title: Integrity of the early secretory pathway promotes, but is not required for, severe acute respiratory syndrome coronavirus RNA synthesis and virus-induced remodeling of endoplasmic reticulum membranes.
abstract: To accommodate its RNA synthesis in the infected cell, severe acute respiratory syndrome coronavirus (SARS-CoV) induces a cytoplasmic reticulovesicular network (RVN) that is derived from endoplasmic reticulum (ER) membranes. We set out to investigate how the early secretory pathway interacts with the RVN and the viral replication/transcription complex (RTC) that is anchored to it. When the secretory pathway was disrupted by brefeldin A (BFA) treatment at the start of infection, RVN formation and viral RTC activity were not blocked and continued up to 11 h postinfection, although RNA synthesis was reduced by ca. 80%. In vitro RTC assays, using membrane fractions from infected cells, demonstrated that BFA does not directly interfere with the activity of the viral RNA-synthesizing enzymes. Confocal microscopy studies showed that early secretory pathway components are not associated with SARS-CoV-induced replication sites, although our studies revealed that infection induces a remarkable redistribution of the translocon subunit Sec61alpha. Ultrastructural studies, including electron tomography, revealed that the formation of the RVN and all its previously documented features can occur in the presence of BFA, despite differences in the volume and morphology of the network. We therefore conclude that early secretory pathway proteins do not play a direct role in RVN morphogenesis or the functionality of the SARS-CoV RTC. The BFA-induced disruption of ER integrity and functionality probably affects the overall quality of the membrane scaffold that is needed to support the viral RTC and/or the availability of specific host factors, which in turn compromises viral RNA synthesis.
authors.affiliation: Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, LUMC E4-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Kèvin
authors.initials: K
authors.lastname: Knoops
authors.forename: Cindy
authors.initials: C
authors.lastname: Swett-Tapia
authors.forename: Sjoerd H E
authors.initials: SH
authors.lastname: van den Worm
authors.forename: Aartjan J W
authors.initials: AJ
authors.lastname: Te Velthuis
authors.forename: Abraham J
authors.initials: AJ
authors.lastname: Koster
authors.forename: A Mieke
authors.initials: AM
authors.lastname: Mommaas
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Snijder
authors.forename: Marjolein
authors.initials: M
authors.lastname: Kikkert
mesh_terms: D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002522:Chlorocebus aethiops; D055032:Electron Microscope Tomography; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology; D054884:Host-Pathogen Interactions; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology; D018613:Microscopy, Confocal; D011506:Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D014709:Vero Cells / Q000648:ultrastructure / Q000821:virology; D014764:Viral Proteins / Q000378:metabolism; D014779:Virus Replication
chemical_list: D011506:Proteins; D012367:RNA, Viral; D014764:Viral Proteins; D020126:Brefeldin A