Scramblase

Reviews of the role of aminophospholipid translocase and scramblase (Schlegel et al, 2000) and the consequences of the appearance of phosphatidylserine on the cell surface (Williamson et al, 2001) in apoptosis of thymocytes have been published. The precise relationship between membrane phospholipid asymmetry and apoptosis is currently a topic of considerable interest. 

Bratton, D.L., 2000, Regulation ofphosphohpid scramblase activity during apoptosis and cell activation by protein kinase Cdelta. J. Biol. Chem. 275 23065-23073. 

Zhao, J., Zhou, Q., Wiedmer, T. and Sims, P.J., 1998a, Level of expression of phosphohpid scramblase regulates induced movement of phosphatidylserine to the cell surface. J. Biol. Chem. 273 6603-6606. 

In many eukaryotic plasma membranes, PS resides in the inner leaflet (Schroit and Zwaal, 1991 Zachowski, 1993). This transbilayer distribution of membrane hpids is not a static situation but a result of balance between the inward and outward translocation of phospholipids across the membranes. Recent studies showed that the transbilayer lipid asymmetry is regulated by several lipid transporter proteins, such as aminophospholipid translocase (Daleke and Lyles, 2000), ATP-binding cassette transporter family (van Helvoort et al, 1996 Klein et al, 1999), and phospholipid scramblase (Zhou et al, 1997 Zhao et al, 1998). An increment of intracellular due to cell activation, cell injury, and apoptosis affects the activities of these transporters, resulting in exposure of PS (Koopman et al, 1994 Verhoven et al, 1995) and PE (Emoto et al, 1997) on the cell surface. 

Fadeel, B., Gleiss, B., Hogstrand, K., Chandra, J., Wiedmer, T., Sims, P., Henter, J.-I, Orrenius, S., and Samah, A., 1999, Phosphatidylserine exposure during apoptosis is a cell type-specific event and does not correlate with plasma membrane phospholipid scramblase expression, Biochem. Biophys. Res. Commun. 266 504-511. 

Amphiphilic compounds are also known as potent modifiers of the bilayer intrinsic radius of curvature and utilize this property to act as a non-specific perturbator of membrane protein function [27]. Catamphiphilic drugs that can interact with the head groups or with the scramblases or flippases can change cell functioning. 

Murakami, M., Kambe, T., Shimbara, S., Higashino, K., Hanasaki, K., Arita, H., Horiguchi, M., Arita, M., Arai, H., Inoue, K. and Kudo, I., 1999, Different functional aspects ofthe group II subfamily (Types IIA and V) and type X secretory phospholipase A(2)s in regulating arachidonic add release and prostaglandin generation. Implications of cyclooxygenase-2 induction and phospholipid scramblase-mediated cellular membrane perturbation../. Biol. Chem., 274 31435-31444. 

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