Herpes Simplex Virus 1 ICP34.5 Alters Mitochondrial Dynamics in Neurons

Abstract

Expression of viral genes and activation of innate antiviral responses during infection result in an increase in reactive oxygen species (ROS) and toxic by-products of energy metabolism which can lead to cell death. The mitochondrion and its associated proteins are crucial regulators of these responses and related pathways such as autophagy and apoptosis. Through a mass spectrometry approach, we have shown that the herpes simplex virus 1 (HSV-1) neurovirulence- and autophagy-modulating protein ICP34.5 interacts with numerous mitochondrion-associated factors. Specifically, we showed that amino acids 68 to 87 of ICP34.5, the domain that binds beclin1 and controls neurovirulence, are necessary for interactions with PGAM5, KEAP1, and other regulators of the antioxidant response, mitochondrial trafficking, and programmed cell death. We further show that while this domain interacts with multiple cellular stress response factors, it does not alter apoptosis or antioxidant gene expression. That said, the attenuated replication of a recombinant virus lacking residues 68 to 87 (termed Δ68-87) in primary human fibroblasts was restored by addition of ferric nitrate. Furthermore, in primary mouse neurons, the perinuclear localization of mitochondria that follows infection with HSV-1 was notably absent following Δ68-87 infection. Through this 20-amino-acid domain, ICP34.5 significantly reduces mitochondrial motility in axons of neurons. We propose the hypothesis that ICP34.5 promotes perinuclear mitochondrial localization by modulating transport of mitochondria through interaction with PGAM5. These data expand upon previous observations of altered mitochondrial dynamics following alphaherpesvirus infections and identify a key determinant of this activity during HSV-1 infections. IMPORTANCE Herpes simplex virus persists lifelong in neurons and can reactivate to cause recurrent lesions in mucosal tissues. A key determinant of virulence is the viral protein ICP34.5, of which residues 68 to 87 significantly contribute to neurovirulence through an unknown mechanism. Our report provides evidence that residues 68 to 87 of ICP34.5 are required for binding mitochondrion-associated factors. These interactions alter mitochondrial dynamics in neurons, thereby facilitating viral replication and pathogenesis.

Cell type-specific response of colon cancer tumor cell lines to oncolytic HSV-1 virotherapy in hypoxia

“…Our results indicated that HO-1 expression in HT29 cells infected with HSV-HMGB1 remained unchanged during hypoxia or normoxia; however, HO-1 was reduced by HSV-ble infection. Studies have shown that ICP34.5 null HSV1 could not interact with KEAP1 a negative regulator of NFR2, hence NFR2 nuclear translocation could not occur and HO-1 expression could be suppressed after ICP34.5 null HSV1 infection [ 43 ].…”

Mitochondrial Protein PGAM5 Emerges as a New Regulator in Neurological Diseases

“…Furthermore, the expression of Miro was reduced in the brain of NRF2 knockout mice (O’Mealey et al, 2017 ), revealing the possibility that PGAM5-KEAP1-NRF2 complex is required for mitochondrial transports in neurons ( Figure 2A ). Another study showed that infection of neurotropic herpes simplex viruses 1 altered mitochondrial motility in neurons via PGAM5 (Manivanh et al, 2020 ). Herpes simplex viruses 1-encoded neurovirulence protein, infected-cell protein 34.5 (ICP34.5), interacted with PGAM5 and reduced mitochondrial velocity in primary superior cervical ganglion neurons and trigeminal neurons.…”

“…Herpes simplex viruses 1-encoded neurovirulence protein, infected-cell protein 34.5 (ICP34.5), interacted with PGAM5 and reduced mitochondrial velocity in primary superior cervical ganglion neurons and trigeminal neurons. Disrupting interaction between ICP34.5 and PGAM5 restored the decreased mitochondrial velocity in neurons upon herpes simplex viruses 1 infection (Manivanh et al, 2020 ). However, ICP34.5/PGAM5 interaction did not affect activation of NRF2 and antioxidant response, suggesting that herpes simplex viruses 1 infection-mediated mitochondrial motility might be independent of PGAM5-KEAP1-NRF2 complex.…”

Anterograde Neuronal Circuit Tracers Derived from Herpes Simplex Virus 1: Development, Application, and Perspectives

“…This process also causes neuronal dysfunction or even cell death. Several proteins have been shown to be highly toxic, including but not limited to ICP0 [ 109 ], ICP4, ICP27 [ 110 ], UL41 (vhs) [ 111 ] and ICP34.5 ( γ34.5 ) [ 112 ]. The most direct attenuation strategy is to delete these toxic viral genes.…”