Single-molecule analysis of epidermal growth factor signaling that leads to ultrasensitive calcium response.
Single-molecule analysis of epidermal growth factor signaling that leads to ultrasensitive calcium response.
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DOI：
10.1529/biophysj.104.053330
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发表时间：
2005-05
影响因子：
3.4
通讯作者：
T. Uyemura;H. Takagi;T. Yanagida;Y. Sako
中科院分区：
文献类型：
--
作者：
T. Uyemura;H. Takagi;T. Yanagida;Y. Sako
信号系统输入输出之间的定量关系是理解信号转导机制的基础信息。在这里，我们报告表皮生长因子（EGF）结合的数量和细胞内钙离子升高的反应概率之间的相关性。EGF分子的结合和细胞内钙离子浓度的变化进行了测定相同的HeLa人上皮细胞。研究发现，300个EGF分子就足以诱导一半细胞的钙反应。与细胞表面表达的EGF受体（EGFR）的数量（50，000）相比，这个数字非常小。有一个S形的相关性之间的响应概率和EGF结合的数量，这意味着一个超灵敏的反应。EGF的簇大小分布的分析表明，EGFR的二聚化有助于这种开关样的超灵敏反应。单分子分析表明，EGF绑定更快的集群的EGFR比单体。这种性质对于在非常少量的EGF结合下有效形成EGFR的信号传导二聚体应该是重要的，并且表明需要在细胞表面上表达过量的EGFR以制备具有与EGF的大的缔合速率常数的EGFR的前二聚体。
Quantitative relationships between inputs and outputs of signaling systems are fundamental information for the understanding of the mechanism of signal transduction. Here we report the correlation between the number of epidermal growth factor (EGF) bindings and the response probability of intracellular calcium elevation. Binding of EGF molecules and changes of intracellular calcium concentration were measured for identical HeLa human epithelial cells. It was found that 300 molecules of EGF were enough to induce calcium response in half of the cells. This number is quite small compared to the number of EGF receptors (EGFR) expressed on the cell surface (50,000). There was a sigmoidal correlation between the response probability and the number of EGF bindings, meaning an ultrasensitive reaction. Analysis of the cluster size distribution of EGF demonstrated that dimerization of EGFR contributes to this switch-like ultrasensitive response. Single-molecule analysis revealed that EGF bound faster to clusters of EGFR than to monomers. This property should be important for effective formation of signaling dimers of EGFR under very small numbers of EGF bindings and suggests that the expression of excess amounts of EGFR on the cell surface is required to prepare predimers of EGFR with a large association rate constant to EGF.