RESUMO
Autophagy cargo recognition and clearance are essential for intracellular protein quality control. SQSTM1/p62 sequesters intracellular aberrant proteins and mediates cargo delivery for their selective autophagic degradation. The formation of p62 non-membrane-bound liquid compartments is critical for its function as a cargo receptor. The regulation of p62 phase separation/condensation has yet been poorly characterised. Using an unbiased yeast two-hybrid screening and complementary approaches, we found that DAXX physically interacts with p62. Cytoplasmic DAXX promotes p62 puncta formation. We further elucidate that DAXX drives p62 liquid phase condensation by inducing p62 oligomerisation. This effect promotes p62 recruitment of Keap1 and subsequent Nrf2-mediated stress response. The present study suggests a mechanism of p62 phase condensation by a protein interaction, and indicates that DAXX regulates redox homoeostasis, providing a mechanistic insight into the prosurvival function of DAXX.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Citoplasma/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Proteínas Nucleares/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteína Sequestossoma-1/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Autofagia/fisiologia , Linhagem Celular , Proteínas Correpressoras , Drosophila , Feminino , Técnicas de Silenciamento de Genes , Células HEK293 , Células HeLa , Humanos , Proteína 1 Associada a ECH Semelhante a Kelch/metabolismo , Masculino , Camundongos , Chaperonas Moleculares , Proteínas Nucleares/genética , Ligação Proteica , Dobramento de Proteína , Domínios e Motivos de Interação entre ProteínasRESUMO
The PI-3 kinase (PI-3K)/mTOR pathway is critical for cell growth and proliferation. Strategies of antagonising this signaling have proven to be detrimental to cell survival. This observation, coupled with the fact many tumours show enhanced growth signaling, has caused dual inhibitors of PI-3K and mTOR to be implicated in cancer treatment, and have thus been studied across various tumour models. Since PI-3K (class-I)/mTOR pathway negatively regulates autophagy, dual inhibitors of PI-3K/mTOR are currently believed to be autophagy activators. However, our present data show that the dual PI-3K/mTOR inhibition (DKI) potently suppresses autophagic flux. We further confirm that inhibition of Vps34/PI3KC3, the class-III PI-3K, causes the blockade to autophagosome-lysosome fusion. Our data suggest that DKI induces cell death independently of apoptosis and necroptosis, whereas autophagy perturbation by DKI may contribute to cell death. Given that autophagy is critical in cellular homeostasis, our study not only clarifies the role of a dual PI-3K/mTOR inhibitor in autophagy, but also suggests that its autophagy inhibition needs to be considered if such an agent is used in cancer chemotherapy.
