Eider San Sebastian

Publications (7) View all

• Article: Design, Synthesis, and Functional Evaluation of Leukocyte Function Associated Antigen-1 Antagonists in Early and Late Stages of Cancer Development.

  Eider San Sebastián, Tahl Zimmerman, Aizpea Zubia, Yosu Vara, Elyette Martin, Finton Sirockin, Annick Dejaegere, Roland H Stote, Xabier Lopez, David Pantoja-Uceda, María Valcárcel, Lorea Mendoza, Fernando Vidal-Vanaclocha, Fernando P Cossío, Francisco J Blanco
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  ABSTRACT: The integrin leukocyte function associated antigen 1 (LFA-1) binds the intercellular adhesion molecule 1 (ICAM-1) by its α(L)-chain inserted domain (I-domain). This interaction plays a key role in cancer and other diseases. We report the structure-based design, small-scale synthesis, and biological activity evaluation of a novel family of LFA-1 antagonists. The design led to the synthesis of a family of highly substituted homochiral pyrrolidines with antiproliferative and antimetastatic activity in a murine model of colon carcinoma, as well as potent antiadhesive properties in several cancer cell lines in the low micromolar range. NMR analysis of their binding to the isolated I-domain shows that they bind to the I-domain allosteric site (IDAS), the binding site of other allosteric LFA-1 inhibitors. These results provide evidence of the potential therapeutic value of a new set of LFA-1 inhibitors, whose further development is facilitated by a synthetic strategy that is versatile and fully stereocontrolled.
  Journal of Medicinal Chemistry 01/2013; · 4.80 Impact Factor
• Article: Comparative normal mode analysis of LFA-1 integrin I-domains.

  Thomas Gaillard, Elyette Martin, Eider San Sebastian, Fernando P Cossío, Xabier Lopez, Annick Dejaegere, Roland H Stote
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  ABSTRACT: The conformational dynamics of the Inserted domain (I-domain) from the lymphocyte function-associated antigen-1 (LFA-1) was investigated by normal mode analysis of multiple structures of the low, intermediate, and high affinity states. LFA-1 is an integrin expressed on leukocytes and is of critical importance in adhesion reactions, like antigen-specific responses, homing, and diapedesis. The main ligand binding site of LFA-1 is the I-domain, which recognizes intercellular adhesion molecules (ICAMs), members of the immunoglobulin superfamily. From experimental crystal structures, a large-scale conformational change of, among others, the alpha7 helix of the I-domain has been observed leading to the proposal that these structural changes are linked to the conformational regulation of LFA-1. The results from the present calculations show that structural changes of the alpha7 helix consistent with those observed in the crystal structures are significantly sampled by the low frequency modes. This was found to be particularly true for the low affinity state of the I-domain, indicating that low frequency motions favor the conformational transition implicated in activation. However, beyond the simple downward shift of the helix implied by the crystal structures, the calculations further show that there is a noticeable swinging-out motion of the helix. The consequences of this motion are discussed in the context of integrin activation and inhibition. Moreover, significant changes in the atomic-level dynamics and in long-range correlated motions of the I-domain were found to occur upon binding of the natural ligand ICAM. These changes were more local upon binding of an allosteric inhibitor. The present study opens the question of how changes in dynamics may contribute to the long-range transmission of signal upon ICAM binding by the LFA-1 I-domain.
  Journal of Molecular Biology 12/2007; 374(1):231-49. · 4.00 Impact Factor
• Article: Metal ion dependent adhesion sites in integrins: a combined DFT and QMC study on Mn2+.

  Eider San Sebastian, Jon M Matxain, Leif A Eriksson, Roland H Stote, Annick Dejaegere, Fernando P Cossio, Xabier Lopez
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  ABSTRACT: The theoretical study of relative energies of different spin states of Mn2+ has been carried out for the isolated cation and for structures in which the cation is coordinated to ligands that represent the first coordination shell in a protein environment that contains a metal ion dependent adhesion site (MIDAS, found in the ligand binding domain of protein LFA-1). The calculations determine whether the ligand field generated by a prototype protein environment affects the relative energies between high, intermediate, and low spin states. Geometry optimizations and vibrational frequency calculations were carried out at the B3LYP/SKBJ+* level of theory. Single point calculations were performed at the B3LYP/6-311++G(2df,2p) and diffusion monte carlo (DMC) levels for the refinement of the electronic energies. These calculations reveal important differences in the relative energies between high/low spin complexes obtained by B3LYP and DMC and show that although both DFT and DMC show similar trends, a higher level method such as DMC is necessary for a quantitative description of the interactions between Mn2+ and its natural ligands. (G)s of acetate-type ligand binding reactions were calculated that show that the higher the spin of the manganese complex, the lower the affinity for the ligand.
  The Journal of Physical Chemistry B 09/2007; 111(30):9099-103. · 3.70 Impact Factor
• Article: On the affinity regulation of the metal-ion-dependent adhesion sites in integrins.

  Eider San Sebastian, Jose M Mercero, Roland H Stote, Annick Dejaegere, Fernando P Cossío, Xabier Lopez
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  ABSTRACT: Density functional theory and a polarizable continuum model are used to (i) understand the affinity modulating mechanisms of the interaction between the metal-ion-dependent adhesion site (MIDAS) of a selected integrin, lymphocyte function-associated antigen-1 (LFA-1) and a ligand mimetic acetate molecule and to (ii) propose a new, promising family of inhibitors to block the interaction of the integrin with intercellular adhesion molecule-1 (ICAM-1). We quantify the effect of isolated factors, such as the metal coordination, the nature of the ligand or the cation present on the MIDAS, and the effect of the permittivity of the media. We show that the affinity for ligand decreases when metal coordination changes from the open conformation to the closed conformation. In addition, Mn2+ and Zn2+ showed to be good competitors for the octahedrically coordinated Mg2+ and yielded excellent affinity values, whereas Ca2+ in an octahedric environment would decrease the affinity for the ligand. Our affinity studies of the open MIDAS showed that nitronate-derived or carboxylic acid-containing ligands may represent new promising scaffolds of future inhibitors. Finally, we show that affinities are always highly favored by low-dielectric environments, which explains the propensity of MIDAS motifs to be surrounded by hydrophobic residues in integrins and highlights the importance of including hydrophobic groups in the inhibitors.
  Journal of the American Chemical Society 04/2006; 128(11):3554-63. · 9.91 Impact Factor
• Source

  Available from: Unai Ugalde

  Article: In vitro fusion between Saccharomyces cerevisiae secretory vesicles and cytoplasmic-side-out plasma membrane vesicles.

  Lorena Arrastua, Eider San Sebastian, Ana F Quincoces, Claude Antony, Unai Ugalde
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  ABSTRACT: The final step in the secretory pathway, which is the fusion event between secretory vesicles and the plasma membrane, was reconstructed using highly purified secretory vesicles and cytoplasmic-side-out plasma membrane vesicles from the yeast Saccharomyces cerevisiae. Both organelle preparations were obtained from a sec 6-4 temperature-sensitive mutant. Fusion was monitored by means of a fluorescence assay based on the dequenching of the lipophilic fluorescent probe octadecylrhodamine B-chloride (R18). The probe was incorporated into the membrane of secretory vesicles, and it diluted in unlabelled cytoplasmic-side-out plasma membrane vesicles as the fusion process took place. The obtained experimental dequenching curves were found by mathematical analysis to consist of two independent but simultaneous processes. Whereas one of them reflected the fusion process between both vesicle populations as confirmed by its dependence on the assay conditions, the other represented a non-specific transfer of the probe. The fusion process may now be examined in detail using the preparation, validation and analytical methods developed in this study.
  Biochemical Journal 04/2003; 370(Pt 2):641-9. · 4.90 Impact Factor