A Peptide Derived from Tenascin-C Induces β1 Integrin Activation through Syndecan-4

Hiroshi Handa,Toshiyuki Ohwaki,Osamu Nagao,Toshimichi Yoshida,Ryo Hayashi,Shogo Miura,Yohei Saito,Yosei Harada,Hiroaki Kodama,Hiroaki Okutsu,Tomohisa Yoshimura,Fumio Fukai,Hisae Imazeki,Sadahiro Kamiya

doi:10.1074/jbc.m705608200

Abstract

Tenascin-C (TN-C) is unique for its cell adhesion modulatory function. We have shown that TNIIIA2, a synthetic 22-mer peptide derived from TN-C, stimulated beta1 integrin-mediated cell adhesion of nonadherent and adherent cell types, by inducing activation of beta1 integrin. The active site of TNIIIA2 appeared cryptic in the TN-C molecule but was exposed by MMP-2 processing of TN-C. The following results suggest that cell surface heparan sulfate (HS) proteoglycan (HSPG), including syndecan-4, participated in TNIIIA2-induced beta1 integrin activation: 1) TNIIIA2 bound to cell surface HSPG via its HS chains, as examined by photoaffinity labeling; 2) heparitinase I treatment of cells abrogated beta1 integrin activation induced by TNIIIA2; 3) syndecan-4 was isolated by affinity chromatography using TNIIIA2-immobilized beads; 4) small interfering RNA-based down-regulation of syndecan-4 expression reduced TNIIIA2-induced beta1 integrin activation, and consequent cell adhesion to fibronectin; 5) overexpression of syndecan-4 core protein enhanced TNIIIA2-induced activation of beta1 integrin. However, treatments that targeted the cytoplasmic region of syndecan-4, including ectopic expression of its mutant truncated with the cytoplasmic domains and treatment with protein kinase Calpha inhibitor Gö6976, did not influence the TNIIIA2 activity. These results suggest that a TNIIIA2-related matricryptic site of the TN-C molecule, exposed by MMP-2 processing, may have bound to syndecan-4 via its HS chains and then induced conformational change in beta1 integrin necessary for its functional activation. A lateral interaction of beta1 integrin with the extracellular region of the syndecan-4 molecule may be involved in this conformation change.

Highlights

Interactions of cells with the extracellular matrix (ECM) are largely mediated by members of the integrin superfamily of adhesive receptors
Some of our results suggest that cell surface heparan sulfate (HS) proteoglycans (HSPG), including syndecan-4, participated in ␤1 integrin activation in response to TNIIIA2, without requiring its cytoplasmic domains
To verify the involvement of syndecan-4/HSPG in the expression of TNIIIA2 activity, we examined the effect of HS chain degradation on TNIIIA2-induced ␤1 integrin activation

Summary

Introduction

Interactions of cells with the ECM are largely mediated by members of the integrin superfamily of adhesive receptors. ␤1 Integrin Activation by Tenascin-C Peptide logical processes such as proteolytic cleavage and conformational change in response to multimerization of ECM proteins, binding to other molecules, or cell-mediated mechanical forces [9, 10]. TNIIIA2, a 22-mer TN-C peptide containing YTITIRGV, stimulated cell adhesion to FN by inducing conformational and functional activation of ␤1 integrin.

Results

Conclusion