Candida species are considered a major cause of opportunistic infections in humans. Although C. albicans is the most common Candida species, C. glabrata already causes 20% of systemic candidiasis and 30% of urinary tract infections. C. glabrata is resistant to fluconazole, a common used antifungal, and has a higher mortality rate compared to C. albicans. The genome of C. glabrata shows a high degree of homology with S. cerevisiae and is haploid. In contrary to C. albicans, C. glabrata has a normal codon usage.
Recently Peeters and colleagues (2006) discovered a mechanism in yeast by which the G alfa protein Gpa2 activates PKA through two kelch-repeat proteins, Krh1 and Krh2, bypassing adenylate cyclase stimulation. Hence, Gpa2 regulates PKA activity via two distinct pathways: through stimulation of adenylate cyclase and through inhibition of the Krh proteins. We showed that the C. glabrata homologues of ScKrh1 and ScKrh2 can complement the respective deletion mutants of S. cerevisiae. This may indicate that a similar bifurcation of the pathway exists in C. glabrata. To further investigate this, we made several strains where genes, which are part of the PKA pathway, are deleted. From these strains the cAMP signal was measured after addition of glucose to the glucose deprived cells. The results show a loss of the cAMP peak in the GPR1 and GPA2 deletion strains. This can indicate that the ligand of the Gpr1 receptor is glucose, as it is the case in S. cerevisiae. This will be investigated in more detail. The colonies of the different deletion strains, when plated on SLD medium, showed a more irregular border compared to the wild type. These mutants will be characterized in more detail in the near future.