Autophagic membranes participate in hepatitis B virus nucleocapsid assembly, precore and core protein trafficking, and viral release

Abstract

Hepatitis B virus (HBV) DNA replication takes place inside the viral core particle and is dependent on autophagy. Here we show that HBV core particles are associated with autophagosomes and phagophores in cells that productively replicate HBV. These autophagic membrane-associated core particles contain almost entirely the hypophosphorylated core protein and are DNA replication competent. As the hyperphosphorylated core protein can be localized to phagophores and the dephosphorylation of the core protein is associated with the packaging of viral pregenomic RNA (pgRNA), these results are in support of the model that phagophores can serve as the sites for the packaging of pgRNA. In contrast, in cells that replicate HBV, the precore protein derivatives, which are related to the core protein, are associated with autophagosomes but not with phagophores via a pathway that is independent of its signal peptide. Interestingly, when the core protein is expressed by itself, it is associated with phagophores but not with autophagosomes. These observations indicate that autophagic membranes are differentially involved in the trafficking of precore and core proteins. HBV induces the fusion of autophagosomes and multivesicular bodies and the silencing of Rab11, a regulator of this fusion, is associated with the reduction of release of mature HBV particles. Our studies thus indicate that autophagic membranes participate in the assembly of HBV nucleocapsids, the trafficking of HBV precore and core proteins, and likely also the egress of HBV particles.

Characterization of Intracellular Precore-Derived Proteins and Their Functions in Hepatitis B Virus-Infected Human Hepatocytes

“…Interestingly, a portion of phosphorylated precore proteins, P-p25 and P-p22, were also associated with membrane compartments in the absence of other HBV proteins ( Fig. 2F ), possibly with autophagosomes, as shown recently ( 36 ). The presence of a small amount of p22 in the supernatant of overexpressing cells as a low-density entity ( Fig.…”

“…2F ). It is likely that some P-p22 and P-p25, phosphorylated in the cytosol, were associated with autophagosomes, as was recently reported ( 36 ). Altogether, we detected phosphorylated and unphosphorylated p22 and p25 in both HBV-infected PHHs and precore-transfected hepatoma cells.…”

“…When p22 was expressed alone, we could detect low levels of p22 in the fractions with lower density than virions ( Fig. 6B , first panel), possibly in some form of vesicles like exosomes ( 36 ). However, when coexpressed with HBc, p22 sedimented into the high-density fractions containing naked capsids, consistent with the formation of intracellular chimeric capsids that were released into the culture supernatant of transfected cells ( Fig.…”

Biosynthesis, structure and biological function of cholesterol glucoside in Helicobacter pylori: A review

“…Studies have shown that some viruses can use autophagy for self-protection and proliferation, such as autophagy membrane that participates in the nucleocapsid assembly and the release of hepatitis B virus. [79] The autophagy induced by poliovirus can increase the viral load of fibroblasts. [80] Because of this characteristic, autophagy has become one of the important mechanisms for studying the entry of pathogens into the host.…”

Antiviral therapy reduces hepatocellular carcinoma through suppressing hepatitis B virus replication may improve ER stress, mitochondrial and metabolic dysfunctions and decrease p62 in hybridized mice with single HBV transgene and miR‐122

“…8 HBV can exploit mitochondria damage-induced autophagy to facilitate its replication and secretion. 20,36 Host hepatocytes catabolize glucose, amino acids, and free fatty acids through autophagy, thereby providing energy and substrates for HBV replication and secretion.…”