A non-canonical role for the autophagy machinery in anti-retroviral signaling mediated by TRIM5α

Abstract

TRIM5α is a key cross-species barrier to retroviral infection, with certain TRIM5 alleles conferring increased risk of HIV-1 infection in humans. TRIM5α is best known as a species-specific restriction factor that directly inhibits the viral life cycle. Additionally, it is also a pattern-recognition receptor (PRR) that activates inflammatory signaling. How TRIM5α carries out its multi-faceted actions in antiviral defense remains incompletely understood. Here, we show that proteins required for autophagy, a cellular self-digestion pathway, play an important role in TRIM5α’s function as a PRR. Genetic depletion of proteins involved in all stages of the autophagy pathway prevented TRIM5α-driven expression of NF-κB and AP1 responsive genes. One of these genes is the preeminent antiviral cytokine interferon β (IFN-β), whose TRIM5-dependent expression was lost in cells lacking the autophagy proteins ATG7, BECN1, and ULK1. Moreover, we found that the ability of TRIM5α to stimulate IFN-β expression in response to recognition of a TRIM5α-restricted HIV-1 capsid mutant (P90A) was abrogated in cells lacking autophagy factors. Stimulation of human macrophage-like cells with the P90A virus protected them against subsequent infection with an otherwise resistant wild type HIV-1 in a manner requiring TRIM5α, BECN1, and ULK1. Mechanistically, TRIM5α was attenuated in its ability to activate the kinase TAK1 in autophagy deficient cells, and both BECN1 and ATG7 contributed to the assembly of TRIM5α-TAK1 complexes. These data demonstrate a non-canonical role for the autophagy machinery in assembling antiviral signaling complexes and in establishing a TRIM5α-dependent antiviral state.

The Interplay of HIV and Autophagy in Early Infection

“…CRISPR/Cas9, a promising technology in the development of strategies against different pathologies, has emerged as a potential anti-HIV-1 tool. One of the first factors targeted by this strategy is TRIM5α, which could be modified to restrict retroviral infection by promoting autophagy against HIV-1, soon after viral entry into the cell (Hatziioannou et al, 2004;Stremlau et al, 2004;Mandell et al, 2014a,b;Richardson et al, 2014;Ribeiro et al, 2016;Saha et al, 2020). Thus, it has been proposed that HSCs harvested from an HIV-positive patient could be transduced with an adeno-associated virus (AAV) vector bearing the Cas9 enzyme together with the single guide RNA (sgRNA) targeting TRIM5α and a repair template to introduce the mutations to target HIV-1 (Weatherley et al, 2017).…”

“…In this regard, biallelic CRISPR/Cas9-mediated editing of the TRIM5α gene has recently been associated with the protection of human T lymphocytic cells against infection by HIV-1 (Désaulniers et al, 2020). Furthermore, a link between TRIM5α and several autophagy factors, such as BECN1, ATG7 and ULK1, has been observed by targeting these genes with the CRISPR/Cas9 editing machinery (Saha et al, 2020). This genetic depletion strategy inhibits the anti-HIV-1 proinflammatory function of TRIM5α impairing its capacity to activate adaptor related protein complex 1 (AP1) and NFKB factors that results in the inhibition of the production of the antiviral IFNB1 (named IFN-β) (Saha et al, 2020).…”

“…Furthermore, a link between TRIM5α and several autophagy factors, such as BECN1, ATG7 and ULK1, has been observed by targeting these genes with the CRISPR/Cas9 editing machinery (Saha et al, 2020). This genetic depletion strategy inhibits the anti-HIV-1 proinflammatory function of TRIM5α impairing its capacity to activate adaptor related protein complex 1 (AP1) and NFKB factors that results in the inhibition of the production of the antiviral IFNB1 (named IFN-β) (Saha et al, 2020). All these data are indicative of the importance of the interplay between TRIM5α and autophagy during HIV-1 infection (Saha et al, 2020).…”

Human TRIM5α: Autophagy Connects Cell-Intrinsic HIV-1 Restriction and Innate Immune Sensor Functioning

“…Strikingly, recent data highlight a role for autophagy in huTRIM5α’s functioning as an innate sensor. Genetic depletion of key autophagy proteins such as Beclin 1, ATG7, and ULK1 was required for huTRIM5α-based activation of AP-1 and NF-κB, and thereby of AP-1 and NF-κB-responsive genes [ 194 ]. In primary immune cells, induction of IFN-β expression in response to huTRIM5α-restricted recognition of HIV-1 capsid mutant (P90A) was dependent on Beclin 1, ATG7, and ULK1.…”

“…In primary immune cells, induction of IFN-β expression in response to huTRIM5α-restricted recognition of HIV-1 capsid mutant (P90A) was dependent on Beclin 1, ATG7, and ULK1. Furthermore, in autophagy deficient cells, huTRIM5α-driven TAK1 activation, which is also Beclin 1 and ATG7-dependent, was attenuated [ 194 ]. Taken together, these data underline that autophagy contributes not only to huTRIM5α-mediated HIV-1 restriction, but also to the role of huTRIM5α as an innate immune sensor of incoming retroviral capsids.…”