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The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts with lower amounts of the scarce but active and stable iridium is an attractive avenue to overcome this economical constraint. Here we report on a class of oxygen-evolving catalysts based on iridium double perovskites which contain 32 wt% less iridium than IrO 2 and yet exhibit a more than threefold higher activity in acid media. According to recently suggested benchmarking criteria, the iridium double perovskites are the most active catalysts for oxygen evolution in acid media reported until now, to the best of our knowledge, and exhibit similar stability to IrO 2 . Iridium oxide is an active and stable catalyst for the oxygen evolution reaction, however Ir is very rare, making it unsuitable for large-scale application. Here the authors develop a class of Ir double perovskites containing less Ir than iridium oxide, but exhibiting 3-fold higher activity in acidic media.

Molecular glue compounds induce protein–protein interactions that, in the context of a ubiquitin ligase, lead to protein degradation 1 . Unlike traditional enzyme inhibitors, these molecular glue degraders act substoichiometrically to catalyse the rapid depletion of previously inaccessible targets 2 . They are clinically effective and highly sought-after, but have thus far only been discovered serendipitously. Here, through systematically mining databases for correlations between the cytotoxicity of 4,518 clinical and preclinical small molecules and the expression levels of E3 ligase components across hundreds of human cancer cell lines 3 – 5 , we identify CR8—a cyclin-dependent kinase (CDK) inhibitor 6 —as a compound that acts as a molecular glue degrader. The CDK-bound form of CR8 has a solvent-exposed pyridyl moiety that induces the formation of a complex between CDK12–cyclin K and the CUL4 adaptor protein DDB1, bypassing the requirement for a substrate receptor and presenting cyclin K for ubiquitination and degradation. Our studies demonstrate that chemical alteration of surface-exposed moieties can confer gain-of-function glue properties to an inhibitor, and we propose this as a broader strategy through which target-binding molecules could be converted into molecular glues. The cyclin-dependent kinase inhibitor CR8 acts as a molecular glue compound by inducing the formation of a complex between CDK12–cyclin K and DDB1, which results in the ubiquitination and degradation of cyclin K.

G-protein-coupled receptors do not only feature the orthosteric pockets, where most endogenous agonists bind, but also a multitude of other allosteric pockets that have come into the focus as potential binding sites for synthetic modulators. Here, to better characterise such pockets, we investigate 557 GPCR structures by exhaustively docking small molecular probes in silico and converting the ensemble of binding locations to pocket-defining volumes. Our analysis confirms all previously identified pockets and reveals nine previously untargeted sites. In order to test for the feasibility of functional modulation of receptors through binding of a ligand to such sites, we mutate residues in two sites, in two model receptors, the muscarinic acetylcholine receptor M 3 and β 2 -adrenergic receptor. Moreover, we analyse the correlation of inter-residue contacts with the activation states of receptors and show that contact patterns closely correlating with activation indeed coincide with these sites. G-protein-coupled receptors bind endogenous ligands at sites that are frequently highly conserved. Here, authors computationally describe alternative allosteric pockets, several of which have not been targeted by synthetic ligands before.

BiP is a major endoplasmic reticulum (ER) chaperone and is suggested to act as primary sensor in the activation of the unfolded protein response (UPR). How BiP operates as a molecular chaperone and as an ER stress sensor is unknown. Here, by reconstituting components of human UPR, ER stress and BiP chaperone systems, we discover that the interaction of BiP with the luminal domains of UPR proteins IRE1 and PERK switch BiP from its chaperone cycle into an ER stress sensor cycle by preventing the binding of its co-chaperones, with loss of ATPase stimulation. Furthermore, misfolded protein-dependent dissociation of BiP from IRE1 is primed by ATP but not ADP. Our data elucidate a previously unidentified mechanistic cycle of BiP function that explains its ability to act as an Hsp70 chaperone and ER stress sensor.

Hydrogen peroxide (H 2 O 2 ) is a major reactive oxygen species in unicellular and multicellular organisms, and is produced extracellularly in response to external stresses and internal cues 1 – 4 . H 2 O 2 enters cells through aquaporin membrane proteins and covalently modifies cytoplasmic proteins to regulate signalling and cellular processes. However, whether sensors for H 2 O 2 also exist on the cell surface remains unknown. In plant cells, H 2 O 2 triggers an influx of Ca 2+ ions, which is thought to be involved in H 2 O 2 sensing and signalling. Here, by using forward genetic screens based on Ca 2+ imaging, we isolated hydrogen-peroxide-induced Ca 2+ increases ( hpca ) mutants in Arabidopsis , and identified HPCA1 as a leucine-rich-repeat receptor kinase belonging to a previously uncharacterized subfamily that features two extra pairs of cysteine residues in the extracellular domain. HPCA1 is localized to the plasma membrane and is activated by H 2 O 2 via covalent modification of extracellular cysteine residues, which leads to autophosphorylation of HPCA1. HPCA1 mediates H 2 O 2 -induced activation of Ca 2+ channels in guard cells and is required for stomatal closure. Our findings help to identify how the perception of extracellular H 2 O 2 is integrated with responses to various external stresses and internal cues in plants, and have implications for the design of crops with enhanced fitness. HPCA1, a member of a previously uncharacterized subfamily of leucine-rich-repeat receptor-like kinases, is the hydrogen-peroxide sensor at the plasma membrane in Arabidopsis .

Desmosterol acts as an endogenous RORγ agonist during differentiation of CD4 + T cells into the T H 17 lineage, where there is increased cholesterol biosynthesis and uptake and decreased cholesterol metabolism and efflux that cause accumulation of desmosterol. Retinoic acid receptor–related orphan receptor γ (RORγt) controls the differentiation of naive CD4 + T cells into the T H 17 lineage, which are critical cells in the pathogenesis of autoimmune diseases. Here we report that during T H 17 differentiation, cholesterol biosynthesis and uptake programs are induced, whereas their metabolism and efflux programs are suppressed. These changes result in the accumulation of the cholesterol precursor, desmosterol, which functions as a potent endogenous RORγ agonist. Generation of cholesterol precursors is essential for T H 17 differentiation as blocking cholesterol synthesis with chemical inhibitors at steps before the formation of active precursors reduces differentiation. Upon activation, metabolic changes also lead to production of specific sterol-sulfate conjugates that favor activation of RORγ over the T H 17-inhibiting sterol receptor LXR. Thus, T H 17 differentiation is orchestrated by coordinated sterol synthesis, mobilization and metabolism to selectively activate RORγ.

The fundamental life-defining processes in living cells, such as replication, division, adaptation, and tissue formation, occur via intertwined metabolic reaction networks that process signals for downstream effects with high precision in a confined, crowded environment. Hence, it is crucial to understand and reenact some of these functions in wholly synthetic cell-like entities (protocells) to envision designing soft materials with life-like traits. Herein, we report on all-DNA protocells composed of a liquid DNA interior and a hydrogel-like shell, harboring a catalytically active DNAzyme, that converts DNA signals into functional metabolites that lead to downstream adaptation processes via site-selective strand displacement reactions. The downstream processes include intra-protocellular phenotype-like changes, prototissue formation via multivalent interactions, and chemical messenger communication between active sender and dormant receiver cell populations for sorted heteroprototissue formation. The approach integrates several tools of DNA-nanoscience in a synchronized way to mimic life-like behavior in artificial systems for future interactive materials. Signal processing for downstream functional and morphological adaptations is crucial for understanding and re-enacting features of living systems. Here, the authors show DNAzyme-containing, metabolic protocells that induce prototissue formation via chemical messenger communication due to in situ cleavage of upstream DNA signals.

Accumulation of mutant proteins is a major cause of many diseases (collectively called proteopathies), and lowering the level of these proteins can be useful for treatment of these diseases. We hypothesized that compounds that interact with both the autophagosome protein microtubule-associated protein 1A/1B light chain 3 (LC3) 1 and the disease-causing protein may target the latter for autophagic clearance. Mutant huntingtin protein (mHTT) contains an expanded polyglutamine (polyQ) tract and causes Huntington’s disease, an incurable neurodegenerative disorder 2 . Here, using small-molecule-microarray-based screening, we identified four compounds that interact with both LC3 and mHTT, but not with the wild-type HTT protein. Some of these compounds targeted mHTT to autophagosomes, reduced mHTT levels in an allele-selective manner, and rescued disease-relevant phenotypes in cells and in vivo in fly and mouse models of Huntington’s disease. We further show that these compounds interact with the expanded polyQ stretch and could lower the level of mutant ataxin-3 (ATXN3), another disease-causing protein with an expanded polyQ tract 3 . This study presents candidate compounds for lowering mHTT and potentially other disease-causing proteins with polyQ expansions, demonstrating the concept of lowering levels of disease-causing proteins using autophagosome-tethering compounds. Compounds that interact with mutant huntingtin and an autophagosomal protein are able to reduce cellular levels of mutant huntingtin by targeting it for autophagic degradation, demonstrating an approach that may have potential for treating proteopathies.

Hypomagnesemia is a significant risk factor for critically ill patients to develop sepsis, a life-threatening disease with a mortality rate over 25%. Our clinic data analysis showed that hypomagnesemia is associated with a decreased monocyte count in septic patients. At the cellular level, we found that Mg 2+ inhibits pyroptosis. Specifically, Mg 2+ limits the oligomerization and membrane localization of gasdermin D N-terminal (GSDMD-NT) upon the activation of either the canonical or noncanonical pyroptotic pathway. Mechanistically, we demonstrated that Ca 2+ influx is a prerequisite for the function of GSDMD-NT. Mg 2+ blocks Ca 2+ influx by inhibiting the ATP-gated Ca 2+ channel P2X7, thereby impeding the function of GSDMD-NT and inhibiting lipopolysaccharide (LPS)-induced noncanonical pyroptosis. Furthermore, Mg 2+ administration protects mice from LPS-induced lethal septic shock. Together, our data reveal the underlying mechanism of how Mg 2+ inhibits pyroptosis and suggest potential clinic applications of magnesium supplementation for sepsis prevention and treatment.

Obesity-induced mitochondria stress and dysfunction results from disorganized mitochondria-associated ER membranes and excess calcium flux. Proper function of the endoplasmic reticulum (ER) and mitochondria is crucial for cellular homeostasis, and dysfunction at either site has been linked to pathophysiological states, including metabolic diseases. Although the ER and mitochondria play distinct cellular roles, these organelles also form physical interactions with each other at sites defined as mitochondria-associated ER membranes (MAMs), which are essential for calcium, lipid and metabolite exchange. Here we show that in the liver, obesity leads to a marked reorganization of MAMs resulting in mitochondrial calcium overload, compromised mitochondrial oxidative capacity and augmented oxidative stress. Experimental induction of ER-mitochondria interactions results in oxidative stress and impaired metabolic homeostasis, whereas downregulation of PACS-2 or IP3R1, proteins important for ER-mitochondria tethering or calcium transport, respectively, improves mitochondrial oxidative capacity and glucose metabolism in obese animals. These findings establish excessive ER-mitochondrial coupling as an essential component of organelle dysfunction in obesity that may contribute to the development of metabolic pathologies such as insulin resistance and diabetes.