Glycobiology Advance Access published online on March 16, 2007
Glycobiology, doi:10.1093/glycob/cwm031
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CHANGES IN GLYCOSYLATION OF VITRONECTIN MODULATE MULTIMERIZATION AND COLLAGEN BINDING DURING LIVER REGENERATION
1 Graduate school of Humanities and Sciences and The Glycoscience Institute, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo, 112-8610 Japan
2 Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8502, Japan
3 Nippi Research Institute of Biomatrix, 1-1, Senju-midoricho, Adachi-ku, Tokyo 120-8601, Japan
* Address correspondence to: Haruko Ogawa, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo, 112-8610 Japan, Tel. 03-5978-5343; Fax. 03-5978-5343; E-mail: ogawa.haruko{at}ocha.ac.jp
Received on February 20, 2007; revised on February 20, 2007; accepted on March 9, 2007
Elucidating the mechanisms and factors regulating multimerization is biologically important in order to modulate the biological activities of functional proteins, especially adhesive proteins in the extracellular matrix (ECM). Vitronectin (VN) is a multifunctional glycoprotein present in plasma and ECM. Linkage of cellular adhesion and fibrinolysis by VN plays an essential role during tissue remodeling. Our previous study determined that the collagen-binding activity of VN was markedly enhanced with the decreased glycosylation during liver regeneration. This study demonstrated how alternations of glycans modulate the biological activity of VN. Human and rat VNs were used because of their similarities in structure and activities. The binding affinity of human VN to immobilized collagen was shown to be higher at pH 4.5 than at pH 7.5, at 37°C than at 4°C. Sedimentation velocity studies indicated that the greater the multimerization of human VN, the better it bound to collagen. The results indicate that the collagen binding of VN was modulated through its multimerization. Stepwise trimming of glycan with various exoglycosidases increased both the multimer size and the collagen binding of human VN indicating that they are modulated by changes in glycosylation. The multimer sizes of VN purified from plasma of partially hepatectomized (PH-) rats and sham-operated (SH-) rats increased by about 45% and 31%, respectively, compared with those of non-operated (NO-) rats. In accordance with this, PH-VN exhibited remarkably enhanced collagen binding than SH-VN and NO-VN on SPR. In the PH rat sera, the multimer VN was increased in both amount and size compared to those in SH- and NO-sera. The results demonstrate that glycan alterations during tissue remodeling induce increased multimerization state to enhance the biological activity of VN.
Key words: vitronectin / multimerization / oligosaccharide / partial hepatectomy / collagen binding / multivalent effect