Wewer U M, Albrechtsen R
Laboratory of Molecular Pathology, University Institute of Pathological Anatomy, Copenhagen, Denmark.
Lab Invest. 1992 Aug;67(2):253-62.
Tetranectin is a recently discovered protein that binds to kringle 4 region of plasminogen (Clemmensen I, Petersen LC, Kluft C. Eur J Biochem 1986; 156:327.
The mRNA encoding human tetranectin was cloned by using degenerate primers in a reverse transcriptase reaction followed by polymerase chain reaction amplification. The resulting polymerase chain reaction product was examined by DNA sequencing and subsequently used as probe for screening a human placental cDNA library. A full length cDNA clone (TET-1) was isolated, characterized, and used for Northern blot and in situ hybridization.
DNA sequencing analysis revealed a 874-base pair cDNA containing an open reading frame of 606 base pairs encoding 202 amino acids. A classical signal peptide was present starting with the initiation methionine. The mature tetranectin chain consisted of 181 amino acids (M(r) = 20,169). The 3' noncoding region contained a single polyadenylation signal and a 26-residue poly A tail. The predicted amino acid sequence of the mature tetranectin chain showed, except for one amino acid, complete identity to that obtained by sequencing of the native protein (Fuhlendorff J, Clemmensen I, Magnusson S, Biochemistry 1987;26:6757). Northern blot of poly A+ revealed a single band of approximately 1 kb. Northern blot analysis of poly A+ isolated from a series of normal human tissues (lung, liver, spleen, kidney, and pancreas) revealed a distinct hybridization band that was especially prominent in the lungs and spleen. No hybridization signal was detected in three carcinoma cell lines examined in parallel. Northern blot analysis of poly A+ RNA isolated from solid tumors revealed a tetranectin specific mRNA band. In situ hybridizations on tissue sections of colon carcinomas and normal colon tissues revealed a strong and distinct hybridization signal of stromal cells in colon carcinomas but not in tumor cells. Only a few stromal cells were labeled in the normal colon. Immunohistochemically, tetranectin was found in a fibrillar-like pattern in the extracellular matrix around the tumor islands and was not detectable in the normal colon stromal tissue. Plasminogen exhibited a similar immunohistochemical staining pattern as tetranectin.
Human tetranectin cDNA comprises 874 base pairs including a 606-base pair open reading frame encoding 202 amino acids including a classical signal peptide. This protein is produced locally by cells of the stromal compartment of tumors and is deposited into the extracellular matrix. Since tetranectin binds to plasminogen we hypothesize that it could function as an anchor and/or reservoir for plasminogen and similar substances that regulate tumor invasion and metastasis as well as tumor angiogenesis.
四连蛋白是一种最近发现的能与纤溶酶原kringle 4区域结合的蛋白质（Clemmensen I，Petersen LC，Kluft C。《欧洲生物化学杂志》1986年；156：327）。
通过在逆转录酶反应中使用简并引物，随后进行聚合酶链反应扩增，克隆编码人四连蛋白的mRNA。所得聚合酶链反应产物经DNA测序检测，随后用作筛选人胎盘cDNA文库的探针。分离、鉴定出一个全长cDNA克隆（TET-1），并将其用于Northern印迹和原位杂交。
DNA测序分析显示一个874个碱基对的cDNA，包含一个606个碱基对的开放阅读框，编码202个氨基酸。从起始甲硫氨酸开始有一个典型的信号肽。成熟的四连蛋白链由181个氨基酸组成（相对分子质量=20,169）。3'非编码区包含一个单一的聚腺苷酸化信号和一个26个残基的聚A尾。成熟四连蛋白链的预测氨基酸序列显示，除一个氨基酸外，与天然蛋白测序结果完全一致（Fuhlendorff J，Clemmensen I，Magnusson S，《生物化学》1987年；26：6757）。聚腺苷酸阳性RNA的Northern印迹显示一条约1 kb的单带。对从一系列正常人组织（肺、肝、脾、肾和胰腺）分离的聚腺苷酸阳性RNA进行Northern印迹分析，发现一条明显的杂交带，在肺和脾中尤为突出。在同时检测的三种癌细胞系中未检测到杂交信号。对从实体瘤分离的聚腺苷酸阳性RNA进行Northern印迹分析，显示一条四连蛋白特异性mRNA带。对结肠癌和正常结肠组织切片进行原位杂交，结果显示结肠癌基质细胞有强烈且明显的杂交信号，而肿瘤细胞中没有。正常结肠中只有少数基质细胞被标记。免疫组织化学分析显示，四连蛋白在肿瘤岛周围的细胞外基质中呈纤维状分布，在正常结肠基质组织中未检测到。纤溶酶原呈现与四连蛋白相似的免疫组织化学染色模式。
人四连蛋白cDNA由874个碱基对组成，包括一个606个碱基对的开放阅读框，编码202个氨基酸，包括一个典型的信号肽。这种蛋白质由肿瘤基质区室的细胞局部产生，并沉积到细胞外基质中。由于四连蛋白与纤溶酶原结合，我们推测它可能作为纤溶酶原和类似物质的锚定物和/或储存库，这些物质可调节肿瘤侵袭、转移以及肿瘤血管生成。
