Vinculin is a permanent component of the membrane skeleton and is incorporated into the (re)organising cytoskeleton upon platelet activation

Vinculin, a 130‐kDa protein discovered in chicken gizzard smooth‐muscle cells and subsequently also described in platelets, is believed to be involved in membrane‐cytoskeleton interactions. In this study we investigated vinculin distribution in human blood platelets. Two skeletal fractions and a remaining cytosolic fraction were prepared with a recently described Triton X‐100 lysis buffer causing minimal post‐lysis breakdown by proteolysis. The presence of vinculin was demonstrated in the membrane skeleton and cytosol of resting and thrombin‐activated human platelets. Upon thrombin stimulation vinculin also appeared in the cytoskeleton. This cytoskeletal incorporation was completed during the early stages of platelet aggregation and secretion, when the uptake of myosin, actin‐binding protein and talin was still not maximal. We conclude therefore, that vinculin may play an important role in the structural (re)organisation of the human platelet cytoskeleton upon platelet activation.