艾滋病病毒(HIV)存在潛藏機制可以長期潛伏在細胞中而逃逸宿主免疫系統(tǒng)的攻擊,，目前已上市的抗HIV藥物均不能選擇性地殺傷感染細胞而根除病毒,。新的研究思路對開發(fā)新型抗HIV藥物顯得非常重要,，研究具有選擇性地殺傷HIV感染細胞而保護正常細胞不受傷害的抗艾滋病藥物是極有前景的方向,。
核糖體失活蛋白(RIPs)具有RNA N-糖苷酶活性,，可以阻遏了延長因子EF-1或EF-2與核糖體的結(jié)合,，抑制蛋白質(zhì)的生物合成,。因此RIPs具有很高的細胞毒性,，常常被開發(fā)成為免疫毒素,、抗病毒和或抗腫瘤藥物。RIP分為3類,，I型,、II型和III型。III型RIP以玉米RIP為代表,，先合成無活性的含有一段25氨基酸的內(nèi)部失活結(jié)構(gòu)域的前體蛋白(PRO-RIP),，PRO-RIP被切除該結(jié)構(gòu)域后才成為有活性的RIP (MOD)。香港中文大學邵鵬柱教授學科組與中國科學院昆明動物研究所動物模型與人類疾病機理重點實驗室鄭永唐研究員學科組合作對玉米RIP的內(nèi)部失活結(jié)構(gòu)域進行一系列的結(jié)構(gòu)修飾和改造,，獲得了對HIV-1蛋白酶特異識別并激活的玉米RIP突變體,。細胞水平實驗的研究表明，突變體對未感染細胞毒性低,，但突變體進入HIV-1感染細胞后則可被細胞內(nèi)的HIV-1蛋白酶識別并切割去除失活結(jié)構(gòu)域轉(zhuǎn)變成為活性蛋白,，從而選擇性地殺傷HIV-1感染細胞,。研究結(jié)果還表明，通過在玉米RIP突變體N端融合表達HIV-1 TAT蛋白的轉(zhuǎn)導肽增加了突變體進入細胞的效率,，對HIV-1感染細胞的殺傷力更強,。玉米RIP突變體也可以被HIV-1蛋白酶耐藥株的蛋白酶識別并激活，因此突變體對HIV-1蛋白酶耐藥株感染細胞也有很好的選擇殺傷性,。該研究成果為研發(fā)特異性靶向HIV感染細胞的新型抗HIV藥物提供了新思路和新策略,。
研究成果在國際著名學術(shù)期刊Nucleic Acids Research 發(fā)表并申請了國家專利。相關(guān)研究獲香港研究資助局,、國家科技部973項目,、國家重大科技專項、中國科學院等項目資助,。（生物谷Bioon.com）
生物谷推薦英文摘要：
Nucleic Acids Res. 2010 October; 38(19): 6803–6812.
doi: 10.1093/nar/gkq551.
A switch-on mechanism to activate maize ribosome-inactivating protein for targeting HIV-infected cells
Sue Ka-Yee Law,1 Rui-Rui Wang,2 Amanda Nga-Sze Mak,1 Kam-Bo Wong,1 Yong-Tang Zheng,2* and Pang-Chui Shaw1*
1Department of Biochemistry and Centre for Protein Science and Crystallography, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong and 2Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
Maize ribosome-inactivating protein (RIP) is a plant toxin that inactivates eukaryotic ribosomes by depurinating a specific adenine residue at the α-sarcin/ricin loop of 28S rRNA. Maize RIP is first produced as a proenzyme with a 25-amino acid internal inactivation region on the protein surface. During germination, proteolytic removal of this internal inactivation region generates the active heterodimeric maize RIP with full N-glycosidase activity. This naturally occurring switch-on mechanism provides an opportunity for targeting the cytotoxin to pathogen-infected cells. Here, we report the addition of HIV-1 protease recognition sequences to the internal inactivation region and the activation of the maize RIP variants by HIV-1 protease in vitro and in HIV-infected cells. Among the variants generated, two were cleaved efficiently by HIV-1 protease. The HIV-1 protease-activated variants showed enhanced N-glycosidase activity in vivo as compared to their un-activated counterparts. They also possessed potent inhibitory effect on p24 antigen production in human T cells infected by two HIV-1 strains. This switch-on strategy for activating the enzymatic activity of maize RIP in target cells provides a platform for combating pathogens with a specific protease.
