D-Glutamamide

Disaccharide containing unit of peptidoglycan from bacterial cell wall, N-acetyl-d-glucosaminyl-N-acetylmuramyl-l-alanyl-d-glutaminamide (gluсosaminyl-muramyl-dipeptide) registered in Russia as an immunomodulatory drug, is shown to participate in slow equilibrium of α and β anomeric forms. Data of NMR spectra and molecular dynamics indicate that the α-anomer predominantly acquires a folded conformation stabilized by intramolecular hydrogen bond between the alanyl carbonyl and muramyl NH proton. The β-form displays a considerable fraction of extended, non-hydrogen bonded structures. In the standard immunoadjuvant test system, the α-form is practically inactive, and the activity of the equilibrium mixture with α : β = 68 : 32 ratio is due to the presence of β-anomer. Such unique α-β selectivity of biological action must be considered at the design of related immunoactive glycopeptides.

Background: Malignant melanoma is known for its aggressive metastatic spread and suppression of the host immune system. Immunosuppression in melanoma is mediated in part by the protein melanoma inhibitory activity (MIA). Objectives: In this study, we assessed the in vitro and in vivo efficacy of the MIA-inhibitory peptide AR71 in the inhibition of MIA-induced immunosuppression. This follows a previous study that revealed an increase in CD3-positive cells and cleaved caspase-3 in an in vivo model of hepatic metastasis after MIA inhibition. Materials and methods: We used Multiplex-ELISAs and qRT-PCR for determining changes in cytokine expression in vitro and in vivo and calcein release assays for determining immune cell response in vitro. Results: By evaluating the serum levels of tumor-associated cytokines of the melanoma-bearing mice, we found beneficial decreases of several cytokines, including TNF-alpha, after AR71 treatment. Additionally, we demonstrated an increase of anti-tumor lymphokine-activated killer (LAK) cell cytotoxicity in the presence of the MIA inhibitor AR71. Stimulation of anti-tumor immune responses by AR71 could be observed via increased numbers of NK cells in the metastases-bearing murine livers in vivo. Conclusion: In summary, inhibition of MIA activity results in reduced immunosuppression in vitro and in vivo.

The peptidyl prolyl cis/trans isomerase (PPIase) Pin1 plays an important role in phosphorylation-dependent events of the cell cycle. This function is linked to its display of two phosphothreonine/phosphoserine-proline binding motifs, one within the type IV WW domain and a second within the parvulin-like catalytic domain. By microinjection of the compound Ac-Phe-D-Thr(PO3H2)-Pip-Nal-Gln-NH2, which inhibits Xenopus laevis Pin1 with a Ki value of 19.4+/-1.5 nM, into the animal pole of X. laevis embryos at the two-cell stage, the impact of Pin1 PPIase activity on cell cycle progression and embryonic development could be analysed, independent of WW domain-mediated phosphoprotein binding. Injected embryos showed a dramatically decreased survival rate at late stages of development that could only be partially compensated by co-injection with mRNAs of enzymatically active Pin1 variants, demonstrating that the phosphorylation-specific PPIase activity of Pin1 is essential for cell division and development in X. laevis.