Decroly E, Benjannet S, Savaria D, Seidah N G
J.A. DeSève Laboratory of Biochemical Neuroendocrinology, University of Montreal, QC, Canada.
FEBS Lett. 1997 Mar 17;405(1):68-72. doi: 10.1016/s0014-5793(97)00156-7.
The intracellular proteolytic processing of HIV envelope glycoprotein gp160 into gp120/gp41 is an essential step for virus infectivity. Several convertases, belonging to the pro-protein convertase family, have been proposed as candidate gp160 processing enzymes. Here we demonstrate using RT-PCR that resting human T4 lymphocytes weakly express PC7, furin, and PC5 mRNA whereas lymphocytes activated under conditions favoring HIV replication express 5-10-fold higher levels of furin and PC7. In this report, we examined the capability of the newly cloned convertase PC7 to cleave gp160 into gp120/gp41 and compared it to furin. This was carried out in a cell-based assay whereby both gp160 and the cognate convertase were co-expressed in the constitutively secreting BSC40 cells and in the regulated AtT20 cells, as well as using two in vitro assays which examined the cleavage of gp160 or of a synthetic peptide spanning the cleavage site. The data demonstrate that PC7 can cleave specifically and in a cell-type specific manner gp160 into gp120gp41, suggesting that both furin and PC7 are so far the major PC-like candidate gp160 convertase in T4 lymphocytes.
HIV包膜糖蛋白gp160在细胞内蛋白水解加工成gp120/gp41是病毒感染性的关键步骤。几种属于前体蛋白转化酶家族的转化酶已被提出作为gp160加工酶的候选者。在此我们利用逆转录聚合酶链反应证明，静息的人T4淋巴细胞微弱表达PC7、弗林蛋白酶和PC5信使核糖核酸，而在有利于HIV复制的条件下激活的淋巴细胞表达的弗林蛋白酶和PC7水平要高出5至10倍。在本报告中，我们检测了新克隆的转化酶PC7将gp160切割成gp120/gp41的能力，并将其与弗林蛋白酶进行比较。这是在基于细胞的检测中进行的，其中gp160和同源转化酶在组成型分泌的BSC40细胞和受调控的AtT20细胞中共同表达，同时还使用了两种体外检测方法来检测gp160或跨越切割位点的合成肽的切割情况。数据表明，PC7能够以细胞类型特异性的方式将gp160特异性切割成gp120/gp41，这表明到目前为止，弗林蛋白酶和PC7都是T4淋巴细胞中主要的类PC候选gp160转化酶。
