The position of lysosomes within the cell determines their luminal pH.
The position of lysosomes within the cell determines their luminal pH.
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DOI：
10.1083/jcb.201507112
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发表时间：
2016-03-14
期刊：
影响因子：
--
通讯作者：
Grinstein S
中科院分区：
文献类型：
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作者：
Johnson DE;Ostrowski P;Jaumouillé V;Grinstein S
与溶酶体相关蛋白的异源表达相结合的腔溶酶体pH的分析表明，外周溶酶体比非核溶酶体碱性更强，Rab 7及其效应物RILP的耗竭与酸化减少相关并可解释酸化减少。我们使用定量比率荧光显微镜检查单个溶酶体的管腔pH值，并报告了一个未被重视的异质性：外周溶酶体的酸性低于非核溶酶体，尽管它们的缓冲能力相当。质子被动（泄漏）渗透性增加，以及液泡H+-腺苷三磷酸酶（V-ATP酶）活性降低，是外周溶酶体酸化能力降低的原因。外周溶酶体组成的改变至少部分是由于对生物合成途径输出物质的更有限的获取。Rab 7和Arl 8b之间的平衡决定了溶酶体的亚细胞定位;更多的外周溶酶体具有降低的Rab 7密度。这反过来又导致Rab-interacting lysosomal protein（RILP）募集减少，RILP是一种调节溶酶体V-ATP酶V1 G1组分募集和稳定性的效应物。溶酶体的故意边缘化与酸化减少和蛋白水解活性受损有关。溶酶体pH的异质性可能是更广泛的功能多样性的指示。
Analysis of luminal lysosomal pH in combination with heterologous expression of lysosomal-associated proteins indicates that peripheral lysosomes are more alkaline than juxtanuclear ones and that depletion of Rab7 and its effector, RILP, are associated with and can account for the reduced acidification. We examined the luminal pH of individual lysosomes using quantitative ratiometric fluorescence microscopy and report an unappreciated heterogeneity: peripheral lysosomes are less acidic than juxtanuclear ones despite their comparable buffering capacity. An increased passive (leak) permeability to protons, together with reduced vacuolar H+–adenosine triphosphatase (V-ATPase) activity, accounts for the reduced acidifying ability of peripheral lysosomes. The altered composition of peripheral lysosomes is due, at least in part, to more limited access to material exported by the biosynthetic pathway. The balance between Rab7 and Arl8b determines the subcellular localization of lysosomes; more peripheral lysosomes have reduced Rab7 density. This in turn results in decreased recruitment of Rab-interacting lysosomal protein (RILP), an effector that regulates the recruitment and stability of the V1G1 component of the lysosomal V-ATPase. Deliberate margination of lysosomes is associated with reduced acidification and impaired proteolytic activity. The heterogeneity in lysosomal pH may be an indication of a broader functional versatility.