IKK epsilon kinase is crucial for viral G protein-coupled receptor tumorigenesis
G protein-coupled receptors (GPCRs) are seven-transmembrane proteins that transmit diverse extracellular signals across a membrane. Herpesvirus genomes encode multiple GPCRs implicated in viral pathogenesis. Kaposi sarcoma-associated herpesvirus GPCR (kGPCR) activates proliferative pathways and, when expressed in endothelium in mice, sufficiently induces angiogenic tumor resembling human Kaposi's sarcoma. IKKε, an IκB kinase (IKK)-related kinase, is implicated in inflammation-driven tumorigenesis. We report here that IKKε is critically required for kGPCR tumorigenesis and links kGPCR to NF-κB activation. Using kGPCR-induced tumor models, we found that IKKε expression was drastically up-regulated in Kaposi sarcoma-like lesions and that loss of IKKε abolished tumor formation. Moreover, kGPCR interacted with and activated IKKε. Activated IKKε promoted NF-κB subunit RelA (also known as p65) phosphorylation, which correlated with NF-κB activation and inflammatory cytokine expression. The robust expression of IKKε and phosphorylated RelA was observed in human Kaposi sarcoma. Finally, a kinase-defective mutant of IKKε effectively abrogated NF-κB activation and tumorigenesis induced by kGPCR. Collectively, our findings uncover a critical IKKε in promoting NF-κB activation and tumorigenesis induced by a viral GPCR.
Available from: jvi.asm.org
[Show abstract] [Hide abstract]
ABSTRACT: All herpesviruses share a remarkable propensity to establish latent infection. Human Kaposi's sarcoma-associated herpesvirus
(KSHV) effectively enters latency after de novo infection, suggesting that KSHV has evolved with strategies to facilitate latent infection. NF-κB activation is imperative
for latent infection of gammaherpesviruses. However, how NF-κB is activated during de novo herpesvirus infection is not fully understood. Here, we report that KSHV infection activates the inhibitor of κB kinase β
(IKKβ) and the IKK-related kinase epsilon (IKKε) to enable host NF-κB activation and KSHV latent infection. Specifically,
KSHV infection activated IKKβ and IKKε that were crucial for latent infection. Knockdown of IKKβ and IKKε caused aberrant
lytic gene expression and impaired KSHV latent infection. Biochemical and genetic experiments identified RelA as a key player
downstream of IKKβ and IKKε. Remarkably, IKKβ and IKKε were essential for phosphorylation of S536 and S468 of RelA, respectively. Phosphorylation of RelA S536 was required for phosphorylation of S468, which activated NF-κB and promoted KSHV latent infection. Expression of the phosphorylation-resistant RelA S536A increased KSHV lytic gene expression and impaired latent infection. Our findings uncover a scheme wherein NF-κB activation
is coordinated by IKKβ and IKKε, which sequentially phosphorylate RelA in a site-specific manner to enable latent infection
after KSHV de novo infection.
Journal of Virology 10/2013; 88(1). DOI:10.1128/JVI.01716-13 · 4.44 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: In this sequel article on Amlexanox I investigate the multi-tasking potential for this drug, a recently discovered readthrough agent with immune-modulatory properties, for management of a wide range of human diseases including ageing modeled as a disease. The focus is not only on correction or disease rescue, but also on early prevention through use of Amlexanox prophylaxis. The concept of readthrough of nonsense mutations is further explored and correlation of nonsense mutation with cancer spread and stage is examined. Many other prevalent disease processes are examined in the light of nonsense-mediated causation, for example, intellectual disability and ageing. A primary aim of my current investigation is to show that both communicable diseases (related to infections from viral and bacterial agents) as well as non-communicable diseases (such as cancer, diabetes and inherited malformations/dysfunctions) may all form suited targets for Amlexanox therapy. As such, ex vivo and in vitro studies and animal models are discussed with the overall theme being to translate positive findings into the clinic. Clearly, this would have a major benefit with management in many inherited disease states and for infectious diseases. Further, a major benefit can be predicted for acquired chronic conditions too. The long understood property of Amlexanox in immune-modulation is exploited in this analysis. By acting through part-control of the NF-kappaB transcriptional factor-inflammatory axis, Amlexanox is capable of modulating the pathophysiology of such processes as cancer, vascular disease and diabetes with obesity. Moderating the response to pathogen challenge is a focus of attention in this present investigation. This is important insofar as Amlexanox mediates inflammatory-axis regulation and host-pathogen interactions, strongly suggesting that it must be explored in this context. As a result of this, interference with this arm of the innate immune system may well have consequences in terms of exposure to certain infectious agents. Detailed animal model systems as well as formal clinical trials are definitely called for to clarify the longer-term adverse reaction this may produce in the face of pathogen exposure. Amlexanox has been clinically approved for many years and, along with other drugs with similar immune-modulating capacity, appears satisfactory for long-term usage. Therefore, in practical terms, pathogen challenge in such a context may not pose significant threat. Overall, clinical trials are universally called for in order to ascertain the full potential for this old drug presenting with some exciting 'new tricks'. I aim to be able to purposefully 'repurpose' Amlexanox and add this drug into the 'Doctor's bag' as a highly valuable medical adjunct to manage a wide plethora of medical conditions.
Journal of Bioanalysis and Biomedicine 12/2013; 05(05). DOI:10.4172/1948-593X.1000095
Available from: Masahiko Ajiro
[Show abstract] [Hide abstract]
ABSTRACT: Approximately 10.8% of human cancers are associated with infection by an oncogenic virus. These viruses include human papillomavirus (HPV), Epstein–Barr virus (EBV), Merkel cell polyomavirus (MCV), human T-cell leukemia virus 1 (HTLV-1), Kaposi's sarcoma-associated herpesvirus (KSHV), hepatitis C virus (HCV) and hepatitis B virus (HBV). These oncogenic viruses, with the exception of HCV, require the host RNA splicing machinery in order to exercise their oncogenic activities, a strategy that allows the viruses to efficiently export and stabilize viral RNA and to produce spliced RNA isoforms from a bicistronic or polycistronic RNA transcript for efficient protein translation. Infection with a tumor virus affects the expression of host genes, including host RNA splicing factors, which play a key role in regulating viral RNA splicing of oncogene transcripts. A current prospective focus is to explore how alternative RNA splicing and the expression of viral oncogenes take place in a cell- or tissue-specific manner in virus-induced human carcinogenesis.
Emerging Microbes and Infections 09/2014; 3(9). DOI:10.1038/emi.2014.62 · 2.26 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.