Neutrophil signaling through PSGL-1, but not through β2 integrins, requires moesin to activate ERKs. (A-B) Neutrophils from the indicated genotype were incubated on immobilized P-selectin or control CD45 in buffer containing Ca²⁺ or in buffer containing EDTA to prevent selectin–PSGL-1 interactions. Cells were lysed and probed by western blotting with antibodies to the indicated protein or to phosphorylated (activated) versions of each protein. (C) Neutrophils from the indicated genotype were incubated on immobilized F(ab′)₂ fragments of isotype control or anti-β2 integrin mAb. Cells were lysed and probed by western blotting with antibodies to the indicated protein or to phosphorylated (activated) versions of each protein. The data are representative of 3 experiments.