HCMV Exploits Molecular Mimicry to Recruit VPS4A for Virus Assembly

Conceitos essenciais

HCMV pUL71 protein contains a viral MIM2-like motif (vMIM2) that binds the VPS4A MIT domain, recruiting VPS4A to the cytoplasmic viral assembly compartment (cVAC) during HCMV infection.

Resumo

The content describes how human cytomegalovirus (HCMV) exploits molecular mimicry to recruit the host cellular protein VPS4A, a key component of the ESCRT machinery, to sites of virus assembly.
Key highlights:

HCMV pUL71 protein contains a short peptide motif in its C-terminal region that resembles the Type 2 MIT-Interacting Motif (MIM2) found in cellular ESCRT-III proteins. This viral MIM2-like motif (vMIM2) binds directly to the N-terminal MIT domain of VPS4A.
Structural modeling and mutagenesis experiments confirm that the pUL71 vMIM2 binds the VPS4A MIT domain in a helix-plus-extended conformation, similar to how cellular MIM2 motifs interact.
The pUL71 vMIM2 interaction with VPS4A is conserved across β-herpesviruses but not in α- or γ-herpesviruses, suggesting a specific role in cytomegalovirus biology.
During HCMV infection, the pUL71 vMIM2 is required for recruitment of VPS4A to the cytoplasmic viral assembly compartment (cVAC), the site of secondary virus envelopment.
However, disrupting the pUL71-VPS4A interaction does not significantly impact HCMV replication or virus particle production, suggesting the vMIM2-mediated recruitment of VPS4A is not essential for efficient virus assembly and release.

Estatísticas

"VPS4A accumulates at the cytoplasmic viral assembly complex (cVAC) of cells infected with human cytomegalovirus (HCMV), the site where nascent virus particles obtain their membrane envelope."
"Sequence analysis, deep-learning structure prediction, molecular dynamics and mutagenic analysis identify a short peptide motif in the C-terminal region of pUL71 that is necessary and sufficient for the interaction with VPS4A."
"Purified GST-pUL71(283–361) binds the VPS4A MIT domain with 2.84 ± 0.33 µM affinity, tighter than the 5.54 ± 1.10 µM interaction measured between VPS4A MIT and the CHMP6 MIM2."
"Umbrella sampling molecular dynamics simulations accurately predicted the effects of individual amino acid substitutions in the pUL71 vMIM2 on binding to the VPS4A MIT domain."

Citações

"VPS4-recruitment via a vMIM2 represents a previously unknown mechanism of molecular mimicry in viruses, extending previous observations that herpesviruses encode proteins with structural and functional homology to cellular ESCRT-III components."
"The ability of molecular dynamics analysis to accurately predict VPS4A-binding behaviours of individual amino acid substitutions in the pUL71 peptide confirms the high quality of the pUL71(300–325):VPS4A MIT structural model."

Principais Insights Extraídos De

Human cytomegalovirus deploys molecular mimicry to recruit VPS4A to sites of virus assembly

by Butt,B. G., ... às www.biorxiv.org 01-04-2024

https://www.biorxiv.org/content/10.1101/2024.01.04.572781v1

Perguntas Mais Profundas

What other cellular processes or pathways might the pUL71 vMIM2-VPS4A interaction influence beyond virus assembly?

The pUL71 vMIM2-VPS4A interaction may have implications beyond virus assembly. Since VPS4 is involved in membrane constriction and fission, its recruitment by pUL71 to the cytoplasmic viral assembly compartment (cVAC) could potentially impact cellular processes related to membrane dynamics. This interaction may influence endosomal sorting, vesicle formation, and membrane remodeling, as these are functions typically associated with the ESCRT machinery. Additionally, the recruitment of VPS4A by pUL71 could affect intracellular trafficking pathways, organelle biogenesis, and potentially even cellular signaling cascades. The presence of VPS4A at the cVAC suggests a role in coordinating membrane dynamics during virus assembly, but the broader impact on cellular processes warrants further investigation.

How might the conservation of the vMIM2 motif across β-herpesviruses, but not α- or γ-herpesviruses, reflect differences in their replication strategies or host cell interactions?

The conservation of the vMIM2 motif across β-herpesviruses, such as human cytomegalovirus (HCMV), human herpesvirus 6 (HHV6), and human herpesvirus 7 (HHV7), but not in α- or γ-herpesviruses, may reflect differences in their replication strategies and host cell interactions. Beta-herpesviruses are known to have complex replication cycles involving multiple stages of envelopment and egress, which likely require intricate interactions with host cell machinery for successful replication. The conservation of the vMIM2 motif suggests a common mechanism for these beta-herpesviruses to interact with the ESCRT machinery, specifically VPS4A, during virus assembly. This interaction may be crucial for the efficient production of infectious virions in beta-herpesviruses, which have evolved to rely on this mechanism for their replication strategies. In contrast, alpha- and gamma-herpesviruses may have evolved alternative mechanisms for virus assembly and egress that do not involve the recruitment of VPS4A via a vMIM2-like motif. These differences in replication strategies and host cell interactions could explain why the vMIM2 motif is conserved specifically in beta-herpesviruses.

Could the pUL71 vMIM2 motif or its interaction with VPS4A be targeted therapeutically to disrupt HCMV infection, or are there redundant mechanisms that would limit the efficacy of such an approach?

The pUL71 vMIM2 motif and its interaction with VPS4A could potentially be targeted therapeutically to disrupt HCMV infection. By disrupting the recruitment of VPS4A to the cVAC, essential processes in virus assembly and maturation could be inhibited, leading to a reduction in viral replication and spread. However, the efficacy of targeting this interaction may be limited by redundant mechanisms that HCMV may have in place to ensure successful replication. HCMV is known to encode multiple proteins involved in virus assembly and egress, and it is possible that alternative pathways or compensatory mechanisms could bypass the need for the pUL71-VPS4A interaction. Additionally, the complex nature of HCMV replication and the multiple interactions between viral and host cell proteins may provide additional layers of redundancy that could limit the effectiveness of targeting a single interaction. Further research is needed to fully understand the role of the pUL71 vMIM2 motif and its interaction with VPS4A in the context of HCMV infection and to assess the feasibility of targeting this interaction as a therapeutic strategy.