Spectrin Content Research Articles

Interaction of plasma lipoproteins with erythrocytes. II. Modulation of membrane-associated enzymes

When incubated with intact erythrocytes, low density lipoproteins (LDL) decrease the phosphate content of erythrocyte spectrin allowing the cells to undergo morphological transformation. The phosphate content of spectrin depends on the balance between the activity of membrane-associated cyclic AMP-independent protein kinases and phosphoprotein phosphates. LDL do not influence the activity of membrane-associated cyclic AMP-independent protein kinases; these lipoproteins activate by 2-fold and greater membrane-associated phosphatases as determined by hydrolysis of p- nitrophenyl phosphate and by phosphate hydrolysis of phosphorylated erythrocyte membrane proteins. We conclude that LDL interact at the exterior surface of the erythrocyte to stimulate dephosphorylation of spectrin. The significance of this conclusion is augmented by the fact that spectrin, the target for LDL-induced dephosphorylation, specifies cell morphology and modulates the distribution of cell-surface receptors. LDL also render erythrocyte acetylcholinesterase less susceptible to inhibition by F −. Lipoproteins in the high density class (HDL) do not stimulate dephosphorylation of spectrin, and they are consequently unable to alter erythrocyte morphology. HDL do prevent the LDL-induced activation of membrane phosphatase. The inhibitory capacity of HDL is observed over the range of LDL : HDL (w/w) which exists in the plasma of normolipemic humans.

Erythrocyte spectrin alteration induced by low‐density lipoprotein

Addition of human plasma low-density lipoproteins (LDL) to intact human erythrocytes induces the erythrocytes to undergo morphologic transition from biconcave disks to echinocytes and spherocytes. The transformation is time-dependent. Two hours are required before echinocytes are detected by scanning electron microscopy. After two hours, LDL also decrease the phosphate content of spectrin by 40% relative to the control, suggesting that these lipoproteins modulate cell shape by influencing phosphorylation-dephosphorylation of a membrane-associated cytoskeletal protein. LDL do not induce depletion of intracellular adenosine triphosphate (ATP), nor do they inhibit cyclic adenosine monophosphate-independent protein kinases which phosphorylate spectrin. LDL stimulate membrane-bound phosphatases by a factor of two, thereby reducing the amount of phosphate covalently bound to membrane proteins. The observed effects are specific for LDL. High-density lipoproteins (HDL) do not stimulate dephosphorylation of spectrin or alter erythrocyte morphology. However, HDL protect the erythrocytes against LDL-induced alterations. These data suggest that the circulating lipoproteins have a role in maintaining erythrocyte morphology by regulating the extent of phosphorylation of spectrin.

Erythrocyte spectrin peak II phosphorylation in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a rapidly progressive crippling disease of young boys that is inherited as an X-linked recessive trait. Previous studies have demonstrated the usefulness of erythrocyte studies in exploring membrane abnormalities in inherited muscular dystrophy. Erythrocyte spectrin peak II protein (m.w. ⋍ 220,000) was more highly phosphorylated under initial rate conditions in DMD than in controls. The extent of peak II phosphorylation was greater in DMD erythrocytes and a Na + stimulated peak II phosphorylation effect (Avruch and Fairbanks 1974) was not found to account for the differences between DMD and controls. The phosphorylated state of spectrin proteins in the membrane was evaluated and no differences in DMD could be measured. The maximal transfer of phosphate from [γ- 32P]ATP to spectrin peak II accounts for approximately 5–10% of the total phosphate content of spectrin.

MORPHOFUNCTIONAL PARAMETERS OF CATTLE ERYTHROCYTES UNDER STRESS AND ITS CORRECTION BY LOW-INTENSITY LASER RADIATION

The study investigated the content of malondialdehyde (MDA), the electrophoretic mobility of erythrocytes (EPME), the spectrum of erythrocyte membrane proteins and the morphology of cattle erythrocytes in in vitro experiments under stress and exposure to low-intensity laser radiation (LLLT). Clinical and experimental studies carried out in the last decade indicate the possibility of modulating the organism adaptive reactions when exposed to such physical factors as low-intensity laser radiation. The work showed that the effect of LLLT on the blood of stressed animals caused the restoration of the studied parameters to the level of physiological norms, while in animals that underwent technological stress, EPME was reduced by 31%, MDA concentration was increased by 65%. The effect of LLLT on the blood of unstressed animals did not lead to a change in EPME and MDA concentration. The study of the protein spectrum of erythrocyte membrane of animals subjected to technological stress revealed that the content of spectrin decreased by 16%, glycophorin C increased by 35%, the morphology of erythrocytes after stress was characterized by an increase in the number of echinocytes, stomatocytes and degeneratively altered erythrocytes. Under the LLLT action on the cow erythrocytes after stress there was a restoration of the morphology of cells and the content of proteins of erythrocyte membranes to the control level.