Keon B H, Schäfer S, Kuhn C, Grund C, Franke W W
Division of Cell Biology, German Cancer Research Center, Heidelberg, Germany.
J Cell Biol. 1996 Aug;134(4):1003-18. doi: 10.1083/jcb.134.4.1003.
Using a monoclonal antibody we have identified and cDNA-cloned a novel type of protein localized, by light and electron microscopy, to the plaque associated with the cytoplasmic face of the tight junction-containing zone (zonula occludens) of polar epithelial cells and of Sertoli cells of testis, but absent from the junctions of vascular endothelia. The approximately 3.7-kb mRNA encodes a polypeptide of 1142 amino acids (calculated molecular weight 126.5 kD, pI 6.25), for which the name "symplekin" (from Greek sigma upsilon mu pi lambda epsilon kappa epsilon iota, nu, to tie together, to weave, to be intertwined) is proposed. However, both the mRNA and the protein can also be detected in a wide range of cell types that do not form tight junctions or are even completely devoid of any stable cell contacts. Careful analyses have revealed that the protein occurs in all these diverse cells in the nucleoplasm, and only in those cells forming tight junctions is it recruited, partly but specifically, to the plaque structure of the zonula occludens. We discuss symplekin as a representative of a group of dual residence proteins which occur and probably function in the nucleus as well as in the plaques exclusive for either tight junctions, adherens junctions, or desmosomes.
我们利用单克隆抗体，通过光学显微镜和电子显微镜鉴定并对一种新型蛋白质进行了cDNA克隆。这种蛋白质定位于极性上皮细胞和睾丸支持细胞含紧密连接区（闭锁小带）胞质面相关的斑块，但血管内皮细胞的连接处没有。约3.7-kb的mRNA编码一个由1142个氨基酸组成的多肽（计算分子量为126.5 kD，pI 6.25），我们提议将其命名为“symplekin”（源自希腊语sigma upsilon mu pi lambda epsilon kappa epsilon iota, nu，意为系在一起、编织、缠绕）。然而，在不形成紧密连接甚至完全没有任何稳定细胞接触的多种细胞类型中也能检测到mRNA和蛋白质。仔细分析表明，该蛋白质存在于所有这些不同细胞的核质中，只有在形成紧密连接的细胞中，它才部分但特异性地被募集到闭锁小带的斑块结构中。我们将symplekin作为一组双重定位蛋白质的代表进行讨论，这类蛋白质在细胞核中存在并可能发挥作用，同时也存在于紧密连接、黏着连接或桥粒所特有的斑块中。
