Fonrose Xavier, Ausseil Frédéric, Soleilhac Emmanuelle, Masson Véronique, David Bruno, Pouny Isabelle, Cintrat Jean-Christophe, Rousseau Bernard, Barette Caroline, Massiot Georges, Lafanechère Laurence
Centre de Criblage pour Molécules Bio-Actives, institut de Recherches en Technologies et Sciences pour le Vivant, Commissariat à l'Energie Atomique-Grenoble, Grenoble, France.
Cancer Res. 2007 Apr 1;67(7):3371-8. doi: 10.1158/0008-5472.CAN-06-3732.
Microtubules are centrally involved in cell division, being the principal components of mitotic spindle. Tubulin, the constituent of microtubules, can be cyclically modified on its alpha-subunit by enzymatic removal of the COOH-terminal tyrosine residue by an ill-defined tubulin carboxypeptidase (TCP) and its readdition by tubulin tyrosine ligase (TTL). We and others have previously shown that suppression of TTL and resulting accumulation of detyrosinated tubulin are frequent in human cancers of poor prognosis. Explanations for the involvement of TTL and detyrosinated tubulin in tumor progression arise from the recent discovery that tubulin detyrosination leads to CAP-Gly protein mislocalization, which correlates with defects in spindle positioning during mitosis. Impaired control of spindle positioning is one factor favoring tumor invasiveness. Thus, TCP could be a target for developing novel therapeutic strategies against advanced stages of cancers. Inhibitors of TCP, by reversing abnormal detyrosinated tubulin accumulation in tumor cells, could impair tumor progression. TCP has never been isolated and this has hampered search of specific inhibitors. In this article, we describe a cell-based assay of TCP activity and its use to screen a library of natural extracts for their inhibitory potency. This led to the isolation of two sesquiterpene lactones. We subsequently found that parthenolide, a structurally related compound, can efficiently inhibit TCP. This inhibitory activity is a new specific property of parthenolide independent of its action on the nuclear factor-kappaB pathway. Parthenolide is also known for its anticancer properties. Thus, TCP inhibition could be one of the underlying mechanisms of these anticancer properties.
微管在细胞分裂中起着核心作用，是有丝分裂纺锤体的主要成分。微管蛋白是微管的组成成分，其α亚基可通过一种不明的微管蛋白羧肽酶（TCP）酶促去除COOH末端酪氨酸残基，并通过微管蛋白酪氨酸连接酶（TTL）重新添加，从而发生周期性修饰。我们和其他人之前已经表明，在预后不良的人类癌症中，TTL的抑制以及由此导致的去酪氨酸化微管蛋白的积累很常见。关于TTL和去酪氨酸化微管蛋白参与肿瘤进展的解释源于最近的发现，即微管蛋白去酪氨酸化会导致CAP-Gly蛋白定位错误，这与有丝分裂期间纺锤体定位缺陷相关。纺锤体定位控制受损是有利于肿瘤侵袭的一个因素。因此，TCP可能是开发针对癌症晚期的新型治疗策略的靶点。TCP抑制剂通过逆转肿瘤细胞中异常的去酪氨酸化微管蛋白积累，可能会损害肿瘤进展。TCP从未被分离出来，这阻碍了对特异性抑制剂的寻找。在本文中，我们描述了一种基于细胞的TCP活性测定方法及其用于筛选天然提取物文库以检测其抑制效力的用途。这导致分离出两种倍半萜内酯。我们随后发现，一种结构相关的化合物小白菊内酯可以有效抑制TCP。这种抑制活性是小白菊内酯的一种新的特异性特性，与其对核因子-κB途径的作用无关。小白菊内酯也因其抗癌特性而闻名。因此，TCP抑制可能是这些抗癌特性的潜在机制之一。
