The adhesion and differentiation-inhibitory activities of the immunoglobulin superfamily member, carcinoembryonic antigen, can be independently blocked
The adhesion and differentiation-inhibitory activities of the immunoglobulin superfamily member, carcinoembryonic antigen, can be independently blocked
复制标题
DOI：
10.1074/jbc.m212500200
复制
发表时间：
2003-04-25
影响因子：
4.8
通讯作者：
Stanners, CP
中科院分区：
文献类型：
--
作者：
Taheri, M;Saragovi, HU;Stanners, CP
Ig超家族成员的外部结构域参与多种结合相互作用，包括亲同性和异亲性，这些相互作用启动导致多种细胞功能执行的分子事件。人癌胚抗原（CEA）是一种被广泛用作临床肿瘤标志物的Ig超家族细胞表面糖蛋白，它可以介导细胞间粘附。最近的证据支持这样一种观点，即不受管制的CEA过表达通过抑制细胞分化和破坏组织结构在肿瘤发生中起重要作用。cea介导的大鼠L6成肌细胞成肌分化的阻断依赖于其外部结构域的亲同结合。我们在这里证明，表达CEA的L6转染细胞可以“跨阻断”表达CEA缺失突变体（DeltaNCEA）的并置分化能力的L6转染细胞的肌发生。这一结果表明分化区细胞间反平行CEA-CEA相互作用的有效性。此外，DeltaNCEA可以通过与特异性抗cea抗体交联获得分化阻断活性，从而暗示在同一细胞表面上平行CEA-CEA相互作用的有效性。位点定向突变证明了CEA的肌源性分化阻断活性涉及氨基末端结构域的三个亚结构域，这些亚结构域先前被证明对其细胞间粘附功能至关重要。与区域桥接亚结构域1和2结合的单克隆抗体单价Fab片段既能抑制细胞间粘附，又能释放成肌分化阻滞。然而，QNDTG亚结构域3的Q80A、Q80R和D82N的氨基酸替换完全削弱了CEA的分化阻断活性，但对细胞间粘附活性没有影响。代表该亚结构域的环化肽在释放分化块方面最有效。
The external domains of Ig superfamily members are involved in multiple binding interactions, both homophilic and heterophilic, that initiate molecular events leading to the execution of diverse cell functions. Human carcinoembryonic antigen (CEA), an Ig superfamily cell surface glycoprotein used widely as a clinical tumor marker, undergoes homophilic interactions that mediate intercellular adhesion. Recent evidence supports the view that deregulated overexpression of CEA has an instrumental role in tumorigenesis through the inhibition of cell differentiation and the disruption of tissue architecture. The CEA-mediated block of the myogenic differentiation of rat L6 myoblasts depends on homophilic binding of its external domains. We show here that L6 transfectant cells expressing CEA can "trans-block" the myogenesis of juxtaposed differentiation-competent L6 transfectant cells expressing a deletion mutant of CEA (DeltaNCEA). This result implies the efficacy of antiparallel CEA-CEA interactions between cells in the differentiation block. In addition, DeltaNCEA can acquire differentiation blocking activity by cross-linking with specific anti-CEA antibodies, thus implying the efficacy of parallel CEA-CEA interactions on the same cell surface. The myogenic differentiation blocking activity of CEA was demonstrated by site-directed mutations to involve three subdomains of the amino-terminal domain, shown previously to be critical for its intercellular adhesion function. Monovalent Fab fragments of monoclonal antibodies binding to the region bridging subdomains 1 and 2 could both inhibit intercellular adhesion and release the myogenic differentiation block. Amino acid substitutions Q80A, Q80R, and D82N in subdomain 3, QNDTG, however, were found to completely ablate the differentiation blocking activity of CEA but had no effect on intercellular adhesion activity. A cyclized peptide representing this subdomain was the most effective at releasing the differentiation block.