Carter R E, Feldman A R, Coyle J T
Department of Psychiatry, Massachusetts General Hospital-East, Charlestown 02129, USA.
Proc Natl Acad Sci U S A. 1996 Jan 23;93(2):749-53. doi: 10.1073/pnas.93.2.749.
This report demonstrates that the investigational prostatic carcinoma marker known as the prostate-specific membrane antigen (PSM) possesses hydrolytic activity with the substrate and pharmacologic properties of the N-acetylated alpha-linked acidic dipeptidase (NAALADase). NAALADase is a membrane hydrolase that has been characterized in the mammalian nervous system on the basis of its catabolism of the neuropeptide N-acetylaspartylglutamate (NAAG) to yield glutamate and N-acetylaspartate and that has been hypothesized to influence glutamatergic signaling processes. The immunoscreening of a rat brain cDNA expression library with anti-NAALADase antisera identified a 1428-base partial cDNA that shares 86% sequence identity with 1428 bases of the human PSM cDNA [Israeli, R. S., Powell, C. T., Fair, W. R. & Heston, W.D.W. (1993) Cancer Res. 53, 227-230]. A cDNA containing the entire PSM open reading frame was subsequently isolated by reverse transcription-PCR from the PSM-positive prostate carcinoma cell line LNCaP. Transient transfection of this cDNA into two NAALADase-negative cell lines conferred NAAG-hydrolyzing activity that was inhibited by the NAALADase inhibitors quisqualic acid and beta-NAAG. Thus we demonstrate a PSM-encoded function and identify a NAALADase-encoding cDNA. Northern analyses identify at least six transcripts that are variably expressed in NAALADase-positive but not in NAALADase-negative rat tissues and human cell lines; therefore, PSM and/or related molecular species appear to account for NAAG hydrolysis in the nervous system. These results also raise questions about the role of PSM in both normal and pathologic prostate epithelial-cell function.
本报告表明，一种名为前列腺特异性膜抗原（PSM）的实验性前列腺癌标志物具有与N-乙酰化α-连接酸性二肽酶（NAALADase）的底物及药理特性相关的水解活性。NAALADase是一种膜水解酶，基于其将神经肽N-乙酰天冬氨酰谷氨酸（NAAG）分解为谷氨酸和N-乙酰天冬氨酸的过程，已在哺乳动物神经系统中得到表征，并且据推测其会影响谷氨酸能信号传导过程。用抗NAALADase抗血清对大鼠脑cDNA表达文库进行免疫筛选，鉴定出一个1428个碱基的部分cDNA，其与人类PSM cDNA的1428个碱基具有86%的序列同一性[以色列，R.S.，鲍威尔，C.T.，费尔，W.R.和赫斯顿，W.D.W.（1993年）《癌症研究》53，227 - 230]。随后通过逆转录PCR从PSM阳性的前列腺癌细胞系LNCaP中分离出一个包含完整PSM开放阅读框的cDNA。将该cDNA瞬时转染到两个NAALADase阴性细胞系中，赋予了它们NAAG水解活性，该活性受到NAALADase抑制剂喹啉酸和β-NAAG的抑制。因此，我们证明了PSM编码的功能并鉴定出一个编码NAALADase的cDNA。Northern分析确定了至少六种转录本，它们在NAALADase阳性的大鼠组织和人类细胞系中差异表达，但在NAALADase阴性的组织和细胞系中不表达；因此，PSM和/或相关分子种类似乎是神经系统中NAAG水解的原因。这些结果也引发了关于PSM在正常和病理性前列腺上皮细胞功能中的作用的问题。
