPs play essential roles in both signalling via phospholipase C and phosphoinositide 3-kinases and in multiple aspects of membrane traffic including regulated exocytosis and vesicle biogenesis.