Investigating the role of inositol polyphosphate kinases that function downstream of phospholipase C in the virulence and drug tolerance of <em>Cryptococcus neoformans</em> — ASN Events
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Investigating the role of inositol polyphosphate kinases that function downstream of phospholipase C in the virulence and drug tolerance of Cryptococcus neoformans (6675)

Cecilia Li 1 , Sophie Lev 1 , Adolfo Saiardi 2 , Desmarini Desmarini 1 , Methee Chayakulkeeree 3 , Ana Traven 4 , Tania Sorrell 1 5 , Julianne Djordjevic 1
  1. Centre for Infectious Diseases and Microbiology, Westmead Millennium Institute and Sydney Medical School, University of Sydney at Westmead Hospital, Westmead, New South Wales, Australia
  2. Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street WC1E 6BT London UK, London, UK
  3. Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
  4. Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
  5. Sydney Emerging Infections and Biosecurity Institute, University of Sydney at Westmead Hospital, Westmead, New South Wales, Australia

We previously demonstrated that fungal phospholipase C1 (Plc1) is essential for homeostasis and virulence of Cryptococcus neoformans (Cn). Our subsequent study established that CnPlc1 provides inositol trisphosphate (IP3) as a substrate for conversion to more complex inositol polyphosphates (IPs) by the IP3 kinase, CnArg1. IP3 content was reduced in CnΔplc1 and markedly increased in CnΔarg1, confirming an epistatic relationship between PLC1 and ARG1. In the present study the KCS1 gene, predicted to encode an IP6 kinase functioning downstream of Arg1, was deleted and the virulence profile of the resulting mutant (CnΔkcs1) was compared to that of CnΔplc1 and CnΔarg1. Absence of IP7-8 in the CnΔkcs1, as determined by inositol radiolabeling and HPLC, is consistent with Kcs1 functioning as an IP6 kinase within the linear pathway Plc1-Arg1-Kcs1. Phenotypic analysis of all three mutants revealed that, similar to CnΔplc1 and CnΔarg1, CnΔkcs1 is compromised in thermotolerance, cell wall integrity, urease and acid phosphatase activity, tolerance to antifungal drugs, melanisation, and virulence in the Galleria mellonella infection model. Secretion of the fungal invasin, phospholipase B (Plb1), was also blocked in all three mutants. However, the size of the capsule, which is also a virulence determinant, was increased in CnΔkcs1 and decreased in CnΔplc1 and CnΔarg1. The suppressing effect of KCS1 and ARG1 deletion on melanisation and Plb1 secretion was further investigated, and demonstrated to occur at the transcriptional (laccase) and post-transcriptional (Plb1) level. In conclusion, these findings demonstrate that Plc1-Arg1-Kcs1 constitute a novel signalling pathway that contributes to the regulation of virulence and drug tolerance in C. neoformans. Studies into how IPKs and their IP products contribute to cellular function and the virulence profile are ongoing.