Reactive Center Loop (RCL) Peptides Derived from Serpins Display Independent Coagulation and Immune Modulating Activities.

Abstract

Serpins regulate coagulation and inflammation, binding serine proteases in suicide-inhibitory complexes. Target proteases cleave the serpin reactive center loop scissile P1-P1' bond, resulting in serpin-protease suicide-inhibitory complexes. This inhibition requires a near full-length serpin sequence. Myxomavirus Serp-1 inhibits thrombolytic and thrombotic proteases, whereas mammalian neuroserpin (NSP) inhibits only thrombolytic proteases. Both serpins markedly reduce arterial inflammation and plaque in rodent models after single dose infusion. In contrast, Serp-1 but not NSP improves survival in a lethal murine gammaherpesvirus68 (MHV68) infection in interferon γ-receptor-deficient mice (IFNγR(-/-)). Serp-1 has also been successfully tested in a Phase 2a clinical trial. We postulated that proteolytic cleavage of the reactive center loop produces active peptide derivatives with expanded function. Eight peptides encompassing predicted protease cleavage sites for Serp-1 and NSP were synthesized and tested for inhibitory function in vitro and in vivo. In engrafted aorta, selected peptides containing Arg or Arg-Asn, not Arg-Met, with a 0 or +1 charge, significantly reduced plaque. Conversely, S-6 a hydrophobic peptide of NSP, lacking Arg or Arg-Asn with -4 charge, induced early thrombosis and mortality. S-1 and S-6 also significantly reduced CD11b(+) monocyte counts in mouse splenocytes. S-1 peptide had increased efficacy in plasminogen activator inhibitor-1 serpin-deficient transplants. Plaque reduction correlated with mononuclear cell activation. In a separate study, Serp-1 peptide S-7 improved survival in the MHV68 vasculitis model, whereas an inverse S-7 peptide was inactive. Reactive center peptides derived from Serp-1 and NSP with suitable charge and hydrophobicity have the potential to extend immunomodulatory functions of serpins.

• Authors: Sriram Ambadapadi, Ganesh Munuswamy-Ramanujam, Donghang Zheng, Colin Sullivan, Erbin Dai, Sufi Morshed, Baron McFadden, Emily Feldman, Melissa Pinard, Robert McKenna, Scott Tibbetts, Alexandra Lucas
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 291 Issue 6 Pg. 2874-87 (Feb 05 2016) ISSN: 1083-351X [Electronic] United States
• PMID: 26620556 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• Immunologic Factors
• Membrane Proteins
• Peptides
• Serp1 protein, mouse

Topics

• Animals
• Blood Coagulation (drug effects, immunology)
• Disease Models, Animal
• Herpesviridae Infections (drug therapy, immunology)
• Humans
• Immunologic Factors (chemical synthesis, chemistry, immunology)
• Jurkat Cells
• Membrane Proteins (chemical synthesis, chemistry, pharmacology)
• Mice
• Mice, Knockout
• Peptides (chemical synthesis, chemistry, pharmacology)
• Rhadinovirus (immunology)
• Vasculitis (drug therapy, immunology)