Phase specific association of heterotrimeric GTP‐binding proteins with the actin‐based cytoskeleton during thrombin receptor‐mediated platelet activation

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Abstract
Subcellular distribution of heterotrimeric GTP‐binding proteins during thrombin receptor‐mediated platelet activation was examined, revealing two phases of translocation to the cytoskeleton. A part of Gi2α and Gsα shows first phase translocation to the low‐speed pellet (15000 × g pellet) within 1 min after activation, suggesting involvement in platelet shape change or granule secretion. In the second phase, Gi2α, Gsα, Gqα, and Gβ translocate to the low‐speed pellet, depending on platelet aggregation. These translocation correlated with the reorganization of the actin‐cytoskeleton and were inhibited by cytochalasin D. Reconstitution experiments also revealed that G proteins are associated with the actin‐cytoskeleton during platelet activation.