The Transmembrane Domain of HIV-1 gp41 Inhibits T-Cell Activation by Targeting Multiple T-Cell Receptor Complex Components through Its GxxxG Motif

Abstract

To successfully infect and persist within its host, HIV-1 utilizes several immunosuppressive motifs within its gp41 envelope glycoprotein to manipulate and evade the immune system. The transmembrane domain (TMD) of gp41 downregulates T-cell receptor (TCR) signaling through a hitherto unknown mechanism. Interactions between TMDs within the membrane milieu have been shown to be typically mediated by particular amino acids, such as interactions between basic and acidic residues and dimerization motifs as GxxxG. The HIV-1 TMD exhibits both a polar arginine (Arg(696)) residue and a GxxxG motif, making them ideal candidates for mediators of TMD-TCR interaction. Using a primary T-cell activation assay and biochemical and biophysical methods, we demonstrate that the gp41 TMD directly interacts with TMDs of the TCR and the CD3 coreceptors (δ, γ, and ε) within the membrane, presumably leading to impairment of complex assembly. Additionally, we reveal that although Arg(696) does not affect TMD immunosuppression, the GxxxG motif is crucial in mediating gp41's TMD interaction with the CD3 coreceptors of the TCR. These findings suggest that compared with other gp41 immunosuppressive motifs, the gp41 TMD has multiple targets within the TCR complex, suggesting less susceptibility to evolutionary pressure and consequently being advantageous for the virus over the host immune response. Furthermore, as the GxxxG motif mediates interactions of the gp41 TMD with multiple receptors, it emerges as an attractive drug target. This multitarget inhibitory mechanism might be a strategy utilized by HIV to interfere with the function of additional host receptors.

Structure of the transmembrane domain ofHIV‐1 envelope glycoprotein

“…In vitro infectivity and cell–cell fusion do not, however, mimic all the conditions under which the virus moves from one cell to another in an infected individual, nor are those assays particularly sensitive to physiologically relevant kinetic parameters. We note that R696 occupies a ‘d’ position in the coiled coil, with its C β facing inwards toward the trimer interface, unlike its configuration in previously proposed models . Its interactions in the trimeric coiled coil are probably those of optimal stability, once having paid the energetic cost of burying its charge.…”

Stability and Water Accessibility of the Trimeric Membrane Anchors of the HIV-1 Envelope Spikes

“…Mutagenesis studies showed that the transmembrane domain (TMD) of gp41 is not merely a membrane anchor, but plays critical roles in membrane fusion and viral infectivity 16–20 . Moreover, recent studies showed that truncations in the cytoplasmic tail of gp41 could alter the antigenic surface of the Env ECD on the opposite side of the membrane 21 , suggesting that the ECD, the TMD, and the membrane proximal regions are conformationally coupled, and thus the conformational stability of the TMD is an important consideration for immunogen design in B-cell based HIV-1 vaccine development.…”

“…Due to the unusual position of the R696, the membrane partition of the gp41 TMD has been controversial 20, 22, 26–27 . Our solvent PRE analysis now confirms that R696 resides in the middle of the membrane (Fig.…”

Intramembrane attenuation of the TLR4-TLR6 dimer impairs receptor assembly and reduces microglia-mediated neurodegeneration

“…It was previously shown that hydrophobic peptides conjugated to lysine tags were correctly oligomerized and inserted into the membrane (35,36). For assays with fluorescent peptides, the addition of rhodamine 5(6)-carboxytetramethylrhodamine N-succinimidyl ester (TAMRA, BioChemika) or NBD-F (2-fold excess) fluorescent probe to the N terminus of the peptides was performed by standard Fmoc chemistry (37).…”