Opposite Effects of Two Human ATG10 Isoforms on Replication of a HCV Sub-genomic Replicon Are Mediated via Regulating Autophagy Flux in Zebrafish

Abstract

Autophagy is a host mechanism for cellular homeostatic control. Intracellular stresses are symptoms of, and responses to, dysregulation of the physiological environment of the cell. Alternative gene transcription splicing is a mechanism potentially used by a host to respond to physiological or pathological challenges. Here, we aimed to confirm opposite effects of two isoforms of the human autophagy-related protein ATG10 on an HCV subgenomic replicon in zebrafish. A liver-specific HCV subreplicon model was established and exhibited several changes in gene expression typically induced by HCV infection, including overexpression of several HCV-dependent genes (argsyn, leugpcr, rasgbd, and scaf-2), as well as overexpression of several ER stress related genes (atf4, chop, atf6, and bip). Autophagy flux was blocked in the HCV model. Our results indicated that the replication of the HCV subreplicon was suppressed via a decrease in autophagosome formation caused by the autophagy inhibitor 3MA, but enhanced via dysfunction in the lysosomal degradation caused by another autophagy inhibitor CQ. Human ATG10, a canonical isoform in autophagy, facilitated the amplification of the HCV-subgenomic replicon via promoting autophagosome formation. ATG10S, a non-canonical short isoform of the ATG10 protein, promoted autophagy flux, leading to lysosomal degradation of the HCV-subgenomic replicon. Human ATG10S may therefore inhibit HCV replication, and may be an appropriate target for future antiviral drug screening.

Functional Genetic Variants in ATG10 Are Associated with Acute Myeloid Leukemia

“…The decreased protein levels of ATG10 long isoform in ATG10 rs1864182G carriers were associated with the reduction of autophagic flux, its canonical function, in agreement with previous observations [ 21 ]. Given the role of autophagy in leukemia [ 52 ], and in chemotherapy susceptibility and resistance [ 53 , 54 , 55 ], this reduction in autophagy could potentially be beneficial to lower the probability of developing AML.…”

“…We next evaluated the protein levels of the ATG10 long isoform, which is mainly involved in autophagy catalytic function [ 21 , 22 ]. In the presence of the ATG10 rs1864182G , a statistically significant decrease of 25% in the ATG10 long isoform levels was observed ( Figure 1 G).…”

“…Q9H0Y0 is composed of 663 nucleotides, encoding 220 amino acids, whereas the isoform Variant X3 has 555 nucleotides coding for 184 amino acids (from www.ncbi.nlm.nih.gov/CCDS/, accessed 12 January 2021). Both short isoforms present identical sequences with the exception of a deletion of 36 amino acids in the N-terminal of Variant X3 [21,22]. The D6RDX3 isoform also has 555 nucleotides coding for 184 amino acids, but the 36 amino acids deletion occur at the C-terminal region.…”

“…ATG10 is an E2-like enzyme that catalyzes the conjugation reaction between ATG12 and ATG5, when interacting with ATG7, an essential set for autophagy vesicle formation [ 20 ]. Interestingly, apart from ATG10 ’s role in autophagy, ATG10 seems to have a non-canonical function in inflammation [ 21 , 22 ].…”

Berberine alleviates liver fibrosis through inducing ferrous redox to activate ROS-mediated hepatic stellate cells ferroptosis

“…Increased numbers of autophagosomes can be due to an increase in the formation of autophagosomes or a reduction in autophagosome turnover caused by late suppression of autophagy. We confirmed that BBR impaired autophagy by monitoring the process of autophagic flux in the presence of autophagy inhibitors chloroquine (CQ) and 3-methyladenine (3-MA) [ 31 ] in GFP-LC3B LX2 cells (Supplementary Fig. 5A–H ).…”