Figure 7.

Platelets contain APAF-1, but do not contain caspase-9. (a) Whole-cell lysates prepared from fresh platelets (i), Jurkat T cells (ii), and MEG-01 MKs (iii) were probed with an anti-APAF-1 pAb. All cells contained an immunodetectable protein with an apparent molecular mass of ∼130 kD, consistent with it being APAF-1. (b) Whole-cell lysates prepared from Jurkat T cells (i), fresh platelets (ii and iii), MEG-01 MKs (iv), and SET-2 MKs (v) were probed by Western blot for caspase-9 with a pAb that recognized both pro- and activated forms. A major band was detected with an apparent molecular mass approximating that of caspase-9 (48 kD) within Jurkat T cells and MKs. The Western blot was stripped and reprobed for β-actin, where β-actin accounts for 30% of platelet protein.