earticle

영어

Eukaryotes evolved a N-glycan-dependent endoplasmic reticulum (ER)-associated degradation (ERAD) pathway to monitor protein folding (1). Specific mannose trimming of the protein-bound oligosaccharide is essential for degradation of misfolded proteins (2). The human-pathogen Cryptococcus neoformans has a unique N-linked glycosylation pathway lacking glucosyltransferases but carrying multiple mannosidases (3). To investigate the molecular assembly of C. neoformans specific-ERAD pathway and its impact on pathogenicity, we disrupted the homologue genes to MNS1 (MNS1A and MNS1B), MNL1 and MNL2. The N-glycan profiles indicated MNS1A and MNS1B as a major and minor α-mannosidases, respectively. Whereas the double deletion of MNS1A and MNS1B generated mild growth retardation under several stress conditions, the simultaneous deletion of MNL1 and MNL2, encoding putative ERAD-associated mannosidases, resulted in hypersensitivity to ER, cell wall and osmostress. Notably, it also showed rather increased resistance to high temperature, caffeine and fluconazole. In vitro analysis of virulence factors revealed reduced capsule mass in all the constructed mutants, suggesting attenuation of virulence. Interestingly, mnl1Δmnl2Δ cells did not survive in capsule-inducing media, implying an essential role of the ERAD pathway under specific growth conditions. Overall, our results show the importance of ERAD pathway in protein quality control system for C. neoformans survival and virulence.