Defining Hsp70 Subnetworks in Dengue Virus Replication Reveals Key Vulnerability in Flavivirus Infection

Abstract

Summary Viral protein homeostasis depends entirely on the machinery of the infected cell. Accordingly, viruses can illuminate the interplay between cellular proteostasis components and their distinct substrates. Here we define how the Hsp70 chaperone network mediates the dengue virus life cycle. Cytosolic Hsp70 isoforms are required at distinct steps of the viral cycle, including entry, RNA replication and virion biogenesis. Hsp70 function at each step is specified by nine distinct DNAJ cofactors. Of these, DnaJB11 relocalizes to virus-induced replication complexes to promote RNA synthesis, while DnaJB6 associates with capsid protein and facilitates virion biogenesis. Importantly, an allosteric Hsp70 inhibitor, JG40, potently blocks infection of different dengue serotypes in human primary blood cells without eliciting viral resistance or exerting toxicity to the host cells. JG40 also blocks replication of other medically-important flaviviruses including yellow fever, West Nile and Japanese encephalitis viruses. Thus, targeting host Hsp70 subnetworks provides a path for broad-spectrum antivirals.

Unrestrained AMPylation targets cytosolic chaperones and activates the heat shock response

“…The concept of modulating the HSF1-mediated HSR has been explored as a potential route for the treatment of neurodegenerative diseases, viral infections, and diverse cancers (29,30). Although the detailed mechanisms of how protein aggregation-associated neurodegenerative diseases develop remain unclear, there is a large body of evidence suggesting a strong tie to the Hsp40/Hsp70/Hsp90 protein-folding machinery as well as the HSR and UPR ER (31).…”

Chaperone-Assisted Protein Folding Is Critical for Yellow Fever Virus NS3/4A Cleavage and Replication

“…Recent work studying the role of chaperones in DENV infection revealed a role for Hsp70 chaperone activity at multiple life cycle steps. Moreover, the chaperone process was found to involve distinct DNAJ cochaperone family members to facilitate viral entry, RNA replication, and virion production (6). DNAJC14 is an Hsp40 cochaperone that assists a wide range of cellular folding processes mediated by Hsp70.…”

“…Since chaperones are upregulated during cellular stress, it is problematic to discern if chaperones are induced by and required for viral replication or are a result of the stress response caused by viral infection. Only recently, Taguwa and colleagues (6) have elucidated the role of the Hsp70 machinery in multiple steps of the dengue virus (DENV) life cycle. Interestingly, the specific activity of Hsp70 in each of these steps is determined by different DNAJ proteins (6).…”

“…Only recently, Taguwa and colleagues (6) have elucidated the role of the Hsp70 machinery in multiple steps of the dengue virus (DENV) life cycle. Interestingly, the specific activity of Hsp70 in each of these steps is determined by different DNAJ proteins (6). In a previous study, we showed that overexpression of an Hsp40 family member, DNAJC14, conferred resistance to several members of the Flaviviridae family.…”

Novel strategies for discovering inhibitors of Dengue and Zika fever

“…The inhibition of Sec61, an ER membrane protein translocator, altered HIV, DENV and influenza proteostasis and inhibited viral replication [8]. Additionally, a drug inhibitor of Hsp70 chaperone network, JG40, potently blocked DENV infections in human primary blood cells without resulting in viral resistance or toxicity [9].…”