p62 Plays a Specific Role in Interferon-γ-Induced Presentation of a Toxoplasma Vacuolar Antigen

• IFN-γ induces ubiquitin and p62 recruitment to Toxoplasma gondii-forming vacuoles
• Atg3/5/7/16L1 and Irgm1/m3 are essential for the ubiquitination and p62 recruitment
• p62 is dispensable for IFN-γ-induced clearance of T. gondii
• p62 plays a specific role in vacuolar-antigen-specific CD8+ T cell activation

SummaryAlso known as Sqstm1, p62 is a selective autophagy adaptor with a ubiquitin-binding domain. However, the role of p62 in the host defense against Toxoplasma gondii infection is unclear. Here, we show that interferon γ (IFN-γ) stimulates ubiquitin and p62 recruitment to T. gondii parasitophorous vacuoles (PVs). Some essential autophagy-related proteins, but not all, are required for this recruitment. Regardless of normal IFN-γ-induced T. gondii clearance activity and ubiquitination, p62 deficiency in antigen-presenting cells (APCs) and mice diminishes the robust IFN-γ-primed activation of CD8+ T cells that recognize the T. gondii-derived antigen secreted into PVs. Because the expression of Atg3 and Irgm1/m3 in APCs is essential for PV disruption, ubiquitin and p62 recruitment, and vacuolar-antigen-specific CD8+ T cell activation, IFN-γ-mediated ubiquitination and the subsequent recruitment of p62 to T. gondii are specifically required for the acquired immune response after PV disruption by IFN-γ-inducible GTPases.

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