A Retro-Inverso Peptide Mimic of CD28 Encompassing the MYPPPY Motif Adopts a Polyproline Type II Helix and Inhibits Encephalitogenic T Cells In Vitro

Abstract

Complete activation of T cells requires two signals: an Ag-specific signal delivered via the TCR by the peptide-MHC complex and a second costimulatory signal largely provided by B7:CD28/CTLA-4 interactions. Previous studies have shown that B7 blockade can either ameliorate experimental autoimmune encephalomyelitis by interfering with CD28 signaling or exacerbate the disease by concomitant blockade of CTLA-4 interaction. Therefore, we developed a functional CD28 mimic to selectively block B7:CD28 interactions. The design, synthesis, and structural and functional properties of the CD28 free peptide, the end group-blocked CD28 peptide, and its retro-inverso isomer are shown. The synthetic T cell-costimulatory receptor peptides fold into a polyproline type II helical structure commonly seen in regions of globular proteins involved in transient protein-protein interactions. The binding determinants of CD28 can be transferred onto a short peptide mimic of its ligand-binding region. The CD28 peptide mimics effectively block the expansion of encephalitogenic T cells in vitro suggesting the potential usefulness of the peptides for the treatment of autoimmune disease conditions requiring down-regulation of T cell responses.

Novel p65 Binding Glucocorticoid-induced Leucine Zipper Peptide Suppresses Experimental Autoimmune Encephalomyelitis

“…Consistent with this structural prediction previously, mutation of Pro 120 has been shown to abrogate the GILZ-p65 interaction (14). Peptides derived from the proline-rich regions of proteins potentially exhibit similar affinity as the entire protein with the interacting partner (7,8,40). We show that the end groups that blocked GILZ-P bind the r-p65 with similar kinetics as the r-GILZ with the strength of interaction in the micromolar range commonly observed for transient intermolecular interactions.…”

“…A conceptually straightforward strategy to develop specific inhibitors of protein-protein interactions is the synthesis of interface peptides derived from the primary sequence of one of the protein binding partners (4). Examples of linear peptides exhibiting PP II conformation include peptides derived from the p85 subunit of PI 3-kinase, CD28-CDR-3 peptide, and protein kinase inhibitors (7)(8)(9).…”

Suppression of Experimental Autoimmune Encephalomyelitis Using Peptide Mimics of CD28

“…Recently, we identified two biologically active CD28 peptide mimics derived from the CD28 CDR-3-like region. An end group-blocked CD28 peptide (EL-CD28) and its retro-inverso isomer (RI-CD28) were synthesized and characterized for their binding properties and biological activity (23). The synthetic CD28 peptides exhibited similar kinetics of interaction as CD28 for binding the CD80 ligand.…”

“…The synthetic CD28 peptides exhibited similar kinetics of interaction as CD28 for binding the CD80 ligand. Moreover, the CD28 peptides were observed to interfere with the activation of encephalitogenic T cells in vitro (23).…”

IGF-1R peptide vaccines/mimics inhibit the growth of BxPC3 and JIMT-1 cancer cells and exhibit synergistic antitumor effects with HER-1 and HER-2 peptides

“…[58][59][60] We have also developed effective inhibitors of vascular endothelial growth factor signaling (VEGF/VEGFR2) 61 that diminish tumor angiogenesis. Furthermore, we have shown that co-targeting HER-2 and VEGF signaling produced superior antitumor effects in vitro and in vivo.…”