Evaluation of kinase inhibitors as potential therapeutics for flavivirus infections.

The recent introduction of Zika virus (ZIKV), the recurrence of dengue virus (DENV), and the lethality of yellow fever virus (YFV) have had a significant impact on Brazilian society and public health. Here, we targeted two cellular kinases implicated in cell proliferation and cancer that are also important for viral replication: mitogen-activated protein kinase kinase (MEK) and Src. We used two MEK inhibitors - trametinib and selumetinib - and two Src inhibitors - saracatinib and bosutinib - to inhibit ZIKV, DENV, and YFV replication in cell culture. The cytotoxicity of the four inhibitors was determined by the observation of abnormal morphology and quantification of adherent cells by crystal violet staining. The antiviral activity of these drugs was assessed based on the reduction of plaque-forming units in cell culture as evidence of the inhibition of the replication of the selected flaviviruses. All four inhibitors showed antiviral activity, but among them, trametinib was the safest and most efficacious against all of the viruses, inhibiting the replication of ZIKV and YFV by 1000-fold, and DENV2/3 by nearly 100-fold. This pan-antiviral effect shows that trametinib could be repurposed for the treatment of flaviviral infections.

A20-binding inhibitor of nuclear factor-kappaB (NF-kappaB)-2 (ABIN-2) is an activator of inhibitor of NF-kappaB (IkappaB) kinase alpha (IKKalpha)-mediated NF-kappaB transcriptional activity.

NF-κB transcription factors are pivotal players in controlling inflammatory and immune responses, as well as cell proliferation and apoptosis. Aberrant regulation of NF-κB and the signaling pathways that regulate its activity have been involved in various pathologies, particularly cancers, as well as inflammatory and autoimmune diseases. NF-κB activation is tightly regulated by the IκB kinase (IKK) complex, which is composed of two catalytic subunits IKKα and IKKß, and a regulatory subunit IKKγ/NEMO. Although IKKα and IKKß share structural similarities, IKKα has been shown to have distinct biological functions. However, the molecular mechanisms that modulate IKKα activity have not yet been fully elucidated. To understand better the regulation of IKKα activity, we purified IKKα-associated proteins and identified ABIN-2. Here, we demonstrate that IKKα and IKKß both interact with ABIN-2 and impair its constitutive degradation by the proteasome. Nonetheless, ABIN-2 enhances IKKα- but not IKKß-mediated NF-κB activation by specifically inducing IKKα autophosphorylation and kinase activity. Furthermore, we found that ABIN-2 serine 146 is critical for the ABIN-2-dependent IKKα transcriptional up-regulation of specific NF-κB target genes. These results imply that ABIN-2 acts as a positive regulator of NF-κB-dependent transcription by activating IKKα.