Intracellular distribution and degradation of immunoglobulin G and immunoglobulin G fragments injected into HeLa cells.
Intracellular distribution and degradation of immunoglobulin G and immunoglobulin G fragments injected into HeLa cells.
复制标题
免疫球蛋白G和免疫球蛋白G片段注入HELA细胞的细胞内分布和降解。
DOI：
10.1083/jcb.96.2.338
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发表时间：
1983-02
影响因子：
7.8
通讯作者：
Rechsteiner, M
中科院分区：
文献类型：
--
作者：
McGarry, T;Hough, R;Rogers, S;Rechsteiner, M
将完整的兔免疫球蛋白G分子（IgG）及其木瓜蛋白酶或胃蛋白酶片段放射性碘标记并注射到HeLa细胞中。完整IgG、Fab 2和Fc片段降解，半衰期为60- 90 h，而Fab片段的半衰期为110 h。这些结果表明，在IgG分子的铰链区的蛋白水解裂解不是其细胞内降解的限速步骤。无铰链人骨髓瘤蛋白Mcg以与散装人IgG相同的速率降解，进一步证明蛋白水解敏感铰链区对IgG分子的细胞内降解并不重要。注射的兔IgG分子的SDS丙烯酰胺凝胶分析显示，重链和轻链以相同的速率降解。还在等电聚焦凝胶上检查了注射的兔IgG和兔IgG片段。Fab、Fab 2和Fc片段降解，与等电点无任何相关性。带正电荷的兔IgG比它们的负对应物消失得更快，与正常细胞内蛋白质报告的趋势相反。两种小鼠单克隆抗体的等电点注射到HeLa细胞后基本上没有变化，这表明观察到的完整兔IgG的改变的等电曲线是由降解而不是蛋白质修饰引起的。IgG片段和完整兔IgG分子的细胞内分布通过注射细胞的薄片的放射自显影来确定。完整的IgG分子被排除在HeLa细胞核之外，而Fab和Fc片段都容易进入细胞核。因此，对于某些蛋白质，进入核区室主要由大小决定。
Intact rabbit immunoglobulin G molecules (IgGs) and their papain or pepsin fragments were radio-iodinated and injected into HeLa cells. Whole IgGs, Fab2, and Fc fragments were degraded with half-lives of 60- 90 h, whereas half-lives of Fab fragments were 110 h. These results indicate that proteolytic cleavage in the hinge region of the IgG molecule is not the rate-limiting step in its intracellular degradation. The hingeless human myeloma protein, Mcg, was degraded at the same rate as bulk human IgG, providing further evidence that the proteolytically susceptible hinge region is not important for intracellular degradation of IgG molecules. SDS acrylamide gel analysis of injected rabbit IgG molecules revealed that heavy and light chains were degraded at the same rate. Injected rabbit IgGs and rabbit IgG fragments were also examined on isoelectric focusing gels. Fab, Fab2, and Fc fragments were degraded without any correlation with respect to isoelectric point. Positively charged rabbit IgGs disappeared more rapidly than their negative counterparts, contrary to the trend reported for normal intracellular proteins. The isoelectric points of two mouse monoclonal antibodies were essentially unchanged after injection into HeLa cells, suggesting that the altered isoelectric profile observed for intact rabbit IgG resulted from degradation and not protein modification. The intracellular distributions of IgG fragments and intact rabbit IgG molecules were determined by autoradiography of thin sections through injected cells. Intact IgG molecules were excluded from HeLa nuclei whereas both Fab and Fc fragments readily entered them. Thus, for some proteins, entry into the nuclear compartment is determined primarily by size.