A Central Role for Phosphorylated p38α in Linking Proteasome Inhibition-Induced Apoptosis and Autophagy.
Autophagy and the ubiquitin proteasome system (UPS), as two major protein degradation pathways, coordinate with each other in regulating programmed cell death. Autophagy can compensate for the UPS impairment-induced cell dysfunction and apoptosis. However, it is not clear how cells maintain the delicate balance between UPS-related apoptosis and autophagy. Here, we showed that proteasome inhibition-mediated UPS impairment can activate the phosphorylated p38α (p-p38α)-dependent apoptotic pathway and autophagy pathway in both neuroblastoma cell line N2a and primary cortical neuronal cells. Multiple indices were utilized for the autophagy detection including LC3II transition, acidic vesicle formation, lysosomal accumulation, and p62 reduction. Blockade of autophagy flux with autophagy inhibitor 3-methyladenine or bafilomycin A1 resulted in further phosphorylation of p38α, polyubiquitinated protein aggregation, and greater apoptotic cell death. On the contrary, enhancement of autophagy by rapamycin attenuated the cell loss by lowering p-p38α level and degrading protein aggregates, indicating a protective role of autophagy in cell stress and apoptosis. Moreover, de-activation of p38α with pharmaceutical p38α inhibitor BIRB796 greatly increased autophagy activation, reduced protein aggregates, and attenuated cell loss, suggesting a bidirectional regulation between p-p38α and autophagy. In addition, manipulation of p-p38α by BIRB796 or p38α knockdown decreased the phosphorylation of key components of the mammalian target of rapamycin (mTOR)-dependent pathway, indicating that the mTOR pathway mediates the p-p38α regulation on autophagy. Overall, our data emphasize p-p38α as a key mediator in the antagonistic interaction between apoptosis and autophagy in response to UPS impairment. Centering p-p38α as a potential regulatory target may provide a dual advantage of proteostasis maintenance and cell survival for simultaneous inhibition of apoptosis and activation of autophagy.
The Key Laboratory of Stem Cell Biology and Neurogenomic Laboratory, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, 200025, China.
Fang
F
Guo
Shanghai University of Medicine and Health Sciences, Shanghai, 201318, China.
Xi-Biao
XB
He
Clinical Research Center on Neurological Diseases, the First Affiliated Hospital, Dalian Medical University, Dalian, 116011, China.
Song
S
Li
The Key Laboratory of Stem Cell Biology and Neurogenomic Laboratory, Institute of Health Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) & Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, 200025, China. wdle@sibs.ac.cn.|Clinical Research Center on Neurological Diseases, the First Affiliated Hospital, Dalian Medical University, Dalian, 116011, China. wdle@sibs.ac.cn.|Collaborative Innovation Center for Brain Science, the First Affiliated Hospital, Dalian Medical University, Dalian, 116011, China. wdle@sibs.ac.cn.
Weidong
W
Le
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D048308:Mitogen-Activated Protein Kinase 14 / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors / Q000494:pharmacology*
D061988:Proteasome Inhibitors; C025946:3-methyladenine; D048308:Mitogen-Activated Protein Kinase 14; D046988:Proteasome Endopeptidase Complex; D000225:Adenine
Apoptosis; Autophagy; Neuronal survival; Phosphorylated p38α; Ubiquitin proteasome system; mTOR