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Four human spectrin genes are now recognized. Two encode alpha spectrins (αI and αII), the other two encode beta spectrins (βI and βII). Multiple alternatively spliced transcripts have also been identified for all but al spectrin, yielding a subtle but rich diversity of possible ap spectrin heterodimer species in most cells. The role of these isoforms and the factors that control their assembly into...
It has been shown that the time course of echinocyte to discocyte transformation caused by exogenous phospholipids is an accurate measure of the flip rate of the phospholipids in the lipid bilayer [1,2]. In order to explore whether shape changes in erythrocytes are indicative of flip rates of water- soluble amphiphiles, the time course of shape changes caused by a large number of amphiphiles was studied...
Transduction of extracellular signals requires activation of membrane-bound receptors. The transmission of the external signal across the plasma membrane often leads to an increase in the intracellular level of calcium [1-3]. In neurons, stimulation can increase the level of calcium more than 1000-fold; from <0.1 pM to 200-300 μM [4], This internal signal triggers calcium-binding proteins such...
In this review we discuss the evidence in support of the concept that a posttranslational modification in β-actin, in which a disulfide bridge is formed between cysteine284 and cysteine373, is the major cause of the formation of the irreversibly sickled cell (ISC). This ISC β-actin modification caused a decreased ability of the ISC membrane skeletal proteins to disassemble, as compared to the control...
A view is presented on different roles which the bilayer part of the membrane and the skeleton play in establishing normal and some abnormal RBC shapes. The system is first studied at the level of elastic properties of red blood cell membrane where the latter is considered to be a trilayered structure. Then the contributions to the membrane energy are introduced which cause the membrane to become...
Although interaction of red blood cell spectrin with phospholipids of the membrane bilayer was first reported more than 20 years ago its physiological significance is still a matter of dispute. In this paper we review the available data on interactions of red blood cell and nonerythroid spectrin with membrane phospholipids. The results from our laboratory indicate that ankyrin and phospholipids (particularly...
Annexins IV and VI were found to interact with human erythrocyte membrane in a calcium-dependent manner. Chemical and enzymatic modification of the membrane constituents pointed to phosphatidylserine as a target membrane molecule responsible for the interaction of the annexin/Ca complexes with the membrane. The membrane-associated annexins were shown to form clusters reflecting, perhaps, the presence...
Brain spectrin (fodrin, calspectin), is an actin binding protein, and composed of two α- and two β-subunits which combine by head-to-head interaction to a heterotetramere. Together with other proteins it forms a proteinaceous meshwork underlying the cytoplasmic surface of the plasma membrane. In the mammalian brain, three forms of spectrins were identified, an axonal, a somato-dendritic and a astroglial...
There are two established pathways linking the membrane cytoskeleton of the red blood cell to integral proteins of the membrane. We review the characteristics of these interactions and give reasons for believing that they are insufficient to engender the exceptional stability and elastic properties that characterise the native membrane. We show that in a model system, consisting of a phospholipid...
The mechanical properties of the red cell are accounted for by its membrane and its membrane skeleton, the latter being a protein network that laminates the inner surface of the lipid bilayer. Hereditary spherocytosis (HS) is the most common of congenital hemolytic anemias. The spherocytes have a reduced lifespan due to their spheroidal shape that alters their resistance and elastic deformability...
Light scattering experiments were undertaken to study binding of the Max transcription factor to its E-box DNA recognition sequence. Translational diffusion coefficients were measured and the average hydrodynamic radii (Rh) of complexes calculated using the Stokes-Einstein equation. We detected both dimerization of Max and the formation of a stable complex with its E-box DNA target. These results...
Spectrin and spectrin-like proteins were found in almost all animal and protozoan cells. Moreover, several reports indicate their presence also in plants. We found that polypeptides reacting with anti-spectrin antibodies are also present in bacteria such as Escherichia coli and Halobacterium salinarium. In Escherichia coli only polypeptide(s) reacting with antibodies directed against a- subunit could...
The cytoskeleton is involved in regulating motile events and properties of the plasma membrane. However, it is now clear that the cytoskeleton can bind signaling molecules, recruiting them adjacent to their substrates, and/or inducing their activation. In platelets, the membrane is lined by a skeleton which in turn associates with membrane glycoproteins. Signaling molecules associate with the membrane...
ras-encoded p21 protein expression was investigated immunohistochemically in 10 specimens of human endometrial adenocarcinoma. The control group consisted of 5 proliferative endometrium slides. The analysis was performed by using the biotin-streptavidin-peroxidase AEC detection system. An immunohistochemical histologic H- score according to Nyholm et al. [1] was calculated in a semiquantitative fashion...
Liver is an epithelial organ which removes many substances from the blood, metabolizes them, and secretes back into circulation or directly into the bile. Liver parenchymal cells (hepatocytes) are involved in the overall detoxification of the organism through the bile. These highly polarized cells are unique among others due to the domain structure of their plasma membrane, organization of their cytoskeleton...
We tested in vitro the role of functional groups and overall structure of sterol skeleton as well as sterol concentration in the ability of erythrocyte membranes to accumulate C27-sterol molecules. It is established that association with erythrocyte membranes of C27-sterols: cholesterol, 7-dehydrocholesterol, cholecalciferol (vitamin D3), calcitriol (lα,25-dihydroxycholecalciferol), ecdysterone (20-hydroxyecdysone)...
A possible physical interpretation of a discontinuous transition between different red blood cell shapes is given. The red blood cell membrane is considered to consist of the bilayer part and the underlaying membrane skeleton. By taking into consideration that the stable cell shape corresponds to the minimum of the membrane energy, that consists of the bilayer and skeleton elastic energies and of...
The effect of divalent cations in concentrations 10-9-10-3M upon the hemolysis of sheep erythrocytes induced by resorcinolic lipids was studied. It was demonstrated that the process of hemolysis is inhibited by divalent cations present in the incubation medium. The extent of inhibition is dependent on both type of the cation and hemolytic agent. In alkylresorcinol-induced hemolysis the most effective...
We investigated the effect of native and modified high density lipoprotein (HDL) and low density lipoprotein (LDL) on the viability and the membrane fluidity of normal and diabetic fibroblasts. Under experimental conditions, HDL did not affect the cultured normal cells. Incubation of HDL with diabetic fibroblasts resulted in a negligible decrease in the cell viability and induced an increase in the...
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