Strategic Research Centre for Molecular and Medical Research, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia.
J Biol Chem. 2012 Jan 20;287(4):2485-99. doi: 10.1074/jbc.M111.302216. Epub 2011 Nov 30.
ATP7A and ATP7B are copper-transporting P(1B)-type ATPases (Cu-ATPases) that are critical for regulating intracellular copper homeostasis. Mutations in the genes encoding ATP7A and ATP7B lead to copper deficiency and copper toxicity disorders, Menkes and Wilson diseases, respectively. Clusterin and COMMD1 were previously identified as interacting partners of these Cu-ATPases. In this study, we confirmed that clusterin and COMMD1 interact to down-regulate both ATP7A and ATP7B. Overexpression and knockdown of clusterin/COMMD1 decreased and increased, respectively, endogenous levels of ATP7A and ATP7B, consistent with a role in facilitating Cu-ATPase degradation. We demonstrate that whereas the clusterin/ATP7B interaction was enhanced by oxidative stress or mutation of ATP7B, the COMMD1/ATP7B interaction did not change under oxidative stress conditions, and only increased with ATP7B mutations that led to its misfolding. Clusterin and COMMD1 facilitated the degradation of ATP7B containing the same Wilson disease-causing C-terminal mutations via different degradation pathways, clusterin via the lysosomal pathway and COMMD1 via the proteasomal pathway. Furthermore, endogenous ATP7B existed in a complex with clusterin and COMMD1, but these interactions were neither competitive nor cooperative and occurred independently of each other. Together these data indicate that clusterin and COMMD1 represent alternative and independent systems regulating Cu-ATPase quality control, and consequently contributing to the maintenance of copper homeostasis.
ATP7A 和 ATP7B 是铜转运 P(1B)-型 ATP 酶（Cu-ATPases），对于调节细胞内铜稳态至关重要。编码 ATP7A 和 ATP7B 的基因突变分别导致 Menkes 和 Wilson 病，这两种疾病均表现为铜缺乏和铜毒性。先前已经鉴定出 clusterin 和 COMMD1 是这些 Cu-ATPases 的相互作用伙伴。在这项研究中，我们证实 clusterin 和 COMMD1 相互作用，下调 ATP7A 和 ATP7B 的表达。clusterin/COMMD1 的过表达和敲低分别降低和增加了内源性 ATP7A 和 ATP7B 的水平，表明其在促进 Cu-ATPase 降解中发挥作用。我们表明，clusterin/ATP7B 相互作用受到氧化应激或 ATP7B 突变的增强，而 COMMD1/ATP7B 相互作用在氧化应激条件下没有改变，仅在导致 ATP7B 错误折叠的 ATP7B 突变时增加。clusterin 和 COMMD1 通过不同的降解途径促进含有相同 Wilson 病致病 C 末端突变的 ATP7B 的降解，clusterin 通过溶酶体途径，COMMD1 通过蛋白酶体途径。此外，内源性 ATP7B 与 clusterin 和 COMMD1 形成复合物，但这些相互作用既不是竞争性的，也不是合作性的，彼此独立发生。这些数据表明，clusterin 和 COMMD1 代表调节 Cu-ATPase 质量控制的替代和独立系统，从而有助于维持铜稳态。
