Latent Transforming Growth Factor β-binding Proteins and Fibulins Compete for Fibrillin-1 and Exhibit Exquisite Specificities in Binding Sites
Latent Transforming Growth Factor β-binding Proteins and Fibulins Compete for Fibrillin-1 and Exhibit Exquisite Specificities in Binding Sites
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DOI：
10.1074/jbc.m809348200
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发表时间：
2009-06-19
影响因子：
4.8
通讯作者：
Sakai, Lynn Y.
中科院分区：
文献类型：
--
作者：
Ono, Robert N.;Sengle, Gerhard;Sakai, Lynn Y.
潜伏性转化生长因子（TGF）β结合蛋白（LTBP）与β-内酰胺酶-1相互作用。这种相互作用对于TGF β的适当隔离和细胞外控制是重要的。表面等离子体共振相互作用的研究表明，残基内的第一个杂交结构域（Hyb 1）的Escherichin-1有助于与LTBP-1和LTBP-4的相互作用。通过其中第三表皮生长因子样结构域（EGF 3）中的残基突变的人表皮生长因子-1多肽调节结合亲和力表明LTBP-1和LTBP-4的结合位点是不同的，并且表明EGF 3也可能对LTBP-4的结合位点贡献残基。此外，纤蛋白-2、纤蛋白-4和纤蛋白-5与EGF 3/Hyb 1中所含的残基结合，但突变的多肽再次表明它们在Eclin-I中的结合位点存在差异。结果表明，这些蛋白质-蛋白质相互作用表现出“精致的特异性”，这是一个常用于描述单克隆抗体相互作用的短语。尽管存在这些差异，LTBP-1和纤维蛋白-1之间的相互作用竞争纤维蛋白-1和这些纤维蛋白之间的相互作用。所有这些蛋白质都被免疫定位于微纤维。然而，在无Fbn-1的成纤维细胞培养物中，LTBP-1和LTBP-4不掺入微纤维中。相反，在无纤蛋白-2（Fbln 2）或无纤蛋白-4（Fbln 4）的培养物中，微管蛋白-1、LTBP-1和LTBP-4掺入微纤维中。这些数据首次表明，LTBP的适当基质组装需要微管蛋白-1，而不是纤蛋白-2或纤蛋白-4。这些研究还表明，纤蛋白可能会影响LTBP的基质隔离，因为这些蛋白质之间的体外相互作用是竞争性的。
Latent transforming growth factor (TGF) beta-binding proteins (LTBPs) interact with fibrillin-1. This interaction is important for proper sequestration and extracellular control of TGF beta. Surface plasmon resonance interaction studies show that residues within the first hybrid domain (Hyb1) of fibrillin-1 contribute to interactions with LTBP-1 and LTBP-4. Modulation of binding affinities by fibrillin-1 polypeptides in which residues in the third epidermal growth factor-like domain (EGF3) are mutated demonstrates that the binding sites for LTBP-1 and LTBP-4 are different and suggests that EGF3 may also contribute residues to the binding site for LTBP-4. In addition, fibulin-2, fibulin-4, and fibulin-5 bind to residues contained within EGF3/Hyb1, but mutated polypeptides again indicate differences in their binding sites in fibrillin-1. Results demonstrate that these protein-protein interactions exhibit "exquisite specificities," a phrase commonly used to describe monoclonal antibody interactions. Despite these differences, interactions between LTBP-1 and fibrillin-1 compete for interactions between fibrillin-1 and these fibulins. All of these proteins have been immunolocalized to microfibrils. However, in fibrillin-1 (Fbn1) null fibroblast cultures, LTBP-1 and LTBP-4 are not incorporated into microfibrils. In contrast, in fibulin-2 (Fbln2) null or fibulin-4 (Fbln4) null cultures, fibrillin-1, LTBP-1, and LTBP-4 are incorporated into microfibrils. These data show for the first time that fibrillin-1, but not fibulin-2 or fibulin-4, is required for appropriate matrix assembly of LTBPs. These studies also suggest that the fibulins may affect matrix sequestration of LTBPs, because in vitro interactions between these proteins are competitive.