Phosphatidylinositol transfer proteins couple lipid transport to phosphoinositide synthesis

Phosphatidylinositol transfer proteins (PITPs) are lipid binding proteins t hat can catalyse the transfer of phosphatidylinositol (PI) from membranes e nriched 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 protei ns of 160 kDa (rdgB alphaI and II), which contain a PITP domain, arp Sound in mammalian cells. PITPs are intimately associated with the compartmentali sed synthesis of different phosphorylated inositol lipids. PI is the primar y inositol lipid that is synthesised at the endo-plasmic reticulum and is f urther phosphorylated in distinct membrane compartments by many specific li pid kinases to generate seven phosphorylated inositol lipids which are requ ired for both signalling and for membrane traffic. PITPs play essential rol es in both signalling via phospholipase C and phosphoinositide 3-kinases an d in multiple aspects of membrane traffic including regulated exocytosis an d vesicle biogenesis.