Aspergillus fumigatusCap59-like protein A is involved in α1,3-mannosylation of GPI-anchors

Abstract

Glycosylphosphatidylinositol (GPI) attaches a variety of eukaryotic proteins to the outer leaflet of the plasma membrane. In fungi, these proteins may also be transferred to the cell wall, to which they are covalently linked via a remnant of the GPI-anchor. They play crucial physiological roles in cell-cell interactions, adhesion or cell wall biogenesis. The biosynthesis of GPI-anchors in the endoplasmic reticulum, their transfer to proteins, early remodelling and transport to the Golgi apparatus has been fairly well described. In contrast, almost nothing is known about the genes and enzymes involved in adding glycan side chains to GPI after protein attachment. In this study, we characterized an α1,3-mannosyltransferase involved in maturation of GPI-anchors from the pathogenic fungus Aspergillus fumigatus. This enzyme shows homology to Cryptococcus neoformans Cap59p, a putative glycosyltransferase involved in capsule formation and virulence, and was thus named Cap59-like protein A (ClpA). Targeted deletion of the clpA gene in A. fumigatus led to absence of α1,3-mannose from mature GPI-anchors. The enzyme was further located to the Golgi-like apparatus of A. fumigatus and was shown to be active in the yeast Saccharomyces cerevisiae.

BcCFEM1, a CFEM Domain-Containing Protein with Putative GPI-Anchored Site, Is Involved in Pathogenicity, Conidial Production, and Stress Tolerance in Botrytis cinerea

“…The result demonstrated that the amino acids G 192 and A 193 are predicted to be the best and second best of potential GPI-modification site, respectively ( Supplementary Figure S1 ). From this result, we inferred that BcCFEM1 contains a putative GPI-anchored site, which possibly anchored to the outer layer of the plasma membrane through a C-terminal GPI anchor or transferred to the cell wall as other fungal GPI-anchored proteins ( Krüger et al, 2016 ).…”

“…Then, we also analyzed the potential modification of BcCFEM1. The result demonstrated that G 192 and A 193 are predicted to be the potential GPI-modification site ( Supplementary Figure S1 ), therefore, BcCFEM1 may be a potential GPI-anchored CFEM protein, which anchored to the outer layer of the cell membrane through a C-terminal GPI anchor or transferred to the cell wall possibly ( Krüger et al, 2016 ). Until now, several studies have reported that GPI-anchored proteins anchor to the plasma membrane and play an important role in maintaining the cell wall and stress tolerance.…”

Galactomannan Produced by Aspergillus fumigatus: An Update on the Structure, Biosynthesis and Biological Functions of an Emblematic Fungal Biomarker

“…The number of mannosyltransferase are functional in A. fumigatus [37,42,[45][46][47]. In S. cerevisiae, Ktr orthologs belong to the GT15 family in the CAZy database and have been characterised as α-1,2-mannosyltransferases playing a role in N-and O-mannosylation of glycoproteins [48][49][50][51].…”

Sphingolipids from the human fungal pathogen Aspergillus fumigatus

“…In A. fumigatus, the glycan moiety of the GPI anchor is composed of five mannose residues linked to a GlcN-IPC (Table I) [57], where the protein is covalently linked to the third mannose residue through a phosphoethanolamine bridge. The main difference with yeast GPI structures is the presence of a fifth mannose residue linked through an α-1,3-bond, which is added by a Golgi α-mannosyl-transferase [57][58][59]. GPI biosynthetic pathway is an essential event to the fungal growth.…”