What does this research mean for the field?

Cigarette smoke exposure promotes alveolar epithelial cell apoptosis in emphysematous COPD by inducing STUB1-mediated ubiquitination and degradation of the anti-apoptotic protein PHLDA1, a process that can be mitigated by Nrf2 activation. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This research seeks to understand how PHLDA1 degradation contributes to the emphysematous phenotype of COPD and identify strategies for its restoration.

May 20, 2026

D108-21 The Role and Mechanism of Enhanced Ubiquitination Degradation of PHLDA1 in the Chronic Obstructive Pulmonary Disease Emphysematous Phenotype

Key Points

This research seeks to understand how PHLDA1 degradation contributes to the emphysematous phenotype of COPD and identify strategies for its restoration.
Investigated mechanisms in cells and human specimens using nucleic acid and protein detection methods.
Utilized techniques including transfection, immunohistochemistry, and flow cytometry.
Explored the role of STUB1 as the E3 ligase mediating PHLDA1 degradation under cigarette smoke exposure.
Identified that cigarette smoke exposure leads to PHLDA1 misfolding and degradation through the ubiquitin-proteasome pathway.
Found that STUB1 regulates PHLDA1 protein stability and its expression is markedly decreased in emphysema.
Activated Nrf2 mitigated PHLDA1 misfolding and reduced type II alveolar epithelial cell apoptosis.

Abstract

Abstract Rationale The emphysema phenotype represents a major subtype of COPD, characterized by destruction to the interlobular septa, progressive loss of lung function, and markedly reduced exercise tolerance. Despite advances in pharmacologic therapy for airway inflammation, no effective treatment currently exists to prevent or reverse alveolar destruction. Identifying molecular targets that promote alveolar repair and halt disease progression is therefore of critical importance. Previous work from our group demonstrated that excessive apoptosis of type II alveolar epithelial cells (ACEII) is a key mechanism underlying emphysematous change. PHLDA1, an anti-apoptotic protein predominantly expressed in type II alveolar epithelial cells, was markedly decreased in lung tissue from patients with emphysematous phenotype compared to those without emphysema. Methods This study investigates the mechanisms in cells and human specimens via nucleic acid detection, protein detection, transfection, CO-IP, immunohistochemistry, immunofluorescence, and flow cytometry; Results The present study explored the mechanism responsible for PHLDA1 expression and potential strategies for its restoration. We found that cigarette smoke exposure induced misfolding of PHLDA1, leading to its degradation via the ubiquitin-proteasome pathway. STUB1 was identified as the E3 ligase mediating this degradation and regulating PHLDA1 protein stability. Activation of the antioxidant transcription factor Nrf2 using its agonist tBHQ mitigated PHLDA1 misfolding and reduced AEC II apoptosis. Conclusion Type II alveolar epithelial cells are markedly reduced in emphysema-associated COPD. PHLDA1, predominantly expressed in these cells, is degraded via the ubiquitin-proteasome pathway, with STUB1 acts as the E3 ligase. Under CSE stimulation, PHLDA1 misfolds and undergoes accelerated degradation; activation of Nrf2 restores its structural integrity and diminishes apoptosis. Thus, STUB1 and Nrf2 represent potential therapeutic targets for modulating PHLDA1 stability and mitigating alveolar damage in emphysematous COPD. This abstract is funded by: Natural Science Foundation of China

Bookmark

D108-21 The Role and Mechanism of Enhanced Ubiquitination Degradation of PHLDA1 in the Chronic Obstructive Pulmonary Disease Emphysematous Phenotype

Key Points

Abstract

Cite This Study