Tenascin C Promiscuously Binds Growth Factors via Its Fifth Fibronectin Type III-Like Domain

Tenascin C (TNC) is an extracellular matrix protein that is upregulated during development as well as tissue remodeling. TNC is comprised of multiple independent folding domains, including 15 fibronectin type III-like (TNCIII) domains. The fifth TNCIII domain (TNCIII5) has previously been shown to bind heparin. Our group has shown that the heparin-binding fibronectin type III domains of fibronectin (FNIII), specifically FNIII12–14, possess affinity towards a large number of growth factors. Here, we show that TNCIII5 binds growth factors promiscuously and with high affinity. We produced recombinant fragments of TNC representing the first five TNCIII repeats (TNCIII1–5), as well as subdomains, including TNCIII5, to study interactions with various growth factors. Multiple growth factors of the platelet-derived growth factor (PDGF) family, the fibroblast growth factor (FGF) family, the transforming growth factor beta (TGF-β) superfamily, the insulin-like growth factor binding proteins (IGF-BPs), and neurotrophins were found to bind with high affinity to this region of TNC, specifically to TNCIII5. Surface plasmon resonance was performed to analyze the kinetics of binding of TNCIII1–5 with TGF-β1, PDGF-BB, NT-3, and FGF-2. The promiscuous yet high affinity of TNC for a wide array of growth factors, mediated mainly by TNCIII5, may play a role in multiple physiological and pathological processes involving TNC.腱生蛋白C（Tenascin C, TNC）是一种细胞外基质蛋白，在发育过程及组织重塑阶段表达会上调。TNC由多个独立的折叠结构域组成，其中包含15个纤连蛋白III型样（Tenascin III, TNCIII）结构域。既往研究已证实，第五个TNCIII结构域（TNCIII5）可结合肝素。本团队此前的研究表明，纤连蛋白（Fibronectin）的肝素结合型III型结构域（FNIII），具体为FNIII12–14，可与大量生长因子结合并展现出较高亲和力。本研究证实，TNCIII5可广泛且高亲和力地结合生长因子。我们制备了覆盖TNC前五个TNCIII重复序列（TNCIII1–5）的重组片段，以及包括TNCIII5在内的亚结构域，以研究其与各类生长因子的相互作用。研究发现，血小板衍生生长因子（Platelet-derived growth factor, PDGF）家族、成纤维细胞生长因子（Fibroblast growth factor, FGF）家族、转化生长因子β（Transforming growth factor beta, TGF-β）超家族、胰岛素样生长因子结合蛋白（Insulin-like growth factor binding proteins, IGF-BPs）以及神经营养因子中的多种生长因子，均可与TNC的该区域（尤其是TNCIII5）高亲和力结合。我们通过表面等离子体共振（Surface plasmon resonance, SPR）技术分析了TNCIII1–5与TGF-β1、PDGF-BB、NT-3及FGF-2的结合动力学。TNC主要通过TNCIII5结构域，对多种生长因子展现出广泛但高亲和力的结合特性，这一特性可能在TNC参与的多种生理及病理过程中发挥作用。