hnRNPA2B1 associated with recruitment of RNA into exosomes plays a key role in HSV-1 release from infected cells.

PMID: 

J Virol. 2020 Apr 15. Epub 2020 Apr 15. PMID: 32295924

Abstract Title: 

hnRNPA2B1 associated with recruitment of RNA into exosomes plays a key role in HSV-1 release from infected cells.

Abstract: 

hnRNPA2B1, an abundant cellular protein has been reported to recruit RNAs bearing a specific sequence (EXO motif) into exosomes. We characterized an exosome population averaging 100+/- 50 nm in diameter and containing a defined set of constitutive exosome markers. This population packages miRNAs and can be directed to block targeted gene expression in a dose dependent fashion. The objectives of these studies were to characterize its role in the recruitment of miRNA. We report 4 key findings (i) hnRNPA2B1 is not a component of exosomes produced in HEp-2 or in HEK293T cells. Hence hnRNPA2B1 carries its cargo at most to the site of exosome assembly but it is not itself incorporated into exosomes. (ii) The accumulation of exosomes produced by cells in which the gene encoding hnRNPA2B1 has been knocked out (ΔhnRNPA2B1) was reduced 3 fold. (iii) In uninfected HEp-2 cells hnRNPA2B1 is localized in the nucleus. In cells infected with herpes simplex virus 1 (HSV-1) hnRNPA2B1 was quantitatively exported to the cytoplasm, at least a fraction of hnRNPA2B1 co-localized with a Golgi marker. Lastly (iv) in ΔhnRNPA2B1 cells there was a 2 to 3-fold reduction in virus yield but a significant (>10 fold) reduction in the HSV-1 released through the apical surface into the extracellular environment. The absence of hnRNPA2B1 had no significant impact on the basolateral export of HSV-1 from infected to uninfected cells by direct cell to cell contact. The results suggest that hnRNPA2B1 plays a key role in the transport of enveloped virus from its site of assembly to the extracellular environment.In this report we show hnRNPA2B1 is not a component of exosomes produced in HEp-2 or in HEK293T cells. In HSV-1 infected cells hnRNPA2B1 was quantitatively translocated from nucleus into the cytoplasm. In infectedΔhnRNPA2B1 cells Golgi dependent transport of virus from the apical surface to the extracellular medium was significantly reduced. In essence, this report supports the hypothesis that hnRNPA2B1 plays a key role in the egress of exosomes and of HSV-1 from infected cells.

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