Lehmann M, Rigot V, Seidah N G, Marvaldi J, Lissitzky J C
URA CNRS 1924, Laboratoire de Biologie Cellulaire, Université Aix-Marseille II, Faculté de Pharmacie, France.
Biochem J. 1996 Aug 1;317 ( Pt 3)(Pt 3):803-9. doi: 10.1042/bj3170803.
In the present report the biosynthesis of the integrin alpha-chains endowed with constitutive endoproteolytic cleavage was evaluated in LoVo cells where furin, a subtilisin-like convertase involved in post-translational endoproteolytic processing, is not functional. It was found that cell-surface alpha 3, alpha 6 and alpha v subunits were not processed endoproteolytically into heavy and light chains as they were in HT29-D4 cells, a furin-competent cell line. Complete removal of N-linked oligosaccharides and pulse-chase experiments confirmed that the cleavage of the alpha 6 integrin subunit occurring 45 min after translation in HT29 cells did not take place in LoVo cells. Apart from cleavage deficiency, alpha 6 subunit glycosylation, association with beta 4 subunits and targeting to the plasma membrane seemed comparable in LoVo and HT29 cells. The pro-alpha 6 and the pro-alpha 3 subunits immunopurified from LoVo cells were highly sensitive to endoproteolysis by recombinant furin. Furin cleavage was calcium dependent and resulted in the conversion of the 140 kDa pro-alpha 6 into a 120 kDa heavy chain. These results suggest strongly that furin is involved in the endoproteolytic processing of cleavable integrin alpha subunits.
在本报告中，我们在洛沃（LoVo）细胞中评估了具有组成型内切蛋白水解切割作用的整合素α链的生物合成。在洛沃细胞中，弗林蛋白酶（一种参与翻译后内切蛋白水解加工的枯草杆菌蛋白酶样转化酶）没有功能。研究发现，细胞表面的α3、α6和αv亚基不像在弗林蛋白酶功能正常的HT29-D4细胞系中那样被内切蛋白水解加工成重链和轻链。完全去除N-连接寡糖以及脉冲追踪实验证实，HT29细胞中翻译后45分钟发生的α6整合素亚基的切割在洛沃细胞中并未发生。除了切割缺陷外，α6亚基的糖基化、与β4亚基的结合以及靶向质膜在洛沃细胞和HT29细胞中似乎相当。从洛沃细胞中免疫纯化的前α6和前α3亚基对重组弗林蛋白酶的内切蛋白水解高度敏感。弗林蛋白酶切割依赖于钙，并导致140 kDa的前α6转化为120 kDa的重链。这些结果有力地表明，弗林蛋白酶参与了可切割整合素α亚基的内切蛋白水解加工。
