Facilitation of electrofusion of mouse lymphoma cells by the proteolytic action of proteases

Cell fusion of mouse lymphoma (L5178Y) was achieved by applying electrical pulses under dielectrophoresis. The presence of dispase, pronase or trypsin facilitated the electric pulse-induced cell fusion. Heat-inactivated pronase was no longer effective. Protease inhibitors (aprotinin and p-tosyl-L-lysine chloromethylketone) suppressed the effect of trypsin. Even in the absence of proteases, the cells pretreated with dispase or pronase underwent fusion with high probabilities, as far as free calcium ions were present in the external solution. It is concluded that facilitation of electrofusion by proteases is due to their proteolytic activities.