Related Experiment Video
Updated: Jun 20, 2026
09:51
Cell-Based Drug Screening for Inhibitors of Autophagy Related 4B Cysteine Peptidase
Published on: June 30, 2023
Atg4D at the interface between autophagy and apoptosis.
Virginie M S Betin1, Jon D Lane
1Cell Biology Laboratories, Department of Biochemistry, University of Bristol, Bristol, UK.
Autophagy
|August 29, 2009
Summary
Human Atg4D, an endopeptidase regulating autophagy, is activated by caspase-3 during apoptosis. This cleavage enhances its activity and induces cytotoxicity via a BH3 domain, not enhanced autophagy.
Area of Science:
- Cellular biology
- Molecular mechanisms of autophagy
- Apoptosis signaling pathways
Background:
- The Atg4 family of endopeptidases is essential for autophagosome biogenesis, controlling Atg8 lipidation and delipidation.
- Regulation of Atg4 activity in living cells remains largely uncharacterized.
- Autophagy and apoptosis are critical cellular processes with complex regulatory networks.
Purpose of the Study:
- To investigate the regulation of the human Atg4D endopeptidase.
- To determine the functional consequences of Atg4D cleavage by caspases during apoptosis.
- To elucidate the mechanism underlying the cytotoxicity of cleaved Atg4D.
Main Methods:
- Biochemical assays to assess Atg4D enzymatic activity.
- Apoptosis induction and cell-based assays.
- Analysis of protein cleavage and localization using molecular biology techniques.
- Assessment of cytotoxicity and its correlation with cellular events.
Main Results:
- Human Atg4D is cleaved by caspase-3 at the DEVD(63)K site during apoptosis.
- Native Atg4D is enzymatically inactive; caspase cleavage activates its GABARAP-L1 priming and delipidation activity.
- Caspase-cleaved Atg4D exhibits significant cytotoxicity, independent of enhanced autophagy.
- The cytotoxicity is mediated by a C-terminal BH3-like domain and involves transient mitochondrial recruitment of Atg4D.
Conclusions:
- Caspase-3-mediated cleavage activates the Atg4D endopeptidase.
- Activated Atg4D contributes to apoptosis-induced cytotoxicity through a mechanism involving its BH3 domain and mitochondrial localization.
- This study reveals a novel regulatory mechanism for Atg4D and its role in linking autophagy machinery to apoptotic pathways.
Related Concept Videos
01:18Autophagic Cell Death
Christian de Duve discovered “autophagy,” a process in which cellular components are engulfed by membrane-bound organelles called autophagosomes. The autophagosomes then fuse with lysosomes to digest the enclosed contents. Autophagy is generally activated in cells to prevent cell death. However, cell death is triggered when the damage is beyond repair.
Autophagy and Apoptosis
Autophagy can activate apoptosis. In normal conditions, the autophagy activating protein Beclin-1 and pro-apoptotic...
Autophagy and Apoptosis
Autophagy can activate apoptosis. In normal conditions, the autophagy activating protein Beclin-1 and pro-apoptotic...
01:22Cellular Injury V: Apoptosis and Autophagy
Cells respond to damage and stress through highly coordinated processes that decide whether they survive or undergo controlled self-destruction. Two major pathways involved in this regulation are apoptosis, a type of programmed cell death, and autophagy, a survival mechanism that helps cells adapt to adverse conditions.ApoptosisApoptosis removes aged or injured cells to maintain tissue balance. During this process, the cell shrinks, chromatin condenses and fragments, and membrane-bound...
01:36Delivery Pathways to the Lysosome
Eukaryotic cells use different mechanisms to eliminate toxic waste obsolete and worn-out substances. Lysosomes play a pivotal role in this, and hence, these substances are carried to the lysosome from other parts of the cell and extracellular space through different pathways. The most elaborately studied pathways to the lysosome are the endocytic pathways.
Endocytosis
In endocytosis, the cell membrane takes up macromolecules and particles from the surrounding medium. Clathrin-mediated...
Endocytosis
In endocytosis, the cell membrane takes up macromolecules and particles from the surrounding medium. Clathrin-mediated...
01:27Autophagy
Autophagy is a self-digesting process by which a cell protects itself from threats both within and outside the cell, ranging from abnormal proteins to invading bacteria. In this process, obsolete components of the cell and invading microbes are degraded by hydrolytic enzymes active in an acidic environment of the lysosomal lumen.
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...
01:17Phagocytosis of Apoptotic Cells
Cells undergoing apoptosis form apoptotic bodies that must be removed immediately to prevent inflammation, autoimmune diseases, and necrosis. Phagocytosis is carried out by professional phagocytes such as macrophages or immature dendritic cells. Non-professional phagocytes such as epithelial cells and fibroblasts also take part in this process; however, they are not as effective as professional phagocytes.
Normal cells contain receptors that prevent them from being recognized by phagocytes.
Normal cells contain receptors that prevent them from being recognized by phagocytes.
01:17The Extrinsic Apoptotic Pathway
The extrinsic apoptotic pathway is initiated when extracellular death-inducing signals, such as specific cytokines, activate the death receptors expressed on the cell surface. The immune cells involved in this pathway are natural killer cells (NK cells) and cytotoxic T-lymphocytes. NK cells are critical in innate immune response, while cytotoxic T-lymphocytes are associated with adaptive immune response. These cells recognize specific receptors expressed on the altered cells and activate...