The Ig Domain Protein CD9P-1 Down-regulates CD81 Ability to Support Plasmodium yoelii Infection

Abstract

Invasion of hepatocytes by Plasmodium sporozoites is a prerequisite for establishment of a malaria natural infection. The molecular mechanisms underlying sporozoite invasion are largely unknown. We have previously reported that CD81 is required on hepatocytes for infection by Plasmodium falciparum and Plasmodium yoelii sporozoites. CD81 belongs to the tetraspanin superfamily of transmembrane proteins. By interacting with each other and with other transmembrane proteins, tetraspanins may play a role in the lateral organization of membrane proteins. In this study, we investigated the role of the two major molecular partners of CD81 in hepatocytic cells, CD9P-1/EWI-F and EWI-2, two transmembrane proteins belonging to a novel subfamily of immunoglobulin proteins. We show that CD9P-1 silencing increases the host cell susceptibility to P. yoelii sporozoite infection, whereas EWI-2 knock-down has no effect. Conversely, overexpression of CD9P-1 but not EWI-2 partially inhibits infection. Using CD81 and CD9P-1 chimeric molecules, we demonstrate the role of transmembrane regions in CD81-CD9P-1 interactions. Importantly, a CD9P-1 chimera that no longer associates with CD81 does not affect infection. Based on these data, we conclude that CD9P-1 acts as a negative regulator of P. yoelii infection by interacting with CD81 and regulating its function.Malaria remains the most important parasitic human disease, responsible for nearly one million deaths each year (1). Plasmodium natural infection is initiated by the inoculation of sporozoites in the host by a female Anopheles mosquito.Within the first hours of infection the motile sporozoites reach the liver and invade hepatocytes, where they further differentiate into a replicative exo-erythrocytic form (EEF) 5 that will ultimately give rise to thousands of merozoites that initiate the pathogenic erythrocytic cycle. Plasmodium sporozoites invade hepatocytes actively by forming a membrane-bound compartment called the parasitophorous vacuole (PV), where the parasite resides for further intracellular development (2, 3). The nature of the molecular interactions mediating sporozoite invasion still remains elusive. Two well-characterized sporozoite surface proteins, the circumsporozoite protein and the thrombospondin-related adhesive protein, are known to interact with the liver heparan sulfate proteoglycans (HSPGs) (2, 3). HSPGs play a role in the initial sequestration of the sporozoites in the liver sinusoids (4, 5), and activate sporozoites for productive invasion, leading to proteolytic processing of the circumsporozoite protein (6). Two sporozoite proteins, P36 and P36p/ P52, were shown to play a major role during infection of hepatocytes (7-9). Both belong to a Plasmodium-specific family characterized by the presence of domains with six conserved cysteines, but their precise function during sporozoite invasion and/or maintenance of the PV early after invasion remains unknown.To date, the only host molecule clearly identified as being essential for sporozoite invasion is CD81. ...

Proteomics of HCV virions reveals an essential role for the nucleoporin Nup98 in virus morphogenesis

“…S4A) but also against other pathogens. PTGFRN (also called CD9P-1 or EWI-F) inhibits the ability of hepatocytes to support Plasmodium sporozoite infection by interacting with CD81 (14). Interestingly, PTGFRN was shown to be up-regulated in HCV-infected cells (13).…”

Normal muscle regeneration requires tight control of muscle cell fusion by tetraspanins CD9 and CD81

“…The anti-mouse CD9 (4.1F12) and CD81 monoclonal antibodies (MT81) have been described elsewhere 50 . Two antibodies for CD9P-1 were used: monoclonal antibody 8G1 described in 25 for immunoprecipitation and a sheep polyclonal anti-mouse FPRP from R&D Systems for western blot, FACS analysis and immunohistochemistry (IHC) (10 mg ml À 1 ). A goat polyclonal anti-mEWI-2 (10 mg ml À 1 ) was purchased from R&D Systems and an anti-mouse a5 integrin mAb MFR5 (10 mg ml FACS analysis.…”

“…Very few studies have addressed the function of these two molecules: EWI-2 expression was shown to modulate integrin functions 23,24 , and the ability of CD81 to support Plasmodium and hepatitis C virus infection of hepatocytic cells is reduced by CD9P-1 (ref. 25) and a truncated form of EWI-2 (ref. 26), respectively.…”

Tetraspanins at a glance

“…The interaction of CD81 with claudin-1, another entry factor, might play a key role in the infection by HCV (Harris et al, 2008). Interestingly, the ability of CD81 to support Plasmodium and HCV infections is negatively regulated by CD9P-1 and a cleavage fragment of EWI-2, respectively (Charrin et al, 2009b;Rocha-Perugini et al, 2008).…”