Elucidating the role of MBP 1 in the

Elucidating the role of MBP 1 in the pathogenesis of Candida albicans Gregory J. Fischer Julie Anderson Daniel Herman Department of Biology University of Wisconsin–Eau Claire Experimental Design Plasmid Construction and Isolation Abstract The yeast species Candida albicans is the most commonly-isolated yeast in human disease. Systemic infections of C. albicans have emerged as important causes of mortality in premature infants and in the immunocompromised, with the number of cases on the rise. To infect host tissue, the usual unicellular form of C. albicans switches into an invasive, multicellular filamentous form. This morphogenesis or conversion to the filamentous state has been shown to contribute significantly to C. albicans’ pathogenicity. We have been investigating the role of the MBP 1 gene in this process. The MBP 1 homolog in the nonpathogenic yeast Saccharomyces cerevisiae has been well studied and plays a role in the G 1 -S transition within the cell cycle. To further our understanding of the function of MBP 1 in C. albicans, we are expressing C. albicans’ MBP 1 within a S. cerevisiae MBP 1 knockout strain to assess whether the MBP 1 protein carries out similar functions in both organisms. Experimental results will help elucidate the role MBP 1 plays in morphogenesis which could lead to novel therapies for these types of infections. Acquiring Double Mutant Genotype of Yeast Strains Used in Study Mating MBP 1 YJJ 1068 MBP 1 JA 2011 YJJ 1000 MBP 1 insert ~2. 5 kb MBP 1 n n 2 n al PG p. ESC-Leu Le u Figure 5: The use of homologous recombination for the creation of a vector construct. C. albicans MBP 1 was placed downstream of a Gal promoter, allowing for conditional expression of MBP 1 in the presence of galactose. MBP 1 Protein Expression Genotype 45% 10% Candida albicans tropicalis glabrata krusei Enzyme MBP 1 myc mbp 1Δ/swi 4Δ [p. LEU-MBP 1 -1] Figure 6: A) Immunoblot using chemiluminescence to detect C. albicans MBP 1 protein under the control of a GAL promoter. Primary and secondary antibodies were used at concentrations of 1: 1000 and 1: 5000, respectively. These results confirmed that C. albicans MBP 1 expression is induced by galactose. B) Schematic of a typical immunoblot using chemiluminescence. A myc-epitope was added to MBP 1 in the expression system and an anti-myc antibody was used to detect the protein. Role of MBP 1 in Cell Cycle MBP 1 myc-fusion protein 93. 9 k. Da B) CLN 1/2 SBF/MBF Swi 6 MBF Complex Bud emergence (CLA 4, BEM 1, BEM 2, BEM 4) DNA replication SPB duplication MBP 1 mbp 1Δ/swi 4Δ [p. LEU-MBP 1 -2] Vector Only Molecular Genetics of Yeast Master Plate Swi 6 SBF Complex Jorgenson, et al. , 2002 Swi 4 B) YJ m J A) bp 100 1+ 0 /sw i 4Δ Y Figure 3: A) Schematic of the activation or inhibition of SBF and MBF by various proteins within S. cerevisiae. During growth phases, in which the size of the cell increases, transcription factor complexes like SBF and MPF are inhibited so that cell division does not occur. Once conditions merit division, SBF and MBF are directly involved with the activation of genes responsible for DNA replication and bud emergence. B) MBP 1 and Swi 4 interact with the adapter protein Swi 6 to form the MBF and SBF complexes respectively. J sw J 1 i 4 + 06 /m 8 bp 1Δ References Alberts B. , D. Gray, J. Lewis, et al. , (1994). Molecular Biology of the Cell Experimental Results Mouse anti-myc ~94 k. Da Figure 2: Prevalence of Candida species in fungal infections for ICU and cancer patients. Recent studies continue to identify C. albicans as the predominant yeast species isolated in fungal infections. A) Donkey anti-mouse Light mbp 1Δ/swi 4Δ Figure 1: Fungal infections, such as OPC, continue to be problematic, especially within NICUs, with antifungal resistant strains emerging. HRP Leu+/Ura-/G 418 S Leu+/Ura+/G 418 S Leu+/Ura-/G 418 R Leu+/Ura+/G 418 R Leu-MBP 1 Image Courtesy C. Halde Phenotype Vector Only 0% Leu Shoham, et al. , 2009 Lalla, et al. , 2010 5% Luminol & H 2 O 2 Ura-MBP 1 15% Ura 20% Leu Cancer Patients B) Galactose Ura-MBP 1 25% Glucose Ura ICU Leu-MBP 1 30% Leu-MBP 1 A) Meiotic Product Characteristics MBP 1+/Swi 4+ MBP 1+/swi 4Δ mbp 1Δ/Swi 4+ mbp 1Δ/swi 4Δ (LETHAL) 50% 35% Sporulation q Separate spores by micro-dissection. q Identify genotype via replica plating. (JA 2011) Prevalence of Candida Species in Various Medical Settings 40% üGJF 2011 leu 2∆1 his 3∆200 ura 3 -52 swi 4∆: : URA 3 mbp 1 ∆: : KNMX 4 [p. LEU-MBP 1] YSMG, Duke Univ. 2 Figure 4: Following transformation, plasmid DNA was isolated and cut to determine whether the MBP 1 insert was present. The results indicate that homologous recombination was successful in DNA of colonies 2 and 5. üYJJ 1000 (Betz, et al. , 2002) Mat a leu 2 ∆1 his 3∆200 ura 3 -52 swi 4∆: : URA 3 üJA 2011 Mat a/α leu-/leu- ura+/ura- mbp 1+/mbp 1∆ swi 4+/swi 4∆ [p. LEU-MBP 1] Pathogenesis q Cases of fungal infections, such as oropharyngeal candidiasis (OPC) continue to be problematic, especially in neonatal intensive care units (Dotis, et al. , 2010). q Recent studies of ICU and cancer patients consistently find C. albicans to be the predominant yeast species isolated (Figure 2) (Shoham, et al. , 2009 & Lalla, et al. , 2010). q There is evidence that MBP 1 plays a role in the filamentous growth of C. albicans and is similar in sequence to the S. cerevisiae gene (Herman, et al. , in progress). üYJJ 1068 (Betz, et al. , 2002) Mat α leu 2∆1 his 3∆200 ura 3 -52 mbp 1∆: : KNMX 4 [p. LEU-MBP 1] 3 rd W Edition. New York: Garland Science. Dotis, J. & E. Roilides (2010). Candidemia in the pediatric intensive care unit: What’s different from candidemia in adults? Current Fungal Infection Reports, 5(1): 49 -55. Jorgenson, P. , J. L. Nishikawa, B. Breitkreutz, & M. Tyers (2002). Systemic Identification of pathways that couple cell growth and division in yeast. Science, 297: 395 -400. Shoham, S. & S. Marwaha (2009). Invasive fungal infections in the ICU. Journal of Intensive Care Medicine, 25(2): 78 -92. KNMX 4 Swi 4 MBP 1 Betz, J. L. , M. Chang, T. M. Washburn. S. E. Porter, C. L. Mueller, & J. A. Jaehning (2002). Phenotypic analysis of Paf 1/RNA polymerase II mutations reveals connections to cell cycle regulation, protein synthesis, and lipid and nucleic acid metabolism. Mol Genet Genomics, 268: 272 -285. Lalla, R. V. M. C. Latortue, C. H. Hong, et al. , (2010). A systemic review of oral fungal infection in patients receiving cancer therapy. Support Care Cancer, 18: 985 -992. T MBP 1 Ura 3 Alberts, et al. , 1994 Glucose Immunoblot Figure 8: Replica plating revealed that a double mutant yeast strain grew on galactose media but not glucose. Yeast with functional S. cerevisiae MBP 1 transformed with vector only was used as a positive control. Immunoblot of the double mutant strain confirmed C. albicans MBP 1 protein expression. Therefore, C. albicans MBP 1 is able to functionally replace the MBP 1 ortholog in S. cerevisiae. Gene Disruptions Swi 4 Galactose Figure 7: A) In the budding yeast lifecycle, haploid yeast cells of opposite mating types undergo conjugation to produce a diploid yeast strain. Mitosis of this diploid strain continues until meiosis is triggered by lack of essential nutrients. Sporulation of the diploid cell results in four haploid meiotic products known as spores. The genotypes of these spores can be determined by separating and growing them on selective media. A mbp 1/swi 4 double mutant was isolated using this technique in order to assess the activity of C. albicans MBP 1. B) Gene disruptions of MBP 1 via Geneticin (G 418) resistance cassette (KNMX 4) in YJJ 1000 strain and Swi 4 disruption using a URA 3 cassette in YJJ 1068 strain. Growth of these strains on media containing Geneticin (G 418) or lacking uracil indicates that genomic MBP 1 and Swi 4 are disrupted. Conclusions q Candida albicans MBP 1 is functionally equivalent to Saccharomyces cerevisiae MBP 1 and is able to rescue the lethal phenotype of a mbp 1/swi 4 double mutant, thus playing a role in the cell cycle. q Suggests that C. albicans MBP 1 activates genes in the G 1/S transition that are orthologous to those targeted by S. cerevisiae MBP 1. q Is evidence that the MBP 1 protein could potentially serve as a drug target for the next generation of antifungal agents. This faculty/student research collaboration was made possible through Differential Tuition and a grant from the Office of Research and Sponsored Programs.