The Heparin-Binding Activity of Secreted Modular Calcium-Binding Protein 1 (SMOC-1) Modulates Its Cell Adhesion Properties.

Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia.
PLoS ONE (Impact Factor: 3.53). 02/2013; 8(2):e56839. DOI: 10.1371/journal.pone.0056839
Source: PubMed

ABSTRACT Secreted modular calcium-binding proteins 1 and 2 (SMOC-1 and SMOC-1) are extracellular calcium- binding proteins belonging to the BM-40 family of proteins. In this work we have identified a highly basic region in the extracellular calcium-binding (EC) domain of the SMOC-1 similar to other known glycosaminoglycan-binding motifs. Size-exclusion chromatography shows that full length SMOC-1 as well as its C-terminal EC domain alone bind heparin and heparan sulfate, but not the related chondroitin sulfate or dermatan sulfate glycosaminoglycans. Intrinsic tryptophan fluorescence measurements were used to quantify the binding of heparin to full length SMOC-1 and the EC domain alone. The calculated equilibrium dissociation constants were in the lower micromolar range. The binding site consists of two antiparallel alpha helices and mutagenesis experiments have shown that heparin-binding residues in both helices must be replaced in order to abolish heparin binding. Furthermore, we show that the SMOC-1 EC domain, like the SMOC-2 EC domain, supports the adhesion of epithelial HaCaT cells. Heparin-binding impaired mutants failed to support S1EC-mediated cell adhesion and together with the observation that S1EC in complex with soluble heparin attenuated cell adhesion we conclude that a functional and accessible S1EC heparin-binding site mediates adhesion of epithelial cells to SMOC-1.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: SMOC2 is a member of the BM-40 (SPARC) family of matricellular proteins, reported to influence signaling in the extracellular compartment. In mice, Smoc2 is expressed in many different tissues and was shown to enhance the response to angiogenic growth factors, mediate cell adhesion, keratinocyte migration and metastasis. Additionally, SMOC2 is associated with vitiligo and craniofacial and dental defects. The function of Smoc2 during early zebrafish development has not been determined to date.Results: In pregastrula zebrafish embryos, smoc2 is expressed ubiquitously. As development progresses, the expression pattern becomes more anteriorly restricted. At the onset of blood cell circulation, smoc2 morphants presented a mild ventralization of posterior structures. Molecular analysis of the smoc2 morphants indicated myelopoietic defects in the rostral blood islands during segmentation stages. Hemangioblast development and further specification of the myeloid progenitor cells were shown to be impaired. Additional experiments indicated that Bmp target genes were downregulated in smoc2 morphants.Conclusion: Our findings reveal that Smoc2 is an essential player in the development of myeloid cells of the anterior lateral plate mesoderm during embryonic zebrafish development. Furthermore, our data show that Smoc2 affects the transcription of Bmp target genes without affecting initial dorsoventral patterning or mesoderm development. Developmental Dynamics, 2014. © 2014 Wiley Periodicals, Inc.
    Developmental Dynamics 11/2014; 243(11). DOI:10.1002/dvdy.24164 · 2.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The main sites of calcium binding were determined for the low molecular weight heparin drug enoxaparin and the synthetic pentasaccharide Arixtra (fondaparinux). [(1)H,(13)C] HSQC pH titrations were carried out to characterize the acid-base properties of these samples both in the presence and absence of calcium. The differences in the titration curves were used to determine the structural components of enoxaparin and fondaparinux responsible for Ca(2+) binding. In enoxaparin both unsubstituted and 2-O-sulfated iduronic acid residues are important in calcium binding and the presence of the 2-O-sulfo group does not seem to influence the Ca(2+) binding capability of the iduronate ring. In fondaparinux changes in chemical shifts upon Ca(2+) binding were smaller than observed for enoxaparin, and were observed for both the glucuronic acid and 2-O-sulfated iduronic acid residues. In enoxaparin significant perturbations of the chemical shift of the N-sulfoglucosamine anomeric carbon in residues connected to 2-O-sulfated iduronic acid were detected on Ca(2+) binding, however it was not possible to determine whether these changes reflect direct involvement in calcium complexation or result from through space interactions or conformational changes.
    Carbohydrate research 11/2013; 384C:13-19. DOI:10.1016/j.carres.2013.11.007 · 2.03 Impact Factor

Full-text (2 Sources)

Available from
Jun 3, 2014