Figure 2.

Hp(2–20)–induced calcium mobilization in transfected HL-60 cells. Receptor interaction with Hp(2–20) (50 μM) was determined by measuring the ability of the peptide to mobilize intracellular calcium in undifferentiated HL-60 cells, stably transfected with either FPR, FPRL1, or FPRL2. Cells expressing the specific monocyte receptor FPRL2 responded with a rise in intracellular [Ca²⁺], which peaked at approximately 300 nM (a). The EC₅₀ of the Hp(2–20)–induced calcium mobilization in FPRL2-expressing cells was around 10 μM, whereas that for FPRL1 was approximately 30-fold lower (b). No significant rise in intracellular [Ca²⁺] occurred when Hp(2–20) was added to cells expressing FPR (a).