Lowering Endogenous Cathepsin D Abundance Results in Reactive Oxygen Species Accumulation and Cell Senescence
Siyuan Su1,2, Xu Zhu1, Liang Lin3
1From the ‡CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China, 100101.
Abstract:
Cathepsin D is reportedly to be closely associated with tumor development, migration, and invasion, but its pathological mechanism is not fully elucidated. We aimed to evaluate phenotypic changes and molecular events in response to cathepsin D knockdown. Lowering endogenous cathepsin D abundance (CR) induced senescence in HeLa cells, leading to reduced rate of cell proliferation and impaired tumorigenesis in a mouse model. Quantitative proteomics revealed that compared with control cells (EV), the abundances of several typical lysosomal proteases were decreased in the lysosomal fraction in CR cells. We further showed that cathepsin D knockdown caused increased permeability of lysosomal membrane and reactive oxygen species accumulation in CR cells, and the scavenging of reactive oxygen species by antioxidant was able to rescue cell senescence. Despite the increased reactive oxygen species, the proteomic data suggested a global reduction of redox-related proteins in CR cells. Subsequent analysis indicated that the transcriptional activity of nuclear factor erythroid-related factor 2 (Nrf2), which regulates the expression of groups of antioxidant enzymes, was down-regulated by cathepsin D knockdown. Importantly, Nrf2 overexpression significantly reduced cell senescence. Although transient oxidative stress promoted the accumulation of Nrf2 in the nucleus, we showed that the Nrf2 protein exited nucleus if oxidative stress persisted. In addition, when cathepsin D was transiently knocked down, the cathepsin-related events followed a sequential order, including lysosomal leakage during the early stage, followed by oxidative stress augmentation, and ultimately Nrf2 down-regulation and senescence. Our results suggest the roles of cathepsin D in cancer cells in maintaining lysosomal integrity, redox balance, and Nrf2 activity, thus promoting tumorigenesis. The MS Data are available via ProteomeXchange with identifier PXD002844.
Insights
Reducing cathepsin D triggers cell senescence by disrupting lysosomal integrity and redox balance, impairing tumor growth. This highlights cathepsin D
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- Cathepsin D is implicated in tumor progression, but its precise role and mechanisms remain unclear.
- Understanding cathepsin D's function is crucial for developing targeted cancer therapies.
Purpose of the Study:
- To investigate the phenotypic and molecular consequences of cathepsin D knockdown in cancer cells.
- To elucidate the role of cathepsin D in maintaining cellular homeostasis and promoting tumorigenesis.
Main Methods:
- HeLa cells with reduced cathepsin D (CR) were analyzed for phenotypic changes and molecular events.
- Quantitative proteomics was employed to compare protein abundance between CR and control (EV) cells.
- Lysosomal membrane permeability, reactive oxygen species (ROS) levels, and nuclear factor erythroid-related factor 2 (Nrf2) activity were assessed.
Main Results:
- Cathepsin D knockdown induced cellular senescence, reduced proliferation, and impaired tumor formation in mice.
- Lysosomal proteases decreased, lysosomal membrane permeability increased, and ROS accumulated upon cathepsin D reduction.
- Cathepsin D knockdown led to decreased Nrf2 transcriptional activity, which was rescued by Nrf2 overexpression.
- A sequential mechanism involving lysosomal leakage, oxidative stress, and Nrf2 downregulation was identified.
Conclusions:
- Cathepsin D is essential for maintaining lysosomal integrity, redox balance, and Nrf2 activity in cancer cells.
- These functions of cathepsin D are critical for promoting tumor development and progression.
- Targeting cathepsin D may represent a viable strategy for cancer treatment by inducing senescence and impairing tumorigenesis.
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