Gerasimaitė Rūta, Mayer Andreas
Department of Biochemistry, University of Lausanne, Ch. des Boveresses 155, Epalinges 1066, Switzerland.
Department of Biochemistry, University of Lausanne, Ch. des Boveresses 155, Epalinges 1066, Switzerland
J Cell Sci. 2017 May 1;130(9):1625-1636. doi: 10.1242/jcs.201061. Epub 2017 Mar 16.
Acidocalcisome-like organelles are found in all kingdoms of life. Many of their functions, such as the accumulation and storage of metal ions, nitrogen and phosphate, the activation of blood clotting and inflammation, depend on the controlled synthesis and turnover of polyphosphate (polyP), a polymer of inorganic phosphate linked by phosphoric anhydride bonds. The exploration of the role of acidocalcisomes in metabolism and physiology requires the manipulation of polyP turnover, yet the complete set of proteins responsible for this turnover is unknown. Here, we identify a novel type of polyphosphatase operating in the acidocalcisome-like vacuoles of the yeast , which we called Ppn2. Ppn2 belongs to the PPP-superfamily of metallophosphatases, is activated by Zn ions and exclusively shows endopolyphosphatase activity. It is sorted to vacuoles via the multivesicular body pathway. Together with Ppn1, Ppn2 is responsible for a substantial fraction of polyphosphatase activity that is necessary to mobilize polyP stores, for example in response to phosphate scarcity. This finding opens the way to manipulating polyP metabolism more profoundly and deciphering its roles in phosphate and energy homeostasis, as well as in signaling.
类酸性钙小体存在于所有生物界。它们的许多功能，如金属离子、氮和磷酸盐的积累与储存、血液凝固和炎症的激活，都依赖于多聚磷酸盐（polyP）的可控合成与周转，多聚磷酸盐是一种通过磷酸酐键连接的无机磷酸盐聚合物。探索酸性钙小体在代谢和生理过程中的作用需要对多聚磷酸盐周转进行调控，然而负责这种周转的完整蛋白质组尚不清楚。在此，我们鉴定出一种在酵母类酸性钙小体液泡中起作用的新型多聚磷酸酶，我们将其命名为Ppn2。Ppn2属于金属磷酸酶的PPP超家族，被锌离子激活，且仅表现出内多聚磷酸酶活性。它通过多泡体途径被分选到液泡中。与Ppn1一起，Ppn2负责相当一部分多聚磷酸酶活性，这对于动员多聚磷酸盐储备是必要的，例如在应对磷酸盐缺乏时。这一发现为更深入地调控多聚磷酸盐代谢以及解读其在磷酸盐和能量稳态以及信号传导中的作用开辟了道路。
