INTRACELLULAR TRAFFICKING OF EPIDERMAL GROWTH-FACTOR FAMILY LIGANDS IS DIRECTLY INFLUENCED BY THE PH SENSITIVITY OF THE RECEPTOR-LIGAND INTERACTION
INTRACELLULAR TRAFFICKING OF EPIDERMAL GROWTH-FACTOR FAMILY LIGANDS IS DIRECTLY INFLUENCED BY THE PH SENSITIVITY OF THE RECEPTOR-LIGAND INTERACTION
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DOI：
10.1074/jbc.270.9.4334
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发表时间：
1995-03-03
影响因子：
4.8
通讯作者：
LAUFFENBURGER, DA
中科院分区：
文献类型：
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作者：
FRENCH, AR;TADAKI, DK;LAUFFENBURGER, DA
使用表皮生长因子（EGF）家族成员以及定点重组人EGF突变体，我们研究了配体结合特性如何影响内体分选。小鼠EGF（mEGF）、人EGF（hEGF）和转化生长因子α（TGF α）在pH 7.4下以相似的亲和力结合人EGF受体（EGFR）。然而，这些配体的结合特性具有显著不同的pH敏感性，导致在较低pH水平下与受体的解离程度不同，这是内体的特征。我们采用稳态分选测定法来确定作为小鼠B82成纤维细胞中细胞内配体分子数量的函数的分选到再循环相对于降解的配体分数。mEGF，hEGF，和TGF α显示显着不同的稳态内体分选模式，对应于其在内体pH值的解离程度。此外，几个重组hEGF突变体具有不同的亲和力表现出改变的内体分选相比，hEGF，表现出类似的配体结合特性和内体分选结果之间的直接关系。EGF配体的细胞内运输也通过测量观察到的降解速率常数进行监测。这些同样显示出与配体结合性质的不同pH敏感性相关的显著差异。
Using members of the epidermal growth factor (EGF) family as well as site-directed recombinant human EGF mutants, we investigated how ligand binding properties influence endosomal sorting. Mouse EGF (mEGF), human EGF (hEGF), and transforming growth factor alpha (TGF alpha) bind to the human EGF receptor (EGFR) with similar affinities at pH 7.4. However, the binding properties of these ligands have substantially different pH sensitivities resulting in varying degrees of dissociation from the receptors at lower pH levels characteristic of endosomes. we employed a steady-state sorting assay to determine the fraction of Ligand sorted to recycling versus degradation as a function of the number of intracellular ligand molecules in mouse B82 fibroblasts. mEGF, hEGF, and TGF alpha display significantly different steady-state endosomal sorting patterns which correspond to the extent of their dissociation at endosomal pH. Moreover, several recombinant hEGF mutants with differing affinities exhibit altered endosomal sorting compared to hEGF, demonstrating a similar direct relationship between ligand binding properties and endosomal sorting outcomes. Intracellular trafficking of the EGF ligands was also monitored by measuring the observed degradation rate constants. These likewise show marked differences that correlate with the differing pH sensitivities of the ligands' binding properties.