Histamine-Releasing Activity and Binding to the Fc∈RIα Human Mast Cell Receptor Subunit of Mast Cell Degranulating Peptide Analogues with Alanine Substitutions

摘要

We have investigated the effects on mast cell binding and the histamine-releasing activity of L-alanine substitutions for the five lysine residues and the proline residue in the MCD peptide (1) sequence. All synthesized analogues Ala~2 (2), Ala~6 (3), Ala~(11) (4), Ala~(12) (5), Ala~(17) (6), and Ala~(21)(7) showed a loss of histamine release compared to the parent MCD peptide 1. The order of decreased potency was 1 > 6 > 7 > 4 > 2 > 3 > 5. The alanine-substituted analogues showed a5- to 6-fold decrease in histamine release for analogues 6, 7, and 4 and a 10-fold decrease for analogue 2. A more significant loss was observed in analogue 3 with a 75-fold loss of activity. The greatest loss of activity was observed with alanine substituting for proline in position 12. This analogue 5 showed a 130-fold loss of histamine release compared to the parent peptide 1. the ability of each analogue to interact with the Fc∈RIα subunit of the human mast cell receptor was analyzed by competitive binding of the fluorescent peptide 1 and the alanine analogues using fluorescence polarization. The binding affinities of analogues 4, 6, and 7 for the mast cell receptor were less than the affinity of the native peptide 1. Analogues 2, 3, and 5 showed an increase in binding affinity, with analogue 5 showing the highest increase compared to the native peptide 1. The order of increased affinity was 5 > 3 > 2 > 1 > 4, 6, 7. On the basis of these results, the possibility that analogue 5 inhibits peptide 1-stimulated histamine release was examined. We found that peptide 5 did not inhibit histamine release by peptide 1. The analogues 2, 3, and especially analogue 5 may be useful leads toward study of agents that prevent binding of IgE to mast cell receptors.