Virus Research 227 (2017) 41–48 Contents lists available at ScienceDirect Virus Research j ourna l h o mepa ge: www.elsevier.com/locate/virusres C-terminal domain on the outer surface of the Macrobrachium rosenbergii nodavirus capsid is required for Sf9 cell binding and internalization Monsicha Somrit a,1 , Atthaboon Watthammawut a,e,1 , Charoonroj Chotwiwatthanakun c,d , Puey Ounjai b,f , Wanida Suntimanawong c , Wattana Weerachatyanukul (Assoc. Prof.) a,∗ a Department of Anatomy, Faculty of Science, Mahidol University, Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand b Department of Biology, Faculty of Science, Mahidol University, Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand c Center of Excellence for Shrimp Molecular Biology and Biotechnology, Faculty of Science, Mahidol University, Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand d Nakhonsawan campus, Mahidol University, Nakhonsawan 60130, Thailand e Department of Anatomy, Faculty of Medicine, Srinakharinwirot University, Bangkok, 10110, Thailand f Center of Excellence on Environmental Health and Toxicology, Office of Higher Education Commission, Ministry of Education, Bangkok, 10400, Thailand a r t i c l e i n f o Article history: Received 8 August 2016 Received in revised form 26 September 2016 Accepted 26 September 2016 Available online 28 September 2016 Keywords: Shrimp Nodavirus Virus-host interaction Internalization VLP a b s t r a c t We have shown that Macrobrachium rosenbergii nodavirus (MrNV) was able to infect Sf9 cells and that MrNV virus-like particles (MrNV-VLPs) were capable nanocontainers for delivering nucleic acid-based materials. Here, we demonstrated that chymotryptic removal of a C-terminal peptide and its truncated variant (F344-MrNV-VLPs) exhibited a drastically reduced ability to interact and internalize into Sf9 cells. Electron microscopic observations revealed that the loss of C-terminal domain either from enzyme hydrolysis or genetic truncation did not affect the generated MrNV-VLPs’ icosahedral conformation, but did drastically affect the VLPs’ internalization ability into Sf9 cells. Homology-based modelling of the MrNV capsid with other icosahedral capsid models revealed that this chymotrypsin-sensitive C-terminal domain was not only exposed on the capsid surface, but also constituted the core of the viral capsid protrusion. These results therefore suggest the importance of the C-terminal domain as a structure for targeted cell interaction which is presumably localized at the protruding domain. This work thus provided the functional insights into the role of the MrNV C-terminal domain in viral entry into Sf9 cells and lead to the development of strategies in combatting MrNV infection in susceptible cells. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Macrobrachium rosenbergii nodavirus (MrNV) is an etiological agent of white tail disease (WTD) that causes large-scale mortality in giant freshwater prawn aquaculture and results in substantial damage to the farming industry of this species (Owens et al., 2009; Sahul Hameed and Bonami, 2012; Wang et al., 2008; Yoganandhan et al., 2006; Zhang et al., 2014). MrNV is classified under the Nodaviridae family which is further divided into the alphanodavirus and betanodavirus genera. It infects a broad range of targets − from aquatic insects to fish (Barke et al., 2002; Bonami et al., 2005; Castri et al., 2001; Delsert et al., 1997; Odegard et al., 2010). MrNV is a ∗ Corresponding author. E-mail address: wattana.wee@mahidol.ac.th (W. Weerachatyanukul). 1 These authors contributed equally to this work. 26–27 nm, non-enveloped, icosahedral virus that houses a positive- sense single-stranded RNA (ssRNA+) genome. The MrNV capsid protein, encoding from the RNA2 genomic segment, is a single polypeptide consisting of 371 amino-acid residues with a calcu- lated molecular mass of about 41.5 kDa (Owens et al., 2009; Qian et al., 2003; Sahul Hameed and Bonami, 2012; Sahul Hameed et al., 2004; Yoganandhan et al., 2006; Zhang et al., 2014). The expres- sion of recombinant MrNV capsid protein in Escherichia coli and the self-assembly of viral capsid subunits into icosahedral virus- like particles (VLPs) have been well established (Goh et al., 2011). Recently, we utilized self-assembling recombinant MrNV-VLPs as an effective nanocontainer for delivering plasmid DNA and dsRNA into the susceptible Sf9 insect cells and shrimp tissue (Jariyapong et al., 2014). Nevertheless, the mechanisms of how the virus infects the cells, particularly, characterization of viral binding ligand and its specific host cell receptor, have yet to be elucidated. http://dx.doi.org/10.1016/j.virusres.2016.09.017 0168-1702/© 2016 Elsevier B.V. All rights reserved.