Bzdega T, Turi T, Wroblewska B, She D, Chung H S, Kim H, Neale J H
Department of Biology, Georgetown University, Washington, D.C. 20057-1229, U.S.A.
J Neurochem. 1997 Dec;69(6):2270-7. doi: 10.1046/j.1471-4159.1997.69062270.x.
N-Acetylaspartylglutamate (NAAG) is the most prevalent peptide neurotransmitter in the mammalian nervous system. NAAG selectively activates the type 3 metabotropic glutamate receptor. It is inactivated by peptidase activity on the extracellular face of the plasma membrane of neurons and glia. The human gene that codes for prostate-specific membrane antigen (PSM) has been shown to produce peptidase activity against NAAG. We cloned the human PSM cDNA and used it to probe a rat hippocampal cDNA library. We identified a cDNA containing a complete coding region that possesses 83% homology with the PSM gene. The predicted 752-amino acid sequence has 85% identity and 91% similarity to the PSM sequence. CHO cells transfected with this cDNA expressed NAAG peptidase activity at a level similar to that obtained from rat brain membranes. The peptidase activity was inhibited by beta-NAAG, quisqualate, and pteroylglutamate but not aspartylglutamate or pteroic acid. In situ hybridization data demonstrated the widespread distribution of the peptidase mRNA in the brain, consistent with the distribution of peptidase activity. The highest levels of hybridization were detected in the hippocampus, dentate gyrus, piriform cortex, choroid plexus of the ventricles, pineal gland, anterior pituitary, and supraoptic nucleus. Three transcripts (estimated at 5, 3.4, and 2.9 kb) were identified in northern blots of rat brain, while in rat kidney the third transcript appeared slightly smaller than 2.9 kb. With use of reverse transcriptase PCR with primers for the 5' end, the central region, and the 3' end of the hippocampal cDNA, the expected amplification products were obtained from rat brain RNA. Spinal cord yielded an amplification product only with primers for the 5' end of the hippocampal cDNA.
N-乙酰天门冬氨酰谷氨酸（NAAG）是哺乳动物神经系统中最普遍的肽类神经递质。NAAG选择性激活3型代谢型谷氨酸受体。它通过神经元和神经胶质细胞质膜细胞外表面的肽酶活性失活。已证明编码前列腺特异性膜抗原（PSM）的人类基因可产生针对NAAG的肽酶活性。我们克隆了人类PSM cDNA并用它来探测大鼠海马cDNA文库。我们鉴定出一个包含完整编码区的cDNA，它与PSM基因具有83%的同源性。预测的752个氨基酸序列与PSM序列具有85%的一致性和91%的相似性。用该cDNA转染的CHO细胞表达的NAAG肽酶活性水平与从大鼠脑膜获得的水平相似。该肽酶活性受到β-NAAG、喹啉酸和蝶酰谷氨酸的抑制，但不受天门冬氨酰谷氨酸或蝶酸的抑制。原位杂交数据表明该肽酶mRNA在脑中广泛分布，这与肽酶活性的分布一致。在海马、齿状回、梨状皮质、脑室脉络丛、松果体、垂体前叶和视上核中检测到最高水平的杂交信号。在大鼠脑的Northern印迹中鉴定出三种转录本（估计分别为5、3.4和2.9 kb），而在大鼠肾中，第三种转录本略小于2.9 kb。使用针对海马cDNA 5'端、中央区域和3'端的引物进行逆转录PCR，从大鼠脑RNA中获得了预期的扩增产物。脊髓仅用针对海马cDNA 5'端的引物产生了扩增产物。
