Model of signaling from GP Ib-IX-V to αIIbβ3 in dA1VWF-adherent platelets. DAG indicates diacylglycerol. See “Discussion.” Not shown are FcR γ-chain and FcγRIIA, signaling proteins associated with GP Ib-IX-V that may participate in GP Ib-IX-V signaling but are not required for it.