Inorganic polyphosphate in eukaryotes - synthesis, detection, metabolism and physiology

无机聚磷酸盐（polyP）是由数十至数百个磷酸残基通过高能磷酸酐键连接而成的生物聚合物。这种益生元普遍存在的聚合物的代谢和功能在原核生物和酵母中得到了很好的了解。尽管息肉蛋白在多细胞真核生物中的含量要低得多，但它与哺乳动物的凝血和骨钙化等重要生理现象有关。虽然一些研究表明息肉蛋白参与不同的细胞功能，包括线粒体稳态、TOR信号传导、伴侣蛋白功能和神经元信号传导，但对高真核生物中息肉蛋白生物学的整体理解仍然很差。其主要原因是缺乏特异性和敏感性的方法来检测和定量polyP，以及在后生动物中负责polyP合成的酶仍然未知。此外，利用化学方法合成息肉p及其类似物来鉴定参与息肉p转换的酶以及探究息肉p的其他细胞功能的研究也不发达。在向DBT和DFG提出的资助印德生命科学基础研究项目的联合项目提案中，我们汇集了我们在生物化学（Rashna Bhandari），化学合成（Henning Jessen）和果蝇遗传学（Manish Jaiswal）方面的互补专业知识，以解决我们对多细胞真核生物中息肉生物学的理解不足。我们将共同努力实现以下目标：a)开发敏感和特异性的检测方法来检测生物样品中的息肉p； b)化学合成息肉p和类似物并实现这些化合物的细胞递送；c)研究肌醇焦磷酸和息肉p在线粒体能量代谢中的相互作用；d)确定高等真核生物中息肉p合成的途径)研究息肉p消耗的生物水平表型效应。这一建议将有助于我们解开polyP在高等真核生物中的合成和功能之谜，并将通过提供新的分析、生化和生物学方法，显著推动该领域的发展。

Inorganic polyphosphate (polyP) is biopolymer of tens to hundreds of phosphate residues linked by a high-energy phosphoanhydride bonds. The metabolism and functions of this prebiotic ubiquitous polymer are quite well understood in prokaryotes and yeast. Although present in multicellular eukaryotes at much lower levels, polyP has been linked to important physiological phenomena such as blood clotting and bone calcification in mammals. While some studies have implicated polyP in different cellular functions including mitochondrial homeostasis, TOR signaling, chaperone function, and neuronal signaling, the overall understanding of polyP biology in high eukaryotes remains poor. The main reasons for this are the lack of specific and sensitive methods for the detection and quantification of polyP, and that the enzyme(s) responsible for polyP synthesis in metazoans is still unknown. Also, the chemical synthesis of polyP and analogues, which can help identify the enzymes involved in polyP turnover, and probe other cellular functions of polyP, is underdeveloped. In this joint project proposal to DBT and DFG for funding Indo-German Fundamental Research Projects in the Life Sciences, we bring together our complementary expertise in Biochemistry (Rashna Bhandari), Chemical Synthesis (Henning Jessen) and Drosophila genetics (Manish Jaiswal) to address the shortcomings in our understanding of polyP biology in multicellular eukaryotes. We will work together to achieve the following objectives:a) Develop sensitive and specific assays to detect polyP in biological samplesb) Chemically synthesize polyP and analogues and achieve the cellular delivery of such compoundsc) Investigate cross-talk between inositol pyrophosphates and polyP in mitochondrial energy metabolismd) Identify the pathway of polyP synthesis in higher eukaryotese) Study organism-level phenotypic effects of polyP depletionIn its entirety, this proposal will help us to unravel the enigmas of polyP synthesis and function in higher eukaryotes and will significantly drive the field by providing novel analytical, biochemical and biological approaches.