Cholesterol in membranes

L. Fiuegold, ed.. Cholesterol in Membrane Models, CRC Press Inc., Boca Raton, Fla., 1993. 

Papahadjopoulos, D., Cowden, M., and Kimelberg, H. (1973a). Role of cholesterol in membranes. Effects of phospholipid-protein interactions, membrane permeability and enzymatic adBiotjhim. Biophys. 

Terova, B., Petersen, G., Hansen, H. S., and Slotte, J. P. (2005). V-Acyl phosphatidylethanolamines affect the lateral distribution of cholesterol in membranes. Biochim. Biophys. Acta 1715, 49 56. Terrazzino, S., Berto, F., Carbonare, M. D., Fabris, M., Guiotto, A., Bernardini, D., and Leon, A. (2004). Stearoylethanolamide exerts anorexic effects in mice via down-regulation ofliver stearoyl-coenzyme A desaturase-1 mma expression. FASEBJ. 18, 1580-1582. 

HuiSW. The spatial distribution of cholesterol in membranes. In YeaglePL, ed. TheBiology of Cholesterol. CRC, Boca Raton, FL, 1988, pp. 213-232. 

In model membranes, ether-linked lipids decrease ion permeability and surface potential, and lower the phase temperature of membrane bilayers when compared to their diacyl counterparts. Ethanolamine plasmalogen is enriched, along with cholesterol, in membrane lipid rafts. These domains have a distinct hydrophobic environment with ordered lipid packing, and plasmalogen can serve to stabilize the interaction of specific raft proteins (Chapter 1). 

Membrane lipids, and particularly cholesterol, are instrumental not only in the control of diffusion across biological membranes but also in the determination of the activity of membrane-bound enzymes, their modulation by hormones and other agents, and the determination of membrane fluidity (for original references, see [4,6]). It is generally accepted that incorporation of cholesterol in a lipid bilayer membrane tends to decrease significantly the permeability of these membranes to water. Movement of water across these membranes occurs primarily by dissolution in the membrane matrix. The decrease in the rate of water transport as a result of cholesterol incorporation is due mainly to a decrease in membrane fluidity. As a general rule, it is found that the presence of cholesterol in membranes or the incorporation of cholesterol into dispersions composed of phosphatidylserine or ganglioside lead to a decrease in the fluidity of the hydrocarbon chains of lipid membranes which are in the liquid-crystalline state [4,20]. 

The question whether or not there is an anion-sensitive ATPase in brush border membranes was reinvestigated by Kinne-Saffran and Kinne [16], They compared the properties of Mg-ATPases in a mitochondrial and a brush-border fraction from rat kidney cortex. The mitochondrial ATPase could be stimulated 90% by bicarbonate, and was very sensitive towards oligomycin, aurovertin, carboxyactryloside and the mitochondrial inhibitor protein. The brush-border Mg-ATPase could only be stimulated 28% by bicarbonate and was inhibited at most 18% by these mitochondrial inhibitors. On the other hand, the antibiotic filipin, which reacts with cholesterol in membranes, inhibits the ATPase activity in the cholesterol-rich brush-border membranes but not that in the cholesterol-poor mitochondria. The filipin treatment, however, increased the bicarbonate sensitivity of the residual ATPase activity in the brush-border preparation, suggesting that there was still some mitochondrial contamination in this preparation. 

The macrolides possess antibiotic properties (E 5.2) and are used in medicine (F 2). The polyene macrolides act against fungi. They form complexes with the cholesterol in membranes. 

Radhakrishnan A, Anderson TG, McCormell HM. Condensed complexes, rafts, and the chemical activity of cholesterol in membranes. Proc Natl Acad Sd USA. 2000 97(23) 12422-12427. 

G. Miller, The use and abuse of flllpin to localize cholesterol in membranes. Cell, Biol. Int. Reps. 8 519 (1984). 

Cholesterol in membrane bilayers has an important modulatory effect on the bilayer phase of phospholipids [2,15]. The sterol interacts strongly with phospholipids and keeps them in an intermediate fluid condition. Thus, above its transition temperature, the presence of cholesterol tends to increase the packing and rigidity of bilayers [19], and below its transition temperature, it expands and fluidizes the bilayers [20]. 

---