Transcriptome Analysis of Chloris virgata, Which Shows the Fastest Germination and Growth in the Major Mongolian Grassland Plant

Plants in Mongolian grasslands are exposed to short, dry summers and long, cold winters. These plants should be prepared for fast germination and growth activity in response to the limited summer rainfall. The wild plant species adapted to the Mongolian grassland environment may allow us to explore useful genes, as a source of unique genetic codes for crop improvement. Here, we identified the Chloris virgata Dornogovi accession as the fastest germinating plant in major Mongolian grassland plants. It germinated just 5 h after treatment for germination initiation and showed rapid growth, especially in its early and young development stages. This indicates its high growth potential compared to grass crops such as rice and wheat. By assessing growth recovery after animal bite treatment (mimicked by cutting the leaves with scissors), we found that C. virgata could rapidly regenerate leaves after being damaged, suggesting high regeneration potential against grazing. To analyze the regulatory mechanism involved in the high growth potential of C. virgata, we performed RNA-seq-based transcriptome analysis and illustrated a comprehensive gene expression map of the species. Through de novo transcriptome assembly with the RNA-seq reads from whole organ samples of C. virgata at the germination stage (2 days after germination, DAG), early young development stage (8 DAG), young development stage (17 DAG), and adult development stage (28 DAG), we identified 21,589 unified transcripts (contigs) and found that 19,346 and 18,156 protein-coding transcripts were homologous to those in rice and Arabidopsis, respectively. The best-aligned sequences were annotated with gene ontology groups. When comparing the transcriptomes across developmental stages, we found an over-representation of genes involved in growth regulation in the early development stage in C. virgata. Plant development is tightly regulated by phytohormones such as brassinosteroids, gibberellic acid, abscisic acid, and strigolactones. Moreover, our transcriptome map demonstrated the expression profiles of orthologs involved in the biosynthesis of these phytohormones and their signaling networks. We discuss the possibility that C. virgata phytohormone signaling and biosynthesis genes regulate early germination and growth advantages. Comprehensive transcriptome information will provide a useful resource for gene discovery and facilitate a deeper understanding of the diversity of the regulatory systems that have evolved in C. virgata while adapting to severe environmental conditions.

Phosphate or nitrate imbalance induces stronger molecular responses than combined nutrient deprivation in roots and leaves of chickpea plants

The negative effects of phosphate (Pi) and/or nitrate (NO₃^- ) fertilizers on the environment have raised an urgent need to develop crop varieties with higher Pi and/or nitrogen use efficiencies for cultivation in low-fertility soils. Achieving this goal depends upon research that focuses on the identification of genes involved in plant responses to Pi and/or NO₃^- starvation. Although plant responses to individual deficiency in either Pi (-Pi/+NO₃^- ) or NO₃^- (+Pi/-NO₃^- ) have been separately studied, our understanding of plant responses to combined Pi and NO₃^- deficiency (-Pi/-NO₃^- ) is still very limited. Using RNA-sequencing approach, transcriptome changes in the roots and leaves of chickpea cultivated under -Pi/+NO₃^- , +Pi/-NO₃^- or -Pi/-NO₃^- conditions were investigated in a comparative manner. -Pi/-NO₃^- treatment displayed lesser effect on expression changes of genes related to Pi or NO₃^- transport, signalling networks, lipid remodelling, nitrogen and Pi scavenging/remobilization/recycling, carbon metabolism and hormone metabolism than -Pi/+NO₃^- or +Pi/-NO₃^- treatments. Therefore, the plant response to -Pi/-NO₃^- is not simply an additive result of plant responses to -Pi/+NO₃^- and +Pi/-NO₃^- treatments. Our results indicate that nutrient imbalance is a stronger stimulus for molecular reprogramming than an overall deficiency.

Genetic Elucidation for Response of Flowering Time to Ambient Temperatures in Asian Rice Cultivars

Climate resilience of crops is critical for global food security. Understanding the genetic basis of plant responses to ambient environmental changes is key to developing resilient crops. To detect genetic factors that set flowering time according to seasonal temperature conditions, we evaluated differences of flowering time over years by using chromosome segment substitution lines (CSSLs) derived from japonica rice cultivars "Koshihikari" × "Khao Nam Jen", each with different robustness of flowering time to environmental fluctuations. The difference of flowering times in 9 years' field tests was large in "Khao Nam Jen" (36.7 days) but small in "Koshihikari" (9.9 days). Part of this difference was explained by two QTLs. A CSSL with a "Khao Nam Jen" segment on chromosome 11 showed 28.0 days' difference; this QTL would encode a novel flowering-time gene. Another CSSL with a segment from "Khao Nam Jen" in the region around Hd16 on chromosome 3 showed 23.4 days" difference. A near-isogenic line (NIL) for Hd16 showed 21.6 days' difference, suggesting Hd16 as a candidate for this QTL. RNA-seq analysis showed differential expression of several flowering-time genes between early and late flowering seasons. Low-temperature treatment at panicle initiation stage significantly delayed flowering in the CSSL and NIL compared with "Koshihikari". Our results unravel the molecular control of flowering time under ambient temperature fluctuations.

Life-Course Monitoring of Endogenous Phytohormone Levels under Field Conditions Reveals Diversity of Physiological States among Barley Accessions

Agronomically important traits often develop during the later stages of crop growth as consequences of various plant-environment interactions. Therefore, the temporal physiological states that change and accumulate during the crop's life course can significantly affect the eventual phenotypic differences in agronomic traits among crop varieties. Thus, to improve productivity, it is important to elucidate the associations between temporal physiological responses during the growth of different crop varieties and their agronomic traits. However, data representing the dynamics and diversity of physiological states in plants grown under field conditions are sparse. In this study, we quantified the endogenous levels of five phytohormones - auxin, cytokinins (CKs), ABA, jasmonate and salicylic acid - in the leaves of eight diverse barley (Hordeum vulgare) accessions grown under field conditions sampled weekly over their life course to assess the ongoing fluctuations in hormone levels in the different accessions under field growth conditions. Notably, we observed enormous changes over time in the development-related plant hormones, such as auxin and CKs. Using 3' RNA-seq-based transcriptome data from the same samples, we investigated the expression of barley genes orthologous to known hormone-related genes of Arabidopsis throughout the life course. These data illustrated the dynamics and diversity of the physiological states of these field-grown barley accessions. Together, our findings provide new insights into plant-environment interactions, highlighting that there is cultivar diversity in physiological responses during growth under field conditions.

Calcium signalling mediates self-incompatibility response in the Brassicaceae

Self-incompatibility in the Brassicaceae is controlled by multiple haplotypes encoding the pollen ligand (S-locus protein 11, SP11, also known as S-locus cysteine-rich protein, SCR) and its stigmatic receptor (S-receptor kinase, SRK). A haplotype-specific interaction between SP11/SCR and SRK triggers the self-incompatibility response that leads to self-pollen rejection, but the signalling pathway remains largely unknown. Here we show that Ca(2+) influx into stigma papilla cells mediates self-incompatibility signalling. Using self-incompatible Arabidopsis thaliana expressing SP11/SCR and SRK, we found that self-pollination specifically induced an increase in cytoplasmic Ca(2+) ([Ca(2+)]cyt) in papilla cells. Direct application of SP11/SCR to the papilla cell protoplasts induced Ca(2+) increase, which was inhibited by D-(-)-2-amino-5-phosphonopentanoic acid (AP-5), a glutamate receptor channel blocker. An artificial increase in [Ca(2+)]cyt in papilla cells arrested wild-type (WT) pollen hydration. Treatment of papilla cells with AP-5 interfered with self-incompatibility, and Ca(2+) increase on the self-incompatibility response was reduced in the glutamate receptor-like channel (GLR) gene mutants. These results suggest that Ca(2+) influx mediated by GLR is the essential self-incompatibility response leading to self-pollen rejection.

Isolation of centromeric-tandem repetitive DNA sequences by chromatin affinity purification using a HaloTag7-fused centromere-specific histone H3 in tobacco

The centromere is a multi-functional complex comprising centromeric DNA and a number of proteins. To isolate unidentified centromeric DNA sequences, centromere-specific histone H3 variants (CENH3) and chromatin immunoprecipitation (ChIP) have been utilized in some plant species. However, anti-CENH3 antibody for ChIP must be raised in each species because of its species specificity. Production of the antibodies is time-consuming and costly, and it is not easy to produce ChIP-grade antibodies. In this study, we applied a HaloTag7-based chromatin affinity purification system to isolate centromeric DNA sequences in tobacco. This system required no specific antibody, and made it possible to apply a highly stringent wash to remove contaminated DNA. As a result, we succeeded in isolating five tandem repetitive DNA sequences in addition to the centromeric retrotransposons that were previously identified by ChIP. Three of the tandem repeats were centromere-specific sequences located on different chromosomes. These results confirm the validity of the HaloTag7-based chromatin affinity purification system as an alternative method to ChIP for isolating unknown centromeric DNA sequences. The discovery of more than two chromosome-specific centromeric DNA sequences indicates the mosaic structure of tobacco centromeres.

Coexistence of NtCENH3 and two retrotransposons in tobacco centromeres

Although a centromeric DNA fragment of tobacco (Nicotiana tabacum), Nt2-7, has been reported, the overall structure of the centromeres remains unknown. To characterize the centromeric DNA sequences, we conducted a chromatin immunoprecipitation assay using anti-NtCENH3 antibody and chromatins isolated from two ancestral diploid species (Nicotiana sylvestris and Nicotiana tomentosiformis) of N. tabacum and isolated a 178-pb fragment, Nto1 from N. tomentosiformis, as a novel centromeric DNA. Fluorescence in situ hybridization (FISH) showed that Nto1 localizes on 24 out of 48 chromosomes in some cells of a BY-2 cell line. To identify the origins of the Nt2-7 and Nto1, a tobacco bacterial artificial chromosome (BAC) library was constructed from N. tabacum, and then screened by polymerase chain reaction (PCR) with primer sets designed from the Nt2-7 and Not1 DNA sequences. Twelve BAC clones were found to localize on the centromeric regions by FISH. We selected three BAC clones for sequencing and identified two centromeric retrotransposons, NtCR and NtoCR, the DNA sequences of which are similar to that of Nt2-7 and Nto1, respectively. Quantitative PCR analysis using coprecipitated DNA with anti-NtCENH3 clearly showed coexistence of NtCENH3 with both retrotransposons. These results indicate the possibility that these two retrotransposons act as centromeric DNA sequences in tobacco. NtoCR was found to be specific to N. tomentosiformis and T genome of N. tabacum, and a NtCR-like centromeric retrotransposon (TGRIV) exists in tomato. This specificity suggests that the times of amplification of these centromeric retrotransposons were different.

Mechanism of the anti-obesity effects induced by a novel melanin-concentrating hormone 1-receptor antagonist in mice

BACKGROUND AND PURPOSE

Melanin-concentrating hormone (MCH) is an orexigenic neuropeptide expressed in the lateral hypothalamus that is involved in feeding and body weight regulation. Intracerebroventricular infusion of a peptidic MCH1 receptor antagonist ameliorated obesity in murine models. Recently, small molecule MCH1 receptor antagonists have been developed and characterized for the treatment of obesity. However, little is known of the mechanism of the anti-obesity effects of MCH1 receptor antagonists.

EXPERIMENTAL APPROACH

To examine the mechanisms of action of the anti-obesity effect of MCH1 receptor antagonists more precisely, we conducted a pair-feeding study in mice with diet-induced obesity (DIO), chronically treated with an orally active and highly selective MCH1 receptor antagonist and examined changes in mRNA expression levels in liver, brown and white adipose tissues. We also assessed the acute effects of the MCH1 receptor antagonist in energy expenditure under thermoneutral conditions.

KEY RESULTS

Treatment with the MCH1 receptor antagonist at 30 mg.kg(-1) for 1 month moderately suppressed feeding and significantly reduced body weight by 24%. In contrast, pair-feeding resulted in a smaller weight reduction of 10%. Treatment with the MCH1 receptor antagonist resulted in a higher body temperature compared with the pair-fed group. TaqMan and calorimetry data suggested that the MCH1 receptor antagonist also stimulated thermogenesis.

CONCLUSIONS AND IMPLICATIONS

Our results indicate that an MCH1 receptor antagonist caused anti-obesity effects im mice by acting on both energy intake and energy expenditure.

Blockade of MCH1 receptor signalling ameliorates obesity and related hepatic steatosis in ovariectomized mice

BACKGROUND AND PURPOSE

Melanin-concentrating hormone (MCH) is a cyclic orexigenic neuropeptide predominantly expressed in the lateral hypothalamus. We investigated the roles of MCH1 receptor signalling in ovariectomy (OVX)-induced obesity in female C57BL/6J mice, an animal model of postmenopausal obesity.

EXPERIMENTAL APPROACH

The effects of blocking signalling via the MCH1 receptor on OVX-induced obesity was investigated by using Mch1r deficient (KO) mice and chronic treatment with a selective MCH1 receptor antagonist.

KEY RESULTS

OVX induced body weight gain and increases in the weight of visceral fat and of liver; these effects were attenuated following OVX in Mch1r KO mice. OVX-induced triglyceride (TG) accumulation and elevated expression of lipogenic genes were significantly ameliorated in the liver of Mch1r KO mice. In agreement with these results, chronic i.c.v. infusion of a selective MCH1 receptor antagonist significantly reduced body weight gain, visceral fat and liver weights in OVX mice, and hepatic TG contents and lipogenic gene expression levels were normalized.

CONCLUSION AND IMPLICATIONS

Our results indicate that MCH1 receptor signalling is involved in the development of fatty liver, as well as obesity, in OVX mice, and suggest a therapeutic potential for MCH1 receptor antagonists in the treatment of obesity and fatty liver.

Identification and characterization of a second melanin-concentrating hormone receptor, MCH-2R

Melanin-concentrating hormone (MCH) is a 19-aa cyclic neuropeptide originally isolated from chum salmon pituitaries. Besides its effects on the aggregation of melanophores in fish several lines of evidence suggest that in mammals MCH functions as a regulator of energy homeostasis. Recently, several groups reported the identification of an orphan G protein-coupled receptor as a receptor for MCH (MCH-1R). We hereby report the identification of a second human MCH receptor termed MCH-2R, which shares about 38% amino acid identity with MCH-1R. MCH-2R displayed high-affinity MCH binding, resulting in inositol phosphate turnover and release of intracellular calcium in mammalian cells. In contrast to MCH-1R, MCH-2R signaling is not sensitive to pertussis toxin and MCH-2R cannot reduce forskolin-stimulated cAMP production, suggesting an exclusive G(alpha)q coupling of the MCH-2R in cell-based systems. Northern blot and in situ hybridization analysis of human and monkey tissue shows that expression of MCH-2R mRNA is restricted to several regions of the brain, including the arcuate nucleus and the ventral medial hypothalamus, areas implicated in regulation of body weight. In addition, the human MCH-2R gene was mapped to the long arm of chromosome 6 at band 6q16.2-16.3, a region reported to be associated with cytogenetic abnormalities of obese patients. The characterization of a second mammalian G protein-coupled receptor for MCH potentially indicates that the control of energy homeostasis in mammals by the MCH neuropeptide system may be more complex than initially anticipated.

A typical Y1 receptor regulates feeding behaviors: effects of a potent and selective Y1 antagonist, J-115814

Neuropeptide Y (NPY) is a potent feeding stimulant. The orexigenic effect of NPY might be caused in part by the action of Y1 receptors. However, the existence of multiple NPY receptors including a possible novel feeding receptor has made it difficult to determine the relative importance of the Y1 receptor in feeding regulation. Herein we certified that the Y1 receptor is a major feeding receptor of NPY by using the potent and selective Y1 antagonist (-)-2-[1-(3-chloro-5-isopropyloxycarbonylaminophenyl)ethylamino]-6-[2-(5-ethyl-4-methyl-1,3-thiazol-2-yl)ethyl]-4-morpholinopyridine (J-115814) and Y1 receptor-deficient (Y1-/-) mice. J-115814 displaced (125)I-peptide YY binding to cell membranes expressing cloned human, rat, and murine Y(1) receptors with K(i) values of 1.4, 1.8, and 1.9 nM, respectively, and inhibited NPY (10 nM)-induced increases in intracellular calcium levels via human Y1 receptors (IC(50) = 6.8 nM). In contrast, J-115814 showed low affinities for human Y2 (K(i) > 10 microM), Y4 (K(i) = 640 nM) and Y5 receptors (K(i) = 6000 nM). Intracerebroventricular (ICV) (10-100 microg) and intravenous (IV) (0.3-30 mg/kg) administration of J-115814 significantly and dose-dependently suppressed feeding induced by ICV NPY (5 microg) in satiated Sprague-Dawley rats. Intraperitoneal (IP) administration of J-115814 (3-30 mg/kg) significantly attenuated spontaneous feeding in db/db and C57BL6 mice. Feeding induced by ICV NPY (5 microg) was unaffected by IP-injected J-115814 (30 mg/kg) in Y1-/- mice and was suppressed in wild-type and Y5-/- mice. These findings clearly suggest that J-115814 inhibits feeding behaviors through the inhibition of the typical Y1 receptor. We conclude that the Y1 receptor plays a key role in regulating food intake.

Different binding sites for the neuropeptide Y Y1 antagonists 1229U91 and J-104870 on human Y1 receptors

The peptidic Y1 antagonist 1229U91 and the non-peptidic antagonist J-104870 have high binding affinities for the human Y1 receptor. These Y1 antagonists show anorexigenic effects on NPY-induced feeding in rats, although they have completely different structures and molecular sizes. To identify the binding sites of these ligands, we substituted amino acid residues of the human Y1 receptor with alanine and examined the abilities of the mutant receptors to bind the radio-labeled ligands. Alanine substitutions, F98A, D104A, T125A, D200A, D205A, L215A, Q219A, L279A, F282A, F286A, W288A and H298A, in the human Y1 receptor lost their affinity for the peptide agonist PYY, but not for 1229U91 and J-104870, while L303A and F173A lost affinity for 1229U91 and J-104870, respectively. N283A retained its affinity for 1229U91, but not for PYY and J-104870. Y47A and N299A retained their affinity for J-104870, but not for PYY and 1229U91. W163A and D287A showed no affinity for any of the three ligands. Taken together, these data indicate that the binding sites of 1229U91 are widely located in the shallow region of the transmembrane (TM) domain of the receptor, especially TM1, TM6 and TM7. In contrast, J-104870 recognized the pocket formed by TM4, TM5 and TM6, based on the molecular modeling of the Y1 receptor and J-104870 complex. In conclusion, 1229U91 and J-104870 have high affinities for Y1 receptors using basically different binding sites. D287 of the common binding site in the TM6 domain could be crucial for the binding of Y1 antagonists.

Requirement of intact disulfide bonds in orexin-A-induced stimulation of gastric acid secretion that is mediated by OX1 receptor activation

Orexin-A is a neuropeptide consisting of 33 amino acids with two intrachain disulfide bonds, namely Cys6-Cys12 and Cys7-Cys14, and is a potent stimulator of food consumption and gastric acid secretion. In contrast, orexin-B, a peptide containing 28 amino acids without disulfide bond, which has no stimulatory action of gastric acid. The objective of the present study was to characterize the receptor-mediated mechanism of orexin-A-induced stimulation of gastric acid secretion using orexin-A-related peptides with modification of disulfide bonds. Intracisternal injection of orexin-A, but not orexin-B or orexin-A (15-33), that does not contain both disulfide bonds stimulated gastric acid secretion in pylorus-ligated conscious rats. The ability of the stimulation of gastric acid output was less in three alanine-substituted orexin-A, [Ala(6,12)]orexin-A, [Ala(7,14)]orexin-A, and [Ala(6,7,12,14)]orexin-A, than orexin-A. Orexins-induced calcium increase was measured in CHO-K1 cells expressing OX1R or OX2R. Orexin-A induced a transient increase in [Ca(2+)]i in CHO-K1/OX1R cells in a dose-dependent manner. EC50 values for OX1R of orexin-A, orexin-B, or orexin-A (15-33) was 0.068, 0.69 or 4.1 nM, respectively, suggesting that peptides containing no disulfide bonds have lower potency for the receptor. Agonistic activity for OX1R of the three orexin-A analogues with modification of one or both disulfide bonds was significantly reduced as compared with that of orexin-A. EC50 values for OX2R of orexin-A and orexin-B was almost equal but potency for the receptor of orexin-A (15-33) and three alanine substituted orexin-A was less than that of orexin-A. A significant inverse relationship between gastric acid output and EC50 values for OX1R, but not OX2R, was observed. These results suggested that the orexin-A-induced acid stimulation requires OX1R activation and that disulfide bonds in orexin-A may have a key role in the receptor activation.

L-152,804: orally active and selective neuropeptide Y Y5 receptor antagonist

Neuropeptide Y (NPY) elicits food intake through the action of hypothalamic G-protein-coupled receptors. Previous publications indicate that the Y5 receptor may represent one of these postulated hypothalamic "feeding" receptors. Using a potent and orally available Y5 antagonist L-152,804, we evaluated the involvement of the Y5 receptor in feeding regulation. L-152,804 displaced [125I]peptide YY (PYY) binding to human and rat Y5 receptors with Ki values of 26 and 31 nM, respectively, and inhibited NPY (100 nM)-induced increase in intracellular calcium levels via human Y5 receptors (IC50 = 210 nM). L-152,804 did not show significant affinity for human Y1, Y2, and Y4 receptors at a dose of 10 microM. Intracerebroventricular (i.c.v.) (30 microg) or oral (10 mg/kg) administration of L-152,804 significantly inhibited food intake evoked by i.c.v.-injected bovine pancreatic peptide (bPP, 5 microg; a moderately selective Y4, Y5 agonist) in satiated SD rats. However L-152,804 did not significantly inhibit i.c.v. NPY (5 microg; a Y1, Y2, Y5 agonist)-induced food intake. These findings suggest that L-152,804 is a selective and potent non-peptide Y5 antagonist with oral bioavailability and brain penetrability. In addition, the anorexigenic effects of L-152,804 on bPP-induced feeding revealed participation of the Y5 receptor in feeding regulation, while i.c.v. administration of NPY does not appear to significantly contribute to Y5 stimulated food intake. We conclude that the potent and orally active Y5 antagonist, L-152,804, represents a useful tool to address the physiological role of the Y5 receptor.

Role of the Y1 receptor in the regulation of neuropeptide Y-mediated feeding: comparison of wild-type, Y1 receptor-deficient, and Y5 receptor-deficient mice

Neuropeptide Y (NPY) increases food intake through the action of hypothalamic NPY receptors. At least six subtypes of NPY, peptide YY (PYY), and pancreatic polypeptide (PP) receptors have been identified in mice. Although the involvement of Y1 and Y5 receptors in feeding regulation has been suggested, the relative importance of each of these NPY receptors and the participation of a novel feeding receptor are still unclear. To address this issue, we generated a Y1 receptor-deficient (Y1-/-) and a Y5 receptor-deficient (Y5-/-) mouse line in which we directly compared the orexigenic effects of NPY and its analogs after intracerebroventricular (icv) administration. The icv NPY-induced food intake was remarkably reduced in Y1-/- mice, but was not significantly altered by inactivation of the Y5 receptor. The Y1 receptor therefore plays a dominant role in NPY-induced feeding. Stimulation of feeding by moderately selective Y5 agonists [PYY-(3-36), human PP, and bovine PP] was reduced in Y5-/- mice, although food intake did not decrease to vehicle control levels. These results indicate that the Y5 receptor functions as one of the feeding receptors. In addition, the finding that Y5-preferring agonists still induce food intake in Y5-/- mice suggests a role for another NPY receptor(s), including the possibility of novel NPY receptors. Surprisingly, despite the limited efficacy of PYY-(3-36) and PPs at the Y1 receptor, food consumption induced by these agonists was significantly diminished in Y1-/- mice compared with that in wild-type controls. These observations suggest that the feeding stimulation induced by NPY and its analogs may be directly or indirectly modulated by the action of the Y1 receptor. We conclude that multiple NPY receptors, possibly including the novel feeding receptor, are involved in the feeding response evoked by NPY and its analogs. Among them, the Y1 receptor plays a key role in NPY-induced feeding in mice.

The novel neuropeptide Y Y(1) receptor antagonist J-104870: a potent feeding suppressant with oral bioavailability

Neuropeptide Y (NPY) is known to induce robust feeding through the action of NPY receptors in the hypothalamus. Among the subtypes of NPY receptors, Y(1) receptors may play a key role in feeding regulation. In the present study, we demonstrated that a novel Y(1) antagonist, J-104870, shows high selectivity and potency for the Y(1) receptor with an anorexigenic effect on NPY-mediated feeding. J-104870 displaced [(125)I]peptide YY (PYY) binding to cloned human and rat Y(1) receptors with K(i) values of 0.29 and 0.54 nM, respectively, and inhibited the NPY (10 nM)-induced increase in intracellular calcium levels (IC(50) = 3.2 nM) in cells expressing human Y(1) receptors. In contrast, J-104870 showed low affinities for human Y(2) (K(i) > 10 microM), Y(4) (K(i) > 10 microM), and Y(5) receptors (K(i) = 6 microM). In rat hypothalamic membranes, J-104870 also completely displaced the binding of [(125)I]1229U91, which is known to bind to the typical Y(1) receptor, with a high affinity (K(i) = 2.0 nM). Intracerebroventricular (ICV) injection of J-104870 (200 microg) significantly suppressed NPY (5 microg)-induced feeding in satiated Sprague-Dawley rats by 74%. Furthermore, ICV and oral administration of J-104870 (200 microg and 100 mg/kg, respectively) significantly suppressed spontaneous food intake in Zucker fatty rats. These findings suggested that J-104870 is a selective and potent nonpeptide Y(1) antagonist with oral bioavailability and brain penetrability. In addition, the anorexigenic effect of J-104870 clearly revealed the participation of the Y(1) receptor in NPY-mediated feeding regulation. The potent and orally active Y(1) antagonist J-104970 is a useful tool for elucidating the physiological roles of NPY in obesity.

NPY-induced feeding involves the action of a Y1-like receptor in rodents

We have reported that the potent peptidic Y1 antagonist, 1229U91, significantly suppressed NPY-induced and spontaneous feeding [32,33]. However, information on the precise selectivity of 1229U91 for NPY receptors is lacking. The Y5 receptor has been considered a key receptor for feeding regulation. In the present study we showed that 1229U91 has high affinities for the human and rat Y1 receptors (Ki = 0.041 nM and 0.16 nM, respectively) and also a high affinity for the human Y4 receptor (Ki = 0.33 nM), whereas it shows moderate affinities for the human Y2, Y5 and rat Y5 receptors (K values of 20-170 nM). Moreover, 1229U91 potently inhibits NPY-induced [Ca2+]i increases in cells expressing human Y1 receptors. In contrast, 1229U91 is an agonist at other NPY receptors like the Y2, Y4 and Y5 receptors. Intracerebroventricular (i.c.v.)-injected 1229U91 (30 microg/head) significantly suppressed human NPY-induced feeding in SD rats, while 1229U91 only moderately inhibited bovine pancreatic polypeptide (bPP; an in vivo Y5 agonist)-induced feeding. These results indicate that the food intake evoked by NPY might be mediated by the Y1 receptor, rather than the Y5 receptor. Thus, the Y1 receptor or possibly a novel Y1-like receptor sensitive to 1229U91 may play a key role in the regulation of NPY-induced feeding.

Cloning and characterization of a new subtype of thyrotropin-releasing hormone receptors

A new subfamily member of thyrotropin releasing hormone (TRH) receptor gene, TRHR2, was isolated from rat brain cDNAs. The deduced amino acid sequence of TRHR2 is 51 % identical to that of rat TRH receptor gene which was reported previously. Northern blot analysis with TRHR2 probe revealed brain-specific expression of a 9.5 kb mRNA. In a binding experiment using the TRHR2-expressing COS cells, specific binding of TRH to TRHR2 was observed with Kd value of 9 nM which was equivalent to the Kd value (= 13 nM) of TRH binding to the TRH receptor previously reported. The active metabolite of TRH, histidyl-proline diketopiperazine, or cyclo(His-Pro), showed no specific binding activity. These results suggest that TRHR2 is a novel subtype of TRH receptor.

A potent neuropeptide Y antagonist, 1229U91, suppressed spontaneous food intake in Zucker fatty rats

Neuropeptide Y (NPY) is one of the most potent orexigenic substances known. 1229U91 was found to be a potent and selective NPY antagonist. To elucidate a physiological role of NPY in hyperphagia in obese animals, we studied the effect of 1229U91 on spontaneous food intake in obese and lean Zucker rats. The food intake of Zucker rats was suppressed by intracerebroventricular administration of 1229U91 more potently in obese than in lean animals without abnormal behavior (31.7 and 67.3% inhibition at doses of 10 and 30 micrograms, respectively, in Zucker fatty rats and 22.2% inhibition at 30 micrograms in lean rats). This compound markedly suppressed NPY-induced food intake at 30 micrograms but did not affect galanin-induced food intake, suggesting that the feeding suppression seen in Zucker fatty and lean rats is pharmacologically and behaviorally specific. These results suggest that NPY is involved in feeding behavior in Zucker fatty rats and that NPY contributes to feeding to a greater degree in Zucker fatty than in lean rats. The hyperphagia in Zucker fatty rats may be due to the abnormal overactivation of the NPYergic system.

Potent neuropeptide Y Y1 receptor antagonist, 1229U91: blockade of neuropeptide Y-induced and physiological food intake

Neuropeptide Y (NPY) is thought to increase food intake through the action of Y1 (-like) receptors in the hypothalamus. To confirm the involvement of Y1 receptors in feeding behavior, selective and potent antagonists for Y1 receptors are required. In the present study, we showed that a peptide, 1229U91 [(Ile,Glu,Pro,Dpr,Tyr,Arg,Leu,Arg, Tyr-NH2)2 cyclic (2,4'),(2',4)-diamide], is a potent and selective antagonist for Y1 receptors. 1229U91 displaced [125I]peptide YY (PYY) binding to membranes of human neuroblastoma-derived SK-N-MC cells that predominantly express Y1 receptors with a K1 value 0.10 nM and inhibited the NPY-induced increase in intracellular calcium levels(IC50 = 0.27 nM). In contrast, the K1 values for [125I]PYY binding to Y2 receptors in membranes of human neuroblastoma-derived SK-N-BE2 cells and rat hypothalamus were 700 nM and more than 1 microM, respectively. Although [125I]PYY could not detect Y1 receptors in the rat hypothalamic membranes, [125I]1229U91 revealed binding sites with a high affinity (Kd = 18 pM), indicating the presence of Y1 receptors in the hypothalamus. Intracerebroventricular injection of 1229U91 (30 micrograms) into male Sprague-Dawley rats completely inhibited NPY (5 micrograms)-induced food intake without any other behavioral change. Furthermore, intracerebroventricular injection of 1229U91 significantly suppressed physiological feeding behavior after overnight fasting. These results indicate that Y1 receptors in the rat hypothalamus mediate NPY-induced food intake, and that physiological feeding behavior after overnight fasting may be largely regulated by NPY via Y1 receptors. 1229U91 may be useful for further elucidating the pathophysiological roles of NPY in feeding behavior.

Prolyl endopeptidase from Aeromonas hydrophila: cloning, sequencing, and expression of the enzyme gene, and characterization of the expressed enzyme

A strain of Aeromonas hydrophila was found to show prolyl endopeptidase activity. The enzyme gene was cloned and expressed in Escherichia coli JM83. A 12 kbp EcoRI fragment containing the enzyme gene was subcloned at the HincII site of pUC19 to construct plasmid pAPEP-3 with a 3.5 kbp insert. E. coli JM83 transformed with this plasmid showed about 100-fold higher activity than the parent Aeromonas. Analysis of the nucleotide sequence of the insert revealed that the mature enzyme-encoding sequence starts just after the ATG initiation codon of the open reading frame. The enzyme was a single polypeptide composed of 689 amino acid residues with a molecular weight of 76,383. It showed properties very similar to those of Flavobacterium prolyl endopeptidase, except that the isoelectric point was 5.5. The amino acid sequence was 56 and 41% homologous to those of Flavobacterium and porcine brain prolyl endopeptidases, respectively. From a survey of sequence homology with other members of the prolyl endopeptidase family, the amino acid residues involved in the catalytic triad were deduced to be Ser-537, His-656, and Asp-512 (or Asp-621).

Prolyl endopeptidase from Flavobacterium meningosepticum: cloning and sequencing of the enzyme gene

The prolyl endopeptidase [EC 3.4.21.26] gene of Flavobacterium meningosepticum was cloned in Escherichia coli with the aid of an oligonucleotide probe which was prepared based on the amino acid sequence. The hybrid plasmid, pFPEP1, with a 3.5 kbp insert at the HincII site of pUC19 containing the enzyme gene, was subcloned into pUC19 to construct plasmid pFPEP3. The whole nucleotide sequence of an inserted HincII-BamHI fragment of plasmid pFPEP3 was determined by the dideoxy chain-terminating method. The purified prolyl endopeptidase was labeled with tritium DFP, and the sequence surrounding the reactive serine residue was found to be Ala (551)-Leu-Ser-Gly-Arg-*Ser-Asn(557). Ser-556 was identified as a reactive serine residue. The enzyme consists of 705 amino acid residues as deduced from the nucleotide sequence and has a molecular weight of 78,705, which coincides well with the value estimated by ultra centrifugal analysis. The amino acid sequence was 38.2% homologous to that of the porcine brain prolyl endopeptidase [Rennex et al. (1991) Biochemistry 30, 2195-2203] and 24.5% homologous to E. coli protease II, which has substrate specificity for basic amino acids [Kanatani et al. (1991) J. Biochem. 110, 315-320].

Chemical modification of neutral protease from Bacillus subtilis var. amylosacchariticus: assignment of tyrosyl residues iodinated

The neutral protease of Bacillus subtilis var. amylosacchariticus (B. amylosacchariticus) was iodinated with a 25-fold molar excess of iodine at pH 9.4 for 3 min at 0 degree C, by which treatment the proteolytic activity toward casein was markedly reduced, while the hydrolytic activity toward an N-blocked peptide substrate was rather increased. The modified enzyme was digested with Staphylococcus aureus V8 protease at pH 8.0 and the amino acid sequences of resultant peptides were compared with those obtained from the native enzyme. One of the peptides was found to have an amino acid sequence of Thr-Ala-Asn-Leu-Ile-Tyr-Glu, which corresponds to residue Nos. 153-159 of the enzyme, where Tyr-158 was identified to be mono-iodotyrosine. The other two peptides were those containing Tyr-21 which was mono- and di-iodinated, respectively. Referring to nitration experiments on the neutral protease and the active site structure of thermolysin, it was concluded that the iodination of Tyr-158 is mainly responsible for the activity changes of B. amylosacchariticus neutral protease.

Protease II from Escherichia coli: sequencing and expression of the enzyme gene and characterization of the expressed enzyme

Protease II gene of Escherichia coli HB101 was cloned and expressed in E. coli JM83. The transformant harboring a hybrid plasmid, pPROII-12, with a 2.4 kbp fragment showed 90-fold higher enzyme activity than the host. The whole nucleotide sequence of the inserted fragment of plasmid pPROII-12 was clarified by the dideoxy chain-terminating method. The sequence that encoded the mature enzyme protein was found to start at an ATG codon, as judged by comparison with amino terminal protein sequencing. The molecular weight of the enzyme was estimated to be 81,858 from the nucleotide sequence. The reactive serine residue of protease II was identified as Ser-532 with tritium DFP. The sequence around the serine residue is coincident with the common sequence of Gly-X-Ser-X-Gly, which has been found in the active site of serine proteases. Except for this region, protease II showed no significant sequence homology with E. coli serine proteases, protease IV and protease La (lon gene), or other known families of serine proteases. However, 25.3% homology was observed between protease II and prolyl endopeptidase from porcine brain. Although the substrate specificities of these two enzymes are quite different, it seems possible to classify protease II as a member of the prolyl endopeptidase family from the structural point of view.

Dye-sensitized photooxidation of neutral protease from Bacillus subtilis var. amylosacchariticus: assignment of histidine residue oxidized

The neutral protease of Bacillus subtilis var. amylosacchariticus was photooxidized in the presence of methylene blue, by which treatment the enzyme was rapidly inactivated. The inactive enzyme was digested with endoproteinase Asp-N, the resultant peptides were separated by HPLC, and their amino acid sequences were compared with those obtained from the unmodified enzyme. Of four peptides that contained histidine residues, only the recovery of one peptide was found to be decreased by the photooxidation with the appearance of a new peptide. Comparisons of amino acid compositions and sequences between these two peptides showed that the latter peptide lacked His228 of the former one, indicating that His228 was photooxidized. This result suggests that His228 is involved in the catalytic reaction of the neutral protease or interaction with substrates.

Cloning and sequencing of the 7 alpha-hydroxysteroid dehydrogenase gene from Escherichia coli HB101 and characterization of the expressed enzyme

The 7 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.159) gene from Escherichia coli HB101 was cloned and expressed in E. coli DH1. The hybrid plasmid pSD1, with a 2.8-kbp insert of chromosomal DNA at the BamHI site of pBR322, was subcloned into pUC19 to construct plasmid pSD3. The entire nucleotide sequence of an inserted PstI-BamHI fragment of plasmid pSD3 was determined by the dideoxy chain-termination method. Within this sequence, the mature enzyme protein-encoding sequence was found to start at a GTG initiation codon and to comprise 765 bp, as judged by comparison with the protein sequence. The deduced amino acid sequence of the enzyme indicated that the molecular weight is 26,778. The transformant of E. coli DH1 harboring pSD3 with a 1.8-kbp fragment showed about 200-fold-higher enzyme activity than the host. The enzyme was purified by a single chromatography step on DEAE-Toyopearl and obtained as crystals, with an activity yield of 39%. The purified enzyme was homogeneous, as judged by sodium dodecyl sulfate gel electrophoresis. The enzyme was most active at pH 8.5 and stable between pH 8 and 9. The enzyme was NAD+ dependent and had a pI of 4.3. The molecular mass was estimated to be 120 kDa by the gel filtration method and 28 kDa by electrophoresis, indicating that the enzyme exists in a tetrameric form.

Chemical modification of neutral protease from Bacillus subtilis var. amylosacchariticus with tetranitromethane: assignment of tyrosyl residues nitrated

A neutral protease from Bacillus subtilis var. amylosacchariticus was modified with tetranitromethane (TNM) at pH 8.0 for 1 h at 25 degrees C, by which treatment the proteolytic activity toward casein was markedly reduced, whereas activity changes toward N-blocked peptide substrates were variable depending upon the substrate used. The modified enzyme was digested with a Staphylococcus aureus V8 protease at pH 7.9 and the resultant peptides were separated by HPLC. Two peptides which contain nitrotyrosyl residue(s) were purified. One of the peptides was found to have an amino acid sequence of Thr-Ala-Asn-Leu-Ile-Tyr-Glu, which corresponds to residue Nos. 153-159 of the neutral protease, and Tyr-158 was identified as PTH-nitrotyrosine. The other one was the amino-terminal peptide of residue Nos. 1-22, and Tyr-21 was shown to be nitrated. From a comparison with the active site structure of thermolysin, which is a zinc metalloprotease with a high sequence homology to B. subtilis neutral proteases, nitration of Tyr-158 was inferred to be closely related to the activity changes of the neutral protease from B. subtilis var. amylosacchariticus.