Ben-Ze'ev A
Exp Cell Res. 1986 Jun;164(2):335-52. doi: 10.1016/0014-4827(86)90033-9.
The organization and synthesis of proteins involved in the formation and stabilization of desmosome-type junctions was investigated in cultured epithelial cells treated with a tumor promoter (12-O-tetradecanoyl-phorbol-13-acetate (TPA]. In Madin-Darby bovine (MDBK) and canine (MDCK) kidney cell colonies, TPA induced a rapid disruption of desmosomes and marked alterations in cell morphology. Within 4-6 h after TPA treatment, cell shape changed from cuboidal to highly irregular, with some very long extensions that contained cytokeratin fibrils, and many flat lamellar protrusions which were devoid of cytokeratin fibrils. These morphological changes in both MDBK and MDCK cells were followed by a dramatic and coordinated inhibition in the synthesis of all cytokeratins, 14-24 h after the addition of TPA, but without a similar effect on the synthesis of vimentin, which is coexpressed in these cells. In contrast, in dense cultures of MDBK and MDCK cells the synthesis of cytokeratins and the organization of desmosomal contacts were not affected by TPA. In an epithelial cell line derived from the bovine mammary gland (BMGE-H) the synthesis of an acidic cytokeratin of 45 kD, which was previously shown to be synthesized at high levels only in dense cultures, was dramatically inhibited by TPA treatment. Cell-free in vitro translation assays with mRNA from control and TPA-treated cells also demonstrated a decrease in the synthesis of cytokeratins in response to TPA. The inhibition of cytokeratin synthesis after TPA treatment was paralleled by a decrease in the synthesis of a high molecular weight (HMW) desmoplakin protein, which was abundant in dense MDBK and BMGE-H cells. The results with TPA-treated cells are suggestive of a coordinated down-regulation in the synthesis of only those cytokeratins and of a desmoplakin which were shown to be regulated by the extent of cell-cell contact. Cytokeratin phosphorylation in TPA-treated cells was low and reflected the decrease in their total mass, suggesting that it was not altered by TPA treatment. The possible linkage between the regulation of synthesis and organization of proteins involved in desmosome formation is discussed.
在用肿瘤启动子（12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA））处理的培养上皮细胞中，研究了参与桥粒型连接形成和稳定的蛋白质的组织和合成情况。在Madin - Darby牛肾（MDBK）和犬肾（MDCK）细胞集落中，TPA诱导桥粒迅速破坏，并使细胞形态发生显著改变。在TPA处理后4 - 6小时内，细胞形状从立方形变为高度不规则，出现一些含有细胞角蛋白原纤维的非常长的延伸部分，以及许多不含细胞角蛋白原纤维的扁平片状突起。在MDBK和MDCK细胞中出现这些形态变化之后，在添加TPA后14 - 24小时，所有细胞角蛋白的合成受到显著且协同的抑制，但对这些细胞中共同表达的波形蛋白的合成没有类似影响。相反，在MDBK和MDCK细胞的致密培养物中，细胞角蛋白的合成和桥粒连接的组织不受TPA影响。在源自牛乳腺的上皮细胞系（BMGE - H）中，一种45 kD的酸性细胞角蛋白的合成受到TPA处理的显著抑制，该细胞角蛋白先前显示仅在致密培养物中高水平合成。用对照细胞和TPA处理细胞的mRNA进行的无细胞体外翻译试验也表明，TPA处理后细胞角蛋白的合成减少。TPA处理后细胞角蛋白合成的抑制与高分子量（HMW）桥粒斑蛋白的合成减少同时发生，该蛋白在致密的MDBK和BMGE - H细胞中含量丰富。TPA处理细胞的结果提示，仅那些被证明受细胞 - 细胞接触程度调节的细胞角蛋白和桥粒斑蛋白的合成存在协同下调。TPA处理细胞中的细胞角蛋白磷酸化水平较低，反映了其总量的减少，表明其未受TPA处理改变。讨论了参与桥粒形成的蛋白质合成调节与组织之间的可能联系。
