Kamiya T, Sugio S, Yamanouchi K, Kagitani Y
Central Research Laboratories, Green Cross Corporation, Osaka, Japan.
Tohoku J Exp Med. 1996 Dec;180(4):297-308. doi: 10.1620/tjem.180.297.
The human Fc fragments of immunoglobulin E (IgE-Fc) expressed in the mammalian COS cells, those mainly consisting of C epsilon 3-C epsilon 4 chains with or without Cys-328 known to be responsible for interchain disulfide bonding, were secreted into the culture medium directed by the yeast Saccharomyces cerevisiae invertase (SUC2) signal sequence (SUC2/Ig2 or SUC2/Ig, respectively) as well as by the human interleukin 2 receptor alpha chain signal sequence (IL2R/Ig2 or IL2R/Ig, respectively). For the binding activity to the human soluble alpha chain of high affinity receptor for IgE, IgE-Fc with Cys328, SUC2/Ig2 and IL2R/Ig2, were active but had smaller activity than native IgE. By comparison IgE-Fc without Cys328, SUC2/Ig and IL2R/Ig, showed lower activity than SUC2/Ig2 and IL2R/Ig2. Immunoprecipitation analysis revealed both SUC2/Ig and SUC2/Ig2 had molecular weights (M(r)s) and degrees of glycosylation similar to IL2R/Ig and IL2R/Ig2, respectively. These results suggested that in mammalian cells the SUC2 signal sequence was functional in directing the heterologous multimeric proteins to the endoplasmic reticulum, resulting in secretion of the active proteins. This finding might show merits on heterologous protein secretion systems.
在哺乳动物COS细胞中表达的免疫球蛋白E的人Fc片段（IgE-Fc），主要由Cε3-Cε4链组成，有或没有已知负责链间二硫键结合的Cys-328，由酵母酿酒酵母转化酶（SUC2）信号序列（分别为SUC2/Ig2或SUC2/Ig）以及人白细胞介素2受体α链信号序列（分别为IL2R/Ig2或IL2R/Ig）引导分泌到培养基中。对于与IgE高亲和力受体的人可溶性α链的结合活性，具有Cys328的IgE-Fc、SUC2/Ig2和IL2R/Ig2具有活性，但活性低于天然IgE。相比之下，没有Cys328的IgE-Fc、SUC2/Ig和IL2R/Ig的活性低于SUC2/Ig2和IL2R/Ig2。免疫沉淀分析表明，SUC2/Ig和SUC2/Ig2的分子量（M(r)s）和糖基化程度分别与IL2R/Ig和IL2R/Ig2相似。这些结果表明，在哺乳动物细胞中，SUC2信号序列在将异源多聚体蛋白引导至内质网方面具有功能，从而导致活性蛋白的分泌。这一发现可能显示出在异源蛋白分泌系统方面的优点。
