Biomedical subjects

Sascha Brunke

Publications and source records attributed to Sascha Brunke.

3 recordsLinked to original sources

PubMed2026

Depletion of the Candida albicans TLO gene family reveals a requirement for alpha TLO genes for wild-type virulence.

Candida albicans uniquely possesses an expanded family of genes (the TLO gene family) that encodes 10-15 paralogues of the Med2 component of the transcriptional regulator Mediator. Previous studies have shown that TLO null mutants are unable to form hyphae and are hypersensitive to environmental stress. However, the reason for the TLO gene expansion remains unclear, and the current study aimed to determine if reduction in the TLO family copy number affected virulence. In order to investigate this, we used CRISPR-Cas9 mutagenesis to generate two TLO-depleted mutants: one mutant retaining only TLOβ2 (CaTLO2) and the second mutant containing only TLOγ5 (CaTLO5). Both TLO-depleted mutants exhibited increased filamentous growth, increased susceptibility to specific stresses and reduced virulence in a murine model of oropharyngeal candidiasis (OPC). In vitro, the CaTLO5 mutant also exhibited impaired hyphal escape from macrophages and reduced hyphal invasion of oral keratinocytes. We then investigated if complementation with TLOα1, a gene previously shown to restore wild-type growth in a Δtlo null mutant, could restore virulence. In vitro infection models showed that TLOα1 could restore true hypha formation, epithelial invasion and hyphal escape from macrophages in the CaTLO5 background. The murine OPC model showed that TLOα1 could restore wild-type virulence in both CaTLO2 and CaTLO5 strains, suggesting an essential role for α-TLO in oral mucosal infection. Together, these findings highlight the functional specialization between the α, β and γ TLO gene groups and establish α-TLO as a major regulator of virulence in C. albicans.

Candida albicans↗

PubMed2006

MfLIP1, a gene encoding an extracellular lipase of the lipid-dependent fungus Malassezia furfur.

Malassezia furfur is a dimorphic fungus and a member of the normal cutaneous microflora of humans. However, it is also a facultative pathogen, associated with a wide range of skin diseases. One unusual feature of M. furfur is an absolute dependency on externally provided lipids which the fungus hydrolyses by lipolytic activity to release fatty acids necessary for both growth and pathogenicity. In this study, the cloning and characterization of the first gene encoding a secreted lipase of M. furfur possibly associated with this activity are reported. The gene, MfLIP1, shows high sequence similarity to other known extracellular lipases, but is not a member of a lipase gene family in M. furfur. MfLIP1 consists of 1464 bp, encoding a protein with a molecular mass of 54.3 kDa, a conserved lipase motif and an N-terminal signal peptide of 26 aa. By using a genomic library, two other genes were identified flanking MfLIP1, one of them encoding a putative secreted catalase, the other a putative amine oxidase. The cDNA of MfLIP1 was expressed in Pichia pastoris and the biochemical properties of the recombinant lipase were analysed. MfLip1 is most active at 40 degrees C and the pH optimum was found to be 5.8. The lipase hydrolysed lipids, such as Tweens, frequently used as the source of fatty acids in M. furfur media, and had minor esterase activity. Furthermore, the lipase is inhibited by different bivalent metal ions. This is the first molecular description of a secreted lipase from M. furfur.

Fungal Proteins↗

PubMed2005

Honey bees navigate according to a map-like spatial memory.

By using harmonic radar, we report the complete flight paths of displaced bees. Test bees forage at a feeder or are recruited by a waggle dance indicating the feeder. The flights are recorded after the bees are captured when leaving the hive or the feeder and are released at an unexpected release site. A sequence of behavioral routines become apparent: (i) initial straight flights in which they fly the course that they were on when captured (foraging bees) or that they learned during dance communication (recruited bees); (ii) slow search flights with frequent changes of direction in which they attempt to "get their bearings"; and (iii) straight and rapid flights directed either to the hive or first to the feeding station and then to the hive. These straight homing flights start at locations all around the hive and at distances far out of the visual catchment area around the hive or the feeding station. Two essential criteria of a map-like spatial memory are met by these results: bees can set course at any arbitrary location in their familiar area, and they can choose between at least two goals. This finding suggests a rich, map-like organization of spatial memory in navigating honey bees.

Animals↗