An inhibition of p62/SQSTM1 caused autophagic cell death of several human carcinoma cells.
Bottom Line: Electron microscopical analysis revealed the formation of autophagosomes with multilayer membranes caused by p62-silencing. p62 silencing-mediated reduced cell viability was restored by both genomic and pharmacological inhibition of autophagy but not that of apoptosis.These findings were also detected in several types of carcinoma cell lines including adenocarcinomas and squamous cell carcinomas.Results of our present study revealed that an inhibition of p62 resulted in the formation of mis-regulated autophagosomes with multilayer membranes and an autophagic cell death, and p62 can therefore be an attractive target for the development of anti-neoplastic agents.
Affiliation: Department of Pathology, School of Medicine, Tohoku University, Sendai, Japan.Show MeSH
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Mentions: We further elucidated the mechanisms of p62 silencing-induced autophagy by an ultrastructural examination. Figure3(a) showed representative electron microscopical images of siRNA-transfected PC9 cells. Autophagic vesicles were not detected in PC9 cells transfected with Control siRNA but when transfected with two sip62s, morphologically identified autophagic vesicles were clearly detected in cytoplasm (Fig.3a). The great majority of autophagic vesicles detected in p62-silenced PC9 cells formed multilayer structures but its average diameter was 0.5–1 μm, the same as representative autophagic vesicles. We also found the small number of the cells with large multilayer vesicles (5–15 μm) containing other multilayer vesicles (Fig.3b). Autophagy inhibition as a result of the transfection of siRNA targeting autophagy-related gene Atg5 reduced the number of multilayer autophagosomes (Fig.3c). These ultrastructural studies indicated that an inhibition of p62 induced the formation of autophagosomes with multilayer membranes.
Affiliation: Department of Pathology, School of Medicine, Tohoku University, Sendai, Japan.