Biology subjects

Mori, T.

Publications and source records attributed to Mori, T..

At least 19 recordsLinked to original sources

bioRxiv2026

Structural mechanism defining product specificity in glycoside hydrolase family 66 cycloisomaltotetraose glucanotransferase

Cyclic oligosaccharides possess industrial advantages, including molecular encapsulation capability and high physicochemical stability, owing to the absence of a reducing end. Recently, a novel cyclic tetrasaccharide, cycloisomaltotetraose (CI4), consisting of four -1,6-linked glucose units, and the enzymes responsible for its synthesis, cycloisomaltotetraose glucanotransferases (CI4Tases), were discovered. Unlike known cycloisomaltooligosaccharide glucanotransferases (CITases) that yield a wide distribution of cyclic products with a degree of polymerization (DP) of 7 or higher, CI4Tases strictly produce CI4. To elucidate the molecular mechanism underlying this strict DP4 specificity, we determined the crystal structures of CI4Tase from Agreia sp. D1110, in its ligand-free form, as well as in complex with the linear hydrolysis product isomaltotetraose (IG4) and with CI4. Structural comparisons revealed that a loop (M247 to R251) blocks the region corresponding to the -5 subsite of typical CITases, narrowing the substrate-binding pocket. This "molecular ruler" mechanism ensures that only a glycan chain of exactly four glucose units is accommodated for cyclization. Among mutants of the residue positioned at the center of bound CI4, the formation of by-products other than CI4 was significantly suppressed in F245L, F245A, and F245W. While the cyclization activity of all F245 mutants decreased, the CI4 hydrolysis activity of these three mutants was also significantly reduced, resulting in an increased specificity for cyclic sugar production. These findings elucidate the strict size-control mechanism of CI4Tase and provide a structural foundation for engineering cycloisomaltooligosaccharide-producing enzymes with optimized transglycosylation efficiency and specificity for industrial applications.

biochemistry↗

bioRxiv2026

Hydration Energetics Shape Antibody Discrimination between Sulfotyrosine and Phosphotyrosine

Chemically similar post-translational modifications can mediate distinct biological functions, but how proteins distinguish between them remains unclear. Sulfotyrosine (sTyr) and phosphotyrosine (pTyr) exemplify this problem because they have similar sizes, local geometries, and electrostatic properties but function in different biological contexts. Here, we used the monoclonal antibody PSG2, which recognizes sTyr independently of the surrounding peptide sequence, to examine how a protein distinguishes these modifications. The crystal structure of PSG2 bound to an sTyr-containing peptide revealed a deep electropositive pocket with no modeled water molecules in direct contact with the sulfate group. Gas-phase density functional theory calculations favored pTyr over sTyr, showing that direct protein-ligand interactions alone are insufficient to explain PSG2 selectivity. Explicit first-shell hydration calculations showed that pTyr has a larger desolvation penalty than sTyr, and accounting for this difference reversed the calculated energetic order. Isothermal titration calorimetry showed favorable enthalpic and entropic contributions to sTyr binding, whereas no detectable heat signal was observed for pTyr. These results show that PSG2 distinguishes sTyr from pTyr through the balance between direct protein-ligand interactions and ligand desolvation.

biophysics↗

bioRxiv2026

Relationship between gonadosomatic index and spawning-capable status based on gonadal histology in the moonfish Mene maculata

The moonfish Mene maculata (Bloch and Schneider, 1801), the sole extant species of the family Menidae, is widely distributed in the Indo-West Pacific. Although its spawning season has previously been inferred from seasonal variation in the gonadosomatic index (GSI), the histological basis for interpreting GSI as an indicator of spawning-capable status remains limited. Here we describe the gonadal structure of male and female M. maculata and evaluate how GSI and standard length relate to spawning-capable status based on germ cell development. The testis was lobular and exhibited an unrestricted spermatogonial distribution, a structure widely observed among neoteleosts, indicating that the phylogenetic distinctiveness of M. maculata was not associated with a distinctive testicular structure. In the spawning-capable female, oocytes at multiple developmental stages, from primary growth to oocyte maturation, co-occurred within the ovary, indicating asynchronous ovarian development. This finding suggests that M. maculata may be a batch spawner rather than a total spawner as previously inferred. The spawning-capable female had a GSI consistent with previously inferred spawning season estimates. By contrast, histologically examined males were spawning capable at GSI values lower than those previously associated with the inferred spawning season, suggesting that male spawning-capable status may persist beyond the period inferred from elevated GSI alone. This study provides the first histological description of reproductive biology in the phylogenetically distinctive M. maculata and establishes a histological basis for interpreting GSI as a reproductive indicator.

ecology↗

bioRxiv2026

Discovery and structural analysis of glycoside hydrolase family 176 α-1,2 glucosidase from Arthrobacter humicola A8F5

Glycoside hydrolases (GHs) exhibit remarkable specificity dictated by the structural configuration of their target glycosidic linkages. While enzymes that process -1,4- and -1,6-linkages in starch or glycogen are well-characterized, those acting on less common bonds, such as -1,2-glucosidic linkages, remain largely underexplored. In this study, we report the discovery and structural elucidation of a novel -1,2-glucosidase from Arthrobacter humicola A8F5 (A8F5 glucosidase), representing a newly uncovered activity within the poorly characterized GH176 family. Biochemical characterizations revealed that A8F5 glucosidase exclusively cleaves -1,2-linkages via an anomer-inverting mechanism, with a distinct preference for short kojioligosaccharides. To circumvent crystallization obstacles caused by high loop flexibility and translational non-crystallographic symmetry, we engineered a loop-truncated variant. This strategy enabled the determination of high-resolution (up to 1.79 [A]) crystal structures of the enzyme in its ligand-free form and in complex with kojibiose, kojitriose, and selaginose. A8F5 glucosidase adopts a (/)6-barrel fold characteristic of clan GH-G. Complementing the crystal structures with AlphaFold3 prediction demonstrated that two prominent active-site loops (loops 3 and 4) adopt a closed conformation that constricts the catalytic pocket, rendering the architecture suitable for short oligosaccharide recognition while restricting access to larger polymers. Furthermore, sequence similarity network analysis highlights vast, uncharacterized functional diversity within the GH176 family. These findings revealed that the GH176 enzyme recognizes and hydrolyses -1,2-glucosidic bonds through a structural framework distinct from that of the previously known clan GH-L GH65 kojibiose hydrolase, expanding the known functional landscape of this enzyme group toward rare -glucans.

biochemistry↗

bioRxiv2026

Circadian temperature compensation is intrinsically linked with metabolism and redox signaling

Circadian rhythms are a universal property of organisms, and a defining property of these oscillators is the ability to maintain a precise period at different temperatures. Indeed, the discovery in the 1950s of this property, known as "temperature compensation," was a watershed event in our understanding of biological timekeeping. Since that time, however, almost no general principles have emerged that uncover the mechanistic basis of how circadian timekeepers defy the rules" of temperature dependence of biochemical reactions. A genetic investigation of circadian temperature compensation revealed that the sensing of metabolism and ensuing modulation of the core mechanism preserves a constant circadian period. Intracellular redox sensing of metabolic rate is intrinsic to this compensation, and this relationship is conserved in bacterial and mammalian cells. These insights explain previously inexplicable observations of the interaction between redox reactions and circadian timekeeping. These results introduce a previously unknown linkage between temperature compensation and metabolism.

cell biology↗

bioRxiv2026

Stable isotope-assisted computational mass spectrometry reveals root-specific alkaloids in Glycyrrhiza species

Licorice (Glycyrrhiza) is a medicinal plant widely used in approximately 70% of traditional Japanese Kampo formulations and is known to produce a wide array of specialized metabolites with diverse pharmacological properties. Although hundreds of metabolites have been reported, the overall chemical diversity of Glycyrrhiza remains poorly characterized. Here, using mass spectrometry data obtained from fully 13C-labeled leaves and roots of Glycyrrhiza uralensis and Glycyrrhiza glabra, we determined the carbon number, followed by molecular formula and substructure prediction in combination with MS/MS similarity-based molecular networking. After excluding redundant ions, including isotopic peaks, adducts, and in-source fragments, we extracted 3,060 unique metabolite features with assigned carbon numbers. Among these, substructure information was assigned to 1,015 features (33%) across the four plant tissues, revealing the tissue-specific metabolome profiles. Furthermore, we discovered five previously unreported alkaloids, homopipecolic acid-conjugated flavonoids, in the roots of G. uralensis and G. glabra, and Glycine max, another member of the Fabaceae family. Two of these structures were validated using nuclear magnetic resonance spectroscopy. We further proposed a biosynthetic route involving a spontaneous reaction between 1-piperideine and malonyl glycoside substrates and confirmed the formation of the conjugated product using authentic standards.

biochemistry↗

bioRxiv2026

Identification of loop regions as motifs determining cellular and organ chirality in Myosin 1C

Left-right (LR) asymmetry occurs throughout the animal kingdom, from microscopic to macroscopic scales; however, how microscale LR asymmetry (chirality) is integrated into higher-order structural LR asymmetry remains unclear. In Drosophila, the actin motor proteins Myosin1D and Myosin1C impose opposite chirality states on cell shape and intracellular F-actin flow, thereby directing dextral and sinistral morphogenesis, respectively. However, the protein motifs that confer their distinct activities in specifying chiral states have remained unknown. Here, we show that loop motifs within the myosin head domain that form actin-binding sites determine enantiomeric chirality. By swapping these loop motifs between Myosin1D and Myosin1C, we demonstrate that Myosin1D acquires sinistral activity when carrying Myosin1C loops. AlphaFold3 and molecular dynamics analyses reveal differences in loop structure and actin-binding energetics that may account for the contrasting chiral activities of Myosin1D and Myosin1C. Our findings identify specific protein motifs that dictate the handedness of actin flow and organ asymmetry, providing a mechanistic link between molecular interactions and macroscopic left-right patterning.

cell biology↗

bioRxiv2026

11β-HSD2 buffers fetal glucocorticoid exposure inducing Per1 expression under maternal stress

Glucocorticoids (GCs) have been proposed as maternal-fetal communication signals. However, fetal circadian rhythms are initially shielded from maternal entrainment, in addition to delayed circadian clock emergence due to CLOCK suppression. Premature CLOCK/BMAL1 activation disrupts Hes7-driven somite-like structure in gastruloids. Given the genomic proximity of Per1 to Hes7 and their transcriptional ripple effect, the physiological significance of delayed cell-autonomous circadian clock development and the temporal program of maternal-fetal communication during the developmental process have remained unclear. Here, based on a marked decline in Hsd11b2, encoding a GC-inactivating 11{beta}-HSD2 enzyme, during organogenesis, we performed split-litter embryo-transfer experiments in which Hsd11b2 knockout (KO) and wild-type (WT) embryos shared the same maternal environment. Amniotic fluid (AF) GCs remained low and arrhythmic under basal conditions. In contrast, maternal stress caused a pronounced GC surge and Per1 induction in KO, suggesting that 11{beta}-HSD2 buffers acute maternal GC surges. Despite the genomic proximity of Per1 to Hes7 and their transcriptional ripple effect, stress-associated and pharmacological GC exposure recapitulated no overt segmentation defects in vivo. Embryonic stem cell-derived gastruloid assays confirmed that neither GC exposure nor Per1 induction arrested Hes7 oscillations, whereas premature CLOCK/BMAL1 activation impaired these processes even in Hes7 KO gastruloid with ectopic rescue, suggesting that interference with the segmentation clock is mediated by premature CLOCK/BMAL1 activation, not by GC-induced Per1 expression. These findings clearly show that maternal GC signals are selectively buffered during early development. In addition, suppression of CLOCK/BMAL1 activity preserves segmentation clock function, indicating delayed circadian clock emergence is actively regulated during embryogenesis. Significance StatementGCs have been proposed as maternal-fetal communication signals. However, initially, circadian clock is not only suppressed but also shielded from maternal entrainment. Premature CLOCK/BMAL1 activation can disrupt Hes7-driven somitogenesis. In a split-litter Hsd11b2-knockout model, AF GCs remained low and arrhythmic basally but surged after maternal stress in KO embryos, inducing Per1. Despite a genomic position effect of Per1-Hes7 and their putative transcriptional coupling, stress-associated or pharmacological GC exposure did not cause segmentation defects in vivo or disrupt Hes7 oscillations in vitro, whereas CLOCK/BMAL1-driven arrest of Hes7 oscillations persisted in gastruloids despite ectopic Hes7 rescue. These findings identify 11{beta}-HSD2 as a developmental buffer and support the physiological importance of the temporal architecture controlling the timing of circadian clock development.

developmental biology↗

bioRxiv2026

The LIF-LIFR Axis Promotes Liver Regeneration via Modulation of Angiogenesis and HGF Release from LSECs

Liver sinusoidal endothelial cells (LSECs) play essential roles in liver regeneration after injury, but the underlying mechanisms remain incompletely defined. Here we report that leukemia inhibitory factor (LIF), which is rapidly induced after liver injury, acts as a key regulator of LSECs-driven liver regeneration through interaction with LSECs-enriched LIF receptor (LIFR). LIF directly stimulates LSECs proliferation and induces hepatocyte growth factor (HGF) release in a dose-dependent manner via LIFR signaling in LSECs, thereby indirectly promoting hepatocyte proliferation. Systemic LIF neutralization or endothelial cells (ECs)-specific Lifr loss impairs liver regeneration, whereas low-titer AAV-mediated LIF expression increases vascular density, elevates circulating HGF, and improves early liver recovery after partial hepatectomy (PHx) in mice. Together, these findings establish LIF-LIFR as a previously unrecognized endothelial axis to promote hepatocyte proliferation and suggest potential therapeutic strategies to enhance liver repair in patients. HighlightsO_LILIF is upregulated after liver injury and LIF neutralization impairs liver recovery. C_LIO_LILIFR displays the highest expression in ECs; endothelial-specific Lifr deletion delays liver regeneration after injury. C_LIO_LILIF mediates a positive feedback loop including LSECs proliferation as well as HGF release via LIFR pathway. C_LIO_LILIF overexpression increases liver-to-body weight ratio in a dose-dependent manner and accelerates liver regeneration at early stage. C_LI Abstract Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/707802v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@13b42feorg.highwire.dtl.DTLVardef@1ab6390org.highwire.dtl.DTLVardef@115c157org.highwire.dtl.DTLVardef@1486993_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

The Nkx2.3-Nr5a1 gene cascade plays a crucial role in spleen-specific vascular architecture and marginal zone formation

NR5A1 is a nuclear receptor and master regulator of steroidogenic tissue development and steroid hormone biosynthesis in the adrenal glands and gonads. Although NR5A1 is expressed in splenic vascular endothelial cells, its function in the adult spleen remains unclear. Using single-cell transcriptomics in mice, we show that NR5A1-positive endothelial cells are heterogeneous and exhibit distinct phenotypes according to their localization in the splenic sinus or marginal sinus. To assess NR5A1 function, we generated a spleen-specific Nr5a1 enhancer deletion model. Enhancer loss resulted in reduced spleen size and ablation of the marginal zone and marginal sinus. In addition, 21-hydroxylase activity in splenic sinusoidal endothelial cells was reduced, particularly in females, leading to decreased levels of adrenocortical steroids in the spleen. Enhancer deletion also induced ectopic lymphatic-like and high endothelial venule-like vasculature similar to those observed in Nkx2.3-deficient mice. Consistently, mutation of the NKX2.3-binding motif within the enhancer abolished NR5A1 expression. Together, these findings identify an Nkx2.3[->]Nr5a1 regulatory axis essential for spleen-specific endothelial cell differentiation and splenic architecture required for blood filtration and marginal zone formation.

developmental biology↗

bioRxiv2025

Cohesin constrains histone modification-driven chromatin dynamics

Gene expressions are regulated by an interplay between epigenetics and spatial genome organization, the deregulation of which has been implicated in the development of cancers, including myeloid neoplasms. However, it is unclear how they coordinately contribute to normal and malignant hematopoiesis. Here, we show that simultaneous dysregulations of histone modifications and chromatin structures caused by mutations of the epigenetic modulator Asxl1 and cohesin subunit Stag2 cooperatively induce ectopic interactions between polycomb-regulated promoters and active enhancers, leading to the aberrant upregulation of hematopoietic stem cell related genes and development of myelodysplastic syndromes (MDS). De-repression of polycomb-regulated genes induces their translocation to the transcriptionally active loci, where active promoters and enhancers are assembled, in the absence of Stag2-mediated chromatin organization. Our findings revealed that cohesin counteracts histone modification-driven chromatin conformations, manifesting the coordinate roles of histone modifiers and cohesin in regulating genome architectures and gene expressions to prevent malignant transformation.

cancer biology↗

bioRxiv2025

Reliable Detection of SGLT2 Protein through Knockout-based Antibody Characterization and Optimized Procedures

IntroductionSodium-glucose cotransporter 2 (SGLT2) is a key mediator of renal glucose reabsorption. Its pharmacological inhibition exerts cardio- and reno-protective benefits. Despite widespread clinical interest, reliable detection of SGLT2 protein remains challenging due to concerns regarding the specificity of available antibodies. MethodsThis study assessed the specificity of eight commercially available anti-SGLT2 antibodies by immunohistochemistry and Western blotting. Genetically engineered Sglt2-deficient mice and rats, generated via clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) technology, were employed as definitive negative controls. Additionally, human kidney tissues, including renal cell carcinoma samples, were analyzed. ResultsAmong the antibodies tested, few exhibited robust specificity, characterized by substantial immunostaining with minimal background in wild-type kidney tissues and complete absence of staining in Sglt2-deficient samples. In renal cell carcinoma samples, a validated antibody detected SGLT2 immunostaining in proximal tubules of non-tumor regions but not in tumor areas. Subcellular localization studies revealed that SGLT2 was enriched within proximal tubular microvilli, partially overlapping with its co-factor PDZK1IP1 (MAP17). LRP2 (megalin) and NHE3 were placed at the microvillar base and did not colocalize with SGLT2. Western blotting identified a specific SGLT2 band at approximately 55 kDa in kidney lysates using several antibodies under optimized procedures. This band was shifted to approximately 45 kDa after enzymatic removal of N-linked glycans. One antibody detected a weak band at the same molecular mass even in kidney lysates from Sglt2-deficient rodents. ConclusionsConsiderable variability exists in the specificity of commercially available anti-SGLT2 antibodies. Only a limited number of antibodies are suitable for reliable detection of SGLT2 in rodent and human samples. Rigorous antibody characterization, including the use of knockout controls and optimized experimental conditions, is essential to ensure reproducibility and prevent misinterpretation in studies investigating the biological and pathophysiological roles of SGLT2.

molecular biology↗

bioRxiv2025

RNA Dynamics Regulate Transcriptional Condensate Vivacity to Drive Gene Coordination

Transcriptional condensates (TCs), enriched with Mediator, orchestrate super-enhancer (SE)-driven gene expression critical for cell identity. However, how their dynamic physical properties shape transcriptional activities remains unclear. Here, we reveal a previously unknown regulatory axis wherein dynamic features of enhancer RNA (eRNA), transcribed but rapidly degraded by the RNA exosome, maintain optimal TC fluidity and stability. Depletion of RNA exosome disrupts TC integrity, altering Mediator and Pol II colocalization, in embryonic stem cells. This TC perturbation attenuates proper transcriptional regulator loading and pause-release regulation, enhances transcriptional noise, and diminishes coordinated eRNA-mRNA expression for SE-associated genes. Multi-omics analyses, live-cell imaging, and computational modeling collectively demonstrate that RNA turnover modulates TC vivacity, facilitating widespread chromatin contacts between SE-containing active A compartments and coordinated transcriptional bursts across SE-associated genes. Our findings establish RNA-dependent condensate dynamics as an essential quality-control mechanism that fine-tunes global transcriptional coordination, maintaining cellular homeostasis and cell identity. HighlightsO_LIRNA exosome is required for the homeostasis of transcriptional condensates (TCs) C_LIO_LIRNA synthesis and decay optimize the fluidity and dynamic properties of TCs C_LIO_LITCs maintain the transcriptional consistency of super-enhancer (SE) genes C_LIO_LITCs support contacts of SE-containing A compartments for coordinated transcription C_LI

molecular biology↗

bioRxiv2025

Phage lysis protein LysM acts as a wedge to block MurJ conformational changes

Many antibiotics target essential cellular processes. To combat multidrug-resistant bacteria, new antibacterial strategies are needed. In the peptidoglycan biogenesis pathway in Escherichia coli, MurJ, the lipid II flippase, is an essential membrane protein. The 37-residue protein M from the Levivirus phage, known as LysM or SglM, targets MurJ and induces cell lysis; however, its molecular mechanism remains unclear. Here, we present the cryo-EM structure of the MurJ/LysM (JM) complex at 3.09 [A] resolution, revealing that LysM interacts with the crevasse between TM2 and TM7 of MurJ, locking MurJ in an outward-facing conformation, with LysM acting like a wedge. Alanine-scanning mutagenesis and pull-down assays revealed key residues responsible for LysM function, and molecular dynamics simulations showed that LysM stabilizes MurJs outward-facing state. These findings demonstrate an unprecedented phage-derived mechanism for blocking lipid II transport, providing a structural framework for designing MurJ-targeted antimicrobial agents.

molecular biology↗

bioRxiv2025

Elucidating Chiral Myosin-Induced Actin Dynamics: From Single Filament Behavior to Collective Structures

The myosin superfamily comprises over 70 classes, each with multiple subclasses, and shows substantial diversity in properties such as velocity, ATPase activity, duty ratio, and directionality. This functional diversity enables the specialized roles of each myosin in various organisms, organs, and cell types. Recent studies have revealed that certain myosins induce chiral curved motions of actin filaments. However, this newly identified property remains largely unexplored. Here, we investigated this chiral motion in vitro using Chara corallina myosin XI (CcXI), which drives fast counterclockwise (CCW) movement of actin filaments. This chiral motion arises from asymmetric displacement at the filaments leading tip, and its curvature depends on the surface density of myosin. Surprisingly, at near-physiological actin concentrations, actin filaments exhibiting chiral curved motion undergo collective motion, spontaneously forming a novel structure--termed the actin chiral ring (ACR)--that exhibits persistent CCW rotation. ACRs display remarkable stability, continuing to rotate at their formation site until ATP is depleted, while maintaining their structure even after rotation ceases. This stability is unprecedented among reported collective motions of cytoskeletal proteins driven by various motors. Our findings demonstrate that myosins with chiral activity can autonomously organize actin filaments into stable, chiral structures through collective motion, providing new insights into actin self-organization by unconventional myosins. This study advances our understanding of the diverse functional roles of unconventional myosins and introduces a new paradigm for cytoskeletal organization. Significance StatementMyosins are motor proteins that move along actin filaments and support various intracellular functions. Recently, some myosins have been found to drive actin filaments along chiral curved paths, but the mechanisms and significance of this behavior remain poorly understood. Here, we analyzed this activity and discovered that it not only drives chiral curved motion of single actin filaments, but also organizes them into stable, unidirectionally rotating ring structures through collective motion. These rings, termed actin chiral rings (ACRs), spontaneously emerge at near-physiological actin concentrations. Our findings uncover a previously unrecognized organizing principle of actin self-assembly driven by myosin with chiral activity and provide a new framework for understanding how cytoskeletal chirality is made.

cell biology↗

bioRxiv2024

Mutual information of high-dimensional random variables: estimation by frontier mutual information

Many natural sources of information, including genes, yield intricate datasets characterized by high-dimensional random variables. However, the computational constraints and information loss have often limited the accuracy of mutual information (MI) computations in such datasets. To address these limitations, we introduce a novel metric, micromutual information, which measures the information exchange at each cell level within high-dimensional contingency tables. This methodology represents an extension of our previous techniques and employs a linear index approach. The method simplifies complex, high-dimensional genetic data into a one-dimensional format, thereby improving computational efficiency while preserving the intricate structure of gene interactions. Theorems are developed which demonstrate how the sum of micromutual information asymptotically converges to the total MI for multidimensional variables. Our findings indicate that the maximum value of micromutual information, termed MIfront, adheres to an extreme value distribution. The observation of MIfront provides a streamlined approach to estimating the total MI, due to the simplicity of measuring the micromutual information of just one cell. This approach has the potential to improve data analysis in genomics and other fields that deal with multidimensional information.

bioinformatics↗

bioRxiv2024

Molecular basis underlying specific interaction of mammalian melanopsins with an antagonist AA92593

Melanopsin functions in intrinsically photosensitive retinal ganglion cells of mammals to regulate circadian clock and pupil constriction. The opsinamide AA92593 has been reported to specifically inhibit mouse and human melanopsin functions as a competitive antagonist against retinal; however, the molecular mechanisms underlying its specificity have not been resolved. In this study, we attempted to identify amino acid residues responsible for the specific interaction of AA92593 with mammalian melanopsins. Our cell-based assays confirmed that AA92593 effectively inhibited the light-induced cellular responses of mammalian melanopsins, but not those of non-mammalian vertebrate and invertebrate melanopsins. These results suggest that amino acid residues specifically conserved among mammalian melanopsins are important for the antagonistic effect of AA92593, and we noticed Phe-94, Ser-188, and Ser-269 as candidate residues. Substitutions of these residues reduced the antagonistic effect of AA92593. We conducted docking and molecular dynamics simulations based on the AlphaFold-predicted melanopsin structure. The simulations indicated that Phe-94, Ser-188, and Ser-269 are located at the AA92593-binding site, and additionally identified Trp-189 and Leu-207 interacting with the antagonist. Substitutions of Trp-189 and Leu-207 affected the antagonistic effect of AA92593. Furthermore, substitutions of these amino acid residues converted AA92593-insensitive melanopsins susceptible to the antagonist. Based on experiments and molecular simulations, five amino acid residues, at positions 94, 188, 189, 207, and 269, were found to be responsible for the specific interaction with AA92593 in mammalian melanopsins.

biochemistry↗

bioRxiv2024

Cholesterol sulfate prevents maternal-fetal conflict by locally modulating immune reactivity

Although placental mammals are at high risk of maternal-fetal immune conflict, it is unclear how the semi-allogeneic fetus avoids rejection. Cholesterol sulfate (CS) is a bioactive metabolite that inhibits leukocyte migration and activation. This study investigated the roles and cells associated with CS in pregnant mice and humans. CS was sequentially produced by maternal-derived endometrial cells and fetal-derived placental trophoblasts before and after placentation. When mated with allogeneic males, CS-deficient mice showed increased fetal resorption rates under induced placental inflammation. This phenotype disappeared when the activity of the CS-producing enzyme was restored in the placenta. Placental CS levels were reduced in patients with "villitis of unknown etiology." Thus, we uncovered the spatiotemporal control of CS production and its relevance to local immunosuppression during pregnancy.

immunology↗