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

本研究计划的目的是研究铁在蛋白酪氨酸磷酸酶（PTP）家族调节中的作用。PTPs通过影响和控制巨噬细胞（MO）与激酶的精细平衡，在调节MO功能中发挥关键作用。通过使激酶底物去磷酸化，PTP可以影响激酶活性水平，从而影响MO功能和先天免疫应答。尽管氧化在PTP的调节中起着重要作用，并且这通过ROS的作用，但我们最近发现，铁可以在PTP的调节中起关键作用，其形式为单核二柠檬酸铁络合物，其精确地将自身装配在PTP的催化口袋中，抑制其活性。我们相信，这种能力在MO功能调节的背景下，特别是参与先天免疫应答的MO功能调节，可以在控制稳态和异常细胞状况中发挥关键作用。 实际的拨款提案旨在研究这种铁物质对MO PTP的特异性（目的1），并分析这种铁介导的PTP调节是否在体内发生（目的2）。在目的1中，我们建议确定是否所有MO PTP（经典，DUS PTP和RPTP）同样受到单核离子柠檬酸盐的调节，以及遵循其亚细胞动员到各个隔室，以便与参与信号传导事件的特定底物相互作用，同时调节先天免疫应答炎症激动剂。 在目标2中，将使用PTP的特异性抑制剂、铁-葡聚糖接种以及使用生理铁缺陷小鼠模型在体内进一步测试上述体外评价的结果。将在细胞、分子和先天免疫水平监测体内铁利用率增加或减少的影响。

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 macrophage (MO) functions by influencing and controlling their fine balance with kinases. By dephosphorylating kinase substrates, PTPs can influence the level of kinase activities and consequently the MO functions and innate immune response. Whereas oxidation plays an important role in the regulation of PTPs and this via the action of ROS, we have recently discovered that iron could play a critical in the regulation of PTPs, under the form of a mononuclear dicitrate iron complex precisely fitting itself within PTP's catalytic pocket inhibiting their activity. We believe that such capacity in the context MO function regulations and particuolarly the ones involved in innate immune response could plays a critical role to control homeostatic and abnormal cellular conditions. The actual grant proposal is designed to study the specificity of this iron species toward MO PTPs (Aim 1) and to analyze whether this iron-mediated modulation of PTPs happens in vivo (Aim 2). In Aim 1, we propose to determine whether all MO PTPs (classic, DUS PTPs and RPTPs) are similarly regulated by mononuclear ion-citrate, as well as to follow their sub-cellular mobilization to various compartments in order to interact with specific substrates involved in the signaling events concurring to regulate innate immunity in response to inflammatory agonists. In Aim 2, the findings stemming from 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 with physiologically iron defective mice. Impact of those augmented or reduced availability or iron in vivo will be monitored at cellular, molecular and innate immunity levels.