FEBS Letters最新文献

The epidermis is a stratified epithelium that functions as the first line of defense against pathogenic invasion and acts as a barrier preventing water loss. In this study, we aimed to decipher the role of 14-3-3ε in the development of the epidermis. We report that loss of 14-3-3ε in the epidermis of juvenile and adult mice reduces cell division in the basal layer and increases the percentage of cells with multiple centrosomes, leading to a reduction in the thickness of the basal and stratified layers. We also demonstrate a decrease in the expression of differentiation markers, although no gross morphological defects in the skin or adverse effects on the survival of the mice were observed. These results suggest that loss of 14-3-3ε in the epidermis may lead to defects in proliferation and differentiation.

Multiple system atrophy (MSA) is a progressive neurodegenerative disease characterized by accumulation of α-synuclein cross-β amyloid filaments in the brain. Previous structural studies of these filaments by cryo-electron microscopy (cryo-EM) revealed three discrete folds distinct from α-synuclein filaments associated with other neurodegenerative diseases. Here, we use cryo-EM to identify a novel, low-populated MSA filament subtype (designated Type I₂) in addition to a predominant class comprising MSA Type II₂ filaments. The 3.3-Å resolution structure of the Type I₂ filament reveals a fold consisting of two asymmetric protofilaments, one of which adopts a novel structure that is chimeric between two previously reported protofilaments. These results further define MSA-specific folds of α-synuclein filaments and have implications for designing MSA diagnostics and therapeutics.

Zinc transporters (ZnTs) act as H⁺/Zn²⁺ antiporters, crucial for zinc homeostasis. Brain-specific ZnT3 expressed in synaptic vesicles transports Zn²⁺ from the cytosol into vesicles and is essential for neurotransmission, with ZnT3 dysfunction associated with neurological disorders. Ubiquitously expressed ZnT4 localized to lysosomes facilitates the Zn²⁺ efflux from the cytosol to lysosomes, mitigating the cell injury risk. Despite their importance, the structures and Zn²⁺ transport mechanisms remain unclear. We characterized the three-dimensional structures of human ZnT3 (inward-facing) and ZnT4 (outward-facing) using cryo-electron microscopy. By combining these structures, we assessed the conformational changes that could occur within the transmembrane domain during Zn²⁺ transport. Our results provide a structural basis for a more comprehensive understanding of the H⁺/Zn²⁺ exchange mechanisms exhibited by ZnTs.

Adenylosuccinate synthetase (AdSS), which catalyses the GTP-dependent conversion of inosine monophosphate (IMP) and aspartic acid to succinyl-AMP, plays a major role in purine biosynthesis. In some bacterial AdSS, it is implicated that IMP binding is important to organize the active site, but in certain plant AdSS, GTP performs this role. Here, we report that in Leishmania donovani AdSS, IMP binding favoured dimerization, induced greater conformational change and improved the protein stability more than GTP binding. IMP binding, which resulted in a network of hydrogen bonds, stabilized the conformation of active site loops and brought the switch loop to a closed conformation, which then facilitated GTP binding. Our results provide a basis for designing better inhibitors of leishmanial AdSS.

Cardiac arrhythmias stemming from abnormal sinoatrial node (SAN) function can lead to sudden death. Developing a biological pacemaker device for treating sick sinus syndrome (SSS) could offer a potential cure. Understanding SAN differentiation is crucial, yet its regulatory mechanism remains unclear. We reanalyzed published RNA-seq data and identified Odz4 as a SAN-specific candidate. In situ hybridization revealed Odz4 expression in the cardiac crescent and throughout the cardiac conduction system (CCS). To assess the role of Odz4 in CCS differentiation, we utilized a Tet-Off inducible system for its intracellular domain (ICD). Embryonic bodies (EBs) exogenously expressing Odz4-ICD exhibited an increased propensity to develop into pacemaker-like cells with enhanced automaticity and upregulated expression of SAN-specific genes. CellChat and GO analyses unveiled SAN-specific enrichment of ligand-receptor sets, especially Ptn-Ncl, and extracellular matrix components in the group exogenously expressing Odz4-ICD. Our findings underscore the significance of Odz4 in SAN development and offer fresh insights into biological pacemaker establishment.

Exo-β-(1,3)-glucanases are promising enzymes for use in the biofuel industry as they hydrolyse sugars such as laminarin, a major constituent of the algal cell wall. This study reports structural and biochemical characterizations of Aspergillus oryzae exo-β-(1,3)-glucanase (AoBgl) belonging to the GH5 family. Purified AoBgl hydrolyses β-(1,3)-glycosidic linkages of the oligosaccharide laminaritriose and the polysaccharide laminarin effectively. We have determined three high-resolution structures of AoBgl: (a) the apo form at 1.75 Å, (b) the complexed form with bound cellobiose at 1.73 Å and (c) the glucose-bound form at 1.20 Å. The crystal structures, molecular dynamics simulation studies and site-directed mutagenesis reveal the mode of substrate binding and interactions at the active site. The results also indicate that AoBgl effectively hydrolyses trisaccharides and higher oligosaccharides. The findings from our structural and biochemical studies would aid in rational engineering efforts to generate superior AoBgl variants and similar GH5 enzymes for their industrial use.

Retraction: A. Mora, K. Sakamoto, E. J. McManus, and D. R. Alessi, "Role of the PDK1-PKB-GSK3 Pathway in Regulating Glycogen Synthase and Glucose Uptake in the Heart," FEBS Letters 579, no. 17 (2005): 3632-3638, https://doi.org/10.1016/j.febslet.2005.05.040. The above article, published online on 06 June 2005 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors; the journal Editor-in-Chief, Michael Brunner; FEBS Press; and John Wiley and Sons Ltd. The journal was contacted by a representative of the research integrity group at the authors' institute, since an institutional investigation revealed inappropriate splicing and duplication of image sections within Fig. 2A, B and Fig. 3A. Consequently, the conclusions of the paper are substantially compromised, and the institute has recommended the paper to be retracted. The editors of the journal agree with the retraction based on the institutional investigation.

Psilocybin, the natural hallucinogen from Psilocybe (magic) mushrooms, is a highly promising drug candidate for the treatment of depression and several other mental health conditions. Biosynthesis of psilocybin from the amino acid l-tryptophan involves four strictly sequential modifications. The third of these, ATP-dependent phosphorylation of the intermediate 4-hydroxytryptamine, is catalysed by PsiK. Here we present a crystallographic analysis and a structure-based mutagenesis study of this kinase, providing insight into its mode of substrate recognition. The results of our work will support future bioengineering efforts aimed at generating variants of psilocybin with enhanced therapeutic properties.

The interaction of sclerostin (Scl) with the low-density lipoprotein receptor-related protein 4 (LRP4) leads to a marked reduction in bone formation by inhibiting the Wnt/β-catenin pathway. To characterize the Scl-LRP4 binding interface, we sorted a combinatorial library of Scl variants and isolated variants with reduced affinity to LRP4. We identified Scl single-mutation variants enriched during the sorting process and verified their reduction in affinity toward LRP4-a reduction that was not a result of changes in the variants' secondary structure or stability. We found that Scl positions K75 (loop 1) and V136 (loop 3) are critical hotspots for binding to LRP4. Our findings establish the foundation for targeting these hotspots for developing novel therapeutic strategies to promote bone formation.

Lambda interferons (IFNLs) provide critical host defense against pathogens encountered at mucosal surfaces. In humans, IFNL signaling is regulated in part by low and cell-type restricted expression of the lambda interferon receptor 1 protein with expression restricted primarily to epithelial cells located at mucosal surfaces. This review will examine the evidence suggesting a role for IFNLR1 transcriptional variants in mediating cell responsiveness to IFNL ligand exposure and regulation of pathway activity.