Biology subjects

Feldmann, C.

Publications and source records attributed to Feldmann, C..

8 recordsLinked to original sources

bioRxiv2026

High Drug-Loading Rucaparib-FdUMP Nanocarriers for Colorectal Cancer Combination Therapy

Combination chemotherapy remains the standard of care for advanced colorectal cancer, yet the clinical benefit is limited by off-target toxicity and insufficient tumor drug exposure. Co-administration of 5-fluorouracil (5-FU) with poly(ADP-ribose) polymerase (PARP) inhibitors such as rucaparib (RUC) can potentiate 5-FU-induced DNA damage by suppressing DNA repair but achieving robust co-delivery at defined ratios and high payload remains challenging. Here, we report high drug-loading core@shell nanocarriers (RUC@[ZrO][FdUMP]) that co-deliver RUC and the active 5-FU metabolite fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP). Nanocarriers were synthesized via a solvent-antisolvent approach to form a tocopherol phosphate (TocP)-stabilized RUC core followed by the growth of an amorphous [ZrO][FdUMP] shell, yielding an overall drug load of 59 wt%. Dual fluorescence (shell incorporation of DUT647 and intrinsic RUC emission) enabled quantitative tracking and revealed rapid uptake in HCT116 and HT29 colorectal cancer cells and tumor accumulation in a subcutaneous HT29 xenograft. In vitro, RUC@[ZrO][FdUMP] showed cytotoxicity comparable to the free-drug combination, induced S-phase arrest, and increased {gamma}H2AX foci, consistent with replication stress and DNA double-strand break formation. Drug-drug interaction analysis demonstrated synergistic activity of the RUC/FdUMP pair in colorectal cancer cells. Together, these results establish RUC@[ZrO][FdUMP] as a high-payload nanocarrier platform for co-delivering synergistic PARP inhibitor/fluoropyrimidine combinations, supporting further development and in vivo evaluation of this co-delivery strategy for colorectal cancer therapy. TOC Graphics O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=50 SRC="FIGDIR/small/727099v1_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@dd9ad6org.highwire.dtl.DTLVardef@e07aecorg.highwire.dtl.DTLVardef@1a63505org.highwire.dtl.DTLVardef@e30d58_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2026

CCZ1 is a modulator of TPC2 activity and melanoma cell migration

The small GTPase RAB7a is a key regulator of melanoma progression by enhancing the activity of the endolysosomal two-pore cation channel TPC2. In this study, we demonstrate that CCZ1--a core component of the RAB7a guanine nucleotide exchange factor (GEF) complex--is essential for mediating this RAB7a-dependent enhancement of TPC2. Unexpectedly, we find that constitutively active (GTP-locked) RAB7a fails to bind and regulate TPC2 in the absence of CCZ1, indicating that CCZ1 contributes to the RAB7a-TPC2 interaction through mechanisms beyond its GEF activity. Furthermore, the CCZ1 facilitated GTPase-activating function on RAB5 is dispensable for modulating TPC2. Notably, in the absence of CCZ1, TPC2 exhibits increased affinity for its agonist, PI(3,5)P2, along with markedly upregulated channel activity. In melanoma cell lines, this upregulation enhances migratory capacity. Our findings identify CCZ1 as a functional inhibitor of TPC2 and highlight its critical role in regulating cancer cell migration.

physiology↗

bioRxiv2025

Differential contribution of HCN1 and HCN4 to the synchronisation of sinoatrial pacemaker cells

The hearts ability to beat with high precision, with a regular and steady rhythm relies on the synchronised activity of pacemaker cells in the sinoatrial node (SAN), which communicate with one another through gap junctions. This process ensures that electrical impulses are organised and reach a critical mass to ignite the electrical activity of the surrounding atrial tissue and trigger the regular heartbeat. HypothesisWe hypothesise that hyperpolarisation-activated, cyclic nucleotide-gated (HCN) channels play a pivotal role in maintaining this synchronisation process. This idea aligns with the well-established role of HCN channels in stabilising the membrane potential in the voltage range of the slow diastolic depolarisation, counteracting voltage fluctuations and effectively filtering out variations in the beating rate from neighbouring cells. AimWe focus on two specific HCN channel subtypes--HCN1 and HCN4--and their contributions to the rapid synchronisation of pacemaker cells, a phenomenon known as phasic entrainment. Using two HCN channel-mutant mouse models, we dissect the distinct roles of HCN1 and HCN4 in this process. MethodsWe employed patch-clamp electrophysiology to determine phase response curves (PRCs) to predict the ability of single cells to interact in the SAN. Using computer simulations, the behaviour of the SAN at the network level was determined. ResultsWe found that HCN1, but not HCN4, is essential for the fast synchronisation of pacemaker cells in the SAN and propose a mechanism by which HCN1 channels regulate this process. ConclusionThese findings highlight HCN1 as a critical component for ensuring the precise and rapid coordination needed for synchronisation of the SAN, for a regular and consistent heartbeat. Translational perspectiveOur work provides essential insights into the cellular and molecular mechanisms governing SAN function and lays the groundwork for several clinically relevant applications. Understanding how If blockers may affect heart rate and rhythm stability is crucial for assessing potential side effects of current and future subtype-specific HCN channel inhibitors. Moreover, our findings could support new diagnostic strategies for detecting patients at risk of SAN dysfunction. Ultimately, these findings pave the way for innovative therapeutic approaches, including targeted channel modulation and future cell or gene therapies to restore pacemaker stability.

physiology↗

bioRxiv2025

Hsp90 buffers behavioral plasticity by regulating Pdf transcription in clock neurons of Drosophila melanogaster

Circadian rhythms are prevalent on Earth and temporally organize behaviour and physiology of organisms to occur in species-specific temporal niches. However, species differ in how strictly individuals are controlled by their circadian clock, suggesting that it may offer a selective advantage for an individual to extend its temporal niche under certain circumstances, for example during stressful environmental conditions. A potential mechanism controlling temporal niche adherence involves the evolutionary capacitor and chaperon protein HSP90, known to assist the proper folding of important signalling molecules. If HSP90 becomes rate limiting (e.g., under environmental stress) hidden genetic variation will be expressed, producing novel and potentially beneficial phenotypes for the individual. While this role of HSP90 is well established for morphological traits, we show here that it extends to regulation of temporal behavioural patterns. We show that within a small subset of clock neurons in the fly brain, HSP83, the fly homologue of HSP90, mitigates inter-individual behavioural plasticity. We provide evidence for the requirement of HSP83 for efficient transcription of the gene encoding the circadian neuropeptide Pigment Dispersing Factor (PDF), and for correct PDF accumulation in central clock neurons. Strikingly, Hsp83 mutants affect synchronized oscillations of the clock protein PERIOD (PER) in subsets of circadian clock neurons in the same way as flies without PDF, further supporting a role of Hsp83 in regulating Pdf. Our findings therefore provide a mechanistic explanation for HSP83 function in regulation of behavioural plasticity, and offer an explanation for how to restrict temporal niche extension to stressful environmental conditions.

neuroscience↗

bioRxiv2025

Milking it: repeated post-weaning suckling events in Galapagos Sea Lions Zalophus Wollebaeki

Milk is not cheap. Mammalian offspring are expected to wean during the early juvenile stages, whether through their own mechanisms or their mothers instigation. To not do so would result in a reproductive trade-off for the mother: continued investment in the health and growth of her current offspring, over a shorter birth interval and the possibility of begetting a fitter pup. Here we show for the first time, using 20 years of data, repeated suckling events between female Galapagos Sea Lions (GSL) Zalophus wollebaeki and their fully adult biological offspring well beyond the expected age of independence and when the offspring are themselves already reproductively active. This behavior, supersuckling, suggests that GSL mother-offspring relationships are more complex and longer lasting than previously thought. To our knowledge, this behavior has not been previously documented in any marine mammal species.

animal behavior and cognition↗

bioRxiv2024

Demonstrating Soft X-Ray Tomography in the lab for correlative cryogenic biological imaging using X-rays and light microscopy

Soft X-ray tomography (SXT) enables native-contrast three-dimensional (3D) imaging of fully hydrated, cryogenically preserved biological samples, revealing ultrastructural details without the need for staining, embedding, or sectioning. Traditionally available only at synchrotron facilities, recent advances in laser-driven plasma sources have led to the development of compact soft X-ray microscopes, such as the SXT-100. The SXT-100 achieves imaging resolutions down to 54 nm full-pitch, with tomograms acquired in 30 minutes to two hours. Integrated with an epifluorescence microscope, the SXT-100 facilitates correlative workflows by bridging fluorescence and electron microscopy while preserving the structural integrity of vitrified samples. We demonstrate the capabilities of the SXT-100 through various use cases, including imaging Euglena gracilis, Saccharomyces cerevisiae yeast cells, and nanoparticles in mammalian cells. The relatively short tomogram acquisition times, the virtually non-destructive nature of soft X-ray tomography, and its quantitative imaging capabilities underscore its potential as a powerful tool for advanced biological imaging. Future developments promise enhanced throughput and deeper integration with emerging correlative imaging modalities, and a wider variety of sample types including tissue.

biophysics↗

bioRxiv2021

Murine norovirus capsid plasticity - Glycochenodeoxycholic acid stabilizes P domain dimers and triggers escape from antibody recognition

The murine norovirus (MNV) capsid protein is the target for various neutralizing antibodies binding to distal tips of its protruding (P)-domain. The bile acid glycochenodeoxycholic acid (GCDCA), an important co-factor for murine norovirus (MNV) infection, has recently been shown to induce conformational changes in surface-loops and a contraction of the virion. Here, we employ protein NMR experiments using stable isotope labeled MNV P-domains to shed light on underlying molecular mechanisms. We observe two separate sets of NMR resonance signals for P-domain monomers and dimers, permitting analysis of the corresponding exchange kinetics. Unlike human norovirus GII.4 P-dimers, which exhibit a half-life in the range of several days, MNV P-dimers are very short lived with a half-life of about 17 s. Addition of GCDCA shifts the equilibrium towards the dimeric form by tightly binding to the P-dimers. In MNV virions GCDCA-mediated stabilization of the dimeric arrangement of P-domains generates a more ordered state, which in turn may entropically assist capsid contraction. Numerous long-range chemical shift perturbations (CSPs) upon addition of GCDCA reflect allosteric conformational changes as a feature accompanying dimer stabilization. In particular, CSPs indicate rearrangement of the EF loop, a target for various neutralizing antibodies. Indeed, treating MNV virions with GCDCA prior to neutralizing antibody exposure abolishes neutralization. These findings advance our understanding of GCDCA-induced structural changes of MNV capsids and experimentally support an intriguing viral immune escape mechanism relying on GCDCA-triggered conformational changes of the P-dimer. Significance StatementThis study sheds light on the role of glycochenodeoxycholic acid (GCDCA) in promoting murine norovirus (MNV) infection and immune escape. Binding of GCDCA to the dimeric P-domain has been well characterized by crystallography and cryo EM studies, showing that upon GCDCA binding, a 90{degrees} rotation of the P-domain occurs, which results in its collapse onto the underlying shell of the virus. Our NMR experiments now reveal P-dimer stability as a new dimension of plasticity of MNV capsids and suggest that capsid contraction is entropically assisted. Conformational changes as a feature of P-dimer stabilization eliminate recognition by neutralizing antibodies, no longer being able to prevent infection. These findings highlight key differences between human and MNV capsid structures, promote our understanding of MNV infection on a molecular level, and reveal a novel immune escape mechanism.

biochemistry↗

bioRxiv2019

Mapping the S1 and S1 subsites of cysteine proteases with new dipeptidyl nitrile inhibitors as trypanocidal agents

The cysteine protease cruzipain is considered to be a validated target for therapeutic intervention in the treatment of Chagas disease. A series of 26 new compounds waswere designed, synthesized, and tested against the recombinant cruzain (Cz) to map its S1/S1' subsites. The same series was evaluated on a panel of four human cysteine proteases (CatB, CatK, CatL, CatS) and Leishmania mexicana CPB, which is a potential target for the treatment of cutaneous leishmaniasis. The synthesized compounds are dipeptidyl nitriles designed based on the most promising combinations of different moieties in P1 (ten), P2 (six), and P3 (four different building blocks). Eight compounds exhibited a Ki smaller than 20.0 nM for Cz, whereas three compounds met these criteria for LmCPB. The three inhibitors had an EC50 value of ca. 4 M, thus being equipotent to benznidazole according to the anti-trypanosomal effects. Our mapping approach and the respective structure-activity relationships provide insights into the specific ligand-target interactions for therapeutically relevant cysteine proteases.\n\nAuthor SummaryDespite many achievements in identifying novel agents for the treatment of tropical and neglected diseases, further research continues to be of fundamental importance. Our research groups have been using the cruzipain cysteine protease in its recombinant form, cruzain (Cz), to identify new trypanocidal agents. Considering the possible interchangeability with other cysteine proteases, the same series of dipeptidyl nitriles was tested in Leishmania mexicana LmCPB. Other potential targets for such inhibitors are human cysteine cathepsins, which are involved in different disease states. Thus, the inhibitors were also tested against cathepsins B, L, K, and S. Our results demonstrate that inhibition of these cysteine proteases can be achieved by appropriate structural modifications of dipeptidyl nitriles. It was also possible to identify trypanocidal agents, equipotent to benznidazole, the current drug of choice used for the treatment of Chagas disease.

biochemistry↗