title: Histamine-releasing activity and binding to the FcepsilonRI alpha human mast cell receptor subunit of mast cell degranulating peptide analogues with alanine substitutions.
abstract: 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 a 5- 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 FcepsilonRIalpha 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.
authors.affiliation: Department of Physiology and Biophysics, Mount Sinai School of Medicine, 1 Gustave L Levy Place, Box 1218, New York, New York 10029, USA. Angeliki.Buku@mssm.edu
authors.forename: A
authors.initials: A
authors.lastname: Buku
authors.forename: M
authors.initials: M
authors.lastname: Mendlowitz
authors.forename: B A
authors.initials: BA
authors.lastname: Condie
authors.forename: J A
authors.initials: JA
authors.lastname: Price
mesh_terms: D000409:Alanine / Q000737:chemistry*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001667:Binding, Competitive; D005260:Female; D005454:Fluorescence Polarization; D006636:Histamine Release / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D010529:Peritoneal Cavity / Q000166:cytology; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D017455:Receptors, IgE / Q000378:metabolism*
chemical_list: D010455:Peptides; D021122:Protein Subunits; D017455:Receptors, IgE; C008331:mast cell degranulating peptide; D000409:Alanine