The endosomal sorting complex required for transport machinery influences haem uptake and capsule elaboration in Cryptococcus neoformans.
Iron availability is a key determinant of virulence in the pathogenic fungus Cryptococcus neoformans. Previous work revealed that the ESCRT (endosomal sorting complex required for transport) protein Vps23 functions in iron acquisition, capsule formation and virulence. Here, we further characterized the ESCRT machinery to demonstrate that defects in the ESCRT-II and III complexes caused reduced capsule attachment, impaired growth on haem and resistance to non-iron metalloprotoporphyrins. The ESCRT mutants shared several phenotypes with a mutant lacking the pH-response regulator Rim101, and in other fungi, the ESCRT machinery is known to activate Rim101 via proteolytic cleavage. We therefore expressed a truncated and activated version of Rim101 in the ESCRT mutants and found that this allele restored capsule formation but not growth on haem, thus suggesting a Rim101-independent contribution to haem uptake. We also demonstrated that the ESCRT machinery acts downstream of the cAMP/protein kinase A pathway to influence capsule elaboration. Defects in the ESCRT components also attenuated virulence in macrophage survival assays and a mouse model of cryptococcosis to a greater extent than reported for loss of Rim101. Overall, these results indicate that the ESCRT complexes function in capsule elaboration, haem uptake and virulence via Rim101-dependent and independent mechanisms.
Michael Smith Laboratories, The University of British Columbia, 2185 East Mall, Vancouver, BC, V6T 1Z4, Canada.
Guanggan
G
Hu
Michael Smith Laboratories, The University of British Columbia, 2185 East Mall, Vancouver, BC, V6T 1Z4, Canada.
Mélissa
M
Caza
Michael Smith Laboratories, The University of British Columbia, 2185 East Mall, Vancouver, BC, V6T 1Z4, Canada.
Brigitte
B
Cadieux
Michael Smith Laboratories, The University of British Columbia, 2185 East Mall, Vancouver, BC, V6T 1Z4, Canada.
Erik
E
Bakkeren
Department of Systems Biotechnology, Chung-Ang University, Anseong, 456-756, Republic of Korea.
Eunsoo
E
Do
Department of Systems Biotechnology, Chung-Ang University, Anseong, 456-756, Republic of Korea.
Won Hee
WH
Jung
Michael Smith Laboratories, The University of British Columbia, 2185 East Mall, Vancouver, BC, V6T 1Z4, Canada.
James W
JW
Kronstad
D000818:Animals; D000935:Antifungal Agents / Q000493:pharmacokinetics; D003453:Cryptococcosis / Q000382:microbiology*; D003455:Cryptococcus neoformans / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004195:Disease Models, Animal; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D015725:Fluconazole / Q000494:pharmacology; D062607:Fungal Capsules / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D009154:Mutation; D010641:Phenotype; D059748:Proteolysis
D000935:Antifungal Agents; D056827:Endosomal Sorting Complexes Required for Transport; D006418:Heme; D015725:Fluconazole; D017868:Cyclic AMP-Dependent Protein Kinases