Mechanism of the concanavalin A-induced change of membrane fluidity of XXXX erythrocytes.

@entity3106 @entity428 @entity1573 @entity2389 @entity6042 @entity141 @entity71225
When @entity1573 erythrocytes labeled with a @entity3106 derivative spin label was treated with concanavalin A (Con A), ESR spectra showed a change in the peaks due to the labels in membrane lipids, indicating an increase of membrane lipid fluidity. Addition of Con A increased the fluidity rapidly. This change was reversible only up to 30 min after adding Con A, and thereafter it gradually became irreversible. However, if the erythrocytes were treated with @entity2389 and @entity6042 , a complete return of fluidity to the normal level could be observed at any stage after the binding of Con A. The observation of freeze-fracture replicas of erythrocyte membranes by transmission electron microscopy also showed that the redistribution of intramembranous particles gradually became irreversible after exposure to Con A. These results suggest that the microfilament-like system, which modulates the distribution of cell surface receptors for Con A, participates in the modulation of membrane fluidity. Phospholipid methylation of @entity1573 erythrocyte membrane was stimulated immediately after the binding of Con A. A methyltransferase inhibitor, @entity71225 , abolished the increase of membrane fluidity within the first 10 min and also that occurring later than 60 min after adding Con A, but it was without effect on the @entity428 found between 20 and 60 min. Removal of extracellular @entity141 had an inhibitory effect on the lasting increase of fluidity. These results suggest that the first increase of membrane fluidity by Con A may be caused by phospholipid methylation, while the second increase may depend on the rearrangement of Con A receptor glycoproteins through cross-linking wit Con A. The irreversible part of the membrane fluidity increase probably depends on @entity141 influx, phospholipid methylation, and peripheral membrane proteins which constitute the microfilament-like system at the membrane inner surface.
