Biochemical Institute, Christian-Albrechts-University of Kiel, Kiel 24118, Germany.
Center of Molecular Neurobiology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
Cell Rep. 2018 Jan 23;22(4):1040-1053. doi: 10.1016/j.celrep.2017.12.100. Epub 2018 Jan 28.
Variants in the phospholipase D3 (PLD3) gene have genetically been linked to late-onset Alzheimer's disease. We present a detailed biochemical analysis of PLD3 and reveal its endogenous localization in endosomes and lysosomes. PLD3 reaches lysosomes as a type II transmembrane protein via a (for mammalian cells) uncommon intracellular biosynthetic route that depends on the ESCRT (endosomal sorting complex required for transport) machinery. PLD3 is sorted into intraluminal vesicles of multivesicular endosomes, and ESCRT-dependent sorting correlates with ubiquitination. In multivesicular endosomes, PLD3 is subjected to proteolytic cleavage, yielding a stable glycosylated luminal polypeptide and a rapidly degraded N-terminal membrane-bound fragment. This pathway closely resembles the delivery route of carboxypeptidase S to the yeast vacuole. Our experiments reveal a biosynthetic route of PLD3 involving proteolytic processing and ESCRT-dependent sorting for its delivery to lysosomes in mammalian cells.
磷脂酶 D3（PLD3）基因的变异与晚发性阿尔茨海默病在遗传上有关。我们对 PLD3 进行了详细的生化分析，并揭示了其在内体和溶酶体中的内源性定位。PLD3 作为一种 II 型跨膜蛋白通过一种（对于哺乳动物细胞）不常见的细胞内生物合成途径到达溶酶体，该途径依赖于 ESCRT（用于运输的内体分选复合物）机制。PLD3 被分拣到多泡体的腔内小泡中，ESCRT 依赖性分拣与泛素化相关。在多泡体中，PLD3 被进行蛋白水解切割，产生一个稳定的糖基化腔内多肽和一个迅速降解的 N 端膜结合片段。这种途径与羧肽酶 S 向酵母液泡的输送途径非常相似。我们的实验揭示了 PLD3 的生物合成途径，涉及蛋白水解加工和 ESCRT 依赖性分拣，以将其输送到哺乳动物细胞的溶酶体中。
