1887

Abstract

The ALS (gglutinin-ike equence) gene family encodes eight large cell-surface glycoproteins. The work presented here focuses on Als2p and Als4p, and is part of a larger effort to deduce the function of each Als protein. Both alleles were deleted from the genome and the phenotype of the mutant strain (Δ/Δ; named 2034) studied. Loss of Als4p slowed germ tube formation of cells grown in RPMI 1640 medium and resulted in decreased adhesion of to vascular endothelial cells. Loss of Als4p did not affect adhesion to buccal epithelial cells, biofilm formation in a catheter model, or adhesion to or destruction of oral reconstituted human epithelium (RHE). Although deletion of one allele was achieved readily, a strain lacking the second allele was not identified despite screening thousands of transformants. The remaining allele was placed under control of the promoter to create an Δ/ strain (named 2342). Real-time RT-PCR analysis of strain 2342 grown in glucose-containing medium (non-inducing conditions) showed that although transcript levels were greatly reduced compared to wild-type cells, some transcript remained. The decreased expression levels were sufficient to slow germ tube formation in RPMI 1640 and Lee medium, reduce adhesion to vascular endothelial cells and to RHE, decrease RHE destruction, and impair biofilm formation. Growth of strain 2342 in maltose-containing medium (inducing conditions) restored the wild-type phenotype in all assays. Real-time RT-PCR analysis demonstrated that in maltose-containing medium, strain 2342 overexpressed compared to wild-type cells; however no overexpression phenotype was apparent. Microarray analysis revealed little transcriptional response to deletion, but showed twofold up-regulation of orf19.4765 in the glucose-medium-grown Δ/ strain. orf19.4765 encodes a protein with features of a glycosylated cell wall protein with similarity to Ccw12p, although initial analysis suggested functional differences between the two proteins. Real-time RT-PCR measurement of and transcript copy number showed a 2·8-fold increase in expression in the Δ/Δ strain and a 3·2-fold increase in expression in the Δ/ strain, suggesting the potential for compensatory function between these related proteins.

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2005-05-01
2024-03-29
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