Cell Erythrocyte ghosts

Tetraphenylporphyrins [69] are hydrophobic compounds and are unable to penetrate unaided into the water-containing tissues of the human body. This only becomes possible on incorporation into a dendrimer or a liposome. Use in the human body has not yet been tested but prehminary experiments have been performed on ruptured red blood cells, erythrocyte ghosts. The blood cells were washed out, and the tetraphenylporphyrin was introduced into the membrane of the ghosts and subjected to photophysical investigation [70]. 

The transfer of radiolabeled phospholipids between vesicles and erythrocyte membranes could be used to assay lipid transfer activity. Intact erythrocytes are not an ideal substrate for routine measurements of transfer activity because some transfer proteins do not readily accelerate the transfer of phospholipids from these membranes. Van Meer et al. (1980) found that a very high concentration of the phosphatidylcholine-specific transfer protein was necessary to exchange the phosphatidylcholine of intact red blood cells. Erythrocyte ghosts are a more active substrate for this protein (Bloj and Zilversmit, 1976). However, the nonspecific transfer protein from bovine liver accelerates the exchange of phospholipid between intact erythrocytes and phosphatidylcholine vesicles (Crain and Zilversmit, 1980c). 

Different tissues have different lipid compositions. The most common lipid components of membranes are PC and PE. Lipid extracts from brain and lung are also rich in PS heart tissue is rich in PG, and liver is rich in PI [567]. Human blood cells, as ghost erythrocytes (with cytoplasm contents removed), are often used as membrane models. These have different compositions between the inner and outer leaflets of the bilayer membrane. Phospholipids account for 46% of the outer leaflet membrane constituents, with PC and Sph about equal in amount. The inner leaflet is richer in phospholipids (55%), with the mix 19% PE, 12% PS, 7% PC and 5% Sph [567],... 

Here, we discuss a solid-state 19F-NMR approach that has been developed for structural studies of MAPs in lipid bilayers, and how this can be translated to measurements in native biomembranes. We review the essentials of the methodology and discuss key objectives in the practice of 19F-labelling of peptides. Furthermore, the preparation of macroscopically oriented biomembranes on solid supports is discussed in the context of other membrane models. Two native biomembrane systems are presented as examples human erythrocyte ghosts as representatives of eukaryotic cell membranes, and protoplasts from Micrococcus luteus as membranes... 

Schwoch G, Passow H (1973) Preparation and properties of human erythrocyte-ghosts. Mol Cell Biochem 2 197-218... 

Polymerizable lipids can be incorporated into e.g. erythrocyte ghost cells by means of hemolysis and polymerized here-... 

Polyphosphate was chosen as a polyelectrolyte in addition to the erythrocyte ghost protein, because van Steveninck demonstrated (17) that polyphosphate plays an important role in membrane transport in yeast cells. The results obtained with polyphosphate, especially on protein-covered membranes, indicate that the possibility of ionic transport is strongly enhanced. 

Figure 8-14 SDS-polyacrylamide gel electrophoresis of human erythrocyte ghosts. (A) From untreated cells. (B) From cells digested externally with chymotrypsin. (C) Inside-out vesicles prepared from cells pretreated with chymotrypsin. (D) The same inside-out vesicles after further treatment with chymotrypsin. (E) Polypeptides released hy the chymotryptic treatment of the inside-out vesides. The peptides are numbered according to the system of Steck232 Hb, hemoglobin. From Luna et al233...

In contrast to the ion exchange theory, much evidence indicates that cells have an active ion pump that removes Na+ from cells and introduces K+. For example, the cytoplasm of the giant axons of nerves of squid can be squeezed out and replaced by ionic solutions. Erythrocyte ghosts can be allowed to reseal with various materials inside. Ion transport into or out of cells has been demonstrated with such preparations and also with intact cells of many types. Such transport is blocked by such inhibitors as cyanide ion, which prevents nearly all oxidative metabolism. However, the cyanide block can be relieved by introduction into the cells of ATP and other phosphate compounds of high group-transfer potential. 

First, a mixture of synthetic or natural phospholipids, polymerizable lipids, and proteins can be converted to liposomes and then be polymerized. Second, polymerizable lipids are introduced into e.g. erythrocyte ghost cells by controlled hemolysis and subsequent polymerization as described by Zimmermann et al.61). This hemolysis technique is based on a reversible dielectric breakdown of the cell membrane. Dielectric breakdown provides a third possible path to the production of bi omembrane models. Zimmermann et al. could show that under certain conditions cells can be fused with other cells or liposomes61). Thus, lipids from artificial liposomes could be incorporated into a cell membrane. A fourth approach has been published by Chapman et al.20). Bacterial cells incorporate polymerizable diacetylene fatty acids into their membrane lipids. The diacetylene units can be photopolymerized in vivo. The investigations discussed in more detail below are based on approaches 1. and 3. 

Loss of hemoglobin by lysed red blood cells (cell membrane lysis). Controlled hemolysis (induced osmotically or electrically) yields hemoglobin-free erythrocyte ghosts . 

The human erythrocyte possesses a characteristic biconcave shape and remarkable viscoelastic properties. Electron microscopy studies performed on red blood cells (RBC), ghosts, and skeletons revealed a two-dimensional lattice of cytoskeletal proteins. This meshwork of proteins was thought to determine the elastic properties of the RBC. This... 

Maitotoxin-induced calcium influx in erythrocyte ghosts and rat glioma C6 cells, and blockade by ganglio-... 

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