Role of iron in the regulation of PTPs: impact on cell signaling and functions

本研究的目的是研究铁在蛋白酪氨酸磷酸酶(PTP)家族的调控中的意义。PTPs通过影响和控制另一个重要的酶家族--激酶，在大多数哺乳动物细胞的调节中发挥关键作用。因此，通过去磷酸化激酶的底物，PTPs可以影响这些激酶的活性水平，从而影响本身正在调节的细胞功能。虽然氧化在PTPs的调节中起着重要的作用，这是通过活性氧物种的作用来实现的，但我们最近发现铁在PTPs的调节中发挥了关键作用，我们甚至发现单核铁可以非常精确地将自己装入PTPs的催化口袋中，从而抑制其活性。我们认为，在调节细胞功能的背景下，这种能力，特别是参与先天性免疫反应的能力，除了ROS之外，在控制动态平衡和异常细胞状况方面发挥着关键作用。在我们研究计划的第一部分，我们建议进行实验，以确定铁是否有效地参与了PTPs的激活，以及控制它们的细胞动员到不同的亚细胞室，以便与参与信号事件的特定底物相互作用，从而诱导免疫细胞功能对各种激动剂的反应。在我们计划的第二部分，我们将使用PTPs的特定抑制剂、接种右旋糖苷铁，以及使用生理缺陷小鼠的铁模型，在体内进一步测试来自上述体外评估的结果。将在细胞、分子和功能水平上监测体内铁的有效性增加或减少的影响。这些研究结果将阐明铁在哺乳动物PTPs调控中的重要性及其对全球信号转导和细胞功能稳态的影响，特别是在整个免疫系统的进化过程中，铁在维持真核细胞的激酶和磷酸酶之间的精细平衡方面发挥着关键作用。

The goal of this research program is to study the implication of iron in the regulation of a family of enzyme named protein tyrosine phosphatase (PTP). PTPs play a critical role in the regulation of majority of mammalian cells by influencing and controlling another important family of enzyme named kinases. By dephosphorylating substrates of kinases, the PTPs can therefore influence the level of activity of those kinases and consequently the cellular functions that are themselves regulating. Whereas oxidation plays an important role in the regulation of PTPs and this via the action of reactive oxygen species, we have recently discovered that iron could play a critical in the regulation of PTPs, we even found that a mononuclear iron can very precisely fit itself within the catalytic pocket of PTPs and consequently inhibit their activity. We believe that such capacity in the context of regulation of cell functions and in particular the ones involved in the innate immune response, are in addition to ROS, plays a critical role to control homeostatic and abnormal cellular conditions. In the first portion of our research program, we are proposing experiments that should permit to determine whether iron is effectively strongly implicated in PTPs activtation, as well as to control their cellular mobilization to various sub-cellular compartment in order to interact with specific substrates involved in the signaling events concurring to induce immune cell functions in response to various agonists. In the second portion of our program, the findings stemming from our in vitro evaluation proposed above, will be further tested in vivo using specific inhibitors for PTPs, inoculation of iron-dextran, as well as to use models using physiologically defective mice for iron. Impact of those augmented or reduced availability or iron in vivo will be monitored at cellular, molecular and functional levels. Findings from these studies will shed light on the importance of iron in the regulation of mammalian PTPs and its impact on global signaling and functional cellular homeostasis, in particular as its critical role to keep the fine balance between kinases and phosphatases of eukaryotic cells throughout evolution of the immune system.