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IntroductionFusarium wilt of banana, also recognized as Panama disease, is caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense tropical race 4 (FOC TR4). In recent years, strategies utilizing biocontrol agents, comprising antifungal microorganisms and their associated bioactive compounds from various environments, have been implemented to control this destructive disease. Our previous study showed that Pseudomonas aeruginosa Gxun-2 had significant antifungal effects against FOC TR4. However, there has been little scientific investigation of the antibacterial or antifungal activity. The aim of this study was to isolate, identify and evaluate the inhibition strength of active compounds in P. aeruginosa Gxun-2, so as to explain the mechanism of the strain inhibition on FOC TR4 from the perspective of compounds.MethodsThe main antibacterial compounds of strain Gxun-2 were isolated, purified and identified using by fermentation extraction, silica gel column chromatography, thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), and nuclear magnetic resonance (NMR) techniques. The effect of the compounds on the mycelial growth, morphology and spore germination of strain FOC TR4 was observed by 96-well plate method and AGAR diffusion method.ResultsAmong the metabolites produced by the strain, four antifungal compounds which were identified phenazine (C12H8N2), phenazine-1-carboxylic acid (PCA) (C13H8N2O2), 2-acetamidophenol (C8H9NO2) and aeruginaldehyde (C10H7NO2S) were identified through HPLC and NMR. Of these compounds, phenazine and PCA exhibited the most pronounced inhibitory effects on the spore germination and mycelial growth of FOC TR4. Phenazine demonstrated potent antifungal activity against FOC TR4 with a minimum inhibitory concentration (MIC) of 6.25 mg/L. The half-maximal effective concentration (EC50) was calculated to be 26.24 mg/L using the toxicity regression equation. PCA exhibited antifungal activity against FOC TR4 with an MIC of 25 mg/L and an EC50 of 89.63 mg/L. Furthermore, phenazine and PCA triggered substantial morphological transformations in the mycelia of FOC TR4, encompassing folding, bending, fracturing, and diminished spore formation.DiscussionThese findings indicate that strain Gxun-2 plays a crucial role in controlling FOC TR4 pathogenesis, predominantly through producing the antifungal compounds phenazine and PCA, and possesses potential as a cost-efficient and sustainable biocontrol agent against Fusarium wilt of banana in forthcoming times.

The aim of this study was to identify the type of siderophore secreted by Pseudomonas aeruginosa Gxun-2, determine the optimal fermentation conditions and investigate the antagonistic effect of fermentation broth on plant pathogens, so as to provide theoretical basis of the strain in agriculture. The chrome azurol sulfonate (CAS) plate and full-band ultraviolet light absorption method was to qualitatively and quantitatively analyze the siderophore production of P. aeruginosa Gxun-2. The iron-producing medium and culture conditions were optimized by the combined method of single-factor, Plackett-Burman and orthogonal tests. Finally, the plate confrontation method was used to assess the antagonistic effect of its fermentation brot on the pathogenic fungus, Fusarium oxysporum f. sp. cubense (FOC4). The results showed that the type of siderophore produced by strain Gxun-2 was isohydroxamic acid type, and the optimal fermentation medium and culture conditions were determined as follows: Sodium succinate 2 g/L, glycerol 10 g/L, ammonium sulfate 1 g/L, initial pH 6.8, temperature 35 ℃, inoculum 1.0% (v/v), and loading volume 140 mL/250 mL. Under these conditions, the siderophore activity unit (Su) of the Gxun-2 fermentation broth reached 81.20%±0.24%, which was 82.84%±0.82% higher than that before optimization, and the inhibition rate on FOC4 reached 70.60%±1.87%, which was 52.68%±4.23% higher than that before optimization.

Urban development in the future is more manifested as the development of urban clusters, and the regional ecological quality is an important basis for its ability to maintain sustainable development. On the basis of the three phases of MODIS remote sensing data from 2000 to 2020, we quantitatively analyzed the spatial and temporal dynamics and evolution of land ecological conditions in Beijing-Tianjin-Hebei region under the background of urbanization by dividing urban green space and constructing a remote sensing ecological index RSEI model, supplemented with trend analysis. Results indicated that (1) The major green spaces in Beijing-Tianjin-Hebei region are medium and high vegetation density areas and show an increasing trend year by year. With the increase of urban gray space as well as artificial green space, the area converted to no vegetation cover area and low vegetation cover area also increases, accounting for 13.58%. (2) The overall trend of vegetation density is increasing and can be divided into three gradients, with the first gradient being three cities, Zhangjiakou, Chengde, and Baoding, accounting for 61% of the whole rising area. The transition types with decreasing vegetation density are mainly found in cities with higher urbanization levels. (3) The ecological status has been improved significantly in the east and south, showing a slow decreasing trend in the mid-west, north, and some urban centers. The ecological status is elevated when positive conversion occurs and decreases when negative conversion occurs, and the rate of decrease (0.038 5/a) is higher than the rate of elevation (0.026 1/a). The results can provide scientific data and theoretical basis for the rational development and scientific management of green space in the Beijing-Tianjin-Hebei region, and have practical significance for the sustainable and coordinated development of regional economy, society, and environment.

BackgroundElderly patients have a high risk of developing postoperative cognitive dysfunction (POCD). Gastrointestinal disorders, such as constipation, in the elderly population may be involved in the pathogenesis of neurological disorders by promoting inflammatory responses due to a ‘leaky gut’. General anesthetic sevoflurane may impair gastrointestinal function in elderly patients to trigger neurological complications following surgery. Therefore, we hypothesized that elderly individuals with gastrointestinal dysfunction may be more vulnerable to sevoflurane and consequently develop POCD.MethodsAged mice were randomly divided into four groups: control (CTRL), CTRL+sevoflurane (Sev), slow transit constipation (STC), and STC + Sev. Mice in the STC and STC + Sev groups were intra-gastrically administrated loperamide (3 mg/kg, twice a day for 7 days) to induce a slow transit constipation (STC) model determined with fecal water content and the time of first white fecal pellet, whereas mice in the other groups received the similar volume of saline. One week later, mice in the CTRL+Sev group and STC + Sev group received 2% sevoflurane for 2 h. The gut permeability evaluated with 4-kDa fluorescein isothiocyanate (FITC)-dextran, serum cytokines, microglia density, TLR4/NF-κB signaling expression, and POCD-like behavioral changes were determined accordingly.ResultsThe loperamide-induced STC mice had decreased fecal water content and prolonged time of first white fecal pellet. Sevoflurane exposure caused significantly increased gut permeability and serum cytokines, as well as the activation of microglia and the TLR4/NF-κB signaling pathway in the prefrontal cortex of the aged STC mice. Sevoflurane also caused cognitive impairment and emotional phenotype abnormality in aged STC mice.ConclusionAged STC mice were more vulnerable to sevoflurane anesthesia and consequently developed POCD-like behavioral changes. Our data suggest that gastrointestinal disorders including constipation may contribute to the development of POCD.

As a gamma-aminobutyric acid type A receptor agonist sevoflurane is a common general anesthetic used in anesthesia and affects the neural development in offspring. We hypothesized that sevoflurane could regulate interneurons via the neuregulin-1-epidermal growth factor receptor-4 (NRG1–ErbB4) pathway in the entorhinal cortex (ECT) of the middle pregnancy. Six female rats in middle pregnancy (14.5 days of pregnancy) were randomly and equally divided into sevoflurane (SeV) and control groups. The rats in the SeV group were exposed to 4% sevoflurane for 3 hours. The expression levels of NRG1 and ErbB4, parvalbumin (PV) and glutamic acid decarboxylase (GAD67), and N-methyl-D-aspartate receptor subunit 2A (NR2A) and subunit 2B (NR2B) in offspring were examined through immunohistochemistry. The pyramidal neurons in the ECT were examined via Golgi staining. The levels of NRG1 and ErbB4 were significantly decreased (P < 0.01) and the levels of PV and GAD67 (interneurons) were found to be decreased in the SeV group (P < 0.01). The level of NR2B was found to be increased while the level of NR2A being decreased in the SeV group (P < 0.01). The development of pyramidal neurons was abnormal in the SeV group (P < 0.05). Conclusively, prenatal sevoflurane exposure could lead to the disturbance of the interneurons by activating the NRG1–ErbB4 pathway and subsequently result in abnormal development of pyramidal neurons in middle pregnancy. Prenatal sevoflurane exposure in middle pregnancy could be potentially harmful to the neural development of rat offspring. This study may reveal a novel pathway in the influence mechanism of sevoflurane on rat offspring.

The balance of excitatory and inhibitory neurons in the central nervous system is critical for maintaining brain function and sevoflurane, a general anesthetic and an GABA receptor modulator, may change the balance of excitatory and inhibitory neurons in the cortex during early brain development. Herein, we investigated whether prenatal sevoflurane exposure (PSE) disturbs cortical neuronal development and brain function. Pregnant rats at the gestational day 14.5 were subjected to sevoflurane exposure at 3.0% for 3 h and their offspring were studied thereafter. We found a significant increase of parvalbumin-positive neurons, vesicular GABA transporter (VGAT) and GAD67 expression, and GABA neurotransmitter, and a significant decrease of vesicular glutamate transporter 1 (VGLUT1) expression and glutamate in the medial prefrontal cortex (mPFC) of offspring. Pyramidal neurons showed atrophy with shorter dendrites, less branches and lower spine density visualized by Golgi stain and a decrease of excitability with the increased miniature inhibitory postsynaptic current (mIPSC) frequency and amplitude, the decreased miniature excitatory postsynaptic current (mEPSC) frequency and excitation/inhibition (E/I) ratio using whole-cell recording in offspring. There was a significant increase of inhibitory synapse in the mPFC detected by electron microscopy. Furthermore, PSE animals showed hypo-excitatory phenotype including depression-like behaviors and learning deficits. Thus, our studies provide novel evidence that PSE causes the persisted imbalance of excitatory and inhibitory neurons in the mPFC, and this is very likely the mechanisms of the sevoflurane-induced brain functional abnormalities.

Abundant evidence has demonstrated an association between parental psychological control and adolescent aggressive behavior. However, the mediating and moderating mechanisms underlying this relation are still under-investigated. Grounded in the social development model and stress-buffering model, this study investigated whether deviant peer affiliation mediates the relation between parental psychological control and adolescent aggressive behavior, and whether this indirect link is moderated by school connectedness. A total of 4265 adolescents (Meanage = 13.66 years, SD = 2.74, 48.63% male) from southern China completed questionnaires regarding parental psychological control, deviant peer affiliation, school connectedness, and aggressive behavior. Structural equation models revealed that the relation between parental psychological control and aggressive behavior is partially mediated by deviant peer affiliation. Moreover, this indirect link was stronger for adolescents with low levels of school connectedness than for those with high levels of school connectedness. This study thus identifies the potential underlying mechanism by which parental psychological control is associated with adolescent aggressive behaviors, which has important implications for theory and prevention.

Although there is abundant evidence that an association between sensation seeking and adolescent Internet gaming addiction (IGA) exists, research has provided little insight into why adolescents with high sensation seeking are more likely to be focused on Internet and video games. Grounded in the social development model and ecological systems theory, this study investigated whether deviant peer affiliation mediated the relationship between sensation seeking and adolescent IGA, and whether this indirect link was moderated by parental knowledge. Participants were 1293 Chinese adolescents (49.65% male, Mage = 12.89 ± 0.52 years) who completed questionnaires assessing sensation seeking, deviant peer affiliation, parental knowledge, and IGA. Structural equation models revealed that the positive association between sensation seeking and adolescent IGA was partially mediated by deviant peer affiliation. In addition, this indirect link was significantly moderated by parental knowledge. Specifically, the indirect path from sensation seeking to adolescent IGA was stronger for adolescents with low parental knowledge than for those with high parental knowledge. Identifying the role of peers and parents in the onset of adolescent IGA has key implications for prevention and intervention.

It is gradually accepted that porosity can be created in burial settings via dissolution by organic acid; TSR derived or hydrothermal fluids. The role of deep-buried carbonate reservoirs is becoming more and more important since the degree and difficulty in petroleum exploration of shallow strata are increasing. A profound understanding of the development scale and prediction of the deep-buried carbonate reservoirs is economically crucial. In addition to the formation mechanism, scale and distribution of burial dissolution pores in burial settings are focused on in recent studies. This paper is based on case studies of deep-buried (>4500 m) carbonate reservoirs from the Tarim Basin and Sichuan Basin. Case studies mentioned includes dissolution simulation experiments proposes that an open system is of crucial importance in the development of large-scale burial dissolution pores, the distribution pattern of which is controlled by lithology, pre-existing porosity, and pore throat structures. These findings provided the basis for evaluation and prediction of deep-buried carbonate reservoirs.

Taking reef-shoal bodies developed in multiple formations in the Tarim and Sichuan Basins as examples, this paper examines the origin of pores and heterogeneity of different types of reef-shoal reservoirs, and tries to find out the distribution rules of various reef-shoal reservoirs. Reef-shoal reservoirs can be classified into two main types, i.e. biohermal reservoirs and grain shoal reservoirs. The former, related to reef framework, mostly in the form of frilled platform margins, can be subdivided into two categories; interior platform reef complex and margin reef complex (sedimentary or tectonic origin). The latter, unrelated to the reef framework, is controlled by the fluctuation of sea level on gentle slope carbonate platforms, are widely developed on carbonate ramps due to the migration of shoals, and can be subdivided into interior platform shoals and platform-margin shoals on steep slopes. Reservoir space within reef-shoal carbonates was primarily formed during syngenetic and burial stages. Syngenetic porosity is controlled by the original rock fabric and dissolution related to the exposure of sequence boundaries, while porosity development and distribution during the burial stage is closely related to that in the syngenetic stage, showing inherited features. Reef-shoal reservoirs are strongly heterogeneous, and complicated with respect to effective reservoir distribution. Platform margin reefs and biohermal shoals coexisting with reefs on the top of shallowing upward sequences are the main reservoirs and rich in porosity. The grain shoals deposited on top of shallowing upward cycles of isolated reefs are also the main zones rich in pores, and usually interbed with tight reservoirs. Overall, grain shoal reservoirs are larger in scale and better in physical properties than biohermal reservoirs. Key words: reef-shoal reservoirs, biohermal reef, grain shoal, reservoir heterogeneity, Tarim Basin, Sichuan Basin

With characteristics and advantages of functional composite materials, they are commendably adopted in numerous fields especially in oxygen electrocatalysis, which is due to the significant synergies between various components. Herein, a novel bifunctional oxygen electrocatalyst (Co-CNT@COF-Pyr) has been synthesized through in-situ growth of covalent organic frameworks (COFs) layers on the outer surface of highly conductive carbon nanotubes (CNTs) followed by coordination with Co(Ⅱ). For electrocatalytic OER, Co-CNT@COF-Pyr reveals a low overpotential (438 ​mV) in alkaline electrolyte (1.0 ​M aqueous solution of KOH) with a current density of 10 ​mA ​cm−2, which is comparable to most discovered COF-based catalysts. For electrocatalytic ORR, Co-CNT@COF-Pyr exhibits a low H2O2 yield range (9.0 ​%–10.1 ​%) and a reaction pathway close to 4e− (n ​= ​3.82–3.80) in alkaline electrolyte (0.1 ​M aqueous solution of KOH) within the test potential range of 0.1–0.6 ​V vs. RHE, which is superior to most reported COF-based catalysts. Hence, this research could not only offer an innovative insight into the construction of composites, but also facilitate the practical application of renewable fuel cells, closed water cycle, and rechargeable metal-air batteries.

In this paper, Al2O3/Cr composite coatings were prepared on the surface of Inconel 718 alloy by cathodic liquid plasma electrolytic deposition (CLPED) and double-glow plasma surface alloying (DGPSA) processes. The microstructure and high-temperature oxidation behavior of Al2O3/Cr composite coating were investigated. The results showed that the Al2O3 interlayer surface was fully covered with Cr coating. The interface between the Al2O3 layer and the Cr metal layer presents a mechanical interlock effect, which can absorb the deformation caused by thermal expansion, thereby reducing the adverse effects of thermal stress. The surface roughness of the Al2O3 coatings decreased after depositing Cr coating. The oxidation weight gain of the Al2O3/Cr composite coatings were significantly lower than that of the substrate, indicating that the Al2O3/Cr composite coatings improved the high-temperature oxidation resistance of Inconel 718 alloy. The oxidation weight gain of the Al2O3/Cr composite coatings at different frequencies were similar, while the Al2O3/Cr composite coating at 400 Hz was lowest. During the high-temperature oxidation process, the Al2O3 interlayer can effectively inhibit the external diffusion of Ni, Fe and other elements in the matrix, which helps to prevent the cracking of the outer oxide film, thereby reducing the oxidation rate.

Laser shock peening (LSP) was used to prepare a fine-grained transition layer on the surface of titanium alloy (TC4), followed by micro-arc oxidation (MAO) to prepare composite coatings. The influence of LSP on the microstructure, phase structure, adhesion, microhardness, corrosion resistance, and wear resistance of the MAO coatings was studied. The results showed that, after LSP treatment, the diffraction peaks of TC4 became wider, the surface grains were significantly refined, and a high-density dislocation was introduced on the TC4 surface forming a nano-crystal cluster. Compared with the MAO coating, the LSP-MAO composite coating had a smaller pore size, increased coating thickness, microhardness, and depth of strengthening layer. The adhesion, corrosion resistance, and wear resistance of the LSP-MAO coating were better than those of the MAO coating.

Abstract Integration of electronic and strain effects with tailored structures is significant to tuning the electrocatalytic activity and stability of the electrocatalysts for the oxygen reduction reaction (ORR). In this study, one‐dimensional PtFe hollow nanochains are synthesized by a facile and effective method, which exhibit a highly open and porous structure. The modulated electronic and strain effects of Pt atoms are verified by extensive structural characterizations, and the mass and specific activities of the prepared catalyst are roughly 7.45 and 12.44 times higher than those of the commercial Pt/C catalyst, respectively. Remarkably, the catalyst demonstrates robust performance with negligible activity decay after an accelerated durability test for 30,000 cycles. The high activity of the catalyst is probably due to the optimized absorption affinity of Pt‐O accelerating the reaction kinetics induced by the cooperation of Fe atoms as well as the unique hollow and curved structures. This study provides new insights into the rational design of high‐performance ORR catalysts with considerable durability.

Abstract As a carbon‐free energy carrier, hydrogen has become the pivot for future clean energy, while efficient hydrogen production and combustion still require precious metal‐based catalysts. Single‐atom catalysts (SACs) with high atomic utilization open up a desirable perspective for the scale applications of precious metals, but the general and facile preparation of various precious metal‐based SACs remains challenging. Herein, a general movable printing method has been developed to synthesize various precious metal‐based SACs, such as Pd, Pt, Rh, Ir, and Ru, and the features of highly dispersed single atoms with nitrogen coordination have been identified by comprehensive characterizations. More importantly, the synthesized Pt‐ and Ru‐based SACs exhibit much higher activities than their corresponding nanoparticle counterparts for hydrogen oxidation reaction and hydrogen evolution reaction (HER). In addition, the Pd‐based SAC delivers an excellent activity for photocatalytic hydrogen evolution. Especially for the superior mass activity of Ru‐based SACs toward HER, density functional theory calculations confirmed that the adsorption of the hydrogen atom has a significant effect on the spin state and electronic structure of the catalysts.

It is challenging to integrate multi-single metal atoms into one support. In this work, the authors demonstrate the production of high-entropy single-atom catalysts via a movable typing method, which enables the anchor up to eleven metals as highly dispersed single-atom active centers on the carbon support for the oxygen reduction reaction.

Abstract Background Osteoarthritis (OA) is thought to be the most prevalent chronic joint disease, especially in Tibet of China. Here, we aimed to explore the integrative lncRNA and mRNA landscape between the OA patients of Tibet and Han. Methods The lncRNA and mRNA expression microarray profiling was performed by SurePrint G3 Human Gene Expression 8x60K v2 Microarray in articular cartilage samples from OA patients of Han nationality and Tibetans, followed by GO, KEGG, and trans-regulation and cis-regulation analysis of lncRNA and mRNA. Results We found a total of 117 lncRNAs and 297 mRNAs differently expressed in the cartilage tissues of Tibetans (n = 5) comparing with those of Chinese Han (n = 3), in which 49 lncRNAs and 158 mRNAs were upregulated, and 68 lncRNAs and 139 mRNAs were downregulated. GO and KEGG analysis showed that several unreported biological processes and signaling pathways were particularly identified. LncRNA-mRNA co-expression analysis revealed a remarkable lncRNA-mRNA relationship, in which OTOA may play a critical role in the different mechanisms of the OA progression between Tibetans and Chinese Han. Conclusion This study identified different lncRNA/mRNA expression profiling between OA patients of Tibetans and Han, which were involved in many characteristic biological processes and signaling pathways.

The electrocatalytic seawater splitting has become an important and necessary way for large-scale hydrogen production with challenges ahead. In this review, a brief introduction to the reaction mechanism of seawater electrocatalytic process is first provided, including the cathodic hydrogen evolution reaction and the anodic oxygen evolution reaction, as well as the competitive chloride evolution reaction. Recent progress in transition metal phosphides-based catalysts for seawater electrolysis, such as phosphorus doped transition metals, binary metal phosphides, and structural engineering are then evaluated and discussed. Finally, the challenges and opportunities of transition metal phosphides are proposed and discussed.

Thermal barrier coatings (TBCs) can improve the high-temperature performance of turbine blades, however, the complex service environment such as Ca-Mg-Al-silicate (CMAS) is the main reason for the coating failure. The corrosive medium (Ca2+ and Si4+) penetrates the TBCs through the porous structure combined with surface defects. In this study, three different sealed layers (Zr, Al, and Al-Y) were deposited on the traditional TBCs by using magnetron sputtering. The cross-sectional morphologies showed the continuous structure of the sealed layer improved the pore filling effect. When O2 is adsorbed at the top position of the Al atom, the lowest adsorption energy of the YAl3 (0001) surface is −5.34 eV which can provide stronger chemical adsorption energies for Al and O. The Al-Y sealed layer was preferred to form an aluminum oxide film. The experimental results of CMAS corrosion showed that Al-Y sealed layer can achieve long-lasting protection because the aluminum yttrium oxide (Al2Y4O9) reacts with CaO and SiO2 at the interface and finally formed Ca3Y2(SiO4)6O2, resulting in rapid crystallization of CMAS.

Objectives Liver echinococcosis is a severe zoonotic disease caused by Echinococcus (tapeworm) infection, which is epidemic in the Qinghai region of China. Here, we aimed to explore biomarkers and establish a predictive model for the diagnosis of liver echinococcosis. Methods Microarray profiling followed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis was performed in liver tissue from patients with liver hydatid disease and from healthy controls from the Qinghai region of China. A protein–protein interaction (PPI) network and random forest model were established to identify potential biomarkers and predict the occurrence of liver echinococcosis, respectively. Results Microarray profiling identified 1152 differentially expressed genes (DEGs), including 936 upregulated genes and 216 downregulated genes. Several previously unreported biological processes and signaling pathways were identified. The FCGR2B and CTLA4 proteins were identified by the PPI networks and random forest model. The random forest model based on FCGR2B and CTLA4 reliably predicted the occurrence of liver hydatid disease, with an area under the receiver operator characteristic curve of 0.921. Conclusion Our findings give new insight into gene expression in patients with liver echinococcosis from the Qinghai region of China, improving our understanding of hepatic hydatid disease.

Targeted expression of gene technique is an important therapeutic strategy for lung cancer. MicroRNA-7 has been well documented as a promising tumor suppressor but never been test in specific gene-promoter-targeted expression in cancer gene therapy. Here, we first evaluated the efficacy of miR-7 expression operated by the promoter of TTF-1, a lineage-specific oncogene in lung cancer, in vitro using an eukaryotic vector of TTF-1-promoter-operated expression of miR-7 (termed as p-T-miR-7). Interestingly, using a nude mice model, the growth and metastasis of human lung cancer cells in vivo were significantly reduced in remote hypodermic injection of the p-T-miR-7 group, accompanied by increased expression of miR-7 and reduced transduction of the Akt and Erk pathway in situ. Mechanism aspect, global gene expression analysis showed that downregulation of NDUFA4, a novel target of miR-7, contributed to the effects of miR-7 expression operated by TTF-1 promoter on the growth and metastasis of human lung cancer cells, as well as altered transduction of the Akt and Erk pathway. Finally, there was no significant difference in weight or histopathology of other organs. These data provided a basis for development of novel modality of miRNA-based targeted expression therapy against clinical lung cancer. Keywords: miR-7, TTF-1, 95D cells, lung cancer, growth, NDUFA4

Matrilin-2 is a widely distributed, oligomeric extracellular matrix protein that forms a filamentous network by binding to a variety of different extracellular matrix proteins. We found matrilin-2 proteolytic products in transfected cell lines in vitro and in mouse tissues in vivo. Two putative cleavage sites were identified in the unique domain of matrilin-2; the first site was located between D851 and L852 in the middle of the domain and the second, at the boundary with the coiled-coil domain at the C-terminus. Deletion of the entire unique domain eliminated the proteolysis of matrilin-2. While the first cleavage site was present in all matrilin-2 oligomers, the second cleavage site became apparent only in the matrilin-2 hetero-oligomers with matrilin-1 or matrilin-3. Analysis using a variety of extracellular protease inhibitors suggested that this proteolytic activity was derived from a member or several members of the ADAMTS family. Recombinant human ADAMTS-4 (aggrecanase-1) and ADAMTS-5 (aggrecanase-2), but not ADAMTS-1, cleaved recombinant matrilin-2, thereby yielding matrilin-2 proteolytic peptides at the predicted sizes. These results suggest that ADAMTS-4 and ADAMTS-5 may destabilize the filamentous network in the extracellular matrix by cleaving matrilin-2 in both homo-oligomers and hetero-oligomers.

GPRC6A is a widely expressed orphan G-protein coupled receptor that senses extracellular amino acids, osteocalcin and divalent cations in vitro. The physiological functions of GPRC6A are unknown.In this study, we created and characterized the phenotype of GPRC6A(-/-) mice. We observed complex metabolic abnormalities in GPRC6A(-/-) mice involving multiple organ systems that express GPRC6A, including bone, kidney, testes, and liver. GPRC6A(-/-) mice exhibited hepatic steatosis, hyperglycemia, glucose intolerance, and insulin resistance. In addition, we observed high expression of GPRC6A in Leydig cells in the testis. Ablation of GPRC6A resulted in feminization of male GPRC6A(-/-) mice in association with decreased lean body mass, increased fat mass, increased circulating levels of estradiol, and reduced levels of testosterone. GPRC6A was also highly expressed in kidney proximal and distal tubules, and GPRC6A(-/-) mice exhibited increments in urine Ca/Cr and PO(4)/Cr ratios as well as low molecular weight proteinuria. Finally, GPRC6A(-/-) mice exhibited a decrease in bone mineral density (BMD) in association with impaired mineralization of bone.GPRC6A(-/-) mice have a metabolic syndrome characterized by defective osteoblast-mediated bone mineralization, abnormal renal handling of calcium and phosphorus, fatty liver, glucose intolerance and disordered steroidogenesis. These findings suggest the overall function of GPRC6A may be to coordinate the anabolic responses of multiple tissues through the sensing of extracellular amino acids, osteocalcin and divalent cations.