Hexosamine biosynthetic pathway promotes the antiviral activity of SAMHD1 by enhancing O-GlcNAc transferase-mediated protein O-GlcNAcylation

Abstract

Rationale: Viruses hijack the host cell machinery to promote viral replication; however, the mechanism by which metabolic reprogramming regulates innate antiviral immunity in the host remains elusive. Herein, we explore how the hexosamine biosynthesis pathway (HBP) and O-linked-N-acetylglucosaminylation (O-GlcNAcylation) regulate host antiviral response against hepatitis B virus (HBV) in vitro and in vivo. Methods: We conducted a metabolomics assay to evaluate metabolic responses of host cells to HBV infection. We systematically explored the role of HBP and protein O-GlcNAcylation in regulating HBV infection in cell and mouse models. O-linked N-acetylglucosamine (O-GlcNAc) target proteins were identified via liquid chromatography-tandem mass spectrometry (LC-MS) and co-immunoprecipitation assays. Additionally, we also examined uridine diphosphate (UDP)-GlcNAc biosynthesis and O-GlcNAcylation levels in patients with chronic hepatitis B (CHB). Results: HBV infection upregulated GLUT1 expression on the hepatocyte surface and facilitated glucose uptake, which provides substrates to HBP to synthesize UDP-GlcNAc, leading to an increase in protein O-GlcNAcylation. Pharmacological or transcriptional inhibition of HBP and O-GlcNAcylation promoted HBV replication. Mechanistically, O-GlcNAc transferase (OGT)-mediated O-GlcNAcylation of sterile alpha motif and histidine/aspartic acid domain-containing protein 1 (SAMHD1) on Ser93 stabilizes SAMHD1 and enhances its antiviral activity. Analysis of clinical samples revealed that UDP-GlcNAc level was increased, and SAMHD1 was O-GlcNAcylated in patients with CHB. Conclusions: HBP-mediated O-GlcNAcylation positively regulates host antiviral response against HBV in vitro and in vivo . The findings reveal a link between HBP, O-GlcNAc modification, and innate antiviral immunity by targeting SAMHD1.

Regulation of O-Linked N-Acetyl Glucosamine Transferase (OGT) through E6 Stimulation of the Ubiquitin Ligase Activity of E6AP

“…Our finding of enhanced OGT ubiquitination and destabilization stimulated by E6 suggests that E6 may take a different role in suppressing OGT activity by pairing with E6AP. E6-stimulated OGT ubiquitination and degradation may help to counteract the antiviral activity of OGT that has been identified as a part of the host defense mechanism against viral infection by hepatitis B virus (HBV), Kaposi’s sarcoma-associated herpesvirus (KSHV), respiratory syncytial virus (RSV), and human immunodeficiency virus (HIV-1) [ 40 , 41 , 42 , 43 , 44 , 45 ]. OGT has been found to enhance the autophagy activity of the host cells through which the HBV viral particles would be degraded, and it can also down-regulate gene expression from the HIV genome inside the host cells [ 41 , 42 , 43 , 44 ].…”

CRISPR/Cas9 knock-in strategy to evaluate phospho-regulation of SAMHD1

“…SAMHD1 regulation certainly is certainly more complex than commonly assumed. In addition to multiple potential phosphorylation sites, SAMHD1 is modified by acetylation, SUMOylation, ubiquitination and O-GlcNAcylation (20,21,(40)(41)(42)(43)(44)(45)(46)(47). Also, SAMHD1 was demonstrated to harbor redox sensitive cysteine residues, which affect both dNTPase and anti-viral activity (48,49).…”

O-GlcNAcylation is a key regulator of multiple cellular metabolic pathways

“…A mutual regulation between the GLUT1 and O-GlcNAcylation may result in: (1) elevated GLUT1 may enhance O-GlcNAcylation by coordinating glucose flow into HBP (2) elevated O-GlcNAcylation may increase GLUT1 expression through a similar molecular mechanism, which may be HIF-1a. Two recent studies provided evidence for this regulatory effect (Wang et al, 2020;Hu et al, 2021).…”

“…Infection by hepatitis B promoted glucose uptake by upregulating GLUT1 expression in hepatocytes, providing substrates for the HBP synthesis of UDP-GlcNAc, leading to increased O-GlcNAcylation (Hu et al, 2021). Acyl-CoA ligase 4 (ACSL4) enhanced O-GlcNAcylation via GLUT1 to promote hepatocellular carcinoma growth and survival, and in turn, O-GlcNAcylation increased ACSL4 expression and promoted cancer growth, potentially involving downstream GLUT1 regulation by ACSL4 (Wang et al, 2020).…”