The Crz1/Sp1 Transcription Factor of Cryptococcus neoformans Is Activated by Calcineurin and Regulates Cell Wall Integrity

• Published in: PloS one Vol. 7; no. 12; p. e51403
• Main Authors: Lev, Sophie, Desmarini, Desmarini, Chayakulkeeree, Methee, Sorrell, Tania C., Djordjevic, Julianne T.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.12.2012; Public Library of Science (PLoS)
• Subjects: Binding Sites; Biology; Calcineurin; Calcineurin - metabolism; Calcium; Calcium (extracellular); Calcium signalling; Candida albicans; Cell Wall - enzymology; Cell Wall - metabolism; Cell walls; Chitin; Chitin synthase; Chitin Synthase - metabolism; Cryptococcus neoformans; Cryptococcus neoformans - metabolism; Defective mutant; Defects; Deoxyribonucleic acid; DNA; Environmental conditions; Fungal infections; Gene expression; Glucose; Green Fluorescent Proteins - genetics; Heat shock; High temperature; Infectious diseases; Integrity; Localization; Medical schools; Medicine; Mutants; Nuclei; Phosphatases; Phylogenetics; Physiology; Protein kinase C; Protein kinases; Proteins; Saccharomyces cerevisiae; Salts; Signal transduction; Sp1 protein; Starvation; Stress, Physiological; Subcellular Fractions - metabolism; Tacrolimus; Temperature effects; Transcription factors; Transcription Factors - genetics; Transcription Factors - metabolism; Yeast
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0051403

Cryptococcus neoformans survives host temperature and regulates cell wall integrity via a calcium-dependent phosphatase, calcineurin. However, downstream effectors of C. neoformans calcineurin are largely unknown. In S. cerevisiae and other fungal species, a calcineurin-dependent transcription factor Crz1, translocates to nuclei upon activation and triggers expression of target genes. We now show that the C. neoformans Crz1 ortholog (Crz1/Sp1), previously identified as a protein kinase C target during starvation, is a bona fide target of calcineurin under non-starvation conditions, during cell wall stress and growth at high temperature. Both the calcineurin-defective mutant, Δcna1, and a CRZ1/SP1 mutant (Δcrz1) were susceptible to cell wall perturbing agents. Furthermore, expression of the chitin synthase encoding gene, CHS6, was reduced in both mutants. We tracked the subcellular localization of Crz1-GFP in WT C. neoformans and Δcna1 in response to different stimuli, in the presence and absence of the calcineurin inhibitor, FK506. Exposure to elevated temperature (30-37°C vs 25°C) and extracellular calcium caused calcineurin-dependent nuclear accumulation of Crz1-GFP. Unexpectedly, 1M salt and heat shock triggered calcineurin-independent Crz1-GFP sequestration within cytosolic and nuclear puncta. To our knowledge, punctate cytosolic distribution, as opposed to nuclear targeting, is a unique feature of C. neoformans Crz1. We conclude that Crz1 is selectively activated by calcium/calcineurin-dependent and independent signals depending on the environmental conditions.