BLEB FORMATION AND F-ACTIN DISTRIBUTION DURING MITOSIS AND TUMOR NECROSIS FACTOR-INDUCED APOPTOSIS

The murine cell line C3HA has been used extensively in studies of the cytopathology that accompanies TNF-induced cytolysis. This cell line u ndergoes an apoptic form of cell death characterized by plasma membran e blebbing and cytoplasmic boiling. Since plasma membrane blebs also a ppear on C3HA cells during mitosis, in this report we have compared th ese blebs with those that appear during apoptosis to determine whether they represent related structures. Our results reveal several differe nces. During mitosis, the blebs that appear are smaller and more heter ogeneous in size than are those that appear during apoptosis. In addit ion, during mitosis bleb formation is preceded by the appearance of mi crovilli on the cell surface. No microvilli are observed during apopto sis. The staining pattern with rhodamine phalloidin also differed betw een mitotic and apoptic blebs, indicating a difference in their conten t of f-actin. The blebs that form during mitosis stained in a bright, uniform manner, suggesting an association with f-actin. In contrast, a poptic blebs were stained only at their base, the bleb itself being de void of f-actin-associated staining. This difference may help explain why mitotic blebs are reintegrated into the cell surface, while the bl ebs that form during apoptosis are not. (C) 1996 Wiley-Liss, Inc.