Investigations on polyethylene glycol-induced cell fusion - freeze fracture observations

Aqueous solutions of more than 35% polyethylene glycol (PEG: m. w. 1500) fuse mammalian monolayer cells. The strong "water affinity" of these solutions and a changed conformation of the PEG molecules seem to us responsible for their fusogenic activity. Aggregation of surface proteins of a single cell membrane and of neighbouring ones, causes protein-free phospholipid areas as well as close cell-cell contacts. After washing off fusogenic PEG solutions, cells, adhering to each other where particle free membrane areas are attached, may start to fuse spot-like at these sites within a 5-60 min. incubation period. The PEG-induced intracellular processes (e.g. increase in vesicles and Golgi-fields) supposedly are involved in expanding the small cytoplasmic connections to polynuclear cells.