SARS-CoV-2 has been spreading around the world for the past year. Recently, several variants such as B.1.1.7 (alpha), B.1.351 (beta), and P.1 (gamma), which share a key mutation N501Y on the receptor-binding domain (RBD), appear to be more infectious to humans. To understand the underlying mechanism, we used a cell surface-binding assay, a kinetics study, a single-molecule technique, and a computational method to investigate the interaction between these RBD (mutations) and ACE2. Remarkably, RBD with the N501Y mutation exhibited a considerably stronger interaction, with a faster association rate and a slower dissociation rate. Atomic force microscopy (AFM)-based single-molecule force microscopy (SMFS) consistently quantified the interaction strength of RBD with the mutation as having increased binding probability and requiring increased unbinding force. Molecular dynamics simulations of RBD–ACE2 complexes indicated that the N501Y mutation introduced additional π-π and π-cation interactions that could explain the changes observed by force microscopy. Taken together, these results suggest that the reinforced RBD–ACE2 interaction that results from the N501Y mutation in the RBD should play an essential role in the higher rate of transmission of SARS-CoV-2 variants, and that future mutations in the RBD of the virus should be under surveillance.

Graphical AbstractHighlights d Deficiency of KDM5 demethylase causes gut dysbiosis and abnormal social behavior in flies d Lactobacillus plantarum administration improves social behavior in kdm5-deficient animals d KDM5 maintains proper immune activity in a transcriptional and microbiota-mediated manner d KDM5 demethylase affects social behavior through the gutmicrobiome-brain axis SUMMARY Loss-of-function mutations in the histone demethylases KDM5A, KDM5B, or KDM5C are found in intellectual disability (ID) and autism spectrum disorders (ASD) patients. Here, we use the model organism Drosophila melanogaster to delineate how KDM5 contributes to ID and ASD. We show that reducing KDM5 causes intestinal barrier dysfunction and changes in social behavior that correlates with compositional changes in the gut microbiota. Therapeutic alteration of the dysbiotic microbiota through antibiotic administration or feeding with a probiotic Lactobacillus strain partially rescues the behavioral, lifespan, and cellular phenotypes observed in kdm5-deficient flies. Mechanistically, KDM5 was found to transcriptionally regulate component genes of the immune deficiency (IMD) signaling pathway and subsequent maintenance of host-commensal bacteria homeostasis in a demethylase-dependent manner. Together, our study uses a genetic approach to dissect the role of KDM5 in the gut-microbiome-brain axis and suggests that modifying the gut microbiome may provide therapeutic benefits for ID and ASD patients.

Coronavirus disease-19 (COVID-19) is spreading around the world for the past year. Enormous efforts have been taken to understand its mechanism of transmission. It is well established now that the SARS-CoV-2 receptor-binding domain (RBD) of the spike protein binds to the human angiotensin-converting enzyme 2 (ACE2) as its first step of entry. Being a single-stranded RNA virus, SARS-CoV-2 is evolving rapidly. Recently, two variants, B.1.1.7 and B.1.351, both with a key mutation N501Y on the RBD, appear to be more infectious to humans. To understand its mechanism, we combined kinetics assay, single-molecule technique, and computational method to compare the interaction between these RBD (mutations) and ACE2. Remarkably, RBD with the N501Y mutation exhibited a considerably stronger inter-action characterized from all these methodologies, while the other two mutations from B.1.351 contributed to a less effect. Surface plasmon resonance and fluorescence-activated cell scan (FACS) assays found that both RBD mutations are of higher binding affinity to ACE2 than the wild type. In addition, atomic force microscopy-based single-molecule force microscopy quantify their strength on living cells, showing a higher binding probability and unbinding force for both mutations. Finally, Steered Molecular Dynamics (SMD) simulations on the dissociation of RBD-ACE2 complexes revealed the possible structural details for the higher force/interaction. Taking together, we suggested that the stronger inter-action from N501Y mutation in RBD should play an essential role in the higher transmission of COVID-19 variants.

Flagella and cilia are critical cellular organelles that provide a means for cells to sense and progress through their environment. The central component of flagella and cilia is the axoneme, which comprises the "9+2" microtubule arrangement, dynein arms, radial spokes, and the nexin-dynein regulatory complex (N-DRC). Failure to properly assemble components of the axoneme leads to defective flagella and in humans leads to a collection of diseases referred to as ciliopathies. Ciliopathies can manifest as severe syndromic diseases that affect lung and kidney function, central nervous system development, bone formation, visceral organ organization, and reproduction. T-Complex-Associated-Testis-Expressed 1 (TCTE1) is an evolutionarily conserved axonemal protein present from Chlamydomonas (DRC5) to mammals that localizes to the N-DRC. Here, we show that mouse TCTE1 is testis-enriched in its expression, with its mRNA appearing in early round spermatids and protein localized to the flagellum. TCTE1 is 498 aa in length with a leucine rich repeat domain at the C terminus and is present in eukaryotes containing a flagellum. Knockout of Tcte1 results in male sterility because Tcte1-null spermatozoa show aberrant motility. Although the axoneme is structurally normal in Tcte1 mutant spermatozoa, Tcte1-null sperm demonstrate a significant decrease of ATP, which is used by dynein motors to generate the bending force of the flagellum. These data provide a link to defining the molecular intricacies required for axoneme function, sperm motility, and male fertility. male infertility | asthenozoospermia | glycolysis | mutant mouse | testis-specific gene F lagella are ancient, analogous cellular structures used for locomotion and as sensory organelles present in all three domains of life (bacteria, archaea, and eukaryotes). The advantages conferred by this organelle are highlighted by the flagella's apparent independent evolution in all three domains (1-3). Of all of the different flagella present among eukaryotes, flagella attached to gametes play a critical function in uniting gametes for fertilization and the perpetuation of a species. Mammalian spermatozoa have a specialized flagellum that contains a midpiece, principal piece, and end piece with the axoneme running along the entire length (4). The flagellum equips sperm with the capability to deliver half of the male's genetic material to the female gamete, the oocyte. In addition to flagella, eukaryotes contain another related structure called cilia. The defining feature of flagella and cilia is the axoneme, the "9+2" microtubule arraignment of two central pairs of microtubules surrounded by nine pairs of microtubule doublets (5). The microtubule motor dynein is anchored to the outer microtubules and responsible for generating the force required to produce the beating pattern of flagella and cilia (6). The force generated by dynein causes sliding of the microtubules among each other; however, the nexin complex anchors the microtubules in place. The nexin complex [or nexin-dynei...

Lymphatic stomata are small openings of lymphatic capillaries on the free surface of the mesothelium. The peritoneal cavity, pleural cavity, and pericardial cavity are connected with lymphatic system via these small openings, which have the function of active absorption. The ultrastructure of the lymphatic stomata and their absorption from the body cavities are important clinically, such as ascites elimination, neoplasm metastasis, and inflammatory reaction. The lymphatic stomata play an important role in the physiological and pathological conditions. Our previous study indicated for the first time that nitric oxide (NO) could regulate the opening and absorption of the lymphatic stomata. It could decrease the level of free intracellular calcium [Ca 2þ ] through increasing the cyclic guanosine monophosphate (cGMP) level in the rat peritoneal mesothelial cells, thus regulating the lymphatic stomata. This process is related with the NO-cGMP- [Ca 2þ ] signal pathway. In this review, we summarize the recent advances in understanding the development and the function of the lymphatic stomata. The ultrastructure and regulations of the lymphatic stomata are also discussed in this review. Anat Rec,

Pathologically, blood-spinal-cord-barrier (BSCB) disruption after spinal cord injury (SCI) leads to infiltration of numerous peripheral macrophages into injured areas and accumulation around newborn vessels. Among the leaked macrophages, M1-polarized macrophages are dominant and play a crucial role throughout the whole SCI process. The aim of our study was to investigate the effects of M1-polarized bone marrow-derived macrophages (M1-BMDMs) on vascular endothelial cells and their underlying mechanism. Microvascular endothelial cell line bEnd.3 cells were treated with conditioned medium or exosomes derived from M1-BMDMs, followed by evaluations of endothelial-to-mesenchymal transition (EndoMT) and mitochondrial function. After administration, we found conditioned medium or exosomes from M1-BMDMs significantly promoted EndoMT of vascular endothelial cells in vitro and in vivo , which aggravated BSCB disruption after SCI. In addition, significant dysfunction of mitochondria and accumulation of reactive oxygen species (ROS) were also detected. Furthermore, bioinformatics analysis demonstrated that miR-155 is upregulated in both M1-polarized macrophages and microglia. Experimentally, exosomal transfer of miR-155 participated in M1-BMDMs-induced EndoMT and mitochondrial ROS generation in bEnd.3 cells, and subsequently activated the NF-κB signaling pathway by targeting downstream suppressor of cytokine signaling 6 (SOCS6), and suppressing SOCS6-mediated p65 ubiquitination and degradation. Finally, a series of rescue assay further verified that exosomal miR155/SOCS6/p65 axis regulated the EndoMT process and mitochondrial function in vascular endothelial cells. In summary, our work revealed a potential mechanism describing the communications between macrophages and vascular endothelial cells after SCI which could benefit for future research and aid in the development of potential therapies for SCI.

One of the key factors in tissue engineering and regenerative medicine is to optimize the interaction between seed cells and scaffolds such that the cells can grow in naturally biomimetic conditions. Their similarity to macromolecules and many unique properties mean that functional nanoparticles have promising potential for the modification and improvement of traditional scaffolds to obtain excellent biocompatibility, tunable stiffness, physical sensing, and stimulus-response capabilities. In the present study, we report magnetic poly(lactic-co-glycolic acid)/polycaprolactone (PLGA/PCL) scaffolds that were fabricated using a combination of the electrospinning technique and layer-by-layer assembly of superparamagnetic iron oxide nanoparticles (IONPs). PLGA/PCL scaffolds assembled with gold nanoparticles were prepared using the same method for comparison. The results showed that the assembled film of nanoparticles on the surface greatly enhanced the hydrophilicity and increased the elastic modulus of the scaffold, which subsequently improved the osteogenesis of the stem cells. Furthermore, the magnetic property of the IONPs proved to be the key factor in enhancing osteogenic differentiation, which explained the superior osteogenic capacity of the magnetic scaffolds compared with that of the gold nanoparticle-assembled scaffold. These results demonstrated the importance of magnetic nanomaterials as a bioactive interface between cells and scaffolds and will promote the design of biomaterials to improve tissue engineering and regenerative medicine efficacy.

Approximately 10–15% of all bone fractures do not heal properly, causing patient morbidity and additional medical care expenses. Therefore, better mechanism-based fracture repair approaches are needed. In this study, a reduced number of osteoclasts (OCs) and autophagosomes/autolysosomes in OC can be observed in GPCR kinase 2-interacting protein 1 (GIT1) knockout (KO) mice on days 21 and 28 post-fracture, compared with GIT1 wild-type (GIT1 WT) mice. Furthermore, in vitro experiments revealed that GIT1 contributes to OC autophagy under starvation conditions. Mechanistically, GIT1 interacted with Beclin1 and promoted Beclin1 phosphorylation at Thr119, which induced the disruption of Beclin1 and Bcl2 binding under starvation conditions, thereby, positively regulating autophagy. Taken together, the findings suggest a previously unappreciated role of GIT1 in autophagy of OCs during fracture repair. Targeting GIT1 may be a potential therapeutic approach for bone fractures.