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Abstract WNT signaling is fundamental in development and homeostasis, but how the Frizzled receptors (FZDs) propagate signaling remains enigmatic. Here, we present the cryo-EM structure of FZD4 engaged with the DEP domain of Dishevelled 2 (DVL2), a key WNT transducer. We uncover a distinct binding mode where the DEP finger-loop inserts into the FZD4 cavity to form a hydrophobic interface. FZD4 intracellular loop 2 (ICL2) additionally anchors the complex through polar contacts. Mutagenesis validates the structural observations. The DEP interface is highly conserved in FZDs, indicating a universal mechanism by which FZDs engage with DVLs. We further reveal that DEP mimics G-protein/β-arrestin/GRK to recognize an active conformation of receptor, expanding current GPCR engagement models. Finally, we identify a distinct FZD4 dimerization interface. Our findings delineate the molecular determinants governing FZD/DVL assembly and propagation of WNT signaling, providing long-sought answers underlying WNT signal transduction.

Abstract The histamine H4 receptor (H4R) plays key role in immune cell function and is a highly valued target for treating allergic and inflammatory diseases. However, structural information of H4R remains elusive. Here, we report four cryo-EM structures of H4R/Gi complexes, with either histamine or synthetic agonists clobenpropit, VUF6884 and clozapine bound. Combined with mutagenesis, ligand binding and functional assays, the structural data reveal a distinct ligand binding mode where D943.32 and a π-π network determine the orientation of the positively charged group of ligands, while E1825.46, located at the opposite end of the ligand binding pocket, plays a key role in regulating receptor activity. The structural insight into H4R ligand binding allows us to identify mutants at E1825.46 for which the agonist clobenpropit acts as an inverse agonist and to correctly predict inverse agonism of a closely related analog with nanomolar potency. Together with the findings regarding receptor activation and Gi engagement, we establish a framework for understanding H4R signaling and provide a rational basis for designing novel antihistamines targeting H4R.

GPR174 is a lysophosphatidylserine (LysoPS) activated GPCR. Here, the authors report the cryo-EM structure of LysoPS-bound human GPR174 in complex with Gs protein. The study reveals how GPR174 recognizes the lipid ligand and engages Gs in a distinct binding mode.

aGPCRs play key roles in multiple physiological processes. Here the authors report cryo-EM structures of GPR110 in complexes with Gq, Gs, Gi, G12 and G13 protein to reveal a detailed mechanism of aGPCR activation via the tethered stalk peptide and principles of G-protein coupling and selectivity on GPR110.

Histamine receptors are effective targets for allergy treatments and antihistamines are the first choice of many allergic disorders, but the exact mechanism of agonist binding and receptor activation remain unknown. Here, the authors present the cryo-EM structure of histamine-bound H1R/Gq complex and propose a mechanism of ligand induced receptor activation.

Plasmodium falciparum multidrug resistance protein 1 (PfMDR1), an adenosine triphosphate (ATP)-binding cassette (ABC) transporter on the digestive vacuole (DV) membrane of the parasite, is associated with the resistance to antimalarial drugs. To understand the mechanisms of PfMDR1, we determined the cryo-electron microscopy structures of this transporter in different states. The transporter in the apo state shows an inward-facing conformation with a large cavity opening to the cytoplasm. Upon ATP binding and dimerization of the nucleotide-binding domains (NBDs), PfMDR1 displays an outward-facing conformation with a cavity toward the DV lumen. Drug resistance-associated mutations were investigated in both structures for their effects, and Y184F was identified as an allosteric activity-enhancing mutation. The amphiphilic substrate-binding site of PfMDR1 was revealed by the complex structure with the antimalarial drug mefloquine and confirmed by mutagenesis studies. Remarkably, a helical structure was found to hinder NBD dimerization and inhibit PfMDR1 activity. The location of this regulatory domain in the N terminus is different from the well-studied R domain in the internal linker region of other ABC transporter family members. The lack of the phosphorylation site of this domain also suggests a different regulation mechanism. [ABSTRACT FROM AUTHOR]

A facile nonaqueous synthetic route is described for preparing anatase nanosheets with exposed {001} facets and high-quality rhombic-shaped anatase nanocrystals with a large percentage of exposed {010} facets. The nanostructured Ti[O.sub.2] has displayed conspicuous activity in the photocatalytic degradation of organic contaminants.

Abstract The oxidation of Ti--48Al--8Cr--2Ag (at. %) was studied for 50 h at 900 and 1000°C. The micro structure of the oxide scales was characterized by means of scan ning-elec tron microscopy (SEM) and high-resolution elec tron microscopy (HREM). The results showed that the mass gain of the alloy at 1000°C was lower than that at 900°C. At 1000°C, a continuous and densescale of quite pure Al2 O3 formed, but at 900°C, a complex scale with an outer layer of Al2O3 + TiO2 and an layer of inner Al2O3. A Laves phase and a Z-phase were found at the scale/substrate interface, which might be a factor beneficial to the formation of Al2O3 [ABSTRACT FROM AUTHOR]