Phospholipid transfer proteins revisited.
Phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) (identical with sterol carrier protein 2) belong to the large and diverse family of intracellular lipid-binding proteins. Although these two proteins may express a comparable phospholipid transfer activity in vitro, recent studies in yeast and mammalian cells have indicated that they serve completely different functions. PI-TP (identical with yeast SEC14p) plays an important role in vesicle flow both in the budding reaction from the trans-Golgi network and in the fusion reaction with the plasma membrane. In yeast, vesicle budding is linked to PI-TP regulating Golgi phosphatidylcholine (PC) biosynthesis with the apparent purpose of maintaining an optimal PI/PC ratio of the Golgi complex. In mammalian cells, vesicle flow appears to be dependent on PI-TP stimulating phosphatidylinositol 4,5-bisphosphate (PIP2) synthesis. This latter process may also be linked to the ability of PI-TP to reconstitute the receptor-controlled PIP2-specific phospholipase C activity. The nsL-TP is a peroxisomal protein which, by its ability to bind fatty acyl-CoAs, is most likely involved in the beta-oxidation of fatty acids in this organelle. This protein constitutes the N-terminus of the 58 kDa protein which is one of the peroxisomal 3-oxo-acyl-CoA thiolases. Further studies on these and other known phospholipid transfer proteins are bound to reveal new insights in their important role as mediators between lipid metabolism and cell functions.
Wirtz
K W
KW
Institute of Biomembranes, Centre for Biomembranes and Lipid Enzymology, Utrecht University, P.O. Box 80054, 3508 TB Utrecht, The Netherlands.
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000502:physiology*; D002417:Cattle; D003065:Coenzyme A / Q000378:metabolism; D018871:Endoplasmic Reticulum, Smooth / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005656:Fungal Proteins / Q000502:physiology; D008322:Mammals / Q000378:metabolism; D008561:Membrane Fusion; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D008830:Microbodies / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000096:biosynthesis; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism*; D010940:Plant Proteins; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism
D002352:Carrier Proteins; D005227:Fatty Acids; D005656:Fungal Proteins; D008563:Membrane Lipids; D008565:Membrane Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D010940:Plant Proteins; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C072087:sterol carrier proteins; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D003065:Coenzyme A