GS143, an inhibitor of E3 ligase β-TrCP, reverses HIV-1 latency without activating T cells via unconventional activation of NFκB

HIV-1 persists indefinitely in individuals living with HIV-1 even after effective treatment with antiretroviral therapy (ART). Upon cessation of the therapy, latently infected memory CD4+ T cells allow for a rapid rebound of the virus. The development of latency reversing agents (LRAs) to activate latent virus promoting immune recognition and clearance of the infected cells is pivotal for the elimination of the latent arm of the infection. Success of this strategy requires the development of potent highly specific LRAs with fewer off-target effects. LRA activity displayed by proteasome inhibitors although not highly specific opens the possibility of exploiting the high degree of specificity of the ubiquitin-proteasome system to develop targeted LRAs. Here we demonstrate that a small molecule GS143, which inhibits β-TrCP, the substrate recognition subunit of the SCF^fi-TrCP E3 ubiquitin protein ligases, exhibits potent LRA activity both in a primary cell model system of latency and cells from aviremic individuals with HIV-1 treated with ART. Furthermore, GS143 reactivates latent HIV-1 without activating T cells, a desirable attribute for LRAs of clinical use. We showed that GS143 acts in a complementary fashion with at least two other classes of LRAs, thereby representing novel drug combinations for targeting HIV-1 latency. Finally, our results suggest that GS143 triggers a novel signaling pathway to reactivate latent HIV-1 that leads to the unconventional activation of NFκB p65, by initiating the noncanonical signaling via NIK, followed by activation of IKK leading to phosphorylation of p65 on S536 and its nuclear translocation. Moreover, we show that β-catenin inhibitors suppress reactivation HIV-1 by GS143, suggesting that β-catenin supports NF-κB output indirectly. Overall, our results suggest that the β-TrCP E3 ligase inhibitor GS143 represents a new type of LRA.