Scheme for signal transduction from the platelet collagen receptor GPVI/FcRγ-chain complex to the actin cytoskeleton.

Engagement of GPVI/FcRγ-chain activates Syk, which phosphorylates SLP-76. SLP-76 recruits PLC-γ2 to the plasma membrane, where Syk phosphorylates and activates it. This mediates Ca⁺⁺mobilization, resulting in the activation of gelsolin, which severs the actin filaments and caps the barbed ends. Engagement of GPVI/FcRγ-chain also results in PI 3-kinase activation. PI 3-kinase mediates the uncapping of the actin filament barbed ends by a mechanism possibly requiring Rac and a new production of ppIs. This induces the actin assembly required for the formation of lamellae.