Herpes Simplex Virus 1 (HSV-1) Infected Cell Protein 0 (ICP0) Targets of Ubiquitination during Productive Infection of Primary Adult Sensory Neurons

An Intrinsic Host Defense against HSV-1 Relies on the Activation of Xenophagy with the Active Clearance of Autophagic Receptors

Autophagy engulfs cellular components in double-membrane-bound autophagosomes for clearance and recycling after fusion with lysosomes. Thus, autophagy is a key process for maintaining proteostasis and a powerful cell-intrinsic host defense mechanism, protecting cells against pathogens by targeting them through a specific form of selective autophagy known as xenophagy. In this context, ubiquitination acts as a signal of recognition of the cargoes for autophagic receptors, which direct them towards autophagosomes for subsequent breakdown. Nevertheless, autophagy can carry out a dual role since numerous viruses including members of the Orthoherpesviridae family can either inhibit or exploit autophagy for its own benefit and to replicate within host cells. There is growing evidence that Herpes simplex virus type 1 (HSV-1), a highly prevalent human pathogen that infects epidermal keratinocytes and sensitive neurons, is capable of negatively modulating autophagy. Since the effects of HSV-1 infection on autophagic receptors have been poorly explored, this study aims to understand the consequences of HSV-1 productive infection on the levels of the major autophagic receptors involved in xenophagy, key proteins in the recruitment of intracellular pathogens into autophagosomes. We found that productive HSV-1 infection in human neuroglioma cells and keratinocytes causes a reduction in the total levels of Ub conjugates and decreases protein levels of autophagic receptors, including SQSTM1/p62, OPTN1, NBR1, and NDP52, a phenotype that is also accompanied by reduced levels of LC3-I and LC3-II, which interact directly with autophagic receptors. Mechanistically, we show these phenotypes are the result of xenophagy activation in the early stages of productive HSV-1 infection to limit virus replication, thereby reducing progeny HSV-1 yield. Additionally, we found that the removal of the tegument HSV-1 protein US11, a recognized viral factor that counteracts autophagy in host cells, enhances the clearance of autophagic receptors, with a significant reduction in the progeny HSV-1 yield. Moreover, the removal of US11 increases the ubiquitination of SQSTM1/p62, indicating that US11 slows down the autophagy turnover of autophagy receptors. Overall, our findings suggest that xenophagy is a potent host defense against HSV-1 replication and reveals the role of the autophagic receptors in the delivery of HSV-1 to clearance via xenophagy.

The role of high mobility group AT-hook 1 in viral infections: Implications for cancer pathogenesis

The crucial role of high mobility group AT-hook 1 (HMGA1) proteins in nuclear processes such as gene transcription, DNA replication, and chromatin remodeling is undeniable. Elevated levels of HMGA1 have been associated with unfavorable clinical outcomes and adverse differentiation status across various cancer types. HMGA1 regulates a diverse array of biological pathways, including tumor necrosis factor-alpha/nuclear factor-kappa B (TNF-α/NF-κB), epidermal growth factor receptor (EGFR), Hippo, Rat sarcoma/extracellular signal-regulated kinase (Ras/ERK), protein kinase B (Akt), wingless-related integration site/beta-catenin (Wnt/beta-catenin), and phosphoinositide 3-kinase/protein kinase B (PI3-K/Akt). While researchers have extensively investigated tumors in the reproductive, digestive, urinary, and hematopoietic systems, mounting evidence suggests that HMGA1 plays a critical role as a tumorigenic factor in tumors across all functional systems. Given its broad interaction network, HMGA1 is an attractive target for viral manipulation. Some viruses, including herpes simplex virus type 1, human herpesvirus 8, human papillomavirus, JC virus, hepatitis B virus, human immunodeficiency virus type 1, severe acute respiratory syndrome Coronavirus 2, and influenza viruses, utilize HMGA1 influence for infection. This interaction, particularly in oncogenesis, is crucial. Apart from the direct oncogenic effect of some of the mentioned viruses, the hit-and-run theory postulates that viruses can instigate cancer even before being completely eradicated from the host cell, implying a potentially greater impact of viruses on cancer development than previously assumed. This review explores the interplay between HMGA1, viruses, and host cellular machinery, aiming to contribute to a deeper understanding of viral-induced oncogenesis, paving the way for innovative strategies in cancer research and treatment.

Cell Intrinsic Determinants of Alpha Herpesvirus Latency and Pathogenesis in the Nervous System

Alpha herpesvirus infections (α-HVs) are widespread, affecting more than 70% of the adult human population. Typically, the infections start in the mucosal epithelia, from which the viral particles invade the axons of the peripheral nervous system. In the nuclei of the peripheral ganglia, α-HVs establish a lifelong latency and eventually undergo multiple reactivation cycles. Upon reactivation, viral progeny can move into the nerves, back out toward the periphery where they entered the organism, or they can move toward the central nervous system (CNS). This latency-reactivation cycle is remarkably well controlled by the intricate actions of the intrinsic and innate immune responses of the host, and finely counteracted by the viral proteins in an effort to co-exist in the population. If this yin-yang- or Nash-equilibrium-like balance state is broken due to immune suppression or genetic mutations in the host response factors particularly in the CNS, or the presence of other pathogenic stimuli, α-HV reactivations might lead to life-threatening pathologies. In this review, we will summarize the molecular virus-host interactions starting from mucosal epithelia infections leading to the establishment of latency in the PNS and to possible CNS invasion by α-HVs, highlighting the pathologies associated with uncontrolled virus replication in the NS.