Specificity of TGF-ß1 signal designated by LRRC33 and integrin αVß8.

Myeloid lineage cells present the latent form of transforming growth factor-ß1 (L-TGF-ß1) to the membrane using an anchor protein LRRC33. Integrin αVß8 activates extracellular L-TGF-ß1 to trigger the downstream signaling functions. However, the mechanism designating the specificity of TGF-ß1 presentation and activation remains incompletely understood. Here, we report cryo-EM structures of human L-TGF-ß1/LRRC33 and integrin αVß8/L-TGF-ß1 complexes. Combined with biochemical and cell-based analyses, we demonstrate that LRRC33 only presents L-TGF-ß1 but not the -ß2 or -ß3 isoforms due to difference of key residues on the growth factor domains. Moreover, we reveal a 2:2 binding mode of integrin αVß8 and L-TGF-ß1, which shows higher avidity and more efficient L-TGF-ß1 activation than previously reported 1:2 binding mode. We also uncover that the disulfide-linked loop of the integrin subunit ß8 determines its exquisite affinity to L-TGF-ß1. Together, our findings provide important insights into the specificity of TGF-ß1 signaling achieved by LRRC33 and integrin αVß8.

Antitumor activity of mianserin (a tetracyclic antidepressant) primarily driven by the inhibition of SLC1A5-mediated glutamine transport.

Targeting tumor metabolic vulnerabilities such as "glutamine addiction" has become an attractive approach for the discovery of novel antitumor agents. Among various mechanisms explored, SLC1A5, a membrane transporter that plays an important role in glutamine cellular uptake, represents a viable target to interfere with tumor's ability to acquire critical nutrients during proliferation. In the present study, a stably transfected HEK293 cell line with human SLC1A5 (HEK293-SLC1A5) was established for the screening and identification of small molecule SLC1A5 inhibitors. This in vitro system, in conjunction with direct measurement of SLC1A5-mediated L-glutamine-2,3,3,4,4-D5 (substrate) uptake, was practical and efficient in ensuring the specificity of SLC1A5 inhibition. Among a group of diverse compounds tested, mianserin (a tetracyclic antidepressant) demonstrated a marked inhibition of SLC1A5-mediated glutamine uptake. Subsequent investigations using SW480 cells demonstrated that mianserin was capable of inhibiting SW480 tumor growth both in vitro and in vivo, and the in vivo antitumor efficacy was correlated to the reduction of glutamine concentrations in tumor tissues. Computational analysis revealed that hydrophobic interactions between SLC1A5 and its inhibitors could be a critical factor in drug design. Taken together, the current findings confirmed the feasibility of targeting SLC1A5-mediated glutamine uptake as a novel approach for antitumor intervention. It is anticipated that structural insights obtained based on homology modeling would lead to the discovery of more potent and specific SLC1A5 inhibitors for clinical development.

Geographical origin identification of two salmonid species via flavor compound analysis using headspace-gas chromatography-ion mobility spectrometry combined with electronic nose and tongue.

The flavor of salmonids is affected by species and origin. Sources of salmonid fish fillets are complex and difficult to identify and label fraud occasionally occurs in the market. In this study, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), electronic nose, electronic tongue and amino acid detection technologies were used to analyze flavor compounds in two salmonid species from different geographical origins. Fingerprints of volatile compounds of salmonid were constructed using HS-GC-IMS technology. Free amino acid (FAA) content differed in salmonids from different geographical origins. Regarding salmonid odor, HS-GC-IMS analysis results were basically consistent with those of the electronic nose. Regarding taste, the conclusions drawn from the electronic tongue were consistent with the amino acid test results. Therefore, our results demonstrate that flavor compounds can be used to distinguish salmonids from different geographical origins, providing a new dimension to food safety and authenticity. Furthermore, HS-GC-IMS, electronic nose and tongue can be used as tools in the market to identify food fraud.

Identification of Structural Features for the Inhibition of OAT3-Mediated Uptake of Enalaprilat by Selected Drugs and Flavonoids.

Enalaprilat is the active metabolite of enalapril, a widely used antihypertension drug. The human organic anion transporter 3 (OAT3), which is highly expressed in the kidney, plays a critical role in the renal clearance of many drugs. While urinary excretion is the primary elimination route of enalaprilat, direct involvement of OAT3 has not been reported so far. In the present study, OAT3-mediated uptake of enalaprilat was first characterized, and the inhibition of OAT3 transport activity was then examined for a number of flavonoid and drug molecules with diverse structures. A varying degree of inhibition potency was demonstrated for flavonoids, with IC50 values ranging from 0.03 to 22.6 µM against OAT3 transport activity. In addition, commonly used drugs such as urate transporter 1 (URAT1) inhibitors also displayed potent inhibition on OAT3-mediated enalaprilat uptake. Pharmacophore and three-dimensional quantitative structure-activity relationship (3D-QSAR) analyses revealed the presence of a polar center and a hydrophobic region involved in OAT3-inhibitor binding. For the polar center, hydroxyl groups present in flavonoids could act as either hydrogen bond donors or acceptors and the number and position of hydroxyl groups were critical drivers for inhibition potency, while carboxyl groups present in some drugs could form ionic bridges with OAT3. The predicted inhibition potencies by comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were correlated well with experimental IC50 values. Taken together, the present study identified OAT3-mediated uptake of enalaprilat as an important mechanism for its renal clearance, which may be liable for drug-drug and herb-drug interactions. The established computational models revealed unique structural features for OAT3 inhibitors and could be used for structure-activity relationship (SAR) analysis of OAT3 inhibition. The clinical relevance of the inhibition of OAT3-mediated enalaprilat uptake warrants further investigation, particularly in populations where herbal remedies and drugs are used concomitantly.

Cellular Synthesis and X-ray Crystal Structure of a Designed Protein Heterocatenane.

Herein, we report the biosynthesis of protein heterocatenanes using a programmed sequence of multiple post-translational processing events including intramolecular chain entanglement, in situ backbone cleavage, and spontaneous cyclization. The approach is general, autonomous, and can obviate the need for any additional enzymes. The catenane topology was convincingly proven using a combination of SDS-PAGE, LC-MS, size exclusion chromatography, controlled proteolytic digestion, and protein crystallography. The X-ray crystal structure clearly shows two mechanically interlocked protein rings with intact folded domains. It opens new avenues in the nascent field of protein-topology engineering.

The E3 Ubiquitin Ligase CRL4 Regulates Proliferation and Progression Through Meiosis in Chinese Mitten Crab Eriocheir sinensis.

The Cullin-RING E3s are multisubunit ubiquitin ligases composed of a scaffold protein known as Cullin, a RING finger protein that regulates diverse cellular pathways; however, their contribution to male gonad development, especially the spermatogenesis of the Chinese mitten crab (Eriocheir sinensis), is not well understood. We identified five evolutionarily conserved Cullins from the transcriptome and genome ofE. sinensis that are potentially involved in regulating male gonad development. The aim of the current study was to determine the mechanisms of Cullin4's effects on spermatogenesis. We observed that Cullin4, p53, and proliferating cell nuclear antigen had a specific expression and localization in primary spermatocytes. We also investigated the accumulation of Cullin substrates by treatment with inhibitor of NEDD8-activating enzyme MLN4924 in vitro. Cell cycle inhibitors p27 and p21 accumulated significantly after 24 and 36 h, respectively. We speculated that p53-mediated spontaneous germ cell apoptosis acts as a quality control mechanism to eliminate defective germ cells and that the Cullin4 complex maintains p53, p21, and p27 homeostasis in primary spermatocytes to regulate spermatogenesis ofE. sinensis Given its widespread evolutionary conservation, Cullin4 may regulate germ line development similarly in other organisms.

FOXL2 down-regulates vitellogenin expression at mature stage in Eriocheir sinensis.

Ovarian development in crustaceans is characterized by rapid production of egg yolk protein in a process called vitellogenesis. In the present study, we investigated the involvement of a DEAD (Asp-Glu-Ala-Asp) box RNA helicase 20 (DDX20), forkhead transcription factor (FOXL)2 and fushi tarazu factor (FTZ-F)1 in the regulation of vitellogenesis. Based on ESTs from the testis and accessory gland of Eriocheir sinensis, we cloned the full-length cDNAs of foxl2 and fushitarazu factor 1 (ftz-f1), which include the conserved structural features of the forkhead family and nuclear receptor 5A (NR5A) family respectively. The expression of foxl2 mRNA surged at the mature stage of the ovary, when vtg mRNA swooped, suggesting that foxl2 negatively affects the vitellogenin (VTG) synthesis at this developmental stage. Etoposide (inducing germ cell apoptosis) treatment up-regulated FOXL2 and DDX20 at both the mRNA and the protein levels, primarily in the follicular cells as shown by immunofluorescence analysis. Furthermore, foxl2, ddx20 and ftz-f1 mRNA levels increased significantly with right-eyestalk ablation. Interactions between FOXL2 and DDX20 or FTZ-F1 were confirmed by co-immunoprecipitation and the forkhead domain of FOXL2 was identified as the specific structure interacting with FTZ-F1. In conclusion, FOXL2 down-regulates VTG expression by binding with DDX20 in regulation of follicular cell apoptosis and with FTZ-F1 to repress the synthesis of VTG at the mature stage. This report is the first to describe the molecular mechanism of VTG synthesis in E. sinensis and may shed new light on the regulation of cytochrome P450 enzyme by FOXL2 and FTZ-F1 in vitellogenesis.

Profiling microRNAs in the testis during sexual maturation stages in Eriocheir sinensis.

MicroRNAs (miRNAs) have been implicated in several cellular processes of reproductive tissues through post-transcriptional regulation of protein coding genes. The presence of miRNAs, their expression patterns and processing machinery genes in different stages of testicular and ovarian cellular development have demonstrated the potential role of miRNAs in testicular and ovarian physiology. The Chinese mitten crab (Eriocheir sinensis) is one of the most important aquaculture species in China and has high commercial value as a food source. The molecular mechanisms underlying testis development in these and other crustaceans, which migrate to a new habitat to breed, remain poorly understood. We focus on the gonad of E. sinensis and systematically examined the expression profile of miRNAs in testes during sexual maturation stages using the Illumina Solexa sequencing technology. We found that the microRNA transcriptome exhibited dynamic expression during crab testis development. Subsequent bioinformatic analysis on both conserved and 15 novel miRNAs illustrated that some miRNAs demonstrated a tissue-specific expression pattern and were associated with target genes involved in reproductive function. Our study illustrates how detailed profiling of miRNA expression during stages of sexual maturation and in different tissues can lead to elucidate the role of miRNAs in regulating the development and differentiation of reproductive organs.

ERK is involved in the process of acrosome reaction in vitro of the Chinese mitten crab, Eriocheir sinensis.

Mitogen-activated protein kinases (MAPKs), also termed extracellular signal-regulated kinases (ERKs), are cytoplasmic and nuclear serine/threonine kinases involved in signal transduction of several extracellular effectors. In mammals, ERKs participate in the regulation of spermatogenesis, mature spermatozoa motility, hyperactivation, and the acrosome reaction. To investigate ERK functions in Eriocheir sinensis reproduction, we successfully cloned the full-length ERK from the testis of E. sinensis (ES-ERK). The 1098-nucleotide open reading frame encodes a 365-amino-acid protein with a predicted molecular weight of 42 kDa. Expressions of ES-ERK in different tissues and testis development stages were detected by the quantitative RT-PCR and Western blotting. ES-ERK is expressed relatively highly in the testis. The expression of ES-ERK protein gradually increased in the spermatid stage, reaching a peak in sperm stage. Western blotting showed a similar expression pattern for the total ES-ERK protein, but phospho-ERK (p-ERK) showed the higher expression in spermatid than sperm stage. We also used trypan blue and hematoxylin and eosin staining to identify structural changes in E. sinensis spermatozoa during the process of acrosome reaction (AR). After stimulating the process of AR, the ES-ERK has translocated from the nucleus to the acrosomal tubule. This result suggested that the ERK MAPK might be involved in the regulation of the E. sinensis acrosome reaction.

Identification of ADAM10 and ADAM17 with potential roles in the spermatogenesis of the Chinese mitten crab, Eriocheir sinensis.

The ADAM (a disintegrin and metalloprotease) family plays an important role in sperm and egg fusion, development, inflammation, adhesion and migration. ADAM10 and ADAM17 are involved in the spermatogenesis. To better understand the role of ADAM10 and ADAM17 in the Chinese mitten crab, Eriocheir sinensis, the full-length cDNAs of ADAM10 and ADAM17 were cloned, and named Es-ADAM10 and Es-ADAM17, respectively. Sequence and structural analysis showed that Es-ADAM10 and Es-ADAM17 have the typical structure of the ADAM family. Quantitative real-time reverse transcription polymerase chain reaction analysis showed that Es-ADAM10 and Es-ADAM17 mRNAs were distributed in the heart, hepatopancreas, intestines, brain, muscle, thoracic ganglia, hemolymph, stomach, testis, ovary, gill and accessory gland. Both mRNAs were highly expressed in the muscles, and relatively high in the testis, ovary and accessory gland. In addition, the Es-ADAM17 mRNA level was detected in every stage of testis development, being relatively high from July to September, the lowest during October and November, increasing from December to January, and reached a peak in January. By contrast, the expression of Es-ADAM10 mRNA was constant during testis development. Immunofluorescence further showed that Es-ADAM10 and Es-ADAM17 proteins were present in the cytoplasm and cytomembrane of spermatocytes, and both detected in the sperm. Furthermore, etoposide induced upregulation of Es-ADAM17 and Es-ADAM10 at both the mRNA and protein levels. This study first showed that Es-ADAM10 and Es-ADAM17 were also involved in the spermatogenesis and mainly participated in the later germ cell apoptosis in E. sinensis.

P38 participates in spermatogenesis and acrosome reaction prior to fertilization in Chinese mitten crab Eriocheir sinensis.

P38 mitogen-activated protein kinases (MAPKs) comprise a family of serine/threonine protein kinases that play important roles in cellular responses to inflammatory cytokines and environmental stresses. These kinases are involved in controlling cell division, differentiation and death in mammalian testes and therefore are critical to spermatogenesis. To explore their functions in male reproduction of Chinese mitten crabs, Eriocheir sinensis p38 (Es-p38) protein expression was determined in different tissues including testes at different developmental stages by Western blot. Es-p38 was expressed in various tissues, with higher levels in the heart, stomach, gills and testes. Total Es-p38 protein levels increased gradually during spermatogenesis, but phosphorylated Es-p38 was much higher in the spermatid (August-October) than the spermatocyte (July-August) and sperm (October-January) stages. Trypan blue staining and hematoxylin/eosin staining were both used to detect sperm motility and changes in sperm morphology during the acrosome reaction (AR) induced by pre-incubation with A23187 in vitro, activated Es-p38 proteins detected by fluorescent microscopy were translocated gradually to nuclear and apical cap regions, accumulating at the anterior of the acrosomal tubule. The results suggest the involvement of p38 MAPK in spermatogenesis and the AR in E. sinensis.

Predominant and substoichiometric isomers of the plastid genome coexist within Juniperus plants and have shifted multiple times during cupressophyte evolution.

Most land plant plastomes contain two copies of a large inverted repeat (IR) that promote high-frequency homologous recombination to generate isomeric genomic forms. Among conifer plastomes, this canonical IR is highly reduced in Pinaceae and completely lost from cupressophytes. However, both lineages have acquired short, novel IRs, some of which also exhibit recombinational activity to generate genomic structural diversity. This diversity has been shown to exist between, and occasionally within, cupressophyte species, but it is not known whether multiple genomic forms coexist within individual plants. To examine the recombinational potential of the novel cupressophyte IRs within individuals and between species, we sequenced the plastomes of four closely related species of Juniperus. The four plastomes have identical gene content and genome organization except for a large 36 kb inversion between approximately 250 bp IR containing trnQ-UUG. Southern blotting showed that different isomeric versions of the plastome predominate among individual junipers, whereas polymerase chain reaction and high-throughput read-pair mapping revealed the substoichiometric presence of the alternative isomeric form within each individual plant. Furthermore, our comparative genomic studies demonstrate that the predominant and substoichiometric arrangements of this IR have changed several times in other cupressophytes as well. These results provide compelling evidence for substoichiometric shifting of plastomic forms during cupressophyte evolution and suggest that substoichiometric shifting activity in plastid genomes may be adaptive.