Liu Hong, Zheng Shufang, Bellemare Véronique, Pelletier Georges, Labrie Fernand, Luu-The Van
Oncology and Molecular Endocrinology Laboratory, Laval University Hospital Research Center (CRCHUL) and Laval University, Quebec, GlV 4G2, Canada.
BMC Biochem. 2007 Feb 5;8:2. doi: 10.1186/1471-2091-8-2.
We have recently discovered that human type 12 17beta-HSD (h17beta-HSD12), a homolog of type 3 17beta-HSD, is a new estrogen-specific 17beta-hydroxysteroid dehydrogenase involved in the production of estradiol (E2). To further characterize this estradiol-producing enzyme, we have isolated the corresponding cDNA in the cynomolgus monkey (Macaca fascicularis), characterized its enzymatic activities and performed cellular localization using in situ hybridization.
Using HEK-293 cells stably expressing Macaca fascicularis type 12 17beta-HSD (mf17beta-HSD12), we have found that the mf17beta-HSD12 catalyzes efficiently and selectively the transformation of El into E2, in analogy with the h17beta-HSD12. We have also quantified the mf17beta-HSD12 mRNA expression levels in a series of Macaca fascicularis tissues using Quantitative RealTime PCR. The Macaca fascicularis 17beta-HSD12 mRNA is widely expressed with the highest levels tissues found in the cerebellum, spleen and adrenal with moderate level observed in all the other examined, namely the testis, ovary, cerebral cortex, liver, heart, prostate, mammary gland, myometrium, endometrium, skin, muscle and pancreas. To gain knowledge about the cellular localization of the mf17beta-HSD12 mRNA expression, we performed in situ hybridization using a 35S-labeled cRNA probe. Strong labeling was observed in epithelial cells and stromal cells of the mammary gland. In the uterus, the labeling is detected in epithelial cells and stromal cells of the endometrium.
These results strongly suggest that the Macaca fascicularis 17beta-HSD12 is an essential partner of aromatase in the biosynthesis of estradiol (E2). It strongly suggests that in the estradiol biosynthesis pathway, the step of 17-ketoreduction comes after the step of the aromatization (the aromatization of 4-androstendione to estrone followed by the conversion of estrone into estradiol by estrogen specific l7beta-HSDs) which is in contrast with the hypothesis suggesting that 4-androstenedione is converted to testosterone followed by the aromatization of testosterone.
我们最近发现，人12型17β-羟类固醇脱氢酶（h17β-HSD12），即3型17β-羟类固醇脱氢酶的同源物，是一种新的参与雌二醇（E2）生成的雌激素特异性17β-羟类固醇脱氢酶。为了进一步表征这种产生雌二醇的酶，我们在食蟹猴（猕猴）中分离出了相应的cDNA，表征了其酶活性，并使用原位杂交进行了细胞定位。
使用稳定表达食蟹猴12型17β-羟类固醇脱氢酶（mf17β-HSD12）的HEK-293细胞，我们发现mf17β-HSD12与h17β-HSD12类似，能高效且选择性地催化E1转化为E2。我们还使用定量实时PCR定量了一系列食蟹猴组织中mf17β-HSD12 mRNA的表达水平。食蟹猴17β-HSD12 mRNA广泛表达，在小脑中表达水平最高，其次是脾脏和肾上腺，在所有其他检测组织（即睾丸、卵巢、大脑皮层、肝脏、心脏、前列腺、乳腺、子宫肌层、子宫内膜、皮肤、肌肉和胰腺）中表达水平中等。为了了解mf17β-HSD12 mRNA表达的细胞定位，我们使用35S标记的cRNA探针进行了原位杂交。在乳腺的上皮细胞和基质细胞中观察到强标记。在子宫中，在内膜的上皮细胞和基质细胞中检测到标记。
这些结果强烈表明，食蟹猴17β-HSD12是雌二醇（E2）生物合成中芳香化酶的重要伙伴。这强烈表明，在雌二醇生物合成途径中，17-酮还原步骤在芳香化步骤之后（4-雄烯二酮芳香化为雌酮，然后通过雌激素特异性17β-羟类固醇脱氢酶将雌酮转化为雌二醇），这与4-雄烯二酮先转化为睾酮然后睾酮芳香化的假设相反。
