The significance of Hsp70 subnetwork for Dengue virus lifecycle

Rewiring cellular networks by members of the Flaviviridae family

Members of the Flaviviridae virus family comprise a large group of enveloped viruses with a single-strand RNA genome of positive polarity. Several genera belong to this family, including the Hepacivirus genus, of which hepatitis C virus (HCV) is the prototype member, and the Flavivirus genus, which contains both dengue virus and Zika virus. Viruses of these genera differ in many respects, such as the mode of transmission or the course of infection, which is either predominantly persistent in the case of HCV or acutely self-limiting in the case of flaviviruses. Although the fundamental replication strategy of Flaviviridae members is similar, during the past few years, important differences have been discovered, including the way in which these viruses exploit cellular resources to facilitate viral propagation. These differences might be responsible, at least in part, for the various biological properties of these viruses, thus offering the possibility to learn from comparisons. In this Review, we discuss the current understanding of how Flaviviridae viruses manipulate and usurp cellular pathways in infected cells. Specifically, we focus on comparing strategies employed by flaviviruses with those employed by hepaciviruses, and we discuss the importance of these interactions in the context of viral replication and antiviral therapies.

Heat shock protein 70 as a supplementary receptor facilitates enterovirus 71 infections in vitro

As one of the major causative agents of hand, foot and mouth disease (HFMD), enterovirus 71 (EV71) is a small, non-enveloped positive stranded RNA virus. Children suffering EV71 infection may cause severe symptoms including neurological complications, pulmonary edema and aseptic meningitis. EV71 is a neurotropic virus and it can cause the damage of nervous cells, cytokine storm and toxic substance. Identifying the factors that mediate viral binding or entry to host cells is important to uncover the mechanisms which viruses utilize to cause diseases in human body. Heat shock protein 70 (HSP70) is induced during virus infection and facilitates proper protein folding during viral propagation. The role that HSP70 plays during EV71 infection is still unclear. In this study, siRNA interference technique and transgenic technique were used to investigate the interaction between HSP70 and EV71 virus. The result demonstrated that the cell surface HSP70 is not essential for EV71 infection but helps the initial binding of virus to host cells and that multiple receptors are involved during EV71 infection. In addition, HSP70 was upregulated in human neuroblastoma cells (SK-N-SH) infected with EV71.

Fluorescent-Linked Enzyme Chemoproteomic Strategy (FLECS) for Identifying HSP70 Inhibitors

Activation of the heat shock response, and in particular upregulation of stress-inducible Hsp70, herein referred to as Hsp70i, in newly transformed cells, appears to protect against protein damaging stimuli, induction of premature oncogene-induced terminal senescence (OIS), and apoptosis, thereby enabling tumor initiation and progression to an aggressive phenotype. Expressed at very low or undetectable levels in normal tissue, the cytoprotective effects of Hsp70i appear to be mediated through its activity as a molecular chaperone allowing proper folding of mutated proteins, and by blocking cell signaling pathways that regulate OIS and apoptosis. Identification of small-molecule inhibitors selective for Hsp70i could provide new therapeutic tools for cancer treatment. However, identification of selective inhibitors of Hsp70i has proven challenging largely because of the affinity of the protein for ATP. Additionally, its chaperone functions do not lend the protein amenable to traditional enzymatic high-throughput screens. Here, we describe the use of fluorescence-linked enzyme chemoproteomic strategy (FLECS) to identify Hsp70i inhibitors. The FLECS assay is a simple binding assay that enables proteins tagged with fluorophors to be rapidly and quantitative screened against small-molecule libraries. We show several case history examples of the methodology that led to the discovery of the Fatty acid synthase inhibitor, FASNALL, the DAPK3 inhibitor HS38, and HS72, an allosteric inhibitor selective for Hsp70i.

The Pacific oyster (Crassostrea gigas) Hsp70 modulates the Ostreid herpes virus 1 infectivity

The Ostreid herpes virus type 1 (OsHV-1) is one of the most devastating pathogen in oyster cultures. Among several factors, as food limitation, oxygen depletion, salinity and temperature variations, episodes of "summer mortality" of the Pacific oyster Crassostrea gigas have also been associated with OsHV-1 infection. Mortalities of C. gigas spat and juveniles have increased significantly in Europe, and contemporary mortality records of this mollusk in México have been associated with the occurrence of OsHV-1. In the present study, the expression of the heat shock protein 70 gene from the Pacific oyster correlates with the abundance of DNA polymerase transcripts from the OsHV-1. This may suggest that the induction on the expression of the Pacific oyster hsp70 may potentially participate in the immune response against the virus. Furthermore, this study reports for the first time a TEM representative image of the OsHV-1 in aqueous solution, which possesses an icosahedral shape with a diameter of 70 nm × 100 nm. Finally, the examined sequence encoding the ORF4 of the OsHV-1 isolate from northwest Mexico showed specific sequence variations when compared with OsHV-1 isolates from distant geographical areas.