HIV-1 Nef Is Transferred from Expressing T Cells to Hepatocytic Cells through Conduits and Enhances HCV Replication

Abstract

HIV-1 infection enhances HCV replication and as a consequence accelerates HCV-mediated hepatocellular carcinoma (HCC). However, the precise molecular mechanism by which this takes place is currently unknown. Our data showed that infectious HIV-1 failed to replicate in human hepatocytic cell lines. No discernible virus replication was observed, even when the cell lines transfected with HIV-1 proviral DNA were co-cultured with Jurkat T cells, indicating that the problem of liver deterioration in the co-infected patient is not due to the replication of HIV-1 in the hepatocytes of the HCV infected host. Instead, HIV-1 Nef protein was transferred from nef-expressing T cells to hepatocytic cells through conduits, wherein up to 16% (average 10%) of the cells harbored the transferred Nef, when the hepatocytic cells were co-cultured with nef-expressing Jurkat cells for 24 h. Further, Nef altered the size and numbers of lipid droplets (LD), and consistently up-regulated HCV replication by 1.5∼2.5 fold in the target subgenomic replicon cells, which is remarkable in relation to the initially indolent viral replication. Nef also dramatically augmented reactive oxygen species (ROS) production and enhanced ethanol-mediated up-regulation of HCV replication so as to accelerate HCC. Taken together, these data indicate that HIV-1 Nef is a critical element in accelerating progression of liver pathogenesis via enhancing HCV replication and coordinating modulation of key intra- and extra-cellular molecules for liver decay.

Alcohol Metabolism Potentiates HIV-Induced Hepatotoxicity: Contribution to End-Stage Liver Disease

“…Since HIV DNA integration is a prerequisite for HIV replication, this suggests that Ach increases it in a small number of hepatocytes, which is visible only if these cells do not undergo rapid apoptosis. Obviously, while exposure to Ach increases both HIV RNA and integrated HIV DNA levels, it does not make HIV-infection productive, corresponding to the previous findings observed in Ach-non-treated HIV-infected hepatocytes [45].…”

Function of ubiquitin (Ub) specific protease 15 (USP15) in HIV-1 replication and viral protein degradation

“…Expression of USP15 was also detected in the ER (Fig. 6B) where Nef protein was detected (Park et al, 2014). Further, USP15 was located in the early endosome (Fig.…”

“…Cells were then washed twice with PBS, fixed in 4% paraformaldehyde, permeabilized with 0.3% Triton X-100 for 5 min, and blocked in 2.5% BSA for 30 min. Cells were incubated with the primary antibody followed by Alexa Fluor 488 or 555 conjugated to secondary antibodies at room temperature for 1 h each and washed three times with PBS to visualize subcellular localization of the indicated proteins with an confocal microscope, as described (Park et al, 2014). …”

“…One of the key molecular features of Nef is that, unlike other viral proteins whose functions are phase- (or stage-) specific in the virus life cycle, Nef is the only known viral element which acts throughout the whole virus life cycle within the host cell: it is translated from the early viral messages (Cullen, 1991; Ferguson et al, 2002; Haseltine, 1991) and stays in the infected cells until the protein is packaged into virion particles (Bukovsky et al, 1997), and thus Nef has temporal advantages to determine the fate of not only viral but also cellular proteins throughout the HIV-1 infectious life cycle. Another notable feature is that subcellular localization of Nef, compared with other viral proteins which localize to specific subcellular compartments, is not confined to the cytoplasmic membrane by myristoylation (Allan et al, 1985; Franchini et al, 1986), but occurs in diverse subcellular organelles, such as endosomes (Dikeakos et al, 2012; Kueck and Neil, 2012; Singh et al, 2009), ER (Park et al, 2014), mitochondria, and even the perinuclear membrane by interacting with cellular protein partners (Kammula et al, 2012). Nef is also known to play a pivotal role in localization of Env glycoprotein and Gag in late endosomes (Sandrin and Cosset, 2006) and in regulation of various cellular proteins by inducing endocytosis (Hanna et al, 1998; Sandrin and Cosset, 2006), suggesting that Nef may have spatial advantages in governing viral and cellular protein fates.…”

Positive-sense RNA viruses reveal the complexity and dynamics of the cellular and viral epitranscriptomes during infection

“…Because HIV-1 cannot successfully replicate in Huh7 or HeLa cell lines, 293T cells were exclusively used for HIV-1 infections (53). Before transfection, 2 × 10 6 cells were seeded per 100 mm plate.…”