中间纤维由大量的核蛋白和细胞质蛋白组成，这些蛋白以组织和分化依赖的方式表达。中间丝的成分在进化过程中高度保守，并且在物种之间表现出高度的保守性(1,2)。细胞角蛋白是上皮细胞中发现的主要结构蛋白，形成了中间丝的细胞质网络(3)。细胞角蛋白由至少20种独特的基因产物组成，分为两类:相对酸性的I型(CK9-CK20)和中性碱性的II型(CK1-CK8)。这些细胞角蛋白以1:1的比例结合成非共价异聚物，这些异聚物进一步组装成角蛋白丝(4,5)。细胞角蛋白的表达主要取决于上皮细胞类型及其分化程度;因此，评估细胞角蛋白表达状态有助于区分癌症和其他类型的癌症(6)。细胞角蛋白18基因(CK18)位于染色体12q13上，长3791个碱基对。它编码一种I型中间丝蛋白，这种蛋白主要存在于许多类型的单层或“简单”上皮组织中，定位于细胞质和核周区(4)。ck18及其共表达的互补型角蛋白伙伴CK8在各种成人上皮器官中持续表达，如肝脏、肺、肾脏、胰腺、胃肠道和乳腺。在缺乏CK8的情况下，CK18蛋白被降解，角蛋白中间丝未形成(8)。在先前转染CK18基因的小鼠成纤维细胞中分离出CK8的cDNA克隆并表达，这导致形成稳定的角蛋白丝(9)。因此，I型角蛋白(CK18)和II型角蛋白(CK8)的存在似乎对角蛋白丝的形成既必要又充分(8,9)。
Application: ICC, IHC, WB, IF
Clonality: Monoclonal
Host: Mouse
Purification: IgG
Reactivity: Monkey, Mouse, Rat, Human
The intermediate filaments consist of a large number of nuclear and cytoplasmic proteins that are expressed in a tissue- and differentiation-dependent manner. The components of the intermediate filaments are highly conserved during evolution and show a high degree of conservation among species (1, 2). Cytokeratins are major structural proteins found in epithelial cells, which form the cytoplasmic network of intermediate filaments (3). Cytokeratins consist of at least 20 unique gene products that fall into two categories: the relatively acidic type I group (CK9–CK20) and the neutral–basic type II group (CK1–CK8). These cytokeratins are combined in a 1:1 ratio into noncovalent heteropolymers, which are further assembled into keratin filaments (4, 5). The expression of cytokeratin proteins depends primarily on the epithelial cell type and its degree of differentiation; therefore, assessments of cytokeratin expression status are useful for distinguishing carcinomas from other types of cancer (6).The cytokeratin 18 gene (CK18) is located on chromo-some 12q13 and is 3,791 base pairs long. It codes for a type I intermediate filament protein that is found primarily in many types of single-layered or “simple” epithelial tissues and is localized in the cytoplasm and perinuclear region (4).CK18 and its coexpressed complementary type II keratin partner, CK8, are persistently expressed in a variety of adult epithelial organs, such as the liver, lung, kidney, pancreas, gastrointestinal tract, and mammary gland, and are also expressed by cancers that arise from these tissues (7). In the absence of CK8, the CK18 protein is degraded and keratin intermediate filaments are not formed (8). A cDNA clone forCK8 was isolated and expressed in mouse fibroblasts that had previously been transfected with the CK18 gene, which resulted in the formation of stable keratin filaments (9).Thus, the presence of a type I (CK18) and a type II (CK8)keratin appears to be both necessary and sufficient for the formation of keratin filaments (8, 9).