vIRA Inhibition of Antiviral Necroptosis and RIPK3 Binding Are Separable Events
Katherine B Ragan1,2, Haripriya Sridharan1,3, Aaron S Stark4,5
1Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, LaMontagne Center for Infectious Disease, University of Texas at Austin, Austin, TX 78712, USA.
Abstract:
Necroptosis is an antiviral form of programmed cell death modulated by proteins that interact via RIP Homotypic Interaction Motifs (RHIMs). The result of the signaling pathways depends on which RHIM-containing proteins are involved: although both host and viral proteins contain RHIMs, virally encoded RHIM proteins, such as murine cytomegalovirus (MCMV)-encoded viral inhibitor of RIP activation (vIRA) serve to prevent cell death. Although every RHIM contains the same core four-amino-acid pattern, there are variations in individual sequences that we hypothesized would determine the differential outcomes in necroptotic signaling. As such, we replaced the RHIM in vIRA with the RHIMs from other proteins involved in the signaling cascade (RIPK1, RIPK3, ZBP1, ICP6) to assess the effect on necroptosis during MCMV infection. Although these RHIM-swap vIRA constructs remained able to bind to RIPK3, in the context of MCMV infection, they lost the ability to prevent necroptosis. These results are consistent with other studies that demonstrate that RHIM-containing proteins form amyloid fibrils unique to the proteins interfacing. Our results provide biological context for the growing model that the outcome of RHIM-based signaling is influenced by the specific amyloid fibril structures that are driven by the unique amino-acid sequences of each RHIM present.
Insights
Viral inhibitor of RIP activation (vIRA) uses RIP Homotypic Interaction Motifs (RHIMs) to block necroptosis. Swapping vIRA
Area of Science:
- Molecular Biology
- Immunology
- Virology
Background:
- Necroptosis is an antiviral programmed cell death pathway regulated by RIP Homotypic Interaction Motifs (RHIMs).
- Viral proteins, like murine cytomegalovirus (MCMV)-encoded viral inhibitor of RIP activation (vIRA), can hijack RHIM interactions to suppress host cell death.
- RHIMs share a core sequence but exhibit variations influencing signaling outcomes.
Purpose of the Study:
- To investigate how specific RHIM sequence variations impact necroptosis regulation during MCMV infection.
- To determine if altering the vIRA RHIM sequence affects its ability to inhibit cell death.
Main Methods:
- Engineered MCMV vIRA constructs with RHIMs from host proteins (RIPK1, RIPK3, ZBP1, ICP6).
- Assessed the ability of these RHIM-swap vIRA constructs to inhibit necroptosis during MCMV infection.
- Confirmed binding interactions between modified vIRA and RIPK3.
Main Results:
- RHIM-swap vIRA constructs maintained binding to RIPK3.
- Despite binding RIPK3, RHIM-swap vIRA constructs failed to prevent necroptosis during MCMV infection.
- These findings suggest RHIM sequence dictates functional outcomes beyond simple binding.
Conclusions:
- The specific amino acid sequence of a RHIM is critical for its function in necroptosis signaling.
- RHIM variations influence the formation of unique amyloid fibril structures, determining signaling pathway outcomes.
- This highlights the role of sequence-specific protein-protein interactions in controlling programmed cell death.
More Related Videos
Related Concept Videos
00:46Feedback Inhibition
02:18The Equilibrium Binding Constant and Binding Strength
02:18The Equilibrium Binding Constant and Binding Strength
00:49Ligand Binding and Linkage
01:49Conserved Binding Sites
Binding sites are often located in large pockets, and if their location on a protein’s surface is unknown, it can be predicted using various approaches. The energetic method computationally...
01:23The Antiviral System of Bacteria and Archaea: CRISPR