Biochemical and structural studies of target lectin SapL1 from the emerging opportunistic microfungus Scedosporium apiospermum

Dania Martínez-Alarcón,Jean-Philippe Bouchara,Annabelle Varrot,Viviane Balloy,Roland J Pieters

doi:10.1038/s41598-021-95008-4

Abstract

Scedosporium apiospermum is an emerging opportunistic fungal pathogen responsible for life-threatening infections in humans. Host–pathogen interactions often implicate lectins that have become therapeutic targets for the development of carbohydrate mimics for antiadhesive therapy. Here, we present the first report on the identification and characterization of a lectin from S. apiospermum named SapL1. SapL1 was found using bioinformatics as a homolog to the conidial surface lectin FleA from Aspergillus fumigatus known to play a role in the adhesion to host glycoconjugates present in human lung epithelium. In our strategy to obtain recombinant SapL1, we discovered the importance of osmolytes to achieve its expression in soluble form in bacteria. Analysis of glycan arrays indicates specificity for fucosylated oligosaccharides as expected. Submicromolar affinity was measured for fucose using isothermal titration calorimetry. We solved SapL1 crystal structure in complex with α-methyl-L-fucoside and analyzed its structural basis for fucose binding. We finally demonstrated that SapL1 binds to bronchial epithelial cells in a fucose-dependent manner. The information gathered here will contribute to the design and development of glycodrugs targeting SapL1.

Highlights

Scedosporium apiospermum is an emerging opportunistic fungal pathogen responsible for lifethreatening infections in humans
We decided to focus on the identified carbohydrate recognition domain (CRD) of SapL1 starting from methionine-75 (Fig. S1)
SapL1 is homologous to the conidial surface lectin FleA from A. fumigatus known to be involved in adhesion to the host glycoconjugates present in bronchial mucus and human lung e pithelium[28]

Summary

Introduction

Scedosporium apiospermum is an emerging opportunistic fungal pathogen responsible for lifethreatening infections in humans. Conidial adhesion is mediated by cell surface molecules (CSM), including carbohydrates where some of the most important described to date for Scedosporium species include peptidorhamnomannans (PRMs)[15,16,17], α-glucans18, melanin[19], ceramide monohexosides[17,20], N-acetylD-glucosamine-containing molecules[21] and mannose/glucose-rich g lycoconjugates[17]. Their presence and/or abundance on the cell surface vary according to the stage of development and is of great relevance to understand fungal pathobiology[17]. This may allow its implementation as a prophylactic therapy for immunocompromised p atients[14]

Methods

Results

Conclusion