Novel signaling pathway leading to α_IIbβ₃ activation. Interaction of VWF or thrombin with their receptors on platelet membrane results in an increase of intracellular cGMP levels, leading to activation of cGMP-dependent protein kinase (PKG). This kinase is upstream of p38 MAPK and ERK2 phosphorylation, which is crucial in α_IIbβ₃ activation.