Lysosomal membrane permeabilization is involved in oxidative stress-induced apoptotic cell death in LAMP2-deficient
Cheuk-Yiu Law1, Chung-Wah Siu1,2, Katherine Fan3
1Cardiology Division, Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, China.
Abstract:
Patients with Danon disease may suffer from severe cardiomyopathy, skeletal muscle dysfunction as well as varying degrees of mental retardation, in which the primary deficiency of lysosomal membrane-associated protein-2 (LAMP2) is considerably associated. Owing to the scarcity of human neurons, the pathological role of LAMP2 deficiency in neural injury of humans remains largely elusive. However, the application of induced pluripotent stem cells (iPSCs) may shed light on overcoming such scarcity. In this study, we obtained iPSCs derived from a patient carrying a mutated LAMP2 gene that is associated with Danon disease. By differentiating such LAMP2-deficient iPSCs into cerebral cortical neurons and with the aid of various biochemical assays, we demonstrated that the LAMP2-deficient neurons are more susceptible to mild oxidative stress-induced injury. The data from MTT assay and apoptotic analysis demonstrated that there was no notable difference in cellular viability between the normal and LAMP2-deficient neurons under non-stressed condition. When exposed to mild oxidative stress (10 μM H2O2), the LAMP2-deficient neurons exhibited a significant increase in apoptosis. Surprisingly, we did not observe any aberrant accumulation of autophagic materials in the LAMP2-deficient neurons under such stress condition. Our results from cellular fractionation and inhibitor blockade experiments further revealed that oxidative stress-induced apoptosis in the LAMP2-deficient cortical neurons was caused by increased abundance of cytosolic cathepsin L. These results suggest the involvement of lysosomal membrane permeabilization in the LAMP2 deficiency associated neural injury.
Insights
Lysosomal membrane-associated protein-2 (LAMP2) deficiency in neurons increases susceptibility to oxidative stress. This study used patient-derived stem cells to show LAMP2 deficiency leads to neural injury via increased cytosolic cathepsin L.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- Danon disease is linked to lysosomal membrane-associated protein-2 (LAMP2) deficiency, causing cardiomyopathy, skeletal issues, and intellectual disability.
- The role of LAMP2 deficiency in human neural injury is unclear due to limited neuron availability.
Purpose of the Study:
- To investigate the pathological role of LAMP2 deficiency in human neural injury using patient-derived induced pluripotent stem cells (iPSCs).
- To determine the cellular mechanisms underlying LAMP2 deficiency-associated neural dysfunction under oxidative stress.
Main Methods:
- Generated iPSCs from a Danon disease patient with a mutated LAMP2 gene.
- Differentiated LAMP2-deficient iPSCs into cerebral cortical neurons.
- Assessed neuronal viability, apoptosis, and autophagic material accumulation under oxidative stress (H2O2).
- Utilized cellular fractionation and inhibitor blockade experiments to identify molecular pathways involved.
Main Results:
- LAMP2-deficient neurons showed no difference in viability under normal conditions but significantly increased apoptosis under mild oxidative stress.
- No aberrant accumulation of autophagic materials was observed in LAMP2-deficient neurons.
- Oxidative stress-induced apoptosis in LAMP2-deficient neurons was attributed to increased cytosolic cathepsin L.
- Results suggest lysosomal membrane permeabilization contributes to neural injury in LAMP2 deficiency.
Conclusions:
- LAMP2 deficiency in human neurons exacerbates injury under oxidative stress.
- Increased cytosolic cathepsin L due to lysosomal membrane permeabilization is a key mechanism in LAMP2 deficiency-associated neural injury.
- Patient-derived iPSCs are a valuable model for studying rare genetic neurological disorders.
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