MFSD1 with its accessory subunit GLMP functions as a general dipeptide uniporter in lysosomes.

The lysosomal degradation of macromolecules produces diverse small metabolites exported by specific transporters for reuse in biosynthetic pathways. Here we deorphanized the major facilitator superfamily domain containing 1 (MFSD1) protein, which forms a tight complex with the glycosylated lysosomal membrane protein (GLMP) in the lysosomal membrane. Untargeted metabolomics analysis of MFSD1-deficient mouse lysosomes revealed an increase in cationic dipeptides. Purified MFSD1 selectively bound diverse dipeptides, while electrophysiological, isotope tracer and fluorescence-based studies in Xenopus oocytes and proteoliposomes showed that MFSD1-GLMP acts as a uniporter for cationic, neutral and anionic dipeptides. Cryoelectron microscopy structure of the dipeptide-bound MFSD1-GLMP complex in outward-open conformation characterized the heterodimer interface and, in combination with molecular dynamics simulations, provided a structural basis for its selectivity towards diverse dipeptides. Together, our data identify MFSD1 as a general lysosomal dipeptide uniporter, providing an alternative route to recycle lysosomal proteolysis products when lysosomal amino acid exporters are overloaded.

Development of Polyphosphate/Nanokaolin-Modified Alginate Sponge by Gas-Foaming and Plasma Glow Discharge Methods for Ultrarapid Hemostasis in Noncompressible Bleeding.

Effective bleeding management strategies in uncontrollable and noncompressible massive hemorrhage are becoming important in both clinical and combat situations. Here, a novel approach was developed to create a superporous and highly absorbable hemostatic sponge through a facile chemical gas-foaming method by cross-linking long-chain polyphosphate along with nanokaolin and Ca2+ in an alginate structure to synergistically activate the coagulation pathway. Natural kaolin obtained from the Marand mine in East Azarbaijan was converted into pseudohexagonal-shaped kaolin nanoparticles (30 to 150 nm) using ball milling followed by a newly developed glow discharge plasma treatment method. The obtained ultralight sponges (>90% porosity) exhibit ultrarapid water/blood absorption capacity (∼4000%) and excellent shape memory, which effectively concentrates coagulation factors. The results of in vitro tests demonstrated that the proposed sponges exhibited enhanced blood clotting ability (BCI < 10%) and superior cohesion with red blood cells (∼100) and platelets (∼80%) compared to commercially available hemostatic products. The in vivo host response results exhibited biosafety with no systemic and significant local inflammatory response by hematological, pathological, and biochemical parameter assessments. In a rat femoral artery complete excision model, the application of alginate/k/polyp nanocomposite sponges resulted in a complete hemostasis time of 60 s by significant reduction of hemostasis time (∼6.7-8.3 fold) and blood loss (∼2-2.8-fold) compared to commercially available hemostatic agents (P < 0.001). In conclusion, distinct physical characteristics accompanied by unique chemical composition multifunctional sponges activate hemostasis synergistically by triggering the XII, XI, X, IX, V, and II factors and the contact pathway and have the ability of rapid hemostasis in noncompressible severe bleeding.

Structures of complete extracellular receptor assemblies mediated by IL-12 and IL-23.

Cell-surface receptor complexes mediated by pro-inflammatory interleukin (IL)-12 and IL-23, both validated therapeutic targets, are incompletely understood due to the lack of structural insights into their complete extracellular assemblies. Furthermore, there is a paucity of structural details describing the IL-12-receptor interaction interfaces, in contrast to IL-23-receptor complexes. Here we report structures of fully assembled mouse IL-12/human IL-23-receptor complexes comprising the complete extracellular segments of the cognate receptors determined by electron cryo-microscopy. The structures reveal key commonalities but also surprisingly diverse features. Most notably, whereas IL-12 and IL-23 both utilize a conspicuously presented aromatic residue on their α-subunit as a hotspot to interact with the N-terminal Ig domain of their high-affinity receptors, only IL-12 juxtaposes receptor domains proximal to the cell membrane. Collectively, our findings will help to complete our understanding of cytokine-mediated assemblies of tall cytokine receptors and will enable a cytokine-specific interrogation of IL-12/IL-23 signaling in physiology and disease.

Synergistic effect of chitosan-alginate composite hydrogel enriched with ascorbic acid and alpha-tocopherol under hypoxic conditions on the behavior of mesenchymal stem cells for wound healing.

BACKGROUND: In regenerative medicine, especially skin tissue engineering, the focus is on enhancing the quality of wound healing. Also, several constructs with different regeneration potentials have been used for skin tissue engineering. In this study, the regenerative properties of chitosan-alginate composite hydrogels in skin wound healing under normoxic and hypoxic conditions were investigated in vitro. METHODS: The ionic gelation method was used to prepare chitosan/alginate (CA) hydrogel containing CA microparticles and bioactive agents [ascorbic acid (AA) and α-tocopherol (TP)]. After preparing composite hydrogels loaded with AA and TP, the physicochemical properties such as porosity, pore size, swelling, weight loss, wettability, drug release, and functional groups were analyzed. Also, the hemo-biocompatibility of composite hydrogels was evaluated by a hemolysis test. Then, the rat bone marrow mesenchymal stem cells (rMSCs) were seeded onto the hydrogels after characterization by flow cytometry. The survival rate was analyzed using MTT assay test. The hydrogels were also investigated by DAPI and H&E staining to monitor cell proliferation and viability. To induce hypoxia, the cells were exposed to CoCl2. To evaluate the regenerative potential of rMSCs cultured on CA/AA/TP hydrogels under hypoxic conditions, the expression of the main genes involved in the healing of skin wounds, including HIF-1α, VEGF-A, and TGF-ß1, was investigated by real-time PCR. RESULTS: The results demonstrated that the prepared composite hydrogels were highly porous, with interconnected pores that ranged in sizes from 20 to 188 µm. The evaluation of weight loss showed that the prepared hydrogels have the ability to biodegrade according to the goals of wound healing. The reduction percentage of CA/AA/TP mass in 21 days was reported as 21.09 ± 0.52%. Also, based on wettability and hemolysis tests of the CA/AA/TP, hydrophilicity (θ = 55.6° and 53.7°) and hemocompatibility with a hemolysis ratio of 1.36 ± 0.19 were evident for them. Besides, MTT assay, DAPI, and H&E staining also showed that the prepared hydrogels provide a suitable substrate for cell growth and proliferation. Finally, based on real-time PCR, increased expression levels of VEGF and TGF-ß1 were observed in rMSCs in hypoxic conditions cultured on the prepared hydrogels. CONCLUSIONS: In conclusion, this study provides evidence that 3D CA/AA/TP composite hydrogels seeded by rMSCs in hypoxic conditions have great potential to improve wound healing.

Biomolecular and cellular effects in skin wound healing: the association between ascorbic acid and hypoxia-induced factor.

The skin serves as a barrier to protect the body from environmental microorganisms and is the largest tissue of the body and any damage must be quickly and effectively repaired. The fundamental purpose of dermal fibroblasts is to produce and secrete extracellular matrix, which is crucial for healing wounds. The production of collagen by dermal fibroblasts requires the cofactor ascorbic acid, a free radical scavenger. In skin wounds, the presence of Ascorbic acid (AA) decreases the expression of pro-inflammatory factors and increases the expression of wound-healing factors. In addition, AA plays an important role in all three phases of wound healing, including inflammation, proliferation, and regeneration. On the other hand, growing evidence indicates that hypoxia improves the wound healing performance of mesenchymal stem cell-conditioned medium compared to the normoxic-conditioned medium. In a hypoxic-conditioned medium, the proliferation and migration of endothelial cells, fibroblasts, and keratinocytes (important cells in accelerating skin wound healing) increase. In this review, the role of AA, hypoxia, and their interactions on wound healing will be discussed and summarized by the in vitro and in vivo studies conducted to date.

A review on the effect of nanocomposite scaffolds reinforced with magnetic nanoparticles in osteogenesis and healing of bone injuries.

Many problems related to disorders and defects of bone tissue caused by aging, diseases, and injuries have been solved by the multidisciplinary research field of regenerative medicine and tissue engineering. Numerous sciences, especially nanotechnology, along with tissue engineering, have greatly contributed to the repair and regeneration of tissues. Various studies have shown that the presence of magnetic nanoparticles (MNPs) in the structure of composite scaffolds increases their healing effect on bone defects. In addition, the induction of osteogenic differentiation of mesenchymal stem cells (MSCs) in the presence of these nanoparticles has been investigated and confirmed by various studies. Therefore, in the present article, the types of MNPs, their special properties, and their application in the healing of damaged bone tissue have been reviewed. Also, the molecular effects of MNPs on cell behavior, especially in osteogenesis, have been discussed. Finally, the present article includes the potential applications of MNP-containing nanocomposite scaffolds in bone lesions and injuries. In summary, this review article highlights nanocomposite scaffolds containing MNPs as a solution for treating bone defects in tissue engineering and regenerative medicine.

Green Synthesized Magnesium Oxide Nanoparticles Reinforce Osteogenesis Properties of Bacterial Cellulose Scaffolds for Bone Tissue Engineering Applications: An In Vitro Assessment.

OBJECTIVE: The use of biocompatible scaffolds with appropriate characteristics to treat large bone defects has attracted significant attention. The main objective of the current study is to fabricate a 3D nanocomposite structure that contains green synthesized magnesium oxide nanoparticles (MgONPs) and bacterial cellulose (BC) nanofibres, as a bioscaffold for bone regeneration. MATERIALS AND METHODS: In this experimental study, Camellia sinensis extract was used as the green method to synthesize MgONPs. The synthesized hydrogels were evaluated for their porosity, morphology, degradation rate, mechanical features, cell attachment, and cytocompatibility. Osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity, real-time reverse transcription-polymerase chain reaction (RT-PCR), and alizarin red staining. RESULTS: MgONPs significantly increased both mechanical strength (P=0.009) and porosity (P=0.01) of the BC hydrogels. Human MG-63 osteoblast proliferation significantly increased in the MgONP-BC group compared to the pure BC group (P=0.003). Expression rates of both the ALP (P=0.001) and osteocalcin (OCN) genes were significantly enhanced in cells seeded on the MgONP-incorporated BC. MG-63 cells had significantly greater calcium deposition and ALP activity (P=0.002) on the MgONP-BC scaffold compared to the BC at day 21. CONCLUSION: The MgONP-BC scaffold can promote the osteogenic activity of osteoblast-like cells, which indicates its therapeutic potential for bone tissue regeneration.

GlycoVHH: optimal sites for introducing N-glycans on the camelid VHH antibody scaffold and use for macrophage delivery.

As small and stable high-affinity antigen binders, VHHs boast attractive characteristics both for therapeutic use in various disease indications, and as versatile reagents in research and diagnostics. To further increase the versatility of VHHs, we explored the VHH scaffold in a structure-guided approach to select regions where the introduction of an N-glycosylation N-X-T sequon and its associated glycan should not interfere with protein folding or epitope recognition. We expressed variants of such glycoengineered VHHs in the Pichia pastoris GlycoSwitchM5 strain, allowing us to pinpoint preferred sites at which Man5GlcNAc2-glycans can be introduced at high site occupancy without affecting antigen binding. A VHH carrying predominantly a Man5GlcNAc2 N-glycan at one of these preferred sites showed highly efficient, glycan-dependent uptake by Mf4/4 macrophages in vitro and by alveolar lung macrophages in vivo, illustrating one potential application of glyco-engineered VHHs: a glycan-based targeting approach for lung macrophage endolysosomal system delivery. The set of optimal artificial VHH N-glycosylation sites identified in this study can serve as a blueprint for targeted glyco-engineering of other VHHs, enabling site-specific functionalization through the rapidly expanding toolbox of synthetic glycobiology.

Application of mesenchymal stem cell sheet for regeneration of craniomaxillofacial bone defects.

Bone defects are among the most common damages in human medicine. Due to limitations and challenges in the area of bone healing, the research field has turned into a hot topic discipline with direct clinical outcomes. Among several available modalities, scaffold-free cell sheet technology has opened novel avenues to yield efficient osteogenesis. It is suggested that the intact matrix secreted from cells can provide a unique microenvironment for the acceleration of osteoangiogenesis. To the best of our knowledge, cell sheet technology (CST) has been investigated in terms of several skeletal defects with promising outcomes. Here, we highlighted some recent advances associated with the application of CST for the recovery of craniomaxillofacial (CMF) in various preclinical settings. The regenerative properties of both single-layer and multilayer CST were assessed regarding fabrication methods and applications. It has been indicated that different forms of cell sheets are available for CMF engineering like those used for other hard tissues. By tackling current challenges, CST is touted as an effective and alternative therapeutic option for CMF bone regeneration.

Dissecting the conformational complexity and mechanism of a bacterial heme transporter.

Iron-bound cyclic tetrapyrroles (hemes) are redox-active cofactors in bioenergetic enzymes. However, the mechanisms of heme transport and insertion into respiratory chain complexes remain unclear. Here, we used cellular, biochemical, structural and computational methods to characterize the structure and function of the heterodimeric bacterial ABC transporter CydDC. We provide multi-level evidence that CydDC is a heme transporter required for functional maturation of cytochrome bd, a pharmaceutically relevant drug target. Our systematic single-particle cryogenic-electron microscopy approach combined with atomistic molecular dynamics simulations provides detailed insight into the conformational landscape of CydDC during substrate binding and occlusion. Our simulations reveal that heme binds laterally from the membrane space to the transmembrane region of CydDC, enabled by a highly asymmetrical inward-facing CydDC conformation. During the binding process, heme propionates interact with positively charged residues on the surface and later in the substrate-binding pocket of the transporter, causing the heme orientation to rotate 180°.

Selective killing of the human gastric pathogen Helicobacter pylori by mitochondrial respiratory complex I inhibitors.

Respiratory complex I is a multicomponent enzyme conserved between eukaryotic cells and many bacteria, which couples oxidation of electron donors and quinone reduction with proton pumping. Here, we report that protein transport via the Cag type IV secretion system, a major virulence factor of the Gram-negative bacterial pathogen Helicobacter pylori, is efficiently impeded by respiratory inhibition. Mitochondrial complex I inhibitors, including well-established insecticidal compounds, selectively kill H. pylori, while other Gram-negative or Gram-positive bacteria, such as the close relative Campylobacter jejuni or representative gut microbiota species, are not affected. Using a combination of different phenotypic assays, selection of resistance-inducing mutations, and molecular modeling approaches, we demonstrate that the unique composition of the H. pylori complex I quinone-binding pocket is the basis for this hypersensitivity. Comprehensive targeted mutagenesis and compound optimization studies highlight the potential to develop complex I inhibitors as narrow-spectrum antimicrobial agents against this pathogen.

Recent advances in nano-scaffolds for tissue engineering applications: Toward natural therapeutics.

Among the promising methods for repairing or replacing tissue defects in the human body and the hottest research topics in medical science today are regenerative medicine and tissue engineering. On the other hand, nanotechnology has been expanded into different areas of regenerative medicine and tissue engineering due to its essential benefits in improving performance in various fields. Nanotechnology, a helpful strategy in tissue engineering, offers new solutions to unsolved problems. Especially considering the excellent physicochemical properties of nanoscale structures, their application in regenerative medicine has been gradually developed, and a lot of research has been conducted in this field. In this regard, various nanoscale structures, including nanofibers, nanosheets, nanofilms, nano-clays, hollow spheres, and different nanoparticles, have been developed to advance nanotechnology strategies with tissue repair goals. Here, we comprehensively review the application of the mentioned nanostructures in constructing nanocomposite scaffolds for regenerative medicine and tissue engineering. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Diagnostic Tools > Biosensing.

Mechanical properties of the rabbit and human decellularized patches for well-tolerated/reinforced organ in cardiac tissue engineering.

Introduction: Natural decellularized patches have been developed as the therapeutic platform for the treatment of different diseases, especially cardiovascular disorders. Decellularized scaffolds (as both cell-seeded and cell-free patches) are broadly studied in heart tissue redevelopment in vivo and in vitro. The designed regenerative bio-scaffold must have desirable physicochemical properties including mechanical stiffness for load-bearing, and appropriate anatomical characteristics to mimic the native biological environment properly and facilitate tissue reconstruction. In this context, the current study was designed to investigate rabbit decellularized derma's similarity with human decellularized skin in terms of mechanical properties for cardiac tissue engineering application. Methods: Fifty two rabbit dermal specimens were provided and divided into two groups: the experimental (decellularized) group and the control (group). Similarly, twelve human skin specimens were divided into the experimental (decellularized) and control groups. Initially, the effect of decellularization on the mechanical performance of scaffolds was analyzed. Then, the mechanical strength of decellularized rabbit skin was compared to decellularized human derma by measuring the stress strain and Young's modulus of the samples. Results: The results showed that rabbit decellularized skin has a similar elastic range to human decellularized skin, despite being more elastic (P>0.05). In addition, after decellularization, both rabbit and human skin showed a non-significant decrease in elasticity (P>0.05). It is worth noting that the elasticity reduction in rabbit samples after skin decellularization was lower than in human samples. Conclusion: According to the results of this study and the similarities of rabbit decellularized derm to human skin and its advantages over it, along with the biological complexity of native cardiac ECM, this scaffold can be used as an alternative matrix for tissue-engineered cardiac patches.

Force-tuned avidity of spike variant-ACE2 interactions viewed on the single-molecule level.

Recent waves of COVID-19 correlate with the emergence of the Delta and the Omicron variant. We report that the Spike trimer acts as a highly dynamic molecular caliper, thereby forming up to three tight bonds through its RBDs with ACE2 expressed on the cell surface. The Spike of both Delta and Omicron (B.1.1.529) Variant enhance and markedly prolong viral attachment to the host cell receptor ACE2, as opposed to the early Wuhan-1 isolate. Delta Spike shows rapid binding of all three Spike RBDs to three different ACE2 molecules with considerably increased bond lifetime when compared to the reference strain, thereby significantly amplifying avidity. Intriguingly, Omicron (B.1.1.529) Spike displays less multivalent bindings to ACE2 molecules, yet with a ten time longer bond lifetime than Delta. Delta and Omicron (B.1.1.529) Spike variants enhance and prolong viral attachment to the host, which likely not only increases the rate of viral uptake, but also enhances the resistance of the variants against host-cell detachment by shear forces such as airflow, mucus or blood flow. We uncover distinct binding mechanisms and strategies at single-molecule resolution, employed by circulating SARS-CoV-2 variants to enhance infectivity and viral transmission.

Cryo-EM structures of pentameric autoinducer-2 exporter from Escherichia coli reveal its transport mechanism.

Bacteria utilize small extracellular molecules to communicate in order to collectively coordinate their behaviors in response to the population density. Autoinducer-2 (AI-2), a universal molecule for both intra- and inter-species communication, is involved in the regulation of biofilm formation, virulence, motility, chemotaxis, and antibiotic resistance. While many studies have been devoted to understanding the biosynthesis and sensing of AI-2, very little information is available on its export. The protein TqsA from Escherichia coli, which belongs to the AI-2 exporter superfamily, has been shown to export AI-2. Here, we report the cryogenic electron microscopic structures of two AI-2 exporters (TqsA and YdiK) from E. coli at 3.35 Å and 2.80 Å resolutions, respectively. Our structures suggest that the AI-2 exporter exists as a homo-pentameric complex. In silico molecular docking and native mass spectrometry experiments were employed to demonstrate the interaction between AI-2 and TqsA, and the results highlight the functional importance of two helical hairpins in substrate binding. We propose that each monomer works as an independent functional unit utilizing an elevator-type transport mechanism.

Isothermal Amplification of Nucleic Acids Coupled with Nanotechnology and Microfluidic Platforms for Detecting Antimicrobial Drug Resistance and Beyond.

Antibiotic resistance is one of the serious health-threatening issues globally, the control of which is indispensable for rapid diagnosis and treatment because of the high prevalence and risks of pathogenicity. Traditional and molecular techniques are relatively expensive, complex, and non-portable, requiring facilities, trained personnel, and high-tech laboratories. Widespread and timely-detection is vital to the better crisis management of rapidly spreading infective diseases, especially in low-tech regions and resource-limited settings. Hence, the need for inexpensive, fast, simple, mobile, and accessible point-of-care (POC) diagnostics is highly demanding. Among different biosensing methods, the isothermal amplification of nucleic acids is favorite due to their simplicity, high sensitivity/specificity, rapidity, and portability, all because they require a constant temperature to work. Isothermal amplification methods are utilized for detecting various targets, including DNA, RNA, cells, proteins, small molecules, ions, and viruses. In this paper, we discuss various platforms, applications, and potentials of isothermal amplification techniques for biosensing of antimicrobial resistance. We also evaluate the potential of these methods, coupled with the novel and rapidly-evolving platforms offered by nanotechnology and microfluidic devices.

Toxicopathological changes induced by combined exposure to noise and toluene in New Zealand White rabbits.

Noise and toluene can have significant adverse effects on different systems in the human body, but little is known about their combination. The aim of this study was to see how their combined action reflects on serum levels of inflammatory cytokines tumour necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1ß), body weight, and pathological changes in the heart, lung, stomach, and spleen tissues. To do that we exposed New Zealand rabbits to 1000 mg/L toluene and 100 dB of white noise in a chamber specifically designed for the purpose over two consecutive weeks. Serum levels of TNF-α and IL-1ß were measured with the enzyme-linked immunosorbent assay (ELISA), whereas Bax and Bcl-2 expressions in tissues were determined with real-time polymerase chain reaction (PCR). Noise and toluene changed TNF-α and IL-1ß serum levels on different days following the end of exposure and significantly increased the Bax/Bcl-2 ratio in the lung and spleen. In addition, they induced different pathological changes in the heart, lung, spleen, and stomach tissues. This study has confirmed that exposure to noise and toluene can induce a range of toxicopathological changes, probably by inducing inflammatory pathways and apoptosis, but their combined effects look weaker than those of its components, although histopathological findings suggest the opposite.

PCL/Col I-based magnetic nanocomposite scaffold provides an osteoinductive environment for ADSCs in osteogenic cues-free media conditions.

BACKGROUND: The bone tissue engineering (BTE) approach has been introduced as an alternative to conventional treatments for large non-healing bone defects. Magnetism promotes stem cells' adherence to biocompatible scaffolds toward osteoblast differentiation. Furthermore, osteogenic differentiation media are expensive and any changes in its composition affect stem cells differentiation. Moreover, media growth factors possess a short half-life resulting in the rapid loss of their functions in vivo. With the above in mind, we fabricated a multilayered nanocomposite scaffold containing the wild type of Type I collagen (Col I) with endogenous magnetic property to promote osteogenesis in rat ADSCs with the minimum requirement of osteogenic differentiation medium. METHODS: Fe3O4 NPs were synthesized by co-precipitation method and characterized using SEM, VSM, and FTIR. Then, a PCL/Col I nanocomposite scaffold entrapping Fe3O4 NPs was fabricated by electrospinning and characterized using SEM, TEM, AFM, VSM, Contact Angle, tensile stretching, and FTIR. ADSCs were isolated from rat adipose tissue and identified by flow cytometry. ADSCs were loaded onto PCL/Col I and PCL/Col I/Fe3O4-scaffolds for 1-3 weeks with/without osteogenic media conditions. The cell viability, cell adhesion, and osteogenic differentiation were evaluated using MTT assay, SEM, DAPI staining, ALP/ARS staining, RT-PCR, and western blotting, respectively. RESULTS: SEM, VSM, and FTIR results indicated that Fe3O4 was synthesized in nano-sized (15-30 nm) particles with spherical-shaped morphology and superparamagnetic properties with approved chemical structure as FTIR revealed. According to SEM images, the fabricated magnetic scaffolds consisted of nanofiber (500-700 nm). TEM images have shown the Fe3O4 NPs entrapped in the scaffold's fiber without bead formation. FTIR spectra analysis confirmed the maintenance of the natural structure of Col I, PCL, and Fe3O4 upon electrospinning. AFM data have shown that MNPs incorporation introduced stripe-like topography to nanofibers, while the depth of the grooves has decreased from 800 to 500 nm. Flow cytometry confirmed the phenotype of ADSCs according to their surface markers (i.e., CD29 and CD105). Additionally, Fe3O4 NP improved nanocomposite scaffold strength, wettability, porosity, biocompatibility and also facilitates the ALP activity, calcium-mineralization. Finally, magnetic nanocomposite scaffolds upregulated osteogenic-related genes or proteins' expression (e.g., Col I, Runx2, OCN, ON, BMP2) in seeded ADSCs with/without osteo-differentiation media conditions. CONCLUSIONS: Together, these results indicate that Fe3O4 NPs within the natural structure of Col I increase osteogenic differentiation in osteogenic cues-free media conditions. This effect could be translated in vivo toward bone defects healing. These findings support the use of natural ECM materials alongside magnetic particles as composite scaffolds to achieve their full therapeutic potential in BTE treatments.

Evidence for a trap-and-flip mechanism in a proton-dependent lipid transporter.

Transport of lipids across membranes is fundamental for diverse biological pathways in cells. Multiple ion-coupled transporters take part in lipid translocation, but their mechanisms remain largely unknown. Major facilitator superfamily (MFS) lipid transporters play central roles in cell wall synthesis, brain development and function, lipids recycling, and cell signaling. Recent structures of MFS lipid transporters revealed overlapping architectural features pointing towards a common mechanism. Here we used cysteine disulfide trapping, molecular dynamics simulations, mutagenesis analysis, and transport assays in vitro and in vivo, to investigate the mechanism of LtaA, a proton-dependent MFS lipid transporter essential for lipoteichoic acid synthesis in the pathogen Staphylococcus aureus. We reveal that LtaA displays asymmetric lateral openings with distinct functional relevance and that cycling through outward- and inward-facing conformations is essential for transport activity. We demonstrate that while the entire amphipathic central cavity of LtaA contributes to lipid binding, its hydrophilic pocket dictates substrate specificity. We propose that LtaA catalyzes lipid translocation by a 'trap-and-flip' mechanism that might be shared among MFS lipid transporters.