Antiapoptotic protein partners fortilin and MCL1 independently protect cells from 5-fluorouracil-induced cytotoxicity
Antiapoptotic protein partners fortilin and MCL1 independently protect cells from 5-fluorouracil-induced cytotoxicity
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DOI：
10.1074/jbc.m401454200
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发表时间：
2004-09-24
影响因子：
4.8
通讯作者：
Fujise, K
中科院分区：
文献类型：
--
作者：
Graidist, P;Phongdara, A;Fujise, K
Fortilin，一种由172个氨基酸组成的抗细胞凋亡多肽(Li，F.，Zhang，D.，and Fujise，K.(2001)J.Biol.化学。47542-47549)，结合抗细胞凋亡蛋白Bcl2家族的一种蛋白mcl1。Fortilin-MCL1相互作用稳定并增加了Fortilin的半衰期，但不一定是MCL1的半衰期(Zhang，D.，Li，F.，Weidner，D.，Mnjoyan，Z.H.，和Fujise，K.(2002)J.Biol)。化学。277、37430-37438)。目前尚不清楚每种蛋白质在多大程度上依赖于另一种蛋白质的凋亡活性。在这里，我们提出的证据表明，Fortilin和MCL1能够作为独立于彼此的抗凋亡蛋白发挥作用。利用本实验室建立的小干扰RNA(SiRNA)介导的基因沉默系统，我们分析了5-氟尿嘧啶(5-FU)对U2OS细胞株在单克隆和多克隆细胞群中联合和单独使用Fortilin和MCL1的保护作用。当MCL1被靶向MCL1的siRNA沉默时，Fortilin仍能以剂量依赖的方式保护细胞免受5-FU的细胞毒性。相反，当Fortilin被Fortilin靶向siRNA沉默时，MCL1也能够以剂量依赖的方式保护细胞免受5-FU诱导的细胞毒性。综上所述，这些数据清楚地表明，Fortilin和MCL1可以相互独立地发挥细胞保护作用。沉默Fortilin和MCL1并不分别改变MCL1和Fortilin的亚细胞定位。Fortilin-MCL1相互作用的生物学意义可能在于，它通过允许MCL1(一种独立的抗凋亡蛋白)稳定另一种独立的抗凋亡蛋白Fortilin来增加细胞对凋亡的抵抗力。
Fortilin, a potent 172-amino acid antiapoptotic polypeptide (Li, F., Zhang, D., and Fujise, K. ( 2001) J. Biol. Chem. 276, 47542-47549), binds MCL1, a protein of the antiapoptotic Bcl-2 family. The fortilin-MCL1 interaction stabilizes and increases the half-life of fortilin but not necessarily of MCL1 (Zhang, D., Li, F., Weidner, D., Mnjoyan, Z. H., and Fujise, K. ( 2002) J. Biol. Chem. 277, 37430-37438). It is not known to what extent each protein depends on the other for its apoptotic activity. Here, we present evidence that fortilin and MCL1 are capable of functioning as antiapoptotic proteins independently of each other. Using a robust small interfering RNA (siRNA)-mediated gene silencing system developed in our laboratory, we analyzed the cytoprotective effects of fortilin and MCL1 together and apart in U2OS cell lines exposed to 5-fluorouracil (5-FU) in both monoclonal and polyclonal cell populations. When MCL1 was silenced by MCL1-targeted siRNA, fortilin was still able to protect cells from 5-FU-induced cytotoxicity in a dose-dependent manner. Conversely, when fortilin was silenced by fortilin-targeted siRNA, MCL1 was also able to protect cells from 5-FU-induced cytotoxicity in a dose-dependent manner. Together, these data clearly suggest that fortilin and MCL1 can exert their cytoprotective activities independently of each other. The silencing of fortilin and MCL1 did not qualitatively change the subcellular localization of MCL1 and fortilin, respectively. The biological significance of fortilin-MCL1 interaction may be that it increases cellular resistance to apoptosis by allowing MCL1, an independently antiapoptotic protein, to stabilize another independently antiapoptotic protein, fortilin.