Sialyl Lewisx epitopes do not occur on acute phase proteins in mice:: relationship to the absence of α3-fucosyltransferase in the liver
Sialyl Lewisx epitopes do not occur on acute phase proteins in mice:: relationship to the absence of α3-fucosyltransferase in the liver
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DOI：
10.1023/a:1006977903048
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发表时间：
1998-04-01
影响因子：
3
通讯作者：
van Dijk, W
中科院分区：
文献类型：
--
作者：
Havenaar, EC;Hoff, RC;van Dijk, W
小鼠经常被用于炎症相关免疫过程研究的模型中。由于已知人类急性期蛋白（APPs）的岩藻糖基化程度会因炎症反应而改变，我们进行了这项研究，以更深入地了解小鼠肝脏中急性期蛋白的岩藻糖基化情况。使用携带编码人类α1 - 酸性糖蛋白（AGP，一种著名的APP）的三个基因簇的小鼠，并对AGP的岩藻糖基化进行了评估。发现转基因人类AGP上完全没有岩藻糖基化，这与人类血清中的AGP形成鲜明对比，人类血清中的AGP大部分通常是α3 - 岩藻糖基化的。值得注意的是，大部分小鼠AGP确实含有岩藻糖残基。在另一种APP，小鼠蛋白酶抑制剂（PI）上也检测到了岩藻糖基化。使用从人乳中分离的α3/4 - 岩藻糖基转移酶（α3/4 - FucT），可以在体外实现转基因人类AGP的α3 - 岩藻糖基化，这表明该糖蛋白本身对岩藻糖基化没有抗性。随后对亲本和转基因小鼠肝细胞膜中可能存在的岩藻糖基转移酶的活性进行测量，仅检测到一种N - 连接核心α6 - FucT，未检测到α2 -、α3 - 或α4 - FucT活性。这表明在肝脏中合成的小鼠血清蛋白AGP和PI上发现的岩藻糖残基很可能是以α6 - 键连接到核心壳二糖基单元上。有趣的是，在人肝细胞膜中可以检测到α6 - 和α3 - FucT活性。上述发现均不受细菌脂多糖诱导急性期反应的影响。这项研究表明：（a）α6 - FucT可能是一种蛋白质特异性糖基转移酶，因为小鼠AGP而非人类AGP可作为受体；（b）与人类肝脏相反，小鼠肝脏不表达任何α3 - FucT活性，从而使小鼠无法在APPs上产生唾液酸化路易斯（x）表位，而该表位是人类炎症反应的重要组成部分。这最后一个发现表明小鼠不适合作为研究人类炎症相关现象的模型，在这些现象中急性期蛋白的糖基化可能起重要作用。
Mice are frequently used in models for the study of immunological processes related to inflammation. Since it is known that the degree of fucosylation of human acute phase proteins (APPs) is altered as a consequence of an inflammatory response, we have undertaken this study to gain more insight into the fucosylation of acute phase proteins as it occurs in mouse liver. Mice carrying the cluster of the three genes encoding human alpha 1-acid glycoprotein (AGP), one of the well known APPs, were used and the fucosylation of AGP was assessed. A complete absence of fucosylation on the transgenic human AGP was found, which is in sharp contrast to AGP in human serum, of which a major proportion is normally alpha 3-fucosylated. Remarkably, a large proportion of mouse AGP did contain fucose residues. Fucosylation was also detected on another APP, mouse protease inhibitor (PI).alpha 3-Fucosylation of the transgenic human AGP can be achieved in vitro, using an alpha 3/4-fucosyltransferase (alpha 3/4-FucT) isolated from human milk, showing that the glycoprotein is not intrinsically resistant to fucosylation. Upon subsequent measurement of the activities of the possible fucosyltransferases present in liver membranes of parent and transgenic mice, only an N-linked-core alpha 6-FucT and no alpha 2-, alpha 3- or alpha 4-FucT activity was detected. This indicates that fucose residues found on the mouse serum proteins AGP and PI, which are synthesized in the liver, are most probably in alpha 6-linkage to the core chitobiosyl unit. Interestingly, both alpha 6- and alpha 3-FucT activity was detectable in human liver membranes. None of the above mentioned findings were influenced by the induction of an acute phase response by administration of bacterial lipopolysaccharide. This study shows that: (a) alpha 6-FucT is probably a protein specific-glycosyltransferase, since mouse AGP, but not human AGP, may be used as an acceptor; (b) in contrast to human liver, mouse liver does not express any alpha 3-FucT-activity, thereby making the mouse incapable of producing the Sialyl Lewis(x) epitope on APPs, which is an important part of the inflammatory reaction in humans. This last finding indicates that the mouse is not suitable as a model for the study of those phenomena related to inflammation in humans, in which glycosylation of acute phase proteins could play a significant role.