Phospholipid transfer proteins revisited

Abstract

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.

Purification and cloning of phosphatidylinositol transfer proteins from Dictyostelium discoideum: homologues of both mammalian PITPs and Saccharomyces cerevisiae Sec14p are found in the same cell

“…Phosphatidylinositol transfer proteins (PITPs) are defined by their ability to mediate the exchange of PtdIns or phosphatidylcholine (PtdCho) monomers between membranes in itro [1]. In mammalian cells, two soluble PITP isoforms have been described, PITPα and PITPβ, which are 77 % identical.…”

“…For example, PtdIns3P exerts its Abbreviations used : GFP, green fluorescent protein ; PITP, phosphatidylinositol transfer protein ; PLC, phospholipase C ; PtdCho, phosphatidylcholine. 1 To whom correspondence should be addressed (e-mail s.cockcroft!ucl.ac.uk).…”

Phosphatidylinositol Transfer Protein Expression Altered by Aging and Parkinson Disease

“…These proteins are involved in phospholipids degradation, phospholipids transport, as well as in dynamic cytoskeleton changes and in function of Golgi system (Wirtz, 1991(Wirtz, , 1997Snoek et al, 1999). It seems that the decrease of PI-TP protein level may be one of the important factors that lead to disturbing of phospholipids signaling and also may be involved in neurodegeneration of CNS.…”

“…Phosphatidylinositol (PI) transfer protein (PI-TP) is a small ubiquitously expressed and abundant protein that transfers PI and phosphatidylcholine (PC) between membranes (Wirtz, 1991(Wirtz, , 1997Geijtenbeerk et al, 1994). Recent studies have shown that the cellular functions of PI-TP are not only connected with phospholipid transfer per se from its site of synthesis in the endoplasmic reticulum to the other membranes but also with other important cell functions as vesicle transport, dynamics of cytoskeleton proteins, and PI metabolism (Thomas et al, 1993b;Liscovitch and Cantley, 1995;Monaco et al, 1998;Snoek et al, 1999).…”

Phosphatidylinositol transfer proteins: From closed for transport to open for exchange

“…Since their purification from bovine brain phosphatidylinositol transfer proteins (PI-TP) have been subject to extensive studies mainly prompted by the hypothesis that these proteins play a key role in intracellular phosphatidylinositol (PI) transport and as a consequence, in PI-dependent signalling pathways (Helmkamp et al, 1974;Wirtz, 1997). To date, two isoforms of PI-TP have been identified: PI-TPa (270 amino acids) and PI-TPb (271 amino acids).…”