Analysis of the Candida albicans Phosphoproteome.
Candida albicans is an important human fungal pathogen in both immunocompetent and immunocompromised individuals. C. albicans regulation has been studied in many contexts, including morphological transitions, mating competence, biofilm formation, stress resistance, and cell wall synthesis. Analysis of kinase- and phosphatase-deficient mutants has made it clear that protein phosphorylation plays an important role in the regulation of these pathways. In this study, to further our understanding of phosphorylation in C. albicans regulation, we performed a deep analysis of the phosphoproteome in C. albicans. We identified 19,590 unique peptides that corresponded to 15,906 unique phosphosites on 2,896 proteins. The ratios of serine, threonine, and tyrosine phosphosites were 80.01%, 18.11%, and 1.81%, respectively. The majority of proteins (2,111) contained at least two detected phosphorylation sites. Consistent with findings in other fungi, cytoskeletal proteins were among the most highly phosphorylated proteins, and there were differences in Gene Ontology (GO) terms for proteins with serine and threonine versus tyrosine phosphorylation sites. This large-scale analysis identified phosphosites in protein components of Mediator, an important transcriptional coregulatory protein complex. A targeted analysis of the phosphosites in Mediator complex proteins confirmed the large-scale studies, and further in vitro assays identified a subset of these phosphorylations that were catalyzed by Cdk8 (Ssn3), a kinase within the Mediator complex. These data represent the deepest single analysis of a fungal phosphoproteome and lay the groundwork for future analyses of the C. albicans phosphoproteome and specific phosphoproteins.
Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
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Willger
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
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Liu
Department of Plant Pathology and Microbiology, University of California, Riverside, California, USA.
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Olarte
Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA.
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ME
Adamo
Department of Plant Pathology and Microbiology, University of California, Riverside, California, USA.
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http://orcid.org/0000-0002-7591-0020
JE
Stajich
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
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Myers
Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA.
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Kettenbach
Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA dhogan@dartmouth.edu.
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Hogan
D002176:Candida albicans / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics / Q000379:methods; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000235:genetics
D005656:Fungal Proteins; D010750:Phosphoproteins; D020543:Proteome; D013912:Threonine; D012694:Serine