Rhesus TRIM5α Disrupts the HIV-1 Capsid at the Inter­Hexamer Interfaces

Abstract

TRIM proteins play important roles in the innate immune defense against retroviral infection, including human immunodeficiency virus type-1 (HIV-1). Rhesus macaque TRIM5α (TRIM5αrh) targets the HIV-1 capsid and blocks infection at an early post-entry stage, prior to reverse transcription. Studies have shown that binding of TRIM5α to the assembled capsid is essential for restriction and requires the coiled-coil and B30.2/SPRY domains, but the molecular mechanism of restriction is not fully understood. In this study, we investigated, by cryoEM combined with mutagenesis and chemical cross-linking, the direct interactions between HIV-1 capsid protein (CA) assemblies and purified TRIM5αrh containing coiled-coil and SPRY domains (CC-SPRYrh). Concentration-dependent binding of CC-SPRYrh to CA assemblies was observed, while under equivalent conditions the human protein did not bind. Importantly, CC-SPRYrh, but not its human counterpart, disrupted CA tubes in a non-random fashion, releasing fragments of protofilaments consisting of CA hexamers without dissociation into monomers. Furthermore, such structural destruction was prevented by inter-hexamer crosslinking using P207C/T216C mutant CA with disulfide bonds at the CTD-CTD trimer interface of capsid assemblies, but not by intra-hexamer crosslinking via A14C/E45C at the NTD-NTD interface. The same disruption effect by TRIM5αrh on the inter-hexamer interfaces also occurred with purified intact HIV-1 cores. These results provide insights concerning how TRIM5α disrupts the virion core and demonstrate that structural damage of the viral capsid by TRIM5α is likely one of the important components of the mechanism of TRIM5α-mediated HIV-1 restriction.

Structural insight into HIV-1 capsid recognition by rhesus TRIM5α

“…It has been shown that a full-length TRIM5α chimera (TRIM5Rh-21R) exists as a mixture of monomers and dimers whereas a truncated TRIM5α (CC-SPRY) is a dimer (11,23,24). We investigated the oligomerization state of PRY/SPRY rh and PRY/SPRY hu .…”

“…This broad, yet specific lattice pattern-sensing ability resides in the capsid-recognition PRY/SPRY domain of TRIM5α (5,13,14,16,22). A TRIM5α truncation construct containing the coiled-coil and the PRY/ SPRY domains (CC-SPRY) is sufficient to bind and disrupt HIV-1 CA assembly (23). However, the lack of detailed structural data on TRIM5α PRY/SPRY poses an obstacle to understanding the pattern-sensing mechanism by which TRIM5α interacts with the retrovirus capsid.…”

How Samhd1 changes our view of viral restriction

“…The TRIM family of proteins comprises both bona fide restriction factors that directly counteract viral replication, as well as other factors that regulate immune sensing [42]. TRIM5α can act as both a restriction factor and a PRR, depending on the retrovirus with which it is challenged [43,44]. Recent work has described the involvements of TRIM5α in innate immune signaling.…”

“…Interaction of TRIM5α with the CA lattice activates the kinase TAK1, which leads to downstream activation of the transcription factors nuclear factor (NF)-κB and activator protein-1 (AP-1) ( Figure 1). Thus, TRIM5α might act as a PRR by modulating proinflammatory cytokine secretion [43,44]. Moreover, the TRIM family of proteins has been involved in autoimmune and autoinflammatory disorders [45].…”

TRIM5α-Mediated Ubiquitin Chain Conjugation Is Required for Inhibition of HIV-1 Reverse Transcription and Capsid Destabilization

“…TRIM5␣ also possesses a C-terminal SPRY domain which is known to recognize determinants in the assembled viral core to mediate restriction (15)(16)(17). Following core binding, TRIM5␣ induces the abortive disassembly of the viral core (18,19). The mechanism by which core disruption occurs is not precisely clear, although numerous studies have suggested that this process is a two-step mechanism, the second of which requires proteasome activity (20)(21)(22)(23).…”