Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India.
Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
J Cell Sci. 2020 Dec 24;133(24):jcs246819. doi: 10.1242/jcs.246819.
The Wilson disease protein, ATP7B maintains copper (herein referring to the Cu ion) homeostasis in the liver. ATP7B traffics from trans-Golgi network to endolysosomes to export excess copper. Regulation of ATP7B trafficking to and from endolysosomes is not well understood. We investigated the fate of ATP7B after copper export. At high copper levels, ATP7B traffics primarily to acidic, active hydrolase (cathepsin-B)-positive endolysosomes and, upon subsequent copper chelation, returns to the trans-Golgi network (TGN). At high copper, ATP7B colocalizes with endolysosomal markers and with a core member of retromer complex, VPS35. Knocking down VPS35 did not abrogate the copper export function of ATP7B or its copper-responsive anterograde trafficking to vesicles; rather upon subsequent copper chelation, ATP7B failed to relocalize to the TGN, which was rescued by overexpressing wild-type VPS35. Overexpressing mutants of the retromer complex-associated proteins Rab7A and COMMD1 yielded a similar non-recycling phenotype of ATP7B. At high copper, VPS35 and ATP7B are juxtaposed on the same endolysosome and form a large complex that is stabilized by photoamino acid labeling and UV-crosslinking. We demonstrate that retromer regulates endolysosome to TGN trafficking of copper transporter ATP7B in a manner that is dependent upon intracellular copper.
威尔逊病蛋白 ATP7B 维持肝脏内的铜(此处指 Cu 离子)稳态。ATP7B 从反式高尔基体网络运输到内溶酶体以输出多余的铜。ATP7B 在内溶酶体和反式高尔基体网络之间的运输调节机制尚未完全清楚。我们研究了铜输出后 ATP7B 的命运。在高铜水平下,ATP7B 主要运输到酸性、活性水解酶(组织蛋白酶-B)阳性的内溶酶体,随后铜螯合后,返回反式高尔基体网络(TGN)。在高铜水平下,ATP7B 与内溶酶体标记物和 retromer 复合物的核心成员 VPS35 共定位。敲低 VPS35 不会破坏 ATP7B 的铜输出功能或其对囊泡的铜响应性顺行运输;相反,在随后的铜螯合后,ATP7B 无法重新定位到 TGN,而过表达野生型 VPS35 可挽救该现象。过表达 retromer 复合物相关蛋白 Rab7A 和 COMMD1 的突变体也导致 ATP7B 出现类似的不可回收表型。在高铜水平下,VPS35 和 ATP7B 并置在同一个内溶酶体上,并形成一个由光氨酸标记和 UV 交联稳定的大型复合物。我们证明,retromer 以依赖于细胞内铜的方式调节铜转运体 ATP7B 从内溶酶体到 TGN 的运输。