METABOLISM OF CARCINOEMBRYONAL ANTIGEN

癌胚抗原(CEA)既可作为同型抗原，又可作为 异型细胞黏附分子。我们的研究表明，CEA可能 参与结直肠癌肝转移的发生 癌症可能是由于其细胞黏附特性造成的。这 研究的重点是肝脏中CEA结合蛋白的结构。这个 肝脏CEA主要结合蛋白是库普弗细胞表面80kD亚基 可能起同源二聚体作用的分子。一种类似的蛋白质是 发现于肺泡巨噬细胞，但不存在于腹膜巨噬细胞或 循环中的单核细胞。将从纯化的蛋白质中获得多肽序列 80kD结合蛋白及其衍生多肽的微测序 PVDF膜。这些数据将用于构建寡核苷酸 作为对从克隆基因获得的序列的检查 8OKD结合蛋白。多克隆和单克隆抗体都将是 制成80kD蛋白质或衍生多肽。负责的基因 因为这个蛋白将从大鼠和人身上克隆和测序 人工合成表达载体探查Kupffer细胞cDNA文库 寡核苷酸、抗体或使用功能性CEA结合试验。 这些信息将用于确定功能领域，并将 重要的是理解这种结合蛋白在引导 特定部位(肺和肝脏)转移。8okD的结合位点 蛋白质已经定位到N-末端和第一个环的交界处 CEA的结构域。这10个氨基酸序列包含一个五肽，具有 补体中五肽(PELPK)的序列同源性 亚组分CLS、基质分解酶和胶原酶1.基质分解酶和 胶原酶是一种降解细胞外基质的酶，已被 与肿瘤细胞的侵袭和转移有关。多肽序列 在CEA的N末端和结合的第一环结构域的交界处 因此，8okD Kupffer细胞蛋白将被缩小到 活动所需的最低结构。8OkD的潜在作用 蛋白质作为基质分解素胶原酶和补体CLS的结合部位 将会被调查。这项研究通过以下方式扩展了我们对机制的认识 Kupffer细胞处理糖蛋白的哪些及其可能的作用 8OkD结合蛋白在结直肠癌细胞中的作用机制 附着并侵入肝脏。

Carcinoembryonic antigen (CEA) can function as both a homotypic and heterotypic cell adhesion molecule. Our studies have shown that CEA may be involved in the development of hepatic metastases from colorectal cancers possibly as a consequence of its cell adhesion properties. This study focuses on the structure of CEA binding proteins in the liver. The major hepatic CEA binding protein is a 80kD subunit Kupffer cell surface molecule that probably functions as a homodimer. A similar protein is found on lung alveolar macrophages, but not on peritoneal macrophages or circulating monocytes. Peptide sequences will be obtained from purified 80kD binding protein and from derived peptides by microsequencing from PVDF membranes. This data will be used to construct oligonucleotide probes and as a check on sequences obtained from cloning the gene for the 8OkD binding protein. Both polyclonal and monoclonal antibodies will be made to the 80kD protein or to derived peptides. The gene responsible for this protein will be cloned and sequenced from both rat and human Kupffer cell cDNA libraries by probing expression vectors with synthetic oligonucleotides, antibodies or using a functional CEA binding assay. This information will be used to pinpoint functional domains and will be important in understanding the role of this binding protein in directing site specific (lung and liver) metastases. The binding site for the 8OkD protein has been located to the junction of the N-terminal and first loop domains of CEA. This 10 amino acid sequence contains a pentapeptide with sequence homology to a pentapeptide (PELPK) found in complement subcomponent Cls, stromelysin and collagenase 1. Stromelysin and collagenase are extracellular matrix degrading enzymes that have been implicated in tumor cell invasion and metastases. The peptide sequence at the junction of the N-terminal and first loop domain of CEA that binds to the 8OkD Kupffer cell protein will therefore, be narrowed down to the minimum structure required for activity. The potential role of the 8OkD protein as a binding site for stromelysin collagenase and complement Cls will be investigated. This study expands our knowledge of mechanisms by which Kupffer cells process glycoproteins and the potential role of the 8OkD binding protein in the mechanism by which colorectal cancer cells attach and invade in the liver.