Brattsand G, Roos G, Marklund U, Ueda H, Landberg G, Nånberg E, Sideras P, Gullberg M
Unit for Cell and Molecular Biology, University of Umeå, Sweden.
Leukemia. 1993 Apr;7(4):569-79.
Activation of protein kinase C results in phosphorylation of a 19-kDa protein termed 19K. Isolation and sequence analysis of a cDNA encoding the 19K protein revealed that this protein has been studied in other systems under different names. The name oncoprotein 18 (Op18) has been proposed on the basis of a postulated up-regulation in neoplastic cells. In the present report we adopt the designation Op18 for the 19K protein, and quantify this phosphoprotein in a series of leukemia/lymphoma cell lines, a panel of non-transformed cells and some terminally differentiated cell types. For this purpose we have developed reagents allowing quantitative Western-blot analysis, and quantification of Op18 on the single cell level by flow cytometric analysis. The data demonstrates a pronounced up-regulation of the Op18 protein in most leukemia/lymphoma cell lines. The HPB-ALL cell line provided the most extreme case and expressed 7 x 10(6) Op18 molecules/cell, which compares with 0.65 x 10(6) Op18 molecules/cell in non-transformed lymphoblastoid cells. The expression of Op18 appears to be restricted to cell types with proliferative potential, but it is clear from our results that up-regulation of Op18 is uncoupled from cellular proliferation. Moreover, by employing an Epstein-Barr virus based shuttle vector, we expressed Op18 cDNA in lymphoblastoid cells. This resulted in a three to fourfold up-regulation of Op18 that did not have any detectable consequences for cell-surface phenotype or cell size. However, increased expression of Op18 resulted in a partial inhibition of cell proliferation. Taken altogether, the results suggest that up-regulation Op18 levels in leukemia/lymphoma cells are strongly associated with, but not a direct cause of tumour progression.
蛋白激酶C的激活导致一种名为19K的19千道尔顿蛋白发生磷酸化。对编码19K蛋白的cDNA进行分离和序列分析后发现，该蛋白在其他系统中曾以不同名称进行过研究。基于肿瘤细胞中假定的上调现象，有人提出了癌蛋白18（Op18）这一名称。在本报告中，我们采用Op18来指代19K蛋白，并对一系列白血病/淋巴瘤细胞系、一组未转化细胞以及一些终末分化细胞类型中的这种磷酸化蛋白进行定量分析。为此，我们开发了相关试剂，可用于定量蛋白质免疫印迹分析，并通过流式细胞术在单细胞水平对Op18进行定量。数据表明，大多数白血病/淋巴瘤细胞系中Op18蛋白有明显上调。HPB - ALL细胞系表现最为极端，每个细胞表达7×10⁶个Op18分子，相比之下，未转化的淋巴母细胞中每个细胞表达0.65×10⁶个Op18分子。Op18的表达似乎仅限于具有增殖潜力的细胞类型，但从我们的结果可以清楚地看出，Op18的上调与细胞增殖并无关联。此外，通过使用基于爱泼斯坦 - 巴尔病毒的穿梭载体，我们在淋巴母细胞中表达了Op18 cDNA。这导致Op18上调了三到四倍，且对细胞表面表型或细胞大小没有任何可检测到的影响。然而，Op18表达的增加导致细胞增殖受到部分抑制。总体而言，结果表明白血病/淋巴瘤细胞中Op18水平的上调与肿瘤进展密切相关，但并非肿瘤进展的直接原因。
