Derivation of ligands for the complement C3a receptor from the C-terminus of C5a

Reena Halai,Meghan L Bellows-Peterson,Will Branchett,James Smadbeck,Chris A Kieslich,Daniel E Croker,Matthew A Cooper,Dimitrios Morikis,Trent M Woodruff,Christodoulos A Floudas,Peter N Monk

doi:10.1016/j.ejphar.2014.10.041

Abstract

The complement cascade is a highly sophisticated network of proteins that are well regulated and directed in response to invading pathogens or tissue injury. Complement C3a and C5a are key mediators produced by this cascade, and their dysregulation has been linked to a plethora of inflammatory and autoimmune diseases. Consequently, this has stimulated interest in the development of ligands for the receptors for these complement peptides, C3a receptor, and C5a1 (C5aR/CD88). In this study we used computational methods to design novel C5a1 receptor ligands. However, functional screening in human monocyte-derived macrophages using the xCELLigence label-free platform demonstrated altered specificity of our ligands. No agonist/antagonist activity was observed at C5a1, but we instead saw that the ligands were able to partially agonize the closely related complement receptor C3a receptor. This was verified in the presence of C3a receptor antagonist SB 290157 and in a stable cell line expressing either C5a1 or C3a receptor alone. C3a agonism has been suggested to be a potential treatment of acute neutrophil-driven traumatic pathologies, and may have great potential as a therapeutic avenue in this arena.

Highlights

Complement activation proceeds through cascades of enzymatic reactions leading to inflammation, phagocytosis, lysis, and augmentation of antibody production (Markiewski and Lambris, 2007)
C5a exerts a number of effects through its classical receptor, C5a1 (C5aR/CD88) (Klos et al, 2013), such as recruiting neutrophils and macrophages to sites of injury, releasing granuleassociated enzymes and vasoactive mediators, increasing vascular permeability and adhesion, inducing smooth muscle contractions and stimulating the release of proinflammatory cytokines
Increased amounts of C5a are associated with a number of pathological conditions, including lupus, ischemia/reperfusion injury, Crohn’s disease, cystic fibrosis, gingivitis, atherosclerosis, myocardial infarction, fibrosis, allergy, diabetes type I, and disorders of the central nervous system (Manthey et al, 2009)

Summary

Introduction

Complement activation proceeds through cascades of enzymatic reactions leading to inflammation, phagocytosis, lysis, and augmentation of antibody production (Markiewski and Lambris, 2007). Two major products of complement activation are the protein fragments C3a and C5a, beneficial in infections and mediating inflammatory diseases (Peng et al, 2009). C5a exerts a number of effects through its classical receptor, C5a1 (C5aR/CD88) (Klos et al, 2013), such as recruiting neutrophils and macrophages to sites of injury, releasing granuleassociated enzymes and vasoactive mediators, increasing vascular permeability and adhesion, inducing smooth muscle contractions and stimulating the release of proinflammatory cytokines. C5a interacts with a second receptor, C5a2, the functions of this receptor are not fully determined (Croker et al, 2013; Li et al, 2013). A recent study has suggested that C3a and C5a1 have opposing roles in neutrophil-mediated pathology (Wu et al, 2013). C3a receptor agonism and C5a1 antagonism may have similar therapeutic effects in acute neutrophil-driven pathologies (Schofield et al, 2013)

Methods

Results

Conclusion