Biology subjects

Wilhelm, H.

Publications and source records attributed to Wilhelm, H..

4 recordsLinked to original sources

bioRxiv2025

Ergosterol-depleted clinical isolates of Nakaseomyces glabratus can develop multi-drug resistance without apparent fitness and virulence defects

ObjectivesNakaseomyces glabratus (formerly Candida glabrata) is a leading cause of invasive candidiasis and rapidly develops antifungal drug resistance during treatment. An increasing number of clinical isolates shows reduced susceptibility to echinocandins and azoles, leaving amphotericin B (AMB) as a last therapeutic option. Resistance of N. glabratus to this drug is rare and its underlying mechanisms are still not fully understood. Here, we describe two independent multidrug resistant (MDR) bloodstream isolates displaying resistance to AMB and anidulafungin (ANF) as well as a reduced susceptibility to azoles. MethodsWhole-genome sequencing and sterol profiling were performed on nine clinical N. glabratus isolates which were resistant to ANF and displayed resistance or low susceptibility to fluconazole (FLU) and AMB. The transcriptional response of reference strain CBS138 and an AMBR+ANFR isolate was analyzed by RNA-seq. Furthermore, PDR1 was deleted in the latter isolate to examine its influence on efflux pump gene expression. Additionally, fitness and virulence of the AMBR+ANFR isolate were examined in growth assays and a Galleria mellonella infection model. ResultsLoss of function mutations in the genes ERG3 and ERG4 is linked to ergosterol depletion and AMB resistance. Ergosterol depletion also contributed to a Pdr1-mediated up-regulation of ERG and ABC transporter genes which was associated with low FLU susceptibility. The AMBR isolates displayed no fitness defects and one of them was fully virulent in a G. mellonella infection model. ConclusionsThese findings demonstrate that ergosterol depletion in N. glabratus leads to AMB resistance without affecting fitness or virulence.

microbiology↗

bioRxiv2022

The sphingolipid inhibitor myriocin increases susceptibility of Candida auris to amphotericin B

The emerging human fungal pathogen Candida auris can cause of hospital outbreaks by transmission between patients and / or medical care staff. It is known for a fast adaption to environmental stress and antifungal treatment. Besides resistance to fluconazole in most isolates, C. auris frequently shows limited susceptibility to echinocandins and even to amphotericin B. Therefore, multidrug resistance (MDR) is frequently found in clinical isolates, leading to a need for new therapeutic targets and compounds. One of those targets could be sphingolipids which are an integral part of the cell membrane and are important for membrane fluidity and the formation of lipid rafts. Here, we show that myriocin-mediated inhibition of the de novo sphingolipid biosynthesis caused severe growth defects in C. auris. Sublethal myriocin concentrations increase fungal susceptibility to amphotericin B and anidulafungin. While the effect is limited for anidulafungin, even isolates that show phenotypic resistance to amphotericin B became susceptible in presence of myriocin. A large-scale screening of 59 clinical isolates validated these initial results and showed that inhibition of the de novo sphingolipid biosynthesis increases C. auris susceptibility to amphotericin B. These observations open new options for future therapeutic strategies and illustrate that sphingolipids might play a pivotal role for the ability of C. auris to develop resistance against amphotericin B.

microbiology↗

bioRxiv2020

Time-resolved profiling reveals ATF3 as a novel mediator of endocrine resistance in breast cancer

Breast cancer is one of the leading causes of death for women worldwide. Patients whose tumors express Estrogen Receptor (ER) account for around 70% of cases and are mostly treated with targeted endocrine therapy. However, 40% of these tumors eventually relapse due to resistance development and further treatment of these patients is highly ineffective. In this study we profiled the early phases of the resistance development process to uncover drivers of this phenomenon. Time-resolved analysis revealed that ATF3, a member of the ATF/CREB family of transcription factors, acts as a novel regulator of the response to therapy via rewiring of central signaling processes towards the adaptation to endocrine treatment. ATF3 was found to be essential in controlling crucial processes such as proliferation, cell cycle and apoptosis during the early response to treatment through the regulation of MAPK/AKT signaling pathways. Its essential role was confirmed in vivo in a mouse model and elevated expression of ATF3 was verified in patient datasets, adding clinical relevance to our findings. This study proposes ATF3 as a novel mediator of endocrine resistance development in breast cancer and elucidates its role in the regulation of downstream pathways activities.

cancer biology↗

bioRxiv2020

Shank2 expression identifies a subpopulation of glycinergic interneurons involved in nociception and altered in an autism mouse model

Patients suffering from Autism Spectrum Disorders (ASD) experience disturbed nociception in form of either hyposensitivity to pain or hypersensitivity and allodynia. We have determined that Shank2-KO mice, which recapitulate the genetic and behavioural disturbances of ASD, display increased sensitivity to formalin pain and thermal, but not mechanical allodynia. We demonstrate that high levels of Shank2 expression identifies a subpopulation of neurons in murine and human dorsal spinal cord, composed mainly by glycinergic interneurons and that loss of Shank2 causes the decrease in NMDAR in excitatory synapses on these inhibitory interneurons. In fact, in the subacute phase of the formalin test, glycinergic interneurons are strongly activated in WT mice but not in Shank2-KO mice. As consequence, nociception projection neurons in lamina I are activated in larger numbers in Shank2-KO mice. Our findings prove that Shank2 expression identifies a new subset of inhibitory interneurons involved in reducing the transmission of nociceptive stimuli and whose unchecked activation is associated with pain hypersensitivity. Thus, we provide evidence that dysfunction of spinal cord pain processing circuits may underlie the nociceptive phenotypes in ASD patients and mouse models.

neuroscience↗