APC pretreatment does not lead to PAR1 desensitization. Cells were incubated for 3 hours with control or 5 nM APC (APC-pretreated) followed by a 10-minute stimulation with the indicated agonists in the absence and presence of cleavage-blocking anti-PAR1. Extracellular signal-related kinase (Erk)–1/2 phosphorylation was analyzed by Western blotting. A typical experiment is shown.