Biochemistry and Cell Biology最新文献

Cadherin-related family member 5 (CDHR5) is an adhesion molecule that is highly enriched in the microvilli found on the surface of transporting epithelial cells of the gut and kidney. CDHR5 localizes to the distal tips of these microvilli as part of an adhesion complex that drives assembly of microvilli into a cohesive apical brush border, a hallmark feature of polarized transporting epithelial cells. Loss of CDHR5 correlates with poor prognosis of colon cancer patients, while forced over-expression of CDHR5 in colorectal cancer cell lines blocks their ability to form tumors in mice. Despite acting as an apparent tumor suppressor, how CDHR5 targets to the apical domain of transporting epithelial cells to exert its tumor suppressor effects is poorly understood. Here, we show that CDHR5 is expressed as three dominant splice isoforms in intestinal epithelial cells that differ only in the presence and composition of a membrane-proximal extracellular mucin-like domain. When present in the CDHR5 ectodomain, this mucin-like domain restricted targeting of the cadherin to apical microvilli. Importantly, we show that this restriction could be bypassed through apparent hetero-oligomer formation between the splice isoforms that have the mucin-like domain and the isoform that does not.

Galanthamine, an alkaloid derived from the Amaryllidaceae family, serves as an acetylcholinesterase inhibitor. Due to its central cholinergic properties, this compound is being actively studied as a potential treatment for Alzheimer's disease. However, the broader scope of its biological effects remains poorly understood. In this study, we explored the therapeutic potential of galanthamine in promoting neuronal differentiation and enhancing neurite outgrowth in neural stem and progenitor cells (NSPCs). Our detailed analysis demonstrated notable changes in neuronal morphology and complexity during maturation following galanthamine exposure. Notably, the compound significantly increased the proportion of neurons with multiple neurites, indicating its ability to stimulate neurite formation and foster the development of complex neuronal networks. Furthermore, galanthamine treatment led to a marked rise in the number of mature-appearing neurons, distinguished by elongated and intricate dendrites, highlighting its potential to enhance neural plasticity and repair mechanisms. Importantly, we also identified that galanthamine facilitates neuronal differentiation in NSPCs by up-regulating the insulin-like growth factor 2 signaling pathway. Collectively, these findings provide valuable insights into galanthamine's role in Alzheimer's disease and emphasize its promise as a therapeutic agent for this neurodegenerative disorder.

The most common medical therapy for endometriosis suppresses ovulation, which is a barrier for patients planning pregnancy. To address this issue, we focused on the cell proliferation-suppressing effects of lactoferrin, which reportedly in various malignant tumours. Despite being a benign disease, endometriotic cells have similar characteristics to malignant tumours, which may be involved in its onset and progression. Endometriotic and endometrial stromal cells were obtained from patients with endometriosis. After culture with 1 mg/mL of bovine lactoferrin, cell proliferation was significantly suppressed in endometriotic stromal cells compared to controls, but this remained unchanged in endometrial stromal cells. Bovine lactoferrin also significantly increased the number of endometriotic stromal cells in the G0/G1 phase and significantly decreased those in the S phase, and suppressed the protein expression of phosphorylated-AKT, phosphorylated-mTOR, phosphorylated-S6K, and cyclin D1. Bovine lactoferrin inhibits the transition from the G1 to the S phase by suppressing the PI3K/Akt/mTOR pathway and reducing the synthesis of cyclin D1, thereby arresting the cell cycle at the G1 phase. Bovine lactoferrin suppressed the proliferation of endometriotic stromal cells without suppressing the proliferation of endometrial stromal cells. Lactoferrin, which allows for pregnancy and lactation during administration, has potential as a novel therapeutic candidate for endometriosis.

The chromatin remodeler SRCAP plays a critical role in depositing the histone variant H2A.Z, which is essential for transcriptional regulation, chromatin accessibility, and neurodevelopmental processes. Despite its known importance, the mechanisms by which SRCAP regulates H2A.Z dynamics during neuronal differentiation remain poorly understood. Here, we investigated the impact of Srcap knockdown on H2A.Z incorporation and transcriptional regulation in N2A cells. Chromatin immunoprecipitation revealed reduced H2A.Z occupancy at activity-dependent and neurodevelopmental genes upon Srcap knockdown, confirming Srcap's role in H2A.Z deposition. Interestingly, CBP recruitment and global histone H3 acetylation were unaffected by Srcap knockdown at steady-state conditions, suggesting an H2A.Z-specific function of Srcap. We also observed that retinoic acid-induced neuronal differentiation leads to dynamic changes in H2A.Z levels at developmental loci, which are disrupted in Srcap-deficient cells. Gene expression analysis revealed altered expression of neurodevelopmental genes in the absence of Srcap, correlating with reduced H2A.Z occupancy. Together, these findings demonstrate that Srcap is essential for regulating H2A.Z dynamics and gene expression during neuronal differentiation, offering new insights into its role in chromatin remodelling and its potential involvement in neurodevelopmental disorders.

Recently, proteomics analyses using databases of unannotated ORFs revealed that ubiquitin (Ub) variants can be encoded and expressed from pseudogenes. One such pseudogene, UBBP4, produces Ub^KEKS, which contains four substitutions (Q2K, K33E, Q49K, and N60S) relative to canonical Ub. Unlike Ub, Ub^KEKS does not promote proteasomal degradation through K48 linkages and instead modifies a distinct set of proteins. To elucidate the structural basis of this divergence, we solved the NMR solution structure of Ub^KEKS and characterized its backbone dynamics by 15N-relaxation. While Ub^KEKS retains the overall helix-grip fold, we observed significant rearrangements and amplified motions in residues governing the Ub pincer mode, a conformational switch that determines whether UIMs engage the canonical I44 interface or the α1-β3 edge. Specifically, Q2K and K33E cooperate to enhance motions on both fast (ps-ns) and slow (µs-ms) timescales within α1, the β1-β2 loop, and β5-regions central to pincer mode regulation. In addition, Q49K, adjacent to I44, perturbs UIM recognition and likely interferes with K48 chain formation and binding to the proteasomal receptor S5a. Collectively, our findings identify structural and dynamical determinants that explain Ub^KEKS's distinct substrate profile and inability to target proteins for degradation.

Chromatin remodeling plays a crucial role in gene expression. Chromatin architecture is governed by the interaction of a variety of proteins and transcription factors, including histones and non-histone chromatin-binding factors. Non-histone proteins, such as high mobility group-associated proteins High Mobility Group A (HMGA), are key players in this process. They do not have transcriptional activity per se but comprise flexible intrinsically disordered proteins (IDP) that interact with nucleosomes to change the compaction of chromatin at enhancers and promoters, thereby modulating the process of transcription. HMGA proteins have attained significant attention for their role in the regulation of gene expression during development, cell differentiation and in cellular senescence. Their molecular interactions are controlled by posttranslational modifications which determine nucleoprotein complex formation and function. This review highlights the role of HMGA proteins in nuclear organization, at telomeres and centromere regions and in senescence-associated heterochromatin foci and links these spatiotemporal chromatin architectural functions to the molecular domain structure of HMGA proteins in fine-tuning dynamic chromatin states.

Dictyostelium discoideum is a single-celled protist that undergoes multicellular development in response to nutrient deprivation. For close to a century, D. discoideum has been used as a model system for studying conserved cellular and developmental processes such as chemotaxis, cell adhesion, and cell differentiation. In the later decades of the 20th century, intensive research efforts examined the synthesis, trafficking, and activity of lysosomal enzymes in D. discoideum. Subsequent work revealed that lysosomes are essential for all stages of the D. discoideum life cycle and the genome encodes dozens of homologs of human lysosomal enzymes, including those associated with lysosomal storage diseases. Additionally, protocols for examining the trafficking and activity of lysosomal enzymes in D. discoideum are well-established. Here, we provide a comprehensive up-to-date review that summarizes our current knowledge of lysosomal enzyme processing and trafficking in D. discoideum, with an eye towards re-establishing D. discoideum as a model eukaryote for studying the functions of conserved lysosomal enzymes and the pathways that regulate their trafficking.

Antibiotics, specifically clindamycin (Clin), cause intestinal dysbiosis, reducing the microbiota with anti-inflammatory properties. Furthermore, Clin can induce alterations in the immune responses and oxidative stress. Lactoferrin, among other activities, participates in the maintenance of intestinal homeostasis and reduces dysbiosis induced by antibiotic treatment. The aim of this study was to analyze the effect of native and iron-saturated bovine LF in a murine model of dysbiosis induced by Clin. Six groups of male C57BL/6 mice were treated with saline (control), Clin, native lactoferrin (nLF), iron-saturated lactoferrin (sLF), nLF/Clin, or sLF/Clin. Oxidation caused in the intestinal cells of the ileum of animals subjected to different treatments was analyzed, focusing on lipid peroxidation and protein carbonyl content. The expression of inflammatory mediators was determined by qRT-PCR. Treatment with Clin did not modify lipid peroxidation, but significantly increased protein carbonyl levels up to almost 5-fold respect to the control, an effect that was reversed by orally administering sLF to mice. Furthermore, Clin increased the expression of interleukin-6 and TNF-α by 1- and 2-fold change, respectively. This effect was reversed by treatment with nLF and sLF, decreasing the expression to basal levels. In conclusion, this study indicates that lactoferrin can prevent some of the effects of Clin on intestinal cells and their associated immune system.