Türeci O, Sahin U, Vollmar E, Siemer S, Göttert E, Seitz G, Parkkila A K, Shah G N, Grubb J H, Pfreundschuh M, Sly W S
Department of Internal Medicine, University of Saarland, 66421 Homburg, Germany.
Proc Natl Acad Sci U S A. 1998 Jun 23;95(13):7608-13. doi: 10.1073/pnas.95.13.7608.
We report the cloning and characterization of a tumor-associated carbonic anhydrase (CA) that was identified in a human renal cell carcinoma (RCC) by serological expression screening with autologous antibodies. The cDNA sequence predicts a 354-amino acid polypeptide with a molecular mass of 39,448 Da that has features of a type I membrane protein. The predicted sequence includes a 29-amino acid signal sequence, a 261-amino acid CA domain, an additional short extracellular segment, a 26-amino acid hydrophobic transmembrane domain, and a hydrophilic C-terminal cytoplasmic tail of 29 amino acids that contains two potential phosphorylation sites. The extracellular CA domain shows 30-42% homology with known human CAs, contains all three Zn-binding histidine residues found in active CAs, and contains two potential sites for asparagine glycosylation. When expressed in COS cells, the cDNA produced a 43- to 44-kDa protein in membranes that had around one-sixth the CA activity of membranes from COS cells transfected with the same vector expressing bovine CA IV. We have designated this human protein CA XII. Northern blot analysis of normal tissues demonstrated a 4.5-kb transcript only in kidney and intestine. However, in 10% of patients with RCC, the CA XII transcript was expressed at much higher levels in the RCC than in surrounding normal kidney tissue. The CA XII gene was mapped by using fluorescence in situ hybridization to 15q22. CA XII is the second catalytically active membrane CA reported to be overexpressed in certain cancers. Its relationship to oncogenesis and its potential as a clinically useful tumor marker clearly merit further investigation.
我们报告了一种肿瘤相关碳酸酐酶（CA）的克隆及特性分析，该酶是通过用自体抗体进行血清学表达筛选，在人肾细胞癌（RCC）中鉴定出来的。cDNA序列预测其为一个354个氨基酸的多肽，分子量为39448Da，具有I型膜蛋白的特征。预测序列包括一个29个氨基酸的信号序列、一个261个氨基酸的CA结构域、一个额外的短细胞外片段、一个26个氨基酸的疏水跨膜结构域以及一个29个氨基酸的亲水性C末端胞质尾，该尾含有两个潜在的磷酸化位点。细胞外CA结构域与已知的人CA有30% - 42%的同源性，包含活性CA中发现的所有三个锌结合组氨酸残基，并且含有两个潜在的天冬酰胺糖基化位点。当在COS细胞中表达时，该cDNA在膜中产生一种43 - 44kDa的蛋白质，其CA活性约为用表达牛CA IV的相同载体转染的COS细胞膜的六分之一。我们将这种人类蛋白质命名为CA XII。对正常组织的Northern印迹分析表明，仅在肾脏和肠道中有一个4.5kb的转录本。然而，在10%的RCC患者中，CA XII转录本在RCC中的表达水平比周围正常肾组织高得多。通过荧光原位杂交将CA XII基因定位到15q22。CA XII是报道的第二种在某些癌症中过度表达的具有催化活性的膜CA。它与肿瘤发生的关系及其作为临床有用肿瘤标志物的潜力显然值得进一步研究。
