V irus and lectin agglutination of erythrocytes: spin label study of membrane lipid-protein interactions

Techniques of spin-label electron spin resonance have been used to prove changes in the structure of the lipid phase of erythrocyte membrane after agglutination by viruses and lectins. When chicken erythrocytes are agglutinated by Sendai and influenza viruses and by the lectins concanavalin A and wheat germ agglutinin, the membrane lipid phase becomes more fluid, as detected by three different lipophilic spin-laveled probes. Colchicine, vinblastine, and tetracaine inhibit the fluidization of chicken erythrocyte membrane by Sendai virus, whereas cytochalasin B has no effect. The effect of colchicine was time dependent, the initial inhibition decreasing with longer preincubation times. Extensive treatment of erythrocytes with proteases or neuraminidase, while not altering the bilayer structure, abolishes the effect of Sendai virus on the erythrocyte membrane, suggesting that a change in the interaction of the receptor protein with the lipid phase occurs upon virus attachment. Glutaraldehyde fixation increased the structural rigidity of the chicken erythrocyte membrane and inhibited the effect of viral agglutination. No change in bilayer structure was observed upon agglutination of human erythrocytes or the isolated plasma membranes of either human or chicken erythrocytes. This result is consistent with the drug sensitivity of the effects of agglutination upon chicken erythrocytes, since human erythrocytes and isolated membranes lack microtubule-like structures.