Myeloid-derived suppressor cells (MDSCs) potently suppress the anti-tumor immune responses and also orchestrate the tumor microenvironment that favors tumor angiogenesis and metastasis. The molecular networks regulating the accumulation and functions of tumor-expanded MDSCs are largely unknown. In this study, we identified microRNA-494 (miR-494), whose expression was dramatically induced by tumor-derived factors, as an essential player in regulating the accumulation and activity of MDSCs by targeting of phosphatase and tensin homolog (PTEN) and activation of the Akt pathway. TGF-β1 was found to be the main tumor-derived factor responsible for the upregulation of miR-494 in MDSCs. Expression of miR-494 not only enhanced CXCR4-mediated MDSC chemotaxis but also altered the intrinsic apoptotic/survival signal by targeting of PTEN, thus contributing to the accumulation of MDSCs in tumor tissues. Consequently, downregulation of PTEN resulted in increased activity of the Akt pathway and the subsequent upregulation of MMPs for facilitation of tumor cell invasion and metastasis. Knockdown of miR-494 significantly reversed the activity of MDSCs and inhibited the tumor growth and metastasis of 4T1 murine breast cancer in vivo. Collectively, our findings reveal that TGF-β1–induced miR-494 expression in MDSCs plays a critical role in the molecular events governing the accumulation and functions of tumor-expanded MDSCs and might be identified as a potential target in cancer therapy.

Hydrogen gas-evolving membrane-bound hydrogenase (MBH) and quinone-reducing complex I are homologous respiratory complexes with a common ancestor, but a structural basis for their evolutionary relationship is lacking. Here, we report the cryo-EM structure of a 14-subunit MBH from the hyperthermophile Pyrococcus furiosus. MBH contains a membrane-anchored hydrogenase module that is highly similar structurally to the quinone-binding Q-module of complex I while its membrane-embedded ion-translocation module can be divided into a H- and a Na-translocating unit. The H-translocating unit is rotated 180° in-membrane with respect to its counterpart in complex I, leading to distinctive architectures for the two respiratory systems despite their largely conserved proton-pumping mechanisms. The Na-translocating unit, absent in complex I, resembles that found in the Mrp H/Na antiporter and enables hydrogen gas evolution by MBH to establish a Na gradient for ATP synthesis near 100°C. MBH also provides insights into Mrp structure and evolution of MBH-based respiratory enzymes.

Polyelectrolyte (PE) hydrogels are typical soft materials with extremely high swelling capacity due to the high osmotic pressure of the dissociated counterions. [1] For example,

SignificanceThe Mycobacterium tuberculosis (Mtb) ClpB is a ring-shaped, ATP-driven disaggregase. The ability to rescue aggregated proteins is crucial for Mtb to grow and persist in the host. Despite extensive studies in the past two decades, it is still not well understood how a bacterial disaggregase couples ATP binding and hydrolysis to peptide translocation. Our cryo-EM study of the Mtb ClpB in the presence of a peptide substrate and the slowly hydrolysable adenosine 5′-[γ-thio]triphosphate revealed two active conformations in the midst of the substrate-threading process. This, together with the resolved nucleotide state in each of the 12 nucleotide-binding domains of the ClpB hexamer, helps define a detailed atomic trajectory that couples ATP binding and hydrolysis to mechanical protein translocation.

Neurotrophins (NTs) are important regulators for the survival, differentiation and maintenance of different peripheral and central neurons. NTs bind to two distinct classes of glycosylated receptor: the p75 neurotrophin receptor (p75(NTR)) and tyrosine kinase receptors (Trks). Whereas p75(NTR) binds to all NTs, the Trk subtypes are specific for each NT. The question of whether NTs stimulate p75(NTR) by inducing receptor homodimerization is still under debate. Here we report the 2.6-A resolution crystal structure of neurotrophin-3 (NT-3) complexed to the ectodomain of glycosylated p75(NTR). In contrast to the previously reported asymmetric complex structure, which contains a dimer of nerve growth factor (NGF) bound to a single ectodomain of deglycosylated p75(NTR) (ref. 3), we show that NT-3 forms a central homodimer around which two glycosylated p75(NTR) molecules bind symmetrically. Symmetrical binding occurs along the NT-3 interfaces, resulting in a 2:2 ligand-receptor cluster. A comparison of the symmetrical and asymmetric structures reveals significant differences in ligand-receptor interactions and p75(NTR) conformations. Biochemical experiments indicate that both NT-3 and NGF bind to p75(NTR) with 2:2 stoichiometry in solution, whereas the 2:1 complexes are the result of artificial deglycosylation. We therefore propose that the symmetrical 2:2 complex reflects a native state of p75(NTR) activation at the cell surface. These results provide a model for NTs-p75(NTR) recognition and signal generation, as well as insights into coordination between p75(NTR) and Trks.

a b s t r a c tInterleukin 10 (IL-10) is a potent anti-inflammatory cytokine that is crucial for dampening the inflammatory response after pathogen invasion, and was found to be produced by macrophages after exposure to lipopolysaccharide (LPS). It remains unclear whether microRNA-mediated regulatory mechanism is involved in LPS-induced IL-10 production. Here we reported that miR-98 expression in macrophages significantly decreased following LPS stimulation. We also found that miR-98 targets the 3'untranslated region of IL-10 transcript. Overexpression of miR-98 inhibited TLR4-triggered IL-10 production and promoted COX-2 expression. We further demonstrated that miR-98 significantly mitigated the induction of endotoxin tolerance, suggesting that miR-98-mediated posttranscriptional control could potentially be involved in fine tuning the critical level of IL-10 production in endotoxin tolerance.

A simple and effective approach is demonstrated to fabricate tough metallosupramolecular hydrogel films of poly(acrylic acid) by one‐pot photopolymerization of the precursor solution in the presence of Zr4+ ions that form coordination complexes with the carboxyl groups and serve as the physical crosslinks of the matrix. Both as‐prepared and equilibrated hydrogel films are transparent, tough, and stable over a wide range of temperature, ionic strength, and pH. The thickness of the films can be easily tailored with minimum value of ≈7 μm. Owing to the fast polymerization and gelation process, kirigami structures can be facilely encoded to the gel films by photolithographic polymerization, affording versatile functions such as additional stretchability and better compliance of the planar films to encapsulate objects with sophisticated geometries that are important for the design of soft electronics. By stencil printing of liquid metal on the hydrogel film with a kirigami structure, the integrated soft electronics shows good compliance to cover curved surfaces and high sensitivity to monitor human motions. Furthermore, this strategy is applied to diverse natural and synthetic macromolecules containing carboxyl groups to develop tough hydrogel films, which will open opportunities for the applications of hydrogel films in biomedical and engineering fields.

It is highly desired yet challenging to develop hydrogels with a combination of excellent mechanical properties and good stability for potential applications. Here we report κ-carrageenan/polyacrylamide double-network (DN) hydrogels with remarkable mechanical performances and high stability in water, which are achieved using zirconium ions to further crosslink the first physical network of κ-carrageenan by forming coordination complexes. Thus, obtained DN hydrogels in equilibrated state with water content of 83−91 wt % were highly transparent and showed tensile breaking stress of 1.5−3.2 MPa, breaking strain of 300−2200%, Young's modulus of 0.2−2.2 MPa, and tearing fracture energy of 0.4−18.5 kJ/m 2 . We found that dual-cross-linking of the κ-carrageenan network, i.e., the coiled-coil junctions and the metal-coordination bonds, was indispensable for the combined mechanical properties and stability of these gels. Essential reasons were rationally discussed based on the results of control experiments. The strategy we described should be applicable to other biopolymer-based hydrogels toward improved mechanical properties and stability, which may promote the applications of tough hydrogels in diverse areas.