Co-expression of glutaminase K and L isoenzymes in human tumour cells
Co-expression of glutaminase K and L isoenzymes in human tumour cells
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DOI：
10.1042/bj20040996
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发表时间：
2005-03-15
影响因子：
4.1
通讯作者：
Matés, JM
中科院分区：
文献类型：
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作者：
Pérez-Gómez, C;Campos-Sandoval, JA;Matés, JM
研究了肿瘤细胞中转氨酶同工酶的表达模式，以阐明其在恶性转化中的作用及其作为临床相关因子的应用的前景。使用白血病细胞从骨髓血的人类患者和几个已建立的人类癌细胞系，我们已经开发了一种竞争性RT（逆转录酶）-PCR检测，同时定量K型（肾型）和L型（肝型）转氨酶mRNA。在所有分析的癌细胞类型中，总是发现两种转录物的共表达和较高量的L型mRNA。然而，成熟淋巴细胞骨髓血的患者患有发育不全不表达K型转录，并显示出15倍的L型转录增加。使用同种型特异性抗体在蛋白质水平也证实了共表达;然而，它与转氨酶转录物的相对丰度无关，并且检测到强的K型蛋白质信号。另一方面，在谷氨酸抑制和磷酸活化肿瘤转氨酶活性方面发现了显著差异。总之，蛋白质数据表明，K亚型将占这些人肿瘤细胞中转氨酶活性的大部分。结果证实，人类癌细胞中两种同工酶的同时表达比以前认为的更频繁。此外，目前的工作和其他以前的数据表明，K亚型是上调的增殖率增加，而流行的L亚型，似乎与休息或静止的细胞状态。
The pattern of expression of glutaminase isoenzymes in tumour cells has been investigated to clarify its role in the malignant transformation and the prospect of its use as a clinically relevant factor. Using leukaemia cells from medullar blood of human patients and several established human cancer cell lines, we have developed a competitive RT (reverse transcriptase)-PCR assay to quantify simultaneously K-type (kidney-type) and L-type (liver-type) glutaminase mRNAs. Co-expression of both transcripts and higher amounts of L-type mRNA were always found in all cancer cell types analysed. However, mature lymphocytes from the medullar blood of a patient suffering aplasia did not express the K-type transcript and showed a 15-fold increase of L-type transcript. Co-expression was also confirmed at the protein level using isoform-specific antibodies; nevertheless, it did not correlate with the relative abundance of glutaminase transcripts and strong K-type protein signals were detected. On the other hand, marked differences were found with regard to glutamate inhibition and phosphate activation of tumour glutaminase activity. Taken together, the protein data suggest that K isoform would account for the majority of glutaminase activity in these human tumour cells. The results confirm that simultaneous expression of both isoenzymes in human cancer cells is a more frequent event than previously thought. Furthermore, the present work and other previous data suggest that K isoform is up-regulated with increased rates of proliferation, whereas prevalence of the L isoform, seems to be related with resting or quiescent cell states.