Immunohistochemical expression of conjugating UGT1A-derived isoforms in normal and tumoral drug-metabolizing tissues in humans
Immunohistochemical expression of conjugating UGT1A-derived isoforms in normal and tumoral drug-metabolizing tissues in humans
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DOI：
10.1002/path.2805
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发表时间：
2011-02-01
影响因子：
7.3
通讯作者：
Guillemette, Chantal
中科院分区：
文献类型：
--
作者：
Bellemare, Judith;Rouleau, Melanie;Guillemette, Chantal
UDP-葡萄糖醛酸转移酶 (UGT) 进行的葡萄糖醛酸化是外源性化合物和内源性化合物代谢的主要结合途径。该途径的改变，例如由常见遗传多态性产生的改变，已被证明对个体的健康有显着影响，影响癌症易感性、对药物的反应和药物引起的毒性。末端外显子的替代使用导致 UGT1A 衍生的剪接变体，即经典的酶促活性亚型 1 (i1) 和新型酶促非活性亚型 2 (i2)。来自异源表达和 RNA 干扰实验的体外功能数据表明，这些 i2 异构体充当葡萄糖醛酸化的负调节剂，可能是通过与活性异构体 1 形成无活性复合物。我们使用针对活性 i1 或无活性 i2 蛋白的特异性抗体来检查它们在主要药物代谢组织中的分布。数据显示，UGT1A_i1和失活的UGT1A_i2在相同的组织结构中共同产生，包括肝脏、肾脏、胃、肠和结肠。对 UGT1As 表达的细胞分布和半定量水平的检查揭示了 i1 和 i2 蛋白的异质表达，与正常组织相比，肝脏肿瘤中 i2 的表达增加，而结肠癌标本中 i1 和 i2 的水平降低。这些表达差异可能与人类结肠癌和肝癌的肿瘤发生有关。我们的数据清楚地表明，在参与药物代谢的主要组织的大多数表达 UGT1A 的细胞类型中，活性和非活性 UGT1A 亚型具有相似的免疫定位。这些表达模式与 UGT1A 基因编码的 i2 的显性失活功能一致。版权所有 (C) 2010 大不列颠及爱尔兰病理学会。由约翰·威利父子有限公司出版
Glucuronidation by UDP-glucuronyltransferase (UGT) enzymes is the prevailing conjugative pathway for the metabolism of both xenobiotics and endogenous compounds. Alterations in this pathway, such as those generated by common genetic polymorphisms, have been shown to significantly impact on the health of individuals, influencing cancer susceptibility, responsiveness to drugs and drug-induced toxicity. Alternative usage of terminal exons leads to UGT1A-derived splice variants, namely the classical and enzymatically active isoforms 1 (i1) and the novel enzymatically inactive isoforms 2 (i2). In vitro functional data from heterologous expression and RNA interference experiments indicate that these i2 isoforms act as negative modulators of glucuronidation, likely by forming inactive complexes with active isoform 1. We used specific antibodies against either active i1 or inactive i2 proteins to examine their distribution in major drug-metabolizing tissues. Data revealed that UGT1A_i1 and inactive UGT1A_i2 are co-produced in the same tissue structures, including liver, kidney, stomach, intestine and colon. Examination of the cellular distribution and semi-quantitative level of expression of UGT1As revealed heterogeneous expression of i1 and i2 proteins, with increased expression of i2 in liver tumours and decreased levels of i1 and i2 in colon cancer specimens, compared to normal tissues. These differences in expression may be relevant to human colon and liver cancer tumorigenesis. Our data clearly demonstrate the similar immunolocalization of active and inactive UGT1A isoforms in most UGT1A-expressing cell types of major tissues involved in drug metabolism. These expression patterns are consistent with a dominant-negative function for the i2 encoded by the UGT1A gene. Copyright (C) 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.