Biology subjects

Sterckx, Y. G.- J.

Publications and source records attributed to Sterckx, Y. G.- J..

5 recordsLinked to original sources

bioRxiv2026

The hearing-essential intracellular domain of PCDH15 reveals a new layer of auditory mechanotransduction

Current models of mechanotransduction in inner-ear hair cells explain how force is transmitted through the extracellular tip link but provide little insight into how force is propagated beneath the plasma membrane. Although the CD2 isoform of PCDH15 has been shown to be essential for hearing in mature mammalian hair cells, its structural and mechanical properties have remained largely unknown. Here, we combine computational sequence analysis, orthogonal biophysical characterization and small-angle X-ray scattering (SAXS) to show that the hearing-essential CD2 intracellular domain is an intrinsically disordered region (IDR) that behaves as a highly expanded acidic polyampholyte. CD2 remains predominantly monomeric in solution and occupies a larger conformational space at physiological-like ionic strength, whereas inclusion of the isoform-shared common region increases self-association. CD2 also contains a conserved regulatory interaction platform, providing a potential link between its polymer properties and cellular regulation. Together, these findings identify the CD2 intracellular domain as a polymer with biophysical properties consistent with a mechanically responsive structural element. Furthermore, they provide a framework for investigating how intracellular polymer mechanics may contribute to force transmission and adaptation in auditory mechanotransduction.

biophysics↗

bioRxiv2026

The CLAMP-Linked Invasion Protein (CLIP) plays an essential role in Plasmodium berghei zoites

Apicomplexan parasites such as Toxoplasma and Plasmodium spp. rely on the sequential secretion of parasite apical organelles, called micronemes and rhoptries, to invade host cells. The claudin-like apicomplexan microneme protein (CLAMP) is a conserved protein that plays an essential role during host cell invasion in Toxoplasma and Plasmodium zoites. Previous studies have shown that CLAMP is essential in Plasmodium merozoites for erythrocyte invasion and also in sporozoites for the invasion of the mosquito vector salivary glands and of mammalian host hepatocytes. In Toxoplasma gondii tachyzoites, CLAMP forms a complex with two other microneme proteins, the Secreted Protein with an Altered Thrombospondin Repeat (SPATR) and the CLAMP-Linked Invasion Protein (CLIP). Both SPATR and CLIP are also expressed in Plasmodium sporozoites, and downregulation of SPATR impacts sporozoite infectivity in P. berghei. In contrast, the role of CLIP in sporozoites remains unknown. To study the function of CLIP, we used a CRISPR-assisted conditional genome editing strategy based on the dimerisable Cre recombinase in the rodent malaria model parasite P. berghei. Deletion of clip in P. berghei blood stages impaired parasite growth and prevented erythrocyte invasion by merozoites. Upon deletion of clip gene in P. berghei transmission stages, sporozoite development in mosquitoes was not affected, but invasion of the mosquito salivary glands was dramatically reduced. In addition, CLIP-deficient sporozoites were impaired in cell traversal and productive invasion of mammalian hepatocytes, associated with a defect in gliding motility, recapitulating the phenotype of CLAMP-deficient parasites. Collectively, our data demonstrate that CLIP plays an essential role in host cell invasion by P. berghei merozoites and sporozoites, and support a conserved role of the CLAMP-CLIP-SPATR complex in invasive stages of apicomplexan parasites.

microbiology↗

bioRxiv2026

A structure-based epitope tagging approach identifies vulnerable sites on the malarial P36-P52 protein complex for antibody-mediated neutralization of Plasmodium sporozoites

Malaria is caused by apicomplexan parasites of the genus Plasmodium, which are transmitted through the bite of Anopheles mosquitoes that inject sporozoites (SPZs) into the skin. SPZs migrate to and infect the liver for an initial round of replication. SPZs and liver stages have long been considered as ideal targets for malaria vaccines. The main SPZ surface protein, the circumsporozoite protein (CSP), is the target of currently approved malaria vaccines and prophylactic antibody therapies. Studies in rodent malaria models have shown that anti-CSP antibodies exert their protective effect mainly in the skin, but some of the most potent anti-CSP monoclonal antibodies show additional protective effects in the vasculature and liver. Other SPZ proteins involved at different steps of the infection process may thus represent additional targets for antibody-mediated neutralization. Three 6-cysteine (6-Cys) domain proteins (P36, P52 and B9) play an essential role during SPZ invasion of hepatocytes, yet their molecular function and whether they can be targeted by neutralizing antibodies remains unknown. Here, to fill this gap, we combined an integrative structural biology approach with functional experiments in the P. berghei rodent malaria model. AlphaFold-based structural modeling followed by experimental validation via electron microscopy and small-angle X-ray scattering indicated that the P36-P52 heterodimer displays a head-to-tail architecture with an interaction interface that is largely conserved among Plasmodium species. The structural models supported the rational design of an epitope tagging approach, which, combined with neutralizing assays, revealed that antibodies against P36 and P52 can efficiently block invasion of hepatocytes by SPZs in culture conditions. The data show that the inhibitory activity of antibodies heavily depends on epitope position and revealed that antibody-exposed vulnerable sites lie on the membrane-distal side of the P36-P52 heterodimer. In contrast, antibodies targeting B9 had no inhibitory effect on SPZ invasion, irrespective of epitope positioning. These data show that the invasion step could be targeted by antibodies and indicate that the P36-P52 complex may be considered as a potential target for the development of next generation pre-erythrocytic malaria vaccines or therapeutic antibodies.

microbiology↗

bioRxiv2025

Insights into the recruitment of the H3K4me3 reader Spp1 by the meiotic double-strand break protein Mer2

The formation of DNA double-strand breaks (DSBs) by Spo11 is tied to the loop-axis organization of meiotic chromosomes. Prior to DSB formation, chromatin loops marked by histone H3K4 trimethylation become tethered to the chromosome axis through interactions between Spp1 and Mer2. Mer2 is an essential partner of Spo11 thought to assemble the DSB machinery via biomolecular condensation, but these molecular assemblies remain poorly characterized. Here, using AlphaFold modeling, biochemical reconstitution, and biophysical validation, we explored the relationship between Mer2, Spp1 and their DNA-bound complexes. The tetrameric coiled-coil domain of Mer2 has four rotationally symmetrical sites that can bind a C-terminal -helix of Spp1. However, binding of one Spp1 subunit appears to allosterically modulate the affinity for the adjacent sites, leading to the assembly of 4x2 Mer2-Spp1 complexes. Mer2 also accommodates multiple DNA duplexes, allowing the assembly of tripartite Mer2-Spp1-DNA complexes with branched DNA substrates and effective recruitment of Spp1 within nucleoprotein condensates. However, because the Spp1- and DNA-binding sites of Mer2 partially overlap, Spp1 recruitment reduces DNA binding by Mer2, which is compensated for by a patch of positively charged residues within Spp1. These findings provide insights into the structural organization of Mer2 and Spp1 and their role in the assembly of the meiotic DSB machinery.

molecular biology↗

bioRxiv2024

Allosteric inhibition of trypanosomatid pyruvate kinases by a camelid single-domain antibody

African trypanosomes are the causative agents of neglected tropical diseases affecting both humans and livestock. Disease control is highly challenging due to an increasing number of drug treatment failures. African trypanosomes are extracellular, blood-borne parasites that mainly rely on glycolysis for their energy metabolism within the mammalian host. Trypanosomal glycolytic enzymes are therefore of interest for the development of trypanocidal drugs. Here, we report the serendipitous discovery of a camelid single-domain antibody (sdAb aka Nanobody) that selectively inhibits the enzymatic activity of trypanosomatid (but not host) pyruvate kinases through an allosteric mechanism. By combining enzyme kinetics, biophysics, structural biology, and transgenic parasite survival assays, we provide a proof-of-principle that the sdAb-mediated enzyme inhibition negatively impacts parasite fitness and growth.

biochemistry↗