The cytoplasmic, transmembrane, and stem regions of glycosyltransferases specify their in vivo functional sublocalization and stability in the Golgi
The cytoplasmic, transmembrane, and stem regions of glycosyltransferases specify their in vivo functional sublocalization and stability in the Golgi
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DOI：
10.1074/jbc.274.51.36107
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发表时间：
1999-12-17
影响因子：
4.8
通讯作者：
Conradt, HS
中科院分区：
文献类型：
--
作者：
Grabenhorst, E;Conradt, HS
我们提供了在高尔基体糖基转移酶的细胞质、跨膜和茎（CTS）区域中存在靶向信号的证据，所述区域介导将它们的细胞内催化活性分选到高尔基体的不同功能亚区室区域中。3-岩藻糖基转移酶VI（FT 6）的CTS区域，并在BHK-1中稳定共表达这些构建体。81细胞与分泌型报告糖蛋白人β-痕量蛋白。在β-痕量蛋白中检测到的唾液酸刘易斯X：刘易斯X比率表明，早期作用的GlcNAc-转移酶I（GnT-I）和III（GnT-III）的CTS区域指定FT 6催化结构域的后向靶向，而晚期作用的人α 1，3-岩藻糖基转移酶VII（FT 7）的CTS区域引起生物合成糖基化途径中FT 6体内活性的前向靶向。对9种不同CTS嵌合体对β-痕量蛋白的体内功能活性的分析允许对高尔基体/反式高尔基体网络内的CTS供体糖基转移酶进行作图：GnT-I <（ST6Gal I，ST3Gal III）< GnT-III < ST8Sia IV < GalT-I <（FT3，FT6）< ST3Gal TV < FT7，供体糖基转移酶对细胞内蛋白水解的敏感性或抗性与它们的CTS一起转移到嵌合酶地区显然，在糖基转移酶的CTS区域中含有至少三种不同的信号：第一，它们的高尔基体保留;第二，它们靶向特定的体内功能区域;第三，它们对细胞内蛋白水解的敏感性，作为调节细胞内周转的工具。
We provide evidence for the presence of targeting signals in the cytoplasmic, transmembrane, and stem (CTS) regions of Golgi glycosyltransferases that mediate sorting of their intracellular catalytic activity into different functional subcompartmental areas of the Golgi, We have constructed chimeras of human alpha 1,3-fucosyltransferase VI (FT6) by replacement of its CTS region with those of late and early acting Golgi glycosyltransferases and have stably coexpressed these constructs in BHK-81 cells together with the secretory reporter glycoprotein human beta-trace protein. The sialyl Lewis X:Lewis X ratios detected in beta-trace protein indicate that the CTS regions of the early acting GlcNAc-transferases I (GnT-I) and III (GnT-III) specify backward targeting of the FT6 catalytic domain, whereas the CTS region of the late acting human alpha 1,3-fucosyltransferase VII (FT7) causes forward targeting of the FT6 in vivo activity in the biosynthetic glycosylation pathway. The analysis of the in vivo functional activity of nine different CTS chimeras toward beta-trace protein allowed for a mapping of the CTS donor glycosyltransferases within the Golgi/trans-Golgi network: GnT-I < (ST6Gal I, ST3Gal III) < GnT-III < ST8Sia IV < GalT-I < (FT3, FT6) < ST3Gal TV < FT7, The sensitivity or resistance of the donor glycosyl transferases toward intracellular proteolysis is transferred to the chimeric enzymes together with their CTS regions. Apparently, there are at least three different signals contained in the CTS regions of glycosyltransferases mediating: first, their Golgi retention; second, their targeting to specific in vivo functional areas; and third, their susceptibility toward intracellular proteolysis as a tool for the regulation of the intracellular turnover.