| Abstrakt: |
The Candida albicans PLB1gene was cloned using a polymerase chain reaction-based approach relying on degenerate oligonucleotide primers designed according to the amino acid sequences of two peptide fragments obtained from a purified candidal enzyme displaying phospholipase activity (Mirbod, F., Banno, Y., Ghannoum, M. A., Ibrahim, A. S., Nakashima, S., Yasuo, K., Cole, G. T., and Nozawa, Y. (1995) Biochim. Biophys. Acta1257, 181–188). Sequence analysis of a 6.7-kilobase pairEcoRI-ClaI genomic clone revealed a single open reading frame of 1818 base pairs that predicts for a pre-protein of 605 residues. Comparison of the putative candidal phospholipase with those of other proteins in data base revealed significant homology to known fungal phospholipase Bs from Saccharomyces cerevisiae(45%), Penicillium notatum(42%), Torulaspora delbrueckii(48%), and Schizosaccharomyces pombe(38%). Thus, we have cloned the gene encoding a C. albicansphospholipase B homolog. This gene, designated caPLB1, was mapped to chromosome 6. Disruption experiments revealed that the caplb1null mutant is viable and displays no obvious phenotype. However, the virulence of strains deleted for caPLB1, as assessed in a murine model for hematogenously disseminated candidiasis, was significantly attenuated compared with the isogenic wild-type parental strain. Although deletion of caPLB1did not produce any detectable effects on candidal adherence to human endothelial or epithelial cells, the ability of the caplb1null mutant to penetrate host cells was dramatically reduced. Thus, phospholipase B may well contribute to the pathogenicity of C. albicansby abetting the fungus in damaging and traversing host cell membranes, processes which likely increase the rapidity of disseminated infection. |
