Membrane-mobility agent-promoted fusion of erythrocytes: Fusibility is correlated with attack by calcium-activated cytoplasmic proteases on membrane proteins

Rat, but not human, erythrocytes undergo fusion promoted by the membrane-mobility agent 2-(2-methoxyethoxy)-ethyl cis-8-(2-octylcyclopropyl)octanoate (A₂C). The difference in behavior is correlated with rat erythrocyte membrane protein degradation caused by Ca²⁺-activated proteases. The human erythrocyte is deficient in such protease activity. Membrane protein degradation is a necessary, but not sufficient, requirement for membrane fusion. Membrane protein degradation probably releases membrane components from certain constraints. In addition, the motion of membrane components precedes fusion and must be promoted by reagents such as A₂C, leading to the creation of fusion-potent lipid areas. This sequence of chemical and physical events occurs in other fusion processes.