Background: Choroid plexus (ChP) is the secretory epithelial structure located in brain ventricles. Choroid plexus tumors (CPTs) are rare neoplasms predominantly occurring in young patients with intensified malignancy in children. CPT treatment is hindered by insufficient knowledge of the tumor pathology and limited availability of valid models.
View Article and Find Full Text PDFHuman development relies on the correct replication, maintenance and segregation of our genetic blueprints. How these processes are monitored across embryonic lineages, and why genomic mosaicism varies during development remain unknown. Using pluripotent stem cells, we identify that several patterning signals-including WNT, BMP, and FGF-converge into the modulation of DNA replication stress and damage during S-phase, which in turn controls chromosome segregation fidelity in mitosis.
View Article and Find Full Text PDFDEAD box (DDX) RNA helicases are a large family of ATPases, many of which have unknown functions. There is emerging evidence that besides their role in RNA biology, DDX proteins may stimulate protein kinases. To investigate if protein kinase-DDX interaction is a more widespread phenomenon, we conducted three orthogonal large-scale screens, including proteomics analysis with 32 RNA helicases, protein array profiling, and kinome-wide in vitro kinase assays.
View Article and Find Full Text PDFIn a human cell, thousands of replication forks simultaneously coordinate duplication of the entire genome. The rate at which this process occurs might depend on the epigenetic state of the genome and vary between, or even within, cell types. To accurately measure DNA replication speeds, we developed single-cell 5-ethynyl-2'-deoxyuridine sequencing to detect nascent replicated DNA.
View Article and Find Full Text PDFDDX RNA helicases promote RNA processing, but DDX3X also activates casein kinase 1 (CK1ε). We show that other DDX proteins also stimulate the protein kinase activity of CK1ε and that this extends to casein kinase 2 (CK2). CK2 enzymatic activity was stimulated by various DDX proteins at high substrate concentrations.
View Article and Find Full Text PDFTrends Cell Biol
December 2022
Wnt signalling is an essential player in tissue formation, notably in the regulation of stem cell function. Wnt signalling is best known for its roles in G1/S progression. However, a complex Wnt programme that also mediates mitotic progression and asymmetric cell division (ACD) is emerging.
View Article and Find Full Text PDFWNT signaling regulates cell cycle progression and fate determination through β-catenin dependent transcription, and its misregulation is often associated with tumorigenesis. Our recent work demonstrated that basal WNT activity is also required to ensure proper chromosome alignment during mitosis through the regulation of kinesin family member 2A (KIF2A).
View Article and Find Full Text PDFCanonical Wnt signaling plays critical roles in development and tissue renewal by regulating β-catenin target genes. Recent evidence showed that β-catenin-independent Wnt signaling is also required for faithful execution of mitosis. However, the targets and specific functions of mitotic Wnt signaling still remain uncharacterized.
View Article and Find Full Text PDFThe tumour suppressors RNF43 and ZNRF3 play a central role in development and tissue homeostasis by promoting the turnover of the Wnt receptors LRP6 and Frizzled (FZD). The stem cell growth factor R-spondin induces auto-ubiquitination and membrane clearance of ZNRF3/RNF43 to promote Wnt signalling. However, the deubiquitinase stabilising ZNRF3/RNF43 at the plasma membrane remains unknown.
View Article and Find Full Text PDFWnt signaling is crucial for proper development, tissue homeostasis and cell cycle regulation. A key role of Wnt signaling is the GSK3β-mediated stabilization of β-catenin, which mediates many of the critical roles of Wnt signaling. In addition, it was recently revealed that Wnt signaling can also act independently of β-catenin.
View Article and Find Full Text PDFWnt/β-catenin signaling plays a key role in embryonic development, stem cell biology, and neurogenesis. However, the mechanisms of Wnt signal transmission, notably how the receptors are regulated, remain incompletely understood. Here we describe that the Parkinson's disease-associated receptor GPR37 functions in the maturation of the N-terminal bulky β-propellers of the Wnt co-receptor LRP6.
View Article and Find Full Text PDFWnt/LRP6 signaling is best known for the β-catenin-dependent regulation of target genes. However, pathway branches have recently emerged, including Wnt/STOP signaling, which act independently of β-catenin and transcription. We review here the molecular mechanisms underlying β-catenin-independent Wnt/LRP6 signaling cascades and their implications for cell biology, development, and physiology.
View Article and Find Full Text PDFThe canonical Wnt signaling pathway is of paramount importance in development and disease. An emergent question is whether the upstream cascade of the canonical Wnt pathway has physiologically relevant roles beyond β-catenin-mediated transcription, which is difficult to study due to the pervasive role of this protein. Here, we show that transcriptionally silent spermatozoa respond to Wnt signals released from the epididymis and that mice mutant for the Wnt regulator Cyclin Y-like 1 are male sterile due to immotile and malformed spermatozoa.
View Article and Find Full Text PDFDuring Xenopus development, Wnt signaling is thought to function first after midblastula transition to regulate axial patterning via β-catenin-mediated transcription. Here, we report that Wnt/glycogen synthase kinase 3 (GSK3) signaling functions posttranscriptionally already in mature oocytes via Wnt/stabilization of proteins (STOP) signaling. Wnt signaling is induced in oocytes after their entry into meiotic metaphase II and declines again upon exit into interphase.
View Article and Find Full Text PDFCanonical Wnt signaling is thought to regulate cell behavior mainly by inducing β-catenin-dependent transcription of target genes. In proliferating cells Wnt signaling peaks in the G2/M phase of the cell cycle, but the significance of this "mitotic Wnt signaling" is unclear. Here we introduce Wnt-dependent stabilization of proteins (Wnt/STOP), which is independent of β-catenin and peaks during mitosis.
View Article and Find Full Text PDFCanonical Wnt signalling plays an important role in development, tissue homeostasis, and cancer. At the cellular level, canonical Wnt signalling acts by regulating cell fate, cell growth, and cell proliferation. With regard to proliferation, there is increasing evidence for a complex interaction between canonical Wnt signalling and the cell cycle.
View Article and Find Full Text PDFThe formation of aggregates by misfolded proteins is thought to be inherently toxic, affecting cell fitness. This observation has led to the suggestion that selection against protein aggregation might be a major constraint on protein evolution. The precise fitness cost associated with protein aggregation has been traditionally difficult to evaluate.
View Article and Find Full Text PDFClpB is a hexameric chaperone that solubilizes and reactivates protein aggregates in cooperation with the Hsp70/DnaK chaperone system. Each of the identical protein monomers contains two nucleotide binding domains (NBD), whose ATPase activity must be coupled to exert on the substrate the mechanical work required for its reactivation. However, how communication between these sites occurs is at present poorly understood.
View Article and Find Full Text PDFClpB is a hexameric molecular chaperone that, together with the DnaK system, has the ability to disaggregate stress-denatured proteins. The hexamer is a highly dynamic complex, able to reshuffle subunits. To further characterize the biological implications of the ClpB oligomerization state, the association equilibrium of the wild-type (wt) protein and of two deletion mutants, which lack part or the whole M domain, was quantitatively analyzed under different experimental conditions, using several biophysical [analytical ultracentrifugation, composition-gradient (CG) static light scattering, and circular dichroism] and biochemical (ATPase and chaperone activity) methods.
View Article and Find Full Text PDFTwo key events in Wnt signal transduction, receptor endocytosis and inactivation of Glycogen Synthase Kinase 3 (GSK3), remain incompletely understood. Taelman et al. (2010) discover that Wnt signaling inactivates GSK3 by sequestering the enzyme in multivesicular bodies, thus linking these two events and providing a new framework for understanding Wnt signaling.
View Article and Find Full Text PDFWnt/beta-catenin signaling is important in stem cell biology, embryonic development, and disease, including cancer. However, the mechanism of Wnt signal transmission, notably how the receptors are activated, remains incompletely understood. We found that the prorenin receptor (PRR) is a component of the Wnt receptor complex.
View Article and Find Full Text PDFIntracellular protein aggregates formed under severe thermal stress can be reactivated by the concerted action of the Hsp70 system and Hsp100 chaperones. We analyzed here the interaction of DnaJ/DnaK and ClpB with protein aggregates. We show that aggregate properties modulate chaperone binding, which in turn determines aggregate reactivation efficiency.
View Article and Find Full Text PDFThermal stress might lead to protein aggregation in the cell. Reactivation of protein aggregates depends on Hsp100 and Hsp70 chaperones. We focus in this study on the ability of DnaK, the bacterial representative of the Hsp70 family, to interact with different aggregated model substrates.
View Article and Find Full Text PDFTo gain further insight into the interactions involved in the allosteric transition of DnaK we have characterized wild-type (wt) protein and three mutants in which ionic interactions at the interface between the two subdomains of the substrate binding domain, and within the lid subdomain have been disrupted. Our data show that ionic contacts, most likely forming an electrically charged network, between the N-terminal region of helix B and an inner loop of the beta-sandwich are involved in maintaining the position of the lid relative to the beta-subdomain in the ADP state but not in the ATP state of the protein. Disruption of the ionic interactions between the C-terminal region of helix B and the outer loops of the beta-sandwich, known as the latch, does not have the same conformational consequences but results equally in an inactive protein.
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