Autophagy plays an important role in maintaining cell function. Abnormal autophagy leads to cell dysfunction and is associated with many diseases such as tumors, immunodeficiency diseases, lysosomal storage disorders, and neurodegenerative diseases. Autophagy is precisely regulated, and PTEN plays an important role in regulating autophagy. As noncoding small RNAs, miRNAs play an important role in the fine regulation of cellular processes. However, the mechanism of the miRNA regulation of PTEN-related autophagy has not been fully elucidated. In this study, our results showed that miR-4465 significantly inhibited the expression of PTEN, upregulated phosphorylated AKT, and thereby inhibited autophagy by activating mTOR in HEK293, HeLa, and SH-SY5Y cells. Further studies indicated that miR-4465 reduced PTEN mRNA levels through posttranscriptional regulation via directly targeting the 3′-UTR. Our novel findings provide useful hints for the comprehensive elucidation of the molecular mechanism of miRNA-regulated PTEN-related autophagy and may also provide some new insights for the exploration of miRNAs in the treatment of PTEN-related diseases.
Background
Poly-GA, a dipeptide repeat protein unconventionally translated from GGGGCC repeat expansions in C9orf72, is abundant in C9orf72-related amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Although the poly-GA aggregates have been identified in C9orf72-ALS/FTD neurons, the effects on UPS and autophagy, and their exact molecular mechanisms have not been fully elucidated.
Results
Herein, our in vivo experiments show that ploy-GA mice expressing 150 repeats but not 30 repeats GA exhibit significant aggregates in cells, behavioral deficits, and activate autophagy in the brain. The in vitro results demonstrate that the aggregated poly-GA induce proteasomal stress through directly binding proteasome subunit PSMD2 to recruit proteasome and impair its function, subsequently activate phosphorylation and ubiquitination of p62 to recruit autophagosome, and ultimately leading to compensatory autophagy activation. While rapamycin treatment significantly improves the degenerative symptoms of mice expressing 150 repeats poly-GA, relieves neuronal injury and reduces neuroinflammation and aggregates in the brain.
Conclusion
In summary, we clarify for the first time the relationship of poly-GA between proteasome and autophagy: poly-GA aggregates recruit autophagosomes only when it forms complex with the proteasome and causes proteasomal stress. Our study provides support for further promoting the comprehension about the pathogenesis of C9orf72 and may bring a hint for the exploration of rapamycin in the treatment of ALS/FTD.
Background
Poly-GA, a dipeptide repeat protein unconventionally translated from GGGGCC repeat expansions in C9orf72, is abundant in C9orf72-related amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Although the poly-GA aggregates have been identified in C9orf72-ALS/FTD neurons, the effects on UPS and autophagy, and their exact molecular mechanisms have not been fully elucidated.
Methods
We generated poly-GA mice,and treated poly-GA mice for 90 days by intraperitoneal injection rapamycin (4 mg/kg) every 2 days until behavioral analysis. GFAP (an astrogliosis marker), Iba1 (a microgliosis marker), GFP, p62, p-p62 (S349), p-p62 (S403) and LC3 proteins expression were quantified in brain tissues by immunohistochemistry, immunofluorescence, immunoblotting. These results were validated in vitro by protein mass spectrometry, co-immunoprecipitation and immunofluorescence.
Results
Herein, our in vivo experiments show that ploy-GA mice expressing 150 repeats but not 30 repeats GA exhibit significant aggregates in cells, behavioral deficits, and activate autophagy in the brain, in vitro results demonstrate that aggregated poly-GA induces proteasomal stress through directly binding proteasome subunit PSMD2 to recruit proteasome and impair its function, subsequently activates phosphorylation and ubiquitination of p62 to recruit autophagosome, ultimately leading to compensatory autophagy activation. While rapamycin treatment significantly improves the degenerative symptoms of mice expressing 150 repeats poly-GA, relieves neuronal injury and reduces neuroinflammation and aggregates in the brain.
Conclusion
In summary, we clarify for the first time the relationship of poly-GA between proteasome and autophagy: poly-GA aggregates recruit autophagosomes only when it forms complex with the proteasome and causes proteasomal stress. Our study provides support for further promoting the comprehension about the pathogenesis of C9orf72 and may bring a hint for the therapy.
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