Structure-based Design of Mimetics for Granulocyte-macrophage Colony Stimulating Factor (GM-CSF)

Abstract

Granulocyte-macrophage colony stimulating factor (GM-CSF) activity has been linked to pro-inflammatory effects in autoimmune syndromes, such as rheumatoid arthritis. Thus GM-CSF mimetics with antagonist activity might play a therapeutic role in these diseases. The human GM-CSF core structure consists of a four alpha-helix bundle, and GM-CSF activity is controlled by its binding to a two-subunit receptor. A number of residues located on the B and C helices of GM-CSF are postulated to interact with the alpha chain of the GM-CSF receptor (GM-CSFR). Several approaches have been successfully utilized to develop peptide mimetics of this site, including peptides from the native sequence, a peptide derived from a recombinant antibody (rAb) light chain which mimicked GM-CSF receptor binding activity, and structurally guided de novo design. Analysis of the rAb light chain had suggested mimicry of GM-CSF with residues mostly contributed by the CDR I region. Key residues involved in CDR I peptide/GM-CSFR binding were identified by truncation and alteration of individual residues, while the structural elements required to antagonize the biological action of GM-CSF were separately tested in binding and inhibitory activity assays of multiple cyclic analogues. A peptide designed to retain the loop conformation of the CDR I region of the rAb light chain competed with GM-CSF for both antibody and receptor binding, but the role of specific residues in antibody versus receptor binding differed markedly. These studies suggest that structural analysis of peptide mimetics can reveal differences in receptor and antibody binding, perhaps including key interactions that impact binding kinetics. Peptide mimetics of other four-helix bundle cytokines are reviewed, including helical and reverse turn mimetics of helical structures. Use of peptide mimetics coupled with structural and kinetic analysis provides a powerful approach to identifying important receptor-ligand interactions, which implications for rational design of novel therapeutics.

Antioxidants inhibit SAA formation and pro-inflammatory cytokine release in a human cell model of alkaptonuria

“…IL-17 shows properties similar to those of IL-1β and TNF-α. They induce in vitro the synthesis of nitric oxide and metalloproteases by chondrocytes and the production of IL-6 and IL-8 by fibroblasts [16]. Eotaxin-1 plays an important role in cartilage degradation in OA [17].…”

A Designed Glycoprotein Analogue of Gc-MAF Exhibits Native-like Phagocytic Activity

“…The grafting of a binding epitope on a folded, stable protein is a well-established approach to the design of biologically active miniature protein. [5][6][7][8][9][10] In this paper, we are applying this approach to the display of post-translationally modified epitopes. Ideally, a scaffold should be stable and monomeric at physiological conditions, soluble, and structurally characterized.…”

“…One possible approach to facilitate the use of Gc-MAF consists of the design of a miniaturized protein analogue on which the active site of Gc-MAF could be displayed. The grafting of a binding epitope on a folded, stable protein is a well-established approach to the design of biologically active miniature protein. − In this paper, we are applying this approach to the display of post-translationally modified epitopes. Ideally, a scaffold should be stable and monomeric at physiological conditions, soluble, and structurally characterized.…”

Heparin-binding Sites in Granulocyte-Macrophage Colony-stimulating Factor

“…This may be partly related to uncertainties in the determination of the domains of GM-CSF involved in binding to its protein receptor (14). Moreover, despite the fact that conserved amino acid sequences corresponding to heparin-binding motifs have been identified (namely the XBBXBX and XBBBXXBX motifs, where B corresponds to a basic residue) (15), a large number of reports have also shown that heparin/heparan sulfate-binding sites in proteins are not always or necessarily defined by a unique sequence or structural motif (16).…”