Proteome analysis of Candida albicans cell wall mutants. (c2011)

Abstract

The fungal pathogen Candida albicans is a leading causative agent of death in immuno-compromised individuals. This pathogenicity involves, among other, morphological switching from yeast to hyphal form. When filamentation is induced, major structural and compositional alterations take place in the cell wall affecting cell wall chitin content and cell wall proteome composition. Knockouts of pir32, hwp2and pga1, three cell wall protein coding genes, have been previously generated by homologous recombination of marker cassettes in our lab. The purpose of this current study is to analyze the role these genes play by comparing the cell wall composition of the mutant strains to the parental wild type strain under both filamentous and non filamentous conditions. Cell wall isolation and total cell wall protein content of these strains showed alterations in the cell wall proteome. Chitin content was found to significantly decrease(50%) in the pga1/pga1 mutant under non filamentous conditions, whereas in the pir32/pi32 mutant, and under similar conditions, a 150% increase in chitin content was recorded, an interesting result bearing in mind that chitin is a key player in cell wall structure and rigidity. Total cell wall protein content ranged from a 50% decrease in the pga1 null to a 50% increase in the pir32 mutant, implying fundamental changes in the cell wall proteome. MALDI-TOF analysis showed differential peptide mass fingerprints of cell wall proteins with many peaks found to be unique to each mutant and to specific growth conditions. These peaks, when entered into available databases, remained unidentified. As such, future work requires analysis of these peaks by MS/MS peptide sequencing in an effort to identify specific up or down regulated proteins represented by these peaks.