Assembly and disassembly of Aspergillus fumigatus conidial rodlets

Isabel Valsecchi (1, 2) , Jennifer Lai (3) , Emmanuel Stephen-Victor (4) , Ariane Pillé (2) , Audrey Beaussart (5, 6) , Victor Lo (3) , Chi L L Pham (3) , Vishukumar Aimanianda (1) , Ann H Kwan (3) , Magalie I Duchateau (7) , Quentin Giai Gianetto (8, 7) , Mariette Matondo (7) , Mélanie Lehoux (9) , Donald C Sheppard (9) , Yves Dufrêne (5) , Jagadeesh J Bayry (4) , J. Iñaki Guijarro (2) , Margaret Sunde (3) , Jean-Paul Latgé (1)

1 Aspergillus
2 Plateforme technologique de RMN biologique - Biological NMR Technological Platform
3 The University of Sydney
4 CRC (UMR_S_1138 / U1138) - Centre de Recherche des Cordeliers
5 UCL - Université Catholique de Louvain = Catholic University of Louvain
6 LIEC - Laboratoire Interdisciplinaire des Environnements Continentaux
7 Plateforme de Protéomique / Proteomics platform
8 C3BI - Centre de Bioinformatique, Biostatistique et Biologie Intégrative
9 McGill University = Université McGill [Montréal, Canada]

The rodlet structure present on the Aspergillus fumigatus conidial surface hides conidia from immune recognition. In spite of the essential biological role of the rodlets, the molecular basis for their self-assembly and dis-aggregation is not known. Analysis of the soluble forms of conidia-extracted and recombinant RodA by NMR spectroscopy has indicated the importance of disulfide bonds and identified two dynamic regions as likely candidates for conformational change and intermolecular interactions during conversion of RodA into the amyloid rodlet structure. Point mutations introduced into the RODA sequence confirmed that (1) mutation of a single cysteine was sufficient to block rodlet formation on the conidial surface and (2) both presumed amyloi-dogenic regions were needed for proper rodlet assembly. Mutations in the two putative amyloidogenic regions retarded and disturbed, but did not completely inhibit, the formation of the rodlets in vitro and on the conidial surface. Even in a disturbed form, the presence of rodlets on the surface of the conidia was sufficient to im-munosilence the conidium. However, in contrast to the parental conidia, long exposure of mutant conidia lacking disulfide bridges within RodA or expressing RodA carrying the double (I115S/I146G) mutation activated dendritic cells with the subsequent secretion of proinflammatory cytokines. The immune reactivity of the RodA mutant conidia was not due to a modification in the RodA structure, but to the exposure of different pathogen-associated molecular patterns on the surface as a result of the modification of the rodlet surface layer. The full degradation of the rodlet layer, which occurs during early germination, is due to a complex array of cell wall bound proteases. As reported earlier, this loss of the rodlet layer lead to a strong anti-fumigatus host immune response in mouse lungs.

Domaines: Biologie structurale [q-bio.BM]; Biochimie [q-bio.BM]; Biophysique; Biologie moléculaire; Immunité innée; Maladies infectieuses; Mycologie

Isabel Valsecchi, Jennifer Lai, Emmanuel Stephen-Victor, Ariane Pillé, Audrey Beaussart, et al.. Assembly and disassembly of Aspergillus fumigatus conidial rodlets. The Cell Surface, 2019, 5, pp.100023. ⟨10.1016/j.tcsw.2019.100023⟩. ⟨pasteur-02306653⟩