A Functional Genomics Approach to Henipavirus Research: The Role of Nuclear Proteins, MicroRNAs and Immune Regulators in Infection and Disease

Pathogenicity and virulence of henipaviruses

Paramyxoviruses are a family of single-stranded negative-sense RNA viruses, many of which are responsible for a range of respiratory and neurological diseases in humans and animals. Among the most notable are the henipaviruses, which include the deadly Nipah (NiV) and Hendra (HeV) viruses, the causative agents of outbreaks of severe disease and high case fatality rates in humans and animals. NiV and HeV are maintained in fruit bat reservoirs primarily in the family Pteropus and spillover into humans directly or by an intermediate amplifying host such as swine or horses. Recently, non-chiropteran associated Langya (LayV), Gamak (GAKV), and Mojiang (MojV) viruses have been discovered with confirmed or suspected ability to cause disease in humans or animals. These viruses are less genetically related to HeV and NiV yet share many features with their better-known counterparts. Recent advances in surveillance of wild animal reservoir viruses have revealed a high number of henipaviral genome sequences distributed across most continents, and mammalian orders previously unknown to harbour henipaviruses. In this review, we summarize the current knowledge on the range of pathogenesis observed for the henipaviruses as well as their replication cycle, epidemiology, genomics, and host responses. We focus on the most pathogenic viruses, including NiV, HeV, LayV, and GAKV, as well as the experimentally non-pathogenic CedV. We also highlight the emerging threats posed by these and potentially other closely related viruses.

Henipaviruses: an expanding global public health concern?

Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic zoonotic viruses of the genus Henipavirus, family Paramyxoviridae that cause severe disease outbreaks in humans and also can infect and cause lethal disease across a broad range of mammalian species. Another related Henipavirus has been very recently identified in China in febrile patients with pneumonia, the Langya virus (LayV) of probable animal origin in shrews. NiV and HeV were first identified as the causative agents of severe respiratory and encephalitic disease in the 1990s across Australia and Southern Asia with mortality rates reaching up to 90%. They are responsible for rare and sporadic outbreaks with no approved treatment modalities. NiV and HeV have wide cellular tropism that contributes to their high pathogenicity. From their natural hosts bats, different scenarios propitiate their spillover to pigs, horses, and humans. Henipavirus-associated respiratory disease arises from vasculitis and respiratory epithelial cell infection while the neuropathogenesis of Henipavirus infection is still not completely understood but appears to arise from dual mechanisms of vascular disease and direct parenchymal brain infection. This brief review offers an overview of direct and indirect mechanisms of HeV and NiV pathogenicity and their interaction with the human immune system, as well as the main viral strategies to subvert such responses.

miR-125a restrains cell migration and invasion by targeting STAT3 in gastric cancer cells

BACKGROUND

Recently, many microRNAs have been found to be involved in the cancer progression including miR-125a. However, the underlying mechanisms of miR-125a in gastric cancer (GC) remain to be completely elucidated.

OBJECTIVE

The study was to investigate the functional role of miR-125a and the expression relevance of signal transducer and activator of transcription 3 (STAT3) and hyaluronan synthase 1 (HAS1).

METHOD

CCK-8 assay, scratch wound healing and transwell assay were conducted to identify the functional role of miR-125a in GC. In addition, using bioinformatics analysis, the target regulation relationship was found in STAT3 and miR-125a. To confirm the relationship, luciferase reporter assay was performed. More importantly, quantitative polymerase chain reaction and western blot assay were carried out to determine the association among miR-125a, STAT3 and HAS1 in GC cells.

RESULTS

Overexpressed miR-125a inhibited the migration and invasion of GC cells through scratch wound healing and transwell assay, and its knockdown displayed adverse effects, but the viability of GC cells did not show significant difference using CCK-8 assay. In addition, we identified that the knockdown of STAT3 or HAS1 remarkably suppressed the migration and invasion abilities of GC cells. Using bioinformatics analysis, miRTar, in particular, indicated that the 3'-untranslated region of STAT3 binds to miR-125a with a high score. Subsequently, we also verified that STAT3 was a target of miR-125a via luciferase reporter assay. Furthermore, we found that upregulated miR-125a expression could conspicuously constrain STAT3 expression at both protein and mRNA levels in MKN45 and NCI-N87 cells using quantitative polymerase chain reaction and Western blot assay, but no significant difference had been found in SGC 7901 cells. To further identify the regulatory relationship between miR-125a and STAT3, downregulation of miR-125a in MKN45 and NCI-N87 cells was carried out, which showed that the protein and mRNA expression levels of STAT3 were declined in two cell lines. Finally, we observed that upregulated miR-125a could lead to the decrease of HAS1 at protein and mRNA levels, whereas its knockdown revealed opposite effects. Meanwhile, we noticed that overexpression of STAT3 could induce the escalation of HAS1 at protein and mRNA expression levels and its knockdown exhibited the adverse outcomes.

CONCLUSION

These findings indicated that miR-125a may control the HAS1 expression in GC progression by targeting STAT3, which is likely to facilitate a better understanding of the regulation mechanisms of miR-125a in GC.

Therapeutic potential of targeting the Eph/ephrin signaling complex

The Eph-ephrin signaling pathway mediates developmental processes and the proper functioning of the adult human body. This distinctive bidirectional signaling pathway includes a canonical downstream signal cascade inside the Eph-bearing cells, as well as a reverse signaling in the ephrin-bearing cells. The signaling is terminated by ADAM metalloproteinase cleavage, internalization, and degradation of the Eph/ephrin complexes. Consequently, the Eph-ephrin-ADAM signaling cascade has emerged as a key target with immense therapeutic potential particularly in the context of cancer. An interesting twist was brought forth by the emergence of ephrins as the entry receptors for the pathological Henipaviruses, which has spurred new studies to target the viral entry. The availability of high-resolution structures of the multi-modular Eph receptors in complexes with ephrins and other binding partners, such as peptides, small molecule inhibitors and antibodies, offers a wealth of information for the structure-guided development of therapeutic intervention. Furthermore, genomic data mining of Eph mutants involved in cancer provides information for targeted drug development. In this review we summarize the distinct avenues for targeting the Eph-ephrin signaling pathway, including its termination by ADAM proteinases. We highlight the latest developments in Eph-related pharmacology in the context of Eph-ephrin-ADAM-based antibodies and small molecules. Finally, the future prospects of genomics- and proteomics-based medicine are discussed.