FIG. 1.

BID cleavage is induced by growth factor withdrawal and is required for BID-accelerated apoptosis in the absence of growth factors. (A) Rat1a fibroblasts or Rat1a fibroblasts overexpressing mAkt (Rat1a-mAkt) or Bcl-2 (Rat1a-Bcl-2) were deprived of serum for 24 h. At different times following serum deprivation BID cleavage was monitored by immunoblotting using an anti-BID antibody (MAB860; R&D Systems). end. BID, endogenous BID. (B) Greater quantities of some of the samples from panel A were run on a new gel, and the appearance of tBID was monitored by immunoblotting using an antibody more sensitive for tBID (AF860; R&D Systems). (C) Kinetics of apoptosis of Rat1a cells overexpressing BID, BID(D59E), or vector control following serum withdrawal. Apoptosis was scored as described in Materials and Methods. All data are depicted graphically as the means ± standard errors of the means for four independent experiments.