title: Differential activities of decapeptide agonists of human C5a: the conformational effects of backbone N-methylation.
abstract: Analogues of the potent, conformationally biased, decapeptide agonist of human C5a anaphylatoxin, C5a(65-74)Y65,F67,P69,P71,D-Ala73 (YSFKPMPLaR, peptide 54), were synthesized with methyl groups occupying specific amide nitrogen atoms along the peptide backbone. This N-methylation induced crucial extended backbone conformations in a manner similar to the two Pro residues, but without eliminating the contributions made by the side-chain of the residue for which Pro was substituted. The presence of backbone N-methyl groups on peptide 54 analogues had pronounced detrimental effects on the ability to bind and activate C5aRs expressed on human PMNs, but not on the ability to contract smooth muscle of human umbilical artery. Several N-methylated analogues of peptide 54 (peptides 56, 67, 124, 125, and 137) were significantly more selective for smooth muscle contraction, which is mediated by tissue resident macrophages, than for enzyme release from PMNs. Indeed, peptide 67, YSFKDMP(MeL)aR was almost 3000-fold more selective for smooth muscle contraction than for PMN enzyme release. Consistent with these differential activities was the observation that peptide 67 expressed a significantly greater binding affinity to C5aRs expressed on rat macrophages than on rat PMNs. This differential activity was also observed in vivo in the rat where peptide 67 induced a hypotensive response similar to peptide 54 and rhuC5a, but without accompanying neutropenia.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198-6805, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Vogen
authors.forename: N J
authors.initials: NJ
authors.lastname: Paczkowski
authors.forename: L
authors.initials: L
authors.lastname: Kirnarsky
authors.forename: A
authors.initials: A
authors.lastname: Short
authors.forename: J B
authors.initials: JB
authors.lastname: Whitmore
authors.forename: S A
authors.initials: SA
authors.lastname: Sherman
authors.forename: S M
authors.initials: SM
authors.lastname: Taylor
authors.forename: S D
authors.initials: SD
authors.lastname: Sanderson
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000187:drug effects* / Q000378:metabolism; D001667:Binding, Competitive; D015936:Complement C5a / Q000819:agonists* / Q000737:chemistry* / Q000494:pharmacology; D015195:Drug Design; D005260:Female; D006801:Humans; D007022:Hypotension / Q000139:chemically induced; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008745:Methylation; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry* / Q000494:pharmacology; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D017208:Rats, Wistar; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement / Q000187:drug effects* / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014469:Umbilical Arteries; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D010446:Peptide Fragments; D010455:Peptides; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement; D011994:Recombinant Proteins; D014662:Vasoconstrictor Agents; C105322:complement C5a, (65-74), Tyr(65)-Phe(67)-Pro(69,71)-Ala(73)-; D015936:Complement C5a