CNOT2 promotes degradation of p62/SQSTM1 as a negative regulator in ATG5 dependent autophagy

Abstract

Though CNOT2 is involved in regulation of adipogenic differentiation, apoptotic cell death and metastasis, the underlying autophagic mechanism of CNOT2 was unknown until now. Thus, in the present study, the critical role of CNOT2 in autophagy was elucidated in association with p62/SQSTM1 signaling. CNOT2 depletion induced p62/SQSTM1 accumulation and LC3B-II conversion, and also increased the number of puncta with impaired autophagic flux. In contrast, CNOT2 overexpression induced downregulation and ubiquitination of p62/SQSTM1 in HEK293 QBI. Furthermore, ubiquitination of p62/SQSTM1 was blocked by autophagy inhibition. Interestingly, CNOT2 was correlated with p62/SQSTM1 in HEK293 QBI cells and also was colocalized with p62/SQSTM1 in H1299 cells. Additionally, ATG5 was upregulated in CNOT2-depleted H1299 cells, while degradation of p62/SQSTM1 by CNOT2 was detected in ATG5+/+ MEF cells but not in ATG5−/− MEF cells. Of note, CNOT2 induced degradation of p62/SQSTM1 in HEK293 QBI cells co-transfected with Myc-ΔLIR/KIR or Myc-ΔUBA, but not with Myc-ΔPB1. Sub G1 population was increased in CNOT2-depleted H1299 cells by late autophagy inhibitors, ammonium chloride and chloroquine compared to 3-methyladenine. Overall, these findings provide novel insight into the critical role of CNOT2 as a negative regulator in ATG5 dependent autophagy.

Liraglutide Enhances Autophagy and Promotes Pancreatic β Cell Proliferation to Ameliorate Type 2 Diabetes in High-Fat-Fed and Streptozotocin-Treated Mice

“…Autophagy plays a critical role in sustaining intracellular homeostasis and cell integrity via improving the state of insulin resistance, modulating cellular lipid metabolism and regulating the activation of the innate immune response [ 13 ]. Previous studies suggest that autophagy can be accurately regulated by autophagy-related genes [ 14 ]. Among these ATG genes, ATG5 protein in a conjugated form with ATG12 and ATG8 (LC3) are associated with the early stages of autophagosome formation [ 15 , 16 ].…”

METTL3 and ALKBH5 oppositely regulate m6A modification of TFEB mRNA, which dictates the fate of hypoxia/reoxygenation-treated cardiomyocytes

“…We found that the BafAinduced accumulation of LC3B-II was significantly enhanced in Mettl3-silenced H9c2 cells compared with the control cells (Figure 2(a)), indicative of an enhanced autophagic flux in Mettl3-depleted cells. Second, because SQSTM1 (sequestosome 1) was negatively correlated with autophagic flux [20], we then assessed the effect of Mettl3 silencing on the SQSTM1 levels. We observed that H/R induced the increase in the levels of SQSTM1 and LC3B-II, suggesting that autophagic flux was impaired by METTL3 upregulation (Figure 2(a)).…”

CCR4‑NOT transcription complex subunit�2�regulates TRAIL sensitivity in non‑small‑cell lung cancer cells via the STAT3 pathway

“…Similar to cIB1, in the case of proteins with an oncogenic or tumor suppressor function, the modulation of the expression may affect TRAIL-mediated cell death. As previously demonstrated, cNOT2 participates in the regulation of angiogenesis, mobility autophagy and proliferation in diverse tumor types (11,15). Based on these oncogenic functions of cNOT2, it was hypothesized that cNOT2 may participate in TRAIL-resistant mechanisms.…”