title: Identification of a major IP5 kinase in Cryptococcus neoformans confirms that PP-IP5/IP7, not IP6, is essential for virulence.
abstract: Fungal inositol polyphosphate (IP) kinases catalyse phosphorylation of IP3 to inositol pyrophosphate, PP-IP5/IP7, which is essential for virulence of Cryptococcus neoformans. Cryptococcal Kcs1 converts IP6 to PP-IP5/IP7, but the kinase converting IP5 to IP6 is unknown. Deletion of a putative IP5 kinase-encoding gene (IPK1) alone (ipk1Δ), and in combination with KCS1 (ipk1Δkcs1Δ), profoundly reduced virulence in mice. However, deletion of KCS1 and IPK1 had a greater impact on virulence attenuation than that of IPK1 alone. ipk1Δkcs1Δ and kcs1Δ lung burdens were also lower than those of ipk1Δ. Unlike ipk1Δ, ipk1Δkcs1Δ and kcs1Δ failed to disseminate to the brain. IP profiling confirmed Ipk1 as the major IP5 kinase in C. neoformans: ipk1Δ produced no IP6 or PP-IP5/IP7 and, in contrast to ipk1Δkcs1Δ, accumulated IP5 and its pyrophosphorylated PP-IP4 derivative. Kcs1 is therefore a dual specificity (IP5 and IP6) kinase producing PP-IP4 and PP-IP5/IP7. All mutants were similarly attenuated in virulence phenotypes including laccase, urease and growth under oxidative/nitrosative stress. Alternative carbon source utilisation was also reduced significantly in all mutants except ipk1Δ, suggesting that PP-IP4 partially compensates for absent PP-IP5/IP7 in ipk1Δ grown under this condition. In conclusion, PP-IP5/IP7, not IP6, is essential for fungal virulence.
authors.affiliation: Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW, Australia.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Li
authors.affiliation: Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW, Australia.
authors.forename: Sophie
authors.initials: S
authors.lastname: Lev
authors.affiliation: Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Saiardi
authors.affiliation: Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW, Australia.
authors.forename: Desmarini
authors.initials: D
authors.lastname: Desmarini
authors.affiliation: Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW, Australia.|Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, NSW, Australia.|Westmead Hospital, Westmead, NSW, Australia.
authors.forename: Tania C
authors.initials: TC
authors.lastname: Sorrell
authors.affiliation: Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, NSW, Australia.|Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, NSW, Australia.|Westmead Hospital, Westmead, NSW, Australia.
authors.forename: Julianne T
authors.initials: JT
authors.lastname: Djordjevic
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D002244:Carbon / Q000378:metabolism; D003453:Cryptococcosis / Q000382:microbiology; D003455:Cryptococcus neoformans / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D003470:Culture Media; D005260:Female; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D055786:Gene Knockout Techniques; D007295:Inositol Phosphates / Q000096:biosynthesis; D042845:Laccase / Q000378:metabolism; D008543:Melanins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D010766:Phosphorylation; D010833:Phytic Acid / Q000096:biosynthesis; D014774:Virulence
chemical_list: D000935:Antifungal Agents; D003470:Culture Media; D005656:Fungal Proteins; D007295:Inositol Phosphates; D008543:Melanins; C402123:inositol heptakisphosphate; C013571:inositol pentaphosphate; D002244:Carbon; D010833:Phytic Acid; D042845:Laccase