H-IPSE Is a Pathogen-Secreted Host Nucleus-Infiltrating Protein (Infiltrin) Expressed Exclusively by the Schistosoma haematobium Egg Stage.

Luke F Pennington,Evaristus C Mbanefo,Michael H Hsieh,David M Heery,Abdulaziz Alouffi,Debalina Ray,Theodore S Jardetzky,Franco H Falcone,Judith A Appleton

doi:10.1128/iai.00301-17

Abstract

ABSTRACTUrogenital schistosomiasis, caused by the parasitic trematode Schistosoma haematobium, affects over 112 million people worldwide. As with Schistosoma mansoni infections, the pathology of urogenital schistosomiasis is related mainly to the egg stage, which induces granulomatous inflammation of affected tissues. Schistosoma eggs and their secretions have been studied extensively for the related organism S. mansoni, which is more amenable to laboratory studies. Indeed, we have shown that IPSE/alpha-1 (here M-IPSE), a major protein secreted from S. mansoni eggs, can infiltrate host cells. Although the function of M-IPSE is unknown, its ability to translocate to the nuclei of host cells and bind DNA suggests a possible role in immune modulation of host cell tissues. Whether IPSE homologs are expressed in other schistosome species has not been investigated. Here, we describe the cloning of two paralog genes, H03-IPSE and H06-IPSE, which are orthologs of M-IPSE, from egg cDNA of S. haematobium. Using PCR and immunodetection, we confirmed that the expression of these genes is restricted to the egg stage and female adult worms, while the H-IPSE protein is detectable only in mature eggs and not adults. We show that both H03-IPSE and H06-IPSE proteins can infiltrate HTB-9 bladder cells when added exogenously to culture medium. Monopartite C-terminal nuclear localization sequence (NLS) motifs conserved in H03-IPSE, SKRRRKY, and H06-IPSE SKRGRKY, are responsible for targeting the proteins to the nucleus of HTB-9 cells, as demonstrated by site-directed mutagenesis and green fluorescent protein (GFP) tagging. Thus, S. haematobium eggs express IPSE homologs that appear to perform similar functions in infiltrating host cells.

Highlights

Stanford University School of Medicine, Stanford, California, USAa; School of Pharmacy, Division of Molecular Therapeutics and Formulation, University of Nottingham, Nottingham, United Kingdomb; Biomedical Research Institute, Rockville, Maryland, USAc; Department of Pathology, University of California, San Francisco, California, USAd; School of Pharmacy, Division of Biomolecular Science and Medicinal Chemistry, University of Nottingham, Nottingham, United Kingdome; Department of Urology, The George Washington University, Washington, DC, USAf
In order to reach the aquatic environment, the eggs deposited by adult female worms in the blood vessels of their mammalian host have to cross several layers of host tissue before they can reach the lumen of the gut or, in the case of Schistosoma haematobium, the bladder
14 IPSE transcript sequences were obtained, and 8 Sanger sequencing runs contained data sufficient for unambiguous base calling throughout the open reading frames (ORFs)

Summary

Introduction

Using PCR and immunodetection, we confirmed that the expression of these genes is restricted to the egg stage and female adult worms, while the H-IPSE protein is detectable only in mature eggs and not adults We show that both H03-IPSE and H06-IPSE proteins can infiltrate HTB-9 bladder cells when added exogenously to culture medium. In order to reach the aquatic environment, the eggs deposited by adult female worms in the blood vessels of their mammalian host have to cross several layers of host tissue before they can reach the lumen of the gut or, in the case of Schistosoma haematobium, the bladder. H-IPSE shares an important biological activity described for M-IPSE: the ability to be taken up by and translocate to the nucleus of host cells

Methods

Results

Conclusion