α-granule thrombospondin-1, von Willebrand factor, and osteonectin degradation.

Western blots compare thrombospondin-1 (A), von Willebrand factor (vWF) (B), and osteonectin (C) in QPD platelet lysates with degraded forms generated by incubating normal platelet ionophore releasate with tcu-PA (lanes and samples as in Figure 8; ng/mL tcu-PA are indicated). (A) When tcu-PA was incubated with normal platelet releasate, α-granule thrombospondin-1 was partially proteolyzed to a form that comigrated with the larger thrombospondin-1 degradation product in QPD platelets (arrow) (lanes compare 24 μL releasate and lysate, after reduced 4%-8% SDS-PAGE). (B) tcu-PA induced the degradation of von Willebrand factor to a form that comigrated with degraded von Willebrand factor in QPD platelets (arrow) (lanes compare 6 μL of releasate and lysate, after reduced 7% SDS-PAGE). (C) tcu-PA also induced the proteolysis of α-granule osteonectin, generating a form that comigrated with degraded osteonectin in QPD platelets (arrow) (lanes compare 9 μL releasate and lysate, after reduced 12% SDS-PAGE).