Zhang M, Sheng S, Maass N, Sager R
Dana Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA.
Mol Med. 1997 Jan;3(1):49-59.
The human maspin gene encodes a protein in the serine proteinase inhibitor (serpin) family with tumor-suppressing functions in cell culture and in nude mice. In order to examine the role of maspin in an intact mammal, we cloned and sequenced the cDNA of mouse maspin. The recombinant protein was produced and its activity in cell culture was assessed.
Mouse maspin (mMaspin) was cloned by screening a mouse mammary gland cDNA library with the human maspin cDNA probe. Northern blot analysis was used to examine the expression patterns in mouse tissues, mammary epithelial cells, and carcinomas. Recombinant mMaspin protein was produced in E. coli. Invasion and motility assays were used to assess the biological function of mMaspin.
mMaspin is 89% homologous with human maspin at the amino acid level. Like its human homolog, mMaspin is expressed in normal mouse mammary epithelial cells and down-regulated in mouse breast tumor cell lines. The expression is altered at different developmental stages in mammary gland. Addition of the recombinant mMaspin protein to mouse tumor cells was shown to inhibit invasion in a dose-dependent manner. As with the human protein, recombinant mMaspin protein also inhibited mouse mammary tumor motility. Deletion in the putative mMaspin reactive site loop (RSL) region resulted in the loss of its inhibitory functions.
mMaspin is the mouse homolog of a human tumor suppressor gene. The expression of mMaspin is down-regulated in tumor cells and is altered at different developmental stages of mammary gland. mMaspin has inhibitory properties similar to those of human maspin in cell culture, suggesting that the homologous proteins play similar physiological roles in vivo.
人类乳腺丝抑蛋白基因编码一种丝氨酸蛋白酶抑制剂（serpin）家族中的蛋白质，在细胞培养和裸鼠实验中具有肿瘤抑制功能。为了研究乳腺丝抑蛋白在完整哺乳动物中的作用，我们克隆并测序了小鼠乳腺丝抑蛋白的cDNA。制备了重组蛋白并评估了其在细胞培养中的活性。
通过用人乳腺丝抑蛋白cDNA探针筛选小鼠乳腺cDNA文库来克隆小鼠乳腺丝抑蛋白（mMaspin）。采用Northern印迹分析检测其在小鼠组织、乳腺上皮细胞和癌组织中的表达模式。在大肠杆菌中制备重组mMaspin蛋白。采用侵袭和运动性实验评估mMaspin的生物学功能。
mMaspin在氨基酸水平上与人乳腺丝抑蛋白有89%的同源性。与其人类同源物一样，mMaspin在正常小鼠乳腺上皮细胞中表达，在小鼠乳腺肿瘤细胞系中表达下调。其表达在乳腺不同发育阶段发生改变。向小鼠肿瘤细胞中添加重组mMaspin蛋白可呈剂量依赖性抑制侵袭。与人类蛋白一样，重组mMaspin蛋白也抑制小鼠乳腺肿瘤的运动性。假定的mMaspin反应位点环（RSL）区域的缺失导致其抑制功能丧失。
mMaspin是人类肿瘤抑制基因的小鼠同源物。mMaspin在肿瘤细胞中的表达下调，且在乳腺不同发育阶段发生改变。mMaspin在细胞培养中具有与人乳腺丝抑蛋白相似的抑制特性，表明同源蛋白在体内发挥相似的生理作用。
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