TY - JOUR
T1 - Synthetic peptides as antagonists of the anaphylatoxin C3a
AU - KRETZSCHMAR, Titus
AU - POHL, Martina
AU - CASARETTO, Monika
AU - PRZEWOSNY, Michael
AU - BAUTSCH, Wilfried
AU - KLOS, Andreas
AU - SAUNDERS, Derek
AU - KÖHL, Jörg
PY - 1992/11/1
Y1 - 1992/11/1
N2 - Peptide compounds resembling the receptor‐binding C‐terminal domain of the anaphylatoxic peptide C3a were synthesized to examine two kinds of C3a antagonism: (a) specific desensitization of C3a‐sensitive cells and (b) competitive binding to the C3a receptor. We used guinea‐pig platelets, which express a C3a receptor and specifically release ATP upon stimulation, to evaluate the actions of the C3a analogues. The ATP liberation can be inhibited by pretreatment (i.e. desensitization) of the guinea‐pig platelets with substimulatory concentrations of C3a or its analogues. Compared to C3a, several peptides were found with at least a tenfold greater difference between the required concentrations for C3a‐specific half‐maximal desensitization (DD50) and half‐maximal platelet activation (ED50). The most potent compounds were YAAALKLAR and Fmoc‐EAALKLAR (Fmoc: 9‐fluorenylmethoxycarbonyl) with an ED50/DD50 of 140 ± 28 and 80 ± 17, respectively (mean ± standard deviation). The ED50/DD50 of human C3a was found to be only 6 ± 2. Some C3a derivatives were also tested in competitive binding studies for their ability to compete with C3a for receptor sites on guinea‐pig platelets. Three of them were considered partial antagonists [YRRGRLAR, YRRGRXLAR and YRRGRXLAR (X=6‐aminohexanoyl)] because their Ki were smaller than their ED50 (Ki/ED50= 0.6 ± 0.3, 0.5 ± 0.1 and 0.4 ± 0.2, respectively). Interestingly, the last two compounds also had ED50/DD50 values greater than 60. Common to all three peptides are N‐terminal arginine‐rich sequences and intramolecular disulfide bridges which introduce conformational constraint.
AB - Peptide compounds resembling the receptor‐binding C‐terminal domain of the anaphylatoxic peptide C3a were synthesized to examine two kinds of C3a antagonism: (a) specific desensitization of C3a‐sensitive cells and (b) competitive binding to the C3a receptor. We used guinea‐pig platelets, which express a C3a receptor and specifically release ATP upon stimulation, to evaluate the actions of the C3a analogues. The ATP liberation can be inhibited by pretreatment (i.e. desensitization) of the guinea‐pig platelets with substimulatory concentrations of C3a or its analogues. Compared to C3a, several peptides were found with at least a tenfold greater difference between the required concentrations for C3a‐specific half‐maximal desensitization (DD50) and half‐maximal platelet activation (ED50). The most potent compounds were YAAALKLAR and Fmoc‐EAALKLAR (Fmoc: 9‐fluorenylmethoxycarbonyl) with an ED50/DD50 of 140 ± 28 and 80 ± 17, respectively (mean ± standard deviation). The ED50/DD50 of human C3a was found to be only 6 ± 2. Some C3a derivatives were also tested in competitive binding studies for their ability to compete with C3a for receptor sites on guinea‐pig platelets. Three of them were considered partial antagonists [YRRGRLAR, YRRGRXLAR and YRRGRXLAR (X=6‐aminohexanoyl)] because their Ki were smaller than their ED50 (Ki/ED50= 0.6 ± 0.3, 0.5 ± 0.1 and 0.4 ± 0.2, respectively). Interestingly, the last two compounds also had ED50/DD50 values greater than 60. Common to all three peptides are N‐terminal arginine‐rich sequences and intramolecular disulfide bridges which introduce conformational constraint.
UR - http://www.scopus.com/inward/record.url?scp=0026475298&partnerID=8YFLogxK
U2 - 10.1111/j.1432-1033.1992.tb17407.x
DO - 10.1111/j.1432-1033.1992.tb17407.x
M3 - Journal articles
C2 - 1446671
AN - SCOPUS:0026475298
SN - 0014-2956
VL - 210
SP - 185
EP - 191
JO - European Journal of Biochemistry
JF - European Journal of Biochemistry
IS - 1
ER -