Section of Organic Chemistry and Biochemistry

Ioánnina, Greece

Section of Organic Chemistry and Biochemistry

Ioánnina, Greece
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Lee W.H.,University of Oxford | Schaffner-Reckinger E.,University of Luxembourg | Tsoukatos D.C.,Section of Organic Chemistry and Biochemistry | Aylward K.,French Institute of Health and Medical Research | And 13 more authors.
PLoS ONE | Year: 2015

Agonist-stimulated platelet activation triggers conformational changes of integrin αIIbβ3, allowing fibrinogen binding and platelet aggregation. We have previously shown that an octapeptide, p1YMESRADR8, corresponding to amino acids 313-320 of the β-ribbon extending from the β-propeller domain of αIIb, acts as a potent inhibitor of platelet aggregation. Here we have performed in silico modelling analysis of the interaction of this peptide with αIIbβ3 in its bent and closed (not swing-out) conformation and show that the peptide is able to act as a substitute for the β-ribbon by forming a clasp restraining the β3 hybrid and βI domains in a closed conformation. The involvement of species-specific residues of the β3 hybrid domain (E356 and K384) and the β1 domain (E297) as well as an intrapeptide bond (pE315-pR317) were confirmed as important for this interaction by mutagenesis studies of αIIbβ3 expressed in CHO cells and native or substituted peptide inhibitory studies on platelet functions. Furthermore, NMR data corroborate the above results. Our findings provide insight into the important functional role of the αIIb β-ribbon in preventing integrin αIIbβ3 head piece opening, and highlight a potential new therapeutic approach to prevent integrin ligand binding. © 2015 Lee et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Karampelas T.,Biomedical Research Foundation of the Academy of Athens | Argyros O.,Biomedical Research Foundation of the Academy of Athens | Sayyad N.,Section of Organic Chemistry and Biochemistry | Spyridaki K.,University of Crete | And 10 more authors.
Bioconjugate Chemistry | Year: 2014

Gemcitabine, a drug with established efficacy against a number of solid tumors, has therapeutic limitations due to its rapid metabolic inactivation. The aim of this study was the development of an innovative strategy to produce a metabolically stable analogue of gemcitabine that could also be selectively delivered to prostate cancer (CaP) cells based on cell surface expression of the Gonadotropin Releasing Hormone-Receptor (GnRH-R). The synthesis and evaluation of conjugated molecules, consisting of gemcitabine linked to a GnRH agonist, is presented along with results in androgen-independent prostate cancer models. NMR and ligand binding assays were employed to verify conservation of microenvironments responsible for binding of novel GnRH-gemcitabine conjugates to the GnRH-R. In vitro cytotoxicity, cellular uptake, and metabolite formation of the conjugates were examined in CaP cell lines. Selected conjugates were efficacious in the in vitro assays with one of them, namely, GSG, displaying high antiproliferative activity in CaP cell lines along with significant metabolic and pharmacokinetic advantages in comparison to gemcitabine. Finally, treatment of GnRH-R positive xenografted mice with GSG showed a significant advantage in tumor growth inhibition when compared to gemcitabine. © 2014 American Chemical Society.


PubMed | University of Oxford, Shanghai JiaoTong University, University of Luxembourg, University of Paris Descartes and Section of Organic Chemistry and Biochemistry
Type: Journal Article | Journal: PloS one | Year: 2015

Agonist-stimulated platelet activation triggers conformational changes of integrin IIb3, allowing fibrinogen binding and platelet aggregation. We have previously shown that an octapeptide, p1YMESRADR8, corresponding to amino acids 313-320 of the -ribbon extending from the -propeller domain of IIb, acts as a potent inhibitor of platelet aggregation. Here we have performed in silico modelling analysis of the interaction of this peptide with IIb3 in its bent and closed (not swing-out) conformation and show that the peptide is able to act as a substitute for the -ribbon by forming a clasp restraining the 3 hybrid and I domains in a closed conformation. The involvement of species-specific residues of the 3 hybrid domain (E356 and K384) and the 1 domain (E297) as well as an intrapeptide bond (pE315-pR317) were confirmed as important for this interaction by mutagenesis studies of IIb3 expressed in CHO cells and native or substituted peptide inhibitory studies on platelet functions. Furthermore, NMR data corroborate the above results. Our findings provide insight into the important functional role of the IIb -ribbon in preventing integrin IIb3 head piece opening, and highlight a potential new therapeutic approach to prevent integrin ligand binding.

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