Reovirus σ3 Protein Limits Interferon Expression and Cell Death Induction

Area of Science:

• Virology
• Immunology
• Cell Biology

Background:

• Mammalian reovirus induces necroptosis, a form of programmed cell death.
• This process requires type I interferon (IFN) signaling and viral replication.
• Reovirus outer capsid protein μ1 negatively regulates necroptosis by limiting RNA synthesis.

Purpose of the Study:

• To investigate the role of reovirus outer capsid protein σ3 in regulating necroptosis.
• To determine if σ3 influences IFN production and innate immune signaling.

Main Methods:

• Small interfering RNA (siRNA)-mediated knockdown of σ3 expression.
• Assessment of necroptosis induction.
• Measurement of viral RNA synthesis.
• Quantification of IFN production.
• Ectopic expression of σ3.
• Analysis of a mutant virus lacking dsRNA binding capacity in σ3.

Main Results:

• Knockdown of σ3 enhanced necroptosis, similar to μ1 knockdown.
• σ3 knockdown increased IFN production without affecting viral RNA synthesis.
• Ectopic expression of σ3 suppressed IFN production post-infection.
• σ3's ability to diminish IFN production was independent of its dsRNA binding capacity.

Conclusions:

• Reovirus σ3 protein limits IFN production to control innate immune signaling and necroptosis.
• This regulation occurs through a mechanism independent of σ3's dsRNA binding ability.
• σ3 plays a novel role in preventing excessive IFN induction and subsequent necroptosis during reovirus infection.