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Transmembrane regions of bovine herpesvirus 1-encoded UL49.5 and glycoprotein M regulate complex maturation and ER-Golgi trafficking


Graul, Małgorzata; Kisielnicka, Edyta; Rychłowski, Michał; Verweij, Marieke C; Tobler, Kurt; Ackermann, Mathias; Wiertz, Emmanuel J H J; Bieńkowska-Szewczyk, Krystyna; Lipińska, Andrea D (2019). Transmembrane regions of bovine herpesvirus 1-encoded UL49.5 and glycoprotein M regulate complex maturation and ER-Golgi trafficking. Journal of General Virology, 100(3):497-510.

Abstract

Bovine herpesvirus 1 (BoHV-1)-encoded UL49.5 (a homologue of herpesvirus glycoprotein N) can combine different functions, regulated by complex formation with viral glycoprotein M (gM). We aimed to identify the mechanisms governing the immunomodulatory activity of BoHV-1 UL49.5. In this study, we addressed the impact of gM/UL49.5-specific regions on heterodimer formation, folding and trafficking from the endoplasmic reticulum (ER) to the trans-Golgi network (TGN) - events previously found to be responsible for abrogation of the UL49.5-mediated inhibition of the transporter associated with antigen processing (TAP). We first established, using viral mutants, that no other viral protein could efficiently compensate for the chaperone function of UL49.5 within the complex. The cytoplasmic tail of gM, containing putative trafficking signals, was dispensable either for ER retention of gM or for the release of the complex. We constructed cell lines with stable co-expression of BoHV-1 gM with chimeric UL49.5 variants, composed of the BoHV-1 N-terminal domain fused to the transmembrane region (TM) from UL49.5 of varicella-zoster virus or TM and the cytoplasmic tail of influenza virus haemagglutinin. Those membrane-anchored N-terminal domains of UL49.5 were sufficient to form a complex, yet gM/UL49.5 folding and ER-TGN trafficking could be affected by the UL49.5 TM sequence. Finally, we found that leucine substitutions in putative glycine zipper motifs within TM helices of gM resulted in strong reduction of complex formation and decreased ability of gM to interfere with UL49.5-mediated major histocompatibility class I downregulation. These findings highlight the importance of gM/UL49.5 transmembrane domains for the biology of this conserved herpesvirus protein complex.

Abstract

Bovine herpesvirus 1 (BoHV-1)-encoded UL49.5 (a homologue of herpesvirus glycoprotein N) can combine different functions, regulated by complex formation with viral glycoprotein M (gM). We aimed to identify the mechanisms governing the immunomodulatory activity of BoHV-1 UL49.5. In this study, we addressed the impact of gM/UL49.5-specific regions on heterodimer formation, folding and trafficking from the endoplasmic reticulum (ER) to the trans-Golgi network (TGN) - events previously found to be responsible for abrogation of the UL49.5-mediated inhibition of the transporter associated with antigen processing (TAP). We first established, using viral mutants, that no other viral protein could efficiently compensate for the chaperone function of UL49.5 within the complex. The cytoplasmic tail of gM, containing putative trafficking signals, was dispensable either for ER retention of gM or for the release of the complex. We constructed cell lines with stable co-expression of BoHV-1 gM with chimeric UL49.5 variants, composed of the BoHV-1 N-terminal domain fused to the transmembrane region (TM) from UL49.5 of varicella-zoster virus or TM and the cytoplasmic tail of influenza virus haemagglutinin. Those membrane-anchored N-terminal domains of UL49.5 were sufficient to form a complex, yet gM/UL49.5 folding and ER-TGN trafficking could be affected by the UL49.5 TM sequence. Finally, we found that leucine substitutions in putative glycine zipper motifs within TM helices of gM resulted in strong reduction of complex formation and decreased ability of gM to interfere with UL49.5-mediated major histocompatibility class I downregulation. These findings highlight the importance of gM/UL49.5 transmembrane domains for the biology of this conserved herpesvirus protein complex.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Virology
Dewey Decimal Classification:570 Life sciences; biology
Scopus Subject Areas:Life Sciences > Virology
Uncontrolled Keywords:UL49.5/glycoprotein M complex; alphaherpesviruses; bovine herpesvirus 1; cytoplasmic domain; glycine zipper; transmembrane region
Language:English
Date:March 2019
Deposited On:07 Jan 2020 15:34
Last Modified:29 Jul 2020 12:24
Publisher:Society for General Microbiology
ISSN:0022-1317
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1099/jgv.0.001224
PubMed ID:30694168

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