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Virion Assembly and Release

Summary

Organism

Homo sapiens (human)

Reactome

R-HSA-9694322

PubChem

R-HSA-9694322

Description

This COVID-19 pathway has been created by a combination of computational inference from SARS-CoV-1 data (https://reactome.org/documentation/inferred-events) and manual curation, as described in the summation for the overall SARS-CoV-2 infection pathway.

The structures of complete SARS-CoV-2 virions, as well as their assembly stages, have been elucidated in great detail by cryo-electron microscopy methods. In particular, the Spike trimer is localized to ERGIC or Golgi compartments upon coexpression of E or M, which prevents syncytia formation (Boson et al, 2020). It is then transported via small transport vesicles to assembly sites (Klein et al, 2020; Mendonça et al, 2021; reviewed by Hardenbrook and Zhang, 2021). Based on work done in related coronaviruses, viral assembly is expected to occur at the ERGIC membrane (reviewed in Masters, 2006; Fehr and Perlman, 2015; Fung and Liu, 2019). Membrane protein components of the virus concentrate at the ERGIC membrane but are also found throughout the secretory system including at the plasma membrane. Accumulation at the site of viral assembly has been shown to depend on interaction between retrieval signals in the cytoplasmic tails of viral proteins and host factors such as the COPI coat, and likely involves repeated rounds of anterograde and retrograde traffic (McBride et al, 2007; Ujike et al, 2016; Tan et al, 2004; Tan et al, 2005; reviewed in McBride and Fielding, 2012; Chang et al, 2014).
Viral assembly is initiated by homotypic interactions of M protein (Tseng et al, 2010; Siu et al, 2008). This forms an M-lattice that contributes to the induction of membrane curvature and additionally acts as a scaffold for the recruitment of the other structural components of the virus (Voss et al, 2009). M protein makes interactions with each of the main components of the mature virus, including E, S and N (He et al, 2004; Luo et al, 2006; Siu et al, 2008; reviewed in Masters, 2006). Electron micrographic studies suggest the final size of the mature virus is ~100 nm. The ribonuclear particle is predominantly helical and is packaged with an outer diamter of ~ 16 nm (Neuman et al, 2006; Neuman et al, 2011; reviewed in Chang et al, 2014). These physical constraints suggest a final stoichiometry in the mature virion of 75 S trimers:1200 M proteins:300 N:1 RNA genome (Neuman et al, 2011; reviewed in Chang et al, 2014). Minor amounts of other viral proteins, including proteins E, 3a and 7a may also be components of the mature virus, although their functions are not well established (reviewed in Schoeman and Fielding, 2019; Liu et al, 2014).

Click on a node on the pathway to see its details. Glycoproteins are marked with a glycoprotein icon in their name.

SPV: a JavaScript Signaling Pathway Visualizer, Bioinformatics, 2018

Displaying **all 3** entries
UniProt ID	Protein Name	Gene Symbol	Pathway Viewer
P0DTC2	Spike glycoprotein	2 S	view
P0DTC3	ORF3a protein	3a	view
P0DTC5	Membrane protein	M	view

Displaying 1 entry
GlyCosmos Lectin	UniProt ID	Lectin Name	Pathway Viewer
GL_002337	P0DTC2	Spike glycoprotein	view

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