BCL-XL directly interacts with BAK in resting platelets. (A) Lysates from washed platelets (20 μg) from 6 healthy volunteers were analyzed by Western blotting for expression of BCL2 proteins. A lysate from CLL cells cultured for 24 hours on CD154-expressing fibroblasts, as well as lysates from Jurkat or HeLa cells, were used as positive controls. (B) Washed platelets from a healthy volunteer were exposed to ABT-263 (100nM) in the presence of z-VAD.fmk (50μM) for 2 hours before lysis and immunoprecipitation of BCL-XL. Interaction of BCL-XL with BAK or BID was assessed by staining with anti-BAK or anti-BID antibody, respectively. (C) Binding of BAK to BCL-XL was quantified using densitometry on lanes 5 and 6 of Western blots as shown in panel B and expressed as a ratio of BAK/BCL-XL in 4 individual samples together with the mean (−).
