Vtc5 Is Localized to the Vacuole Membrane by the Conserved AP-3 Complex to Regulate Polyphosphate Synthesis in Budding Yeast.
Vtc5 Is Localized to the Vacuole Membrane by the Conserved AP-3 Complex to Regulate Polyphosphate Synthesis in Budding Yeast.
复制标题
DOI：
10.1128/mbio.00994-21
复制
发表时间：
2021-10-26
期刊：
影响因子：
6.4
通讯作者：
Downey M
中科院分区：
文献类型：
--
作者：
Bentley-DeSousa A;Downey M
多聚磷酸盐（polyP）是无机磷酸盐的富含能量的聚合物，组装成长度从3个残基到数千个残基的链。它们被认为存在于地球上的所有细胞中，并在从磷酸盐稳态到细胞信号传导、感染控制和血液凝固的各种功能中发挥作用。在芽殖酵母酿酒酵母中，聚P链由液泡结合的液泡转运蛋白伴侣（VTC）复合物合成，该复合物合成聚P，同时将其转运到液泡腔中，在那里它以高浓度储存。VTC的活性是由一个辅助亚基Vtc 5促进的。在这项工作中，我们发现，保守的AP-3复合物是必要的适当的Vtc 5定位到液泡膜。在人类细胞中，先前的工作已经证明AP-3亚基的突变引起Hermansky-Pudlak综合征，这是一种罕见的疾病，其分子表型包括血小板致密颗粒中聚P积累减少。在酵母AP-3突变体中，我们发现Vtc 5被转运所需的内体分选复合物（ESCRT）重新路由到液泡腔，在那里它被液泡蛋白酶Pep 4降解。缺乏功能性AP-3的细胞具有降低的聚P水平，表明Vtc 5的膜定位是其体内VTC刺激活性所必需的。我们的工作提供了深入了解的分子贩运的关键调节聚磷代谢酵母。我们推测，AP-3也可能是负责提供聚P调节蛋白的血小板致密颗粒在高等真核生物。
Polyphosphates (polyP) are energy-rich polymers of inorganic phosphates assembled into chains ranging from 3 residues to thousands of residues in length. They are thought to exist in all cells on earth and play roles in an eclectic mix of functions ranging from phosphate homeostasis to cell signaling, infection control, and blood clotting. In the budding yeast Saccharomyces cerevisiae, polyP chains are synthesized by the vacuole-bound vacuolar transporter chaperone (VTC) complex, which synthesizes polyP while simultaneously translocating it into the vacuole lumen, where it is stored at high concentrations. VTC’s activity is promoted by an accessory subunit called Vtc5. In this work, we found that the conserved AP-3 complex is required for proper Vtc5 localization to the vacuole membrane. In human cells, previous work has demonstrated that mutation of AP-3 subunits gives rise to Hermansky-Pudlak syndrome, a rare disease with molecular phenotypes that include decreased polyP accumulation in platelet dense granules. In yeast AP-3 mutants, we found that Vtc5 is rerouted to the vacuole lumen by the endosomal sorting complex required for transport (ESCRT), where it is degraded by the vacuolar protease Pep4. Cells lacking functional AP-3 have decreased levels of polyP, demonstrating that membrane localization of Vtc5 is required for its VTC stimulatory activity in vivo. Our work provides insight into the molecular trafficking of a critical regulator of polyP metabolism in yeast. We speculate that AP-3 may also be responsible for the delivery of polyP regulatory proteins to platelet dense granules in higher eukaryotes.