Biology subjects

Oberkampf, M.

Publications and source records attributed to Oberkampf, M..

4 recordsLinked to original sources

bioRxiv2026

Targeting Sec61 to Silence Pathogenic Light-Chain Production in AL Amyloidosis

Unstable immunoglobulin light chains (LCs) secreted by clonal plasma cells drive organ damage in AL amyloidosis, yet no therapy exist to directly suppress their biosynthesis. Here, we targeted the Sec61 translocon to block LC biogenesis. In patient-derived plasma cells, the Sec61 blocker mycolactone redirected nascent LCs to proteasomal degradation, inducing proteotoxic stress that synergized with bortezomib. In vivo, this combination reduced plasma-cell engraftment and LC secretion but caused toxicity, underscoring the need for Sec61 client selectivity. Proteomic profiling of a model patient-derived plasma cell line treated with the synthetic Sec61 inhibitors A317 and A347 revealed intermediate- and narrow-spectrum client selectivity, respectively, while retaining activity against the LC. However, unlike A317, the more selective A347 failed to inhibit diverse amyloidogenic LCs in a signal-peptide reporter assay. In primary plasma cells from an AL cohort, A317 consistently reduced pathogenic LC production while sparing matched non-malignant bone marrow cells. Together, these findings establish Sec61 as a therapeutic target in AL amyloidosis and identify the need to balance client selectivity with coverage of diverse amyloidogenic LC signal peptides.

cell biology↗

bioRxiv2023

The TcdE holin drives toxin secretion and virulence in Clostridioides difficile.

Clostridioides difficile is the leading cause of healthcare associated infections. The Pathogenicity Locus (PaLoc) toxins TcdA and TcdB promote host disease. These toxins lack canonical N-terminal signal sequences for translocation across the bacterial membrane, suggesting alternate mechanisms of release, which have included targeted secretion and passive release from cell lysis. While the holin TcdE has been implicated in TcdA and TcdB release, its role in vivo remains unknown. Here, we show profound reductions in toxin secretion in tcdE mutants in the highly virulent strains UK1 (epidemic ribotype 027, Clade 3) and VPI10463 (ribotype 087, Clade 1). Notably, tcdE deletion in either strain rescued highly susceptible gnotobiotic mice from lethal infection by reducing acute extracellular toxin to undetectable levels, limiting mucosal damage, and enabling long-term survival, in spite of continued toxin gene expression in tcdE mutants. Our findings confirm TcdEs critical functions in vivo for toxin secretion and C. difficile virulence.

microbiology↗

bioRxiv2021

c-di-AMP signaling is required for bile salts resistance and long-term colonization by Clostridioides difficile

To cause disease, the important human enteropathogen Clostridioides difficile must colonize the gastro-intestinal tract but little is known on how this organism senses and responds to the harsh host environment to adapt and multiply. Nucleotide second messengers are signaling molecules used by bacteria to respond to changing environmental conditions. In this study, we showed for the first time that c-di-AMP is produced by C. difficile and controls the uptake of potassium, making it essential for growth. We found that c-di-AMP is involved in biofilm formation, cell wall homeostasis, osmotolerance as well as detergent and bile salt resistance in C. difficile. In a colonization mouse model, a strain lacking GdpP, a c-di-AMP degrading enzyme, failed to persist in the gut in contrast to the parental strain. We identified OpuR as a new regulator that binds c-di-AMP and represses the expression of the compatible solute transporter OpuC. Interestingly, an opuR mutant is highly resistant to a hyperosmotic or bile salt stress compared to the parental strain while an opuCA mutant is more susceptible A short exposure of C. difficile cells to bile salts resulted in a decrease of the c-di-AMP concentrations reinforcing the hypothesis that changes in membrane characteristics due to variations of the cellular turgor or membrane damages constitute a signal for the adjustment of the intracellular c-di-AMP concentration. Thus, c-di-AMP is a signaling molecule with pleiotropic effects that controls osmolyte uptake to confer osmotolerance and bile salt resistance in C. difficile and that is important for colonization of the host. One Sentence Summaryc-di-AMP is an essential regulatory molecule conferring resistance to osmotic and bile salt stresses by controlling osmolyte uptake and contributing to gut persistence in the human enteropathogen Clostridioides difficile.

microbiology↗

bioRxiv2021

Metabolic adaption to extracellular pyruvate triggers biofilm formation in Clostridioides difficile

Clostridioides difficile infections are associated with gut microbiome dysbiosis and are the leading cause of hospital acquired diarrhoea. The infectious process is strongly influenced by the microbiota and successful infection relies on the absence of specific microbiota-produced metabolites. Deoxycholic acid (DOC) and short chain fatty acids are microbiota-produced metabolites that limit the growth of C. difficile and protect the host against this infection. In a previous study, we showed that DOC causes C. difficile to form strongly adherent biofilms after 48 h. Here, our objectives were to identify and characterize key molecules and events required for biofilm formation in the presence of DOC. We applied time-course transcriptomics and genetics to identify sigma factors, metabolic processes and type IV pili that drive biofilm formation. These analyses revealed that extracellular pyruvate induces biofilm formation in the presence of DOC. In the absence of DOC, pyruvate supplementation was sufficient to induce biofilm formation in a process that was dependent on pyruvate uptake by the membrane protein CstA. In the context of the human gut, microbiota-generated pyruvate is a metabolite that limits pathogen colonization. Taken together our results suggest that pyruvate-induced biofilm formation might act as a key process driving C. difficile persistence in the gut.

microbiology↗