INDUCTION OF CELL-FUSION IN CULTURED FIBROBLASTS AND EPITHELIAL-CELLS BY MICROINJECTION OF EGTA, GTP-GAMMA-S AND ANTIFODRIN ANTIBODIES

CaCl2, EGTA, GTP gamma S and anti-alpha-fodrin antibodies were injected into fibroblast-like IMR-33 cells and Madin-Darby bovine kidney (MDBK) epithelial cells cultured both in the presence and absence of cycloheximide and fetal calf serum. EGTA, GTP gamma S and antifodrin antibody induced fusion of MDBK cells within one hour after injection. The cells formed polykaryons with up to 15 nuclei, reaching an average fusion index of 20%. IMR-33 cells fused at a slower kinetics and only upon injection of GTP gamma S or antifodrin antibodies. No fusions were seen in serum-deprived, quiescent cells. On the other hand, cycloheximide treatment did not prevent the fusions. The results show that cells can be induced to fuse by using agents that interfere with the regulation of the G-proteins, intracellular calcium level or membrane skeleton. We suggest that the putative fusogens are resident proteins of the plasma membrane which become exposed upon destabilization of the membrane skeleton.