A fungus-specific glucosylceramide (GlcCer), which contains a unique sphingoid base possessing two double bonds and a methyl substitution, is essential for pathogenicity in fungi. Although the biosynthetic pathway of the GlcCer has been well elucidated, little is known about GlcCer catabolism because a GlcCer-degrading enzyme (glucocerebrosidase) has yet to be identified in fungi. We found a homologue of endoglycoceramidase tentatively designated endoglycoceramidase-related protein 1 (EGCrP1) in several fungal genomic databases. The recombinant EGCrP1 hydrolyzed GlcCer but not other glycosphingolipids, whereas endoglycoceramidase hydrolyzed oligosaccharide- linked glycosphingolipids but not GlcCer. Disruption of egcrp1 in Cryptococcus neoformans, a typical pathogenic fungus causing cryptococcosis, resulted in the accumulation of fungus-specific GlcCer and immature GlcCer that possess sphingoid bases without a methyl substitution concomitant with a dysfunction of polysaccharide capsule formation. These results indicated that EGCrP1 participates in the catabolism of GlcCer and especially functions to eliminate immature GlcCer in vivo that are generated as by-products due to the broad specificity of GlcCer synthase. We conclude that EGCrP1, a glucocerebrosidase identified for the first time in fungi, controls the quality of GlcCer by eliminating immature GlcCer incorrectly generated in C. neoformans, leading to accurate processing of fungus-specific GlcCer.
glycosphingolipid, Cryptococcus neoformans, glucosylceramide, EGCase II
NCBI PubMed ID: 22072709Publication DOI: 10.1074/jbc.M111.311340Journal NLM ID: 2985121RPublisher: Baltimore, MD: American Society for Biochemistry and Molecular Biology
Correspondence: Ito M
Institutions: Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan, Department of Metabolome, Graduate School of Medicine, University of Tokyo, Tokyo, Japan, Institute for Advanced Biosciences, Keio University, Yamagata, Japan, Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Aichi, Japan, New Energy and Industrial Technology Development Organization (NEDO), MUZA, Kanagawa, Japan, Laboratory for Molecular Membrane Neuroscience, RIKEN Brain Science Institute, Wako, Japan
Methods: DNA sequencing, SDS-PAGE, DNA techniques, TLC, GLC, ESI-MS/MS, MALDI-TOF MS, HPLC, extraction, CC, protein detection, enzymatic assay, derivatization
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