FIG. 3.

Activated Akt attenuates growth factor withdrawal and BID-induced BAK oligomerization. (A) Rat1a, Rat1a-mAkt, and Rat1a-Bcl-2 cell lines were deprived of serum and mitochondrion-enriched fractions were isolated at different times after serum deprivation. The isolated mitochondrial fractions were subjected to protein cross-linking with bismaleimidohexane. Following cross-linking mitochondria were lysed and subjected to Western blot analysis using anti-BAK antibodies. Oligomerization of BAK was monitored by the appearance of higher-molecular-weight species consistent with BAK dimers and trimers, as well as by the disappearance of BAK monomers. (B) The same experiment as in panel A, except that cell lines overexpressing BID were used. (C) BAK oligomerization assay was performed 13 h after infection of Rat1a and Rat1a-mAkt cells with tBID- or control GFP-expressing retrovirus. Arrowheads, oligomers; asterisks, nonspecific bands.