Tubacin, an HDAC6 Selective Inhibitor, Reduces the Replication of the Japanese Encephalitis Virus via the Decrease of Viral RNA Synthesis

Abstract

Japanese encephalitis virus (JEV), a neurotropic flavivirus, annually causes over 30,000 Japanese Encephalitis (JE) cases in East and Southeast Asia. Histone deacetylases (HDACs) modulate lysine acetylation of histones and non-histone proteins, regulating many processes including inflammation and antiviral immune response. This study investigated antiviral activity of pan- and selective-HDAC inhibitors as host-targeting agents against JEV. Among HDAC inhibitors, selective HDAC6 inhibitors (tubastatin-A (TBSA) and tubacin) concentration-dependently inhibited JEV-induced cytopathic effect and apoptosis, as well as reduced virus yield in human cerebellar medulloblastoma cells. The 50% inhibitory concentration (IC50) values of virus yield was 0.26 μM for tubacin and 1.75 μM for TBSA, respectively. Tubacin (IC50 of 1.52 μM), but not TBSA, meaningfully blocked the production of intracellular infectious virus particles. In time-of-addition assays, the greatest potency of antiviral activity was observed in the mode of pre-treatment with tubacin (IC50 of 1.89 μM) compared to simultaneous (IC50 of 4.88 μM) and post-treatment (IC50 of 2.05 μM) modes. Interestingly, tubacin induced the hyperacetylation of a HDAC6 substrate Hsp90 and reduced the interaction of Hsp90 with JEV NS5 protein. Novobiocin, an Hsp90 inhibitor, diminished the NS5 protein amount and virus replication in JEV-infected cells. Meantime, tubacin suppressed the NS5 expression and antisense RNA genome synthesis in infected cells. Tubacin-induced Hsp90 hyperacetylation was suggested to influence the NS5 activity in JEV replication. Therefore, tubacin had a high potential of a host-targeting agent against JEV, exhibiting preventive and therapeutic activities against JEV infection.

Flavivirus Nonstructural Protein NS5 Dysregulates HSP90 to Broadly Inhibit JAK/STAT Signaling

“…Thus, HSP90 inhibitors phenocopy JAK/STAT antagonism by flaviviruses, a similarity of function that we confirmed with side-by-side analyses. Our data revealed for the first time that flavivirus NS5 binds HSP90 to mediate broad STAT inhibition, which extends upon descriptive reports from other groups that identified JEV, DENV, and ZIKV NS5 interaction with HSP90, but did not define the relevance of this interaction [39][40][41]. Several DENV proteins have also been shown to bind HSP90 [37].…”

Detection of Nuclear Protein Profile Changes by Human Metapneumovirus M2-2 Protein Using Quantitative Differential Proteomics

“…Histone proteins are key components of chromatin, acting as spools around which DNA winds, and play a significant role in gene regulation. Additionally, their function in viral infections is being increasingly acknowledged [ 51 , 52 , 53 , 54 ]. Currently, there are five major families of histones: H1/H5, H2A, H2B, H3, and H4.…”

The Major Capsid Protein, VP1, of the Mouse Polyomavirus Stimulates the Activity of Tubulin Acetyltransferase 1 by Microtubule Stabilization

“…It was demonstrated that the polymerase of the Japanese encephalitis virus needs to be stabilized by Hsp90. The inhibition of HDAC6 leads to Hsp90 hyperacetylation, polymerase destabilization, and decreases viral replication [65]. Chaperones are involved in the MPyV life cycle, so their activity maintenance by HDAC6 may be important for viral propagation.…”