Protein Kinase C Activates Human Lipocalin-type Prostaglandin D Synthase Gene Expression through De-repression of Notch-HES Signaling and Enhancement of AP-2β Function in Brain-derived TE671 Cells

Biochemical and Structural Characteristics, Gene Regulation, Physiological, Pathological and Clinical Features of Lipocalin-Type Prostaglandin D2 Synthase as a Multifunctional Lipocalin

Lipocalin-type prostaglandin (PG) D₂ synthase (L-PGDS) catalyzes the isomerization of PGH₂, a common precursor of the two series of PGs, to produce PGD₂. PGD₂ stimulates three distinct types of G protein-coupled receptors: (1) D type of prostanoid (DP) receptors involved in the regulation of sleep, pain, food intake, and others; (2) chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2) receptors, in myelination of peripheral nervous system, adipocyte differentiation, inhibition of hair follicle neogenesis, and others; and (3) F type of prostanoid (FP) receptors, in dexamethasone-induced cardioprotection. L-PGDS is the same protein as β-trace, a major protein in human cerebrospinal fluid (CSF). L-PGDS exists in the central nervous system and male genital organs of various mammals, and human heart; and is secreted into the CSF, seminal plasma, and plasma, respectively. L-PGDS binds retinoic acids and retinal with high affinities (Kd < 100 nM) and diverse small lipophilic substances, such as thyroids, gangliosides, bilirubin and biliverdin, heme, NAD(P)H, and PGD₂, acting as an extracellular carrier of these substances. L-PGDS also binds amyloid β peptides, prevents their fibril formation, and disaggregates amyloid β fibrils, acting as a major amyloid β chaperone in human CSF. Here, I summarize the recent progress of the research on PGD₂ and L-PGDS, in terms of its “molecular properties,” “cell culture studies,” “animal experiments,” and “clinical studies,” all of which should help to understand the pathophysiological role of L-PGDS and inspire the future research of this multifunctional lipocalin.

Lipocalin-type prostaglandin D synthase regulates light-induced phase advance of the central circadian rhythm in mice

We previously showed that mice lacking pituitary adenylate cyclase-activating polypeptide (PACAP) exhibit attenuated light-induced phase shift. To explore the underlying mechanisms, we performed gene expression analysis of laser capture microdissected suprachiasmatic nuclei (SCNs) and found that lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is involved in the impaired response to light stimulation in the late subjective night in PACAP-deficient mice. L-PGDS-deficient mice also showed impaired light-induced phase advance, but normal phase delay and nonvisual light responses. Then, we examined the receptors involved in the response and observed that mice deficient for type 2 PGD₂ receptor DP2/CRTH2 (chemoattractant receptor homologous molecule expressed on Th2 cells) show impaired light-induced phase advance. Concordant results were observed using the selective DP2/CRTH2 antagonist CAY10471. These results indicate that L-PGDS is involved in a mechanism of light-induced phase advance via DP2/CRTH2 signaling.

Kawaguchi et al. show that mice deficient in lipocalin-type prostaglandin (PG) D synthase (L-PGDS) exhibit impaired light-induced phase advance, but normal phase delay and nonvisual light responses. This study suggests the role of L-PGDS for the light-induced phase advance possibly via a chemoattractant receptor DP2/CRTH2.

The cloning and activity of human Hes1 gene promoter

The aim of the current study was to obtain and analyze the activity of the human Hes1 gene promoter. The genomic DNA of human HeLa cell was used as template, polymerase chain reaction (PCR) was used to amplify the 5' end sequence of Hes1 gene and then the amplified segment was connected to pMD18‑T vector. Subsequently, double enzyme digestion was used for identification and the sequence was detected; the promoter with the correct sequence was inserted into pGL3‑Basic, and the sequence was identified by double enzyme digestion. The recombinant DNA with correct sequence was transiently transfected into cervical cancer cells, and the dual luciferase reporter gene assay system was used to detect the activity of the promoter. The results demonstrated that the human Hes1 gene promoter amplified by PCR was the same as that of the sequence in the gene bank, and the dual luciferase reporter gene assay system demonstrated that there was promoter activity in cervical cancer cells. In conclusion, the Hes1 luciferase reporter recombinant vector was successfully established and transfected into HeLa cells to verify that it has promoter activity, and the core area of the promoter has several tumor‑promoting and tumor suppressor genes. This provides a basis for understanding the regulatory mechanism of Hes1 transcription and translation.

Multiple roles of the prostaglandin D2 signaling pathway in reproduction

Prostaglandins signaling molecules are involved in numerous physiological processes. They are produced by several enzyme-limited reactions upon fatty acids, which are catalyzed by two cyclooxygenases and prostaglandin synthases. In particular, the prostaglandins E2(PGE2), D2(PGD2), and F2(PGF2α) have been shown to be involved in female reproductive mechanisms. Furthermore, widespread expression of lipocalin- and hematopoietic-PGD2synthases in the male reproductive tract supports the purported roles of PGD2in the development of both embryonic and adult testes, sperm maturation, and spermatogenesis. In this review, we summarize the putative roles of PGD2signaling and the roles of both PGD2synthases in testicular formation and function. We review the data reporting the involvement of PGD2signaling in the differentiation of Sertoli and germ cells of the embryonic testis. Furthermore, we discuss the roles of lipocalin-PGD2synthase in steroidogenesis and spermatogenesis, in terms of lipid molecule transport and PGD2production. Finally, we discuss the hypothesis that PGD2signaling may be affected in certain reproductive diseases, such as infertility, cryptorchidism, and testicular cancer.

A chromatin immunoprecipitation (ChIP) protocol for use in whole human adipose tissue

Chromatin immunoprecipitation (ChIP) has become a central method when studying in vivo protein-DNA interactions, with the major challenge being the hope to capture "authentic" interactions. While ChIP protocols have been optimized for use with specific cell types and tissues including adipose tissue-derived cells, a working ChIP protocol addressing the challenges imposed by fresh whole human adipose tissue has not been described. Utilizing human paired omental and subcutaneous adipose tissue obtained during elective abdominal surgeries, we have carefully identified and optimized individual steps in the ChIP protocol employed directly on fresh tissue fragments. We describe a complete working protocol for using ChIP on whole adipose tissue fragments. Specific steps required adaptation of the ChIP protocol to human whole adipose tissue. In particular, a cross-linking step was performed directly on fresh small tissue fragments. Nuclei were isolated before releasing chromatin, allowing better management of fat content; a sonication protocol to obtain fragmented chromatin was optimized. We also demonstrate the high sensitivity of immunoprecipitated chromatin from adipose tissue to freezing. In conclusion, we describe the development of a ChIP protocol optimized for use in studying whole human adipose tissue, providing solutions for the unique challenges imposed by this tissue. Unraveling protein-DNA interaction in whole human adipose tissue will likely contribute to elucidating molecular pathways contributing to common human diseases such as obesity and type 2 diabetes.

Very long-chain-fatty acids enhance adipogenesis through coregulation of Elovl3 and PPARγ in 3T3-L1 cells

Here, we show that Elovl3 (elongation of very long-chain fatty acids 3) was involved in the regulation of the progression of adipogenesis through activation of peroxisome proliferator-activated receptor (PPAR)γ in mouse adipocytic 3T3-L1 cells. The expression of the Elovl3 gene increased during adipogenesis, the expression pattern of which was similar to that of the PPARγ gene. Troglitazone, a PPARγ agonist, enhanced Elovl3 expression in adipocytes, as it did that of other PPARγ target genes. Promoter-reporter analysis demonstrated that three PPAR-responsive elements in the Elovl3 gene promoter had the potential to activate its expression in 3T3-L1 cells. Moreover, a chromatin immunoprecipitation assay revealed that PPARγ bound these PPAR-responsive elements of the Elovl3 promoter. When the Elovl3 mRNA level was suppressed by its siRNAs, the level of intracellular triglycerides was significantly decreased, and the expression levels of adipogenic, lipolytic, and lipogenic genes were also repressed. In a mammalian two-hybrid assay, C18:1 and C20:1 very long-chain fatty acids (VLCFAs), which are the products of Elovl3 and activated PPARγ function. In addition, these same VLCFAs could prevent the Elovl3 siRNA-mediated suppression of adipogenesis by enhancing the expression of adipogenic, lipolytic, and lipogenic genes in adipocytes. Moreover, this VLCFAs-mediated activation was repressed by a PPARγ antagonist. These results indicate that the expression of the Elovl3 gene was activated by PPARγ during adipogenesis. Elovl3-produced C18:1 and C20:1 VLCFAs acted as agonists of PPARγ in 3T3-L1 cells. Thus, the Elovl3-PPARγ cascade is a novel regulatory circuit for the regulation of adipogenesis through improvement of PPARγ function in adipocytes.

Activation of adipogenesis by lipocalin-type prostaglandin D synthase-generated Δ¹²-PGJ₂ acting through PPARγ-dependent and independent pathways

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS)-produced PGD(2) accelerates adipogenesis. In this study, we investigated the molecular mechanism of PGD(2)-mediated activation of adipogenesis in mouse adipocytic 3T3-L1 cells. LC/MS analysis showed that Δ(12)-PGJ(2), one of the PGD(2) metabolites, was predominantly produced in the differentiated 3T3-L1 cells. Δ(12)-PGJ(2) enhanced the expression of adipogenic genes in a Δ(12)-PGJ(2)-concentration-dependent manner. Suppression of the expression of the adipogenic genes by L-PGDS siRNA or AT-56, an L-PGDS inhibitor, was cleared by the addition of Δ(12)-PGJ(2). Moreover, the production of adiponectin and leptin was increased by treatment with Δ(12)-PGJ(2). Furthermore, the results of a mammalian two-hybrid assay demonstrated that Δ(12)-PGJ(2) enhanced the PPARγ-mediated transcription activity. However, Δ(12)-PGJ(2)-activated expression of adipogenic genes such as fatty acid binding protein 4 (aP2) and stearoyl-CoA desaturase was inhibited only at 38% and 42%, respectively, by treatment with GW9662, a PPARγ antagonist in 3T3-L1 cells, although Troglitazone-mediated activation of the expression of these adipogenic genes was completely suppressed by GW9662, suggesting the existence of a PPARγ-independent mechanism for Δ(12)-PGJ(2)-activated adipogenesis. These results, taken together, indicate that Δ(12)-PGJ(2) is a dominant metabolite of L-PGDS-produced PGD(2) during adipogenesis and acts as an activator for adipogenesis through both PPARγ-dependent and -independent mechanisms in 3T3-L1 cells.

The genetic signature of perineuronal oligodendrocytes reveals their unique phenotype

Oligodendrocytes--best known for assembling central nervous system myelin--can be categorized as precursors, myelin-forming cells and non-myelinating perineuronal cells. Perineuronal oligodendrocytes have been well characterized morphologically and ultrastructurally, but knowledge about their function remains scanty. It has been proposed that perineuronal oligodendrocytes support neurons and, following injury, transform into myelin-synthesizing cells. Recent findings implicating perineuronal oligodendrocytes in cytoarchitectural abnormalities in the prefrontal cortex of schizophrenia and other psychiatric disorders shed new light on these cells. We have obtained the genetic signature of perineuronal oligodendrocytes by identifying gene expression differences between oligodendrocyte subpopulations using cell-specific tags, microarray technology, quantitative time-resolved polymerase chain reaction and bioinformatics tools. We show that perineuronal cells are the progeny of oligodendrocyte progenitors and, hence, are members of the oligodendrocyte lineage. Physiologically they exhibit a novel phenotype. Their expression of PDGFR-αβ and its growth factor ligand PDGF-CC sets them apart from members of their lineage as this receptor precludes their response to the same growth factors that act on myelinating cells. Their coordinate expression and context-specific usage of transcription factors Olig2, Ascl1 and Pax6, together with the prominent presence of transcription factors Pea3, Lhx2 and Otx2--not hitherto linked to the oligodendrocyte lineage--suggested a cell with features that blur the boundary between a neuron and a glial cell. But they also maintain a reservoir of untranslated transcripts encoding major myelin proteins presumably for a demyelinating episode. This first molecular characterization of perineuronal oligodendrocytes revealed the striking difference between the myelinating and non-myelinating phenotypes.

Forkhead transcription factor Foxa1 is a novel target gene of C/EBPβ and suppresses the early phase of adipogenesis

Forkhead/winged helix transcription factors (Foxs) regulate differentiation, metabolism, and development. Although Foxa1 is expressed in adipocytes, the roles and regulation of Foxa1 in them remain unclear. Here, we found that under the control of C/EBPβ, Foxa1 suppressed lipid accumulation and concomitantly caused a decrease in adipogenic gene expression in adipocytes. Foxa1 was expressed in undifferentiated mouse 3T3-L1 cells and in the early phase of adipogenesis, with its highest expression at 3h after the initiation of adipogenesis, which was followed by a subsequent decrease. SiRNA-mediated suppression of Foxa1 expression activated the expression of adipogenic genes such as PPARγ. Moreover, siRNAs for C/EBPβ, but not those for C/EBPδ, reduced Foxa1 mRNA and protein levels. The results of a promoter-reporter assay and chromatin immunoprecipitation assay demonstrated that C/EBPβ bound to the C/EBP binding element at -529 of the mouse Foxa1 promoter. Furthermore, siRNA-mediated knockdown of C/EBPβ decreased the promoter activity of mouse Foxa1 gene. These results suggest that Foxa1 plays a suppressive role in the early phase of adipogenesis, acting under the control of C/EBPβ, and might be involved in the regulation of the rate of progression of the early phase of adipogenesis.

Pronounced adipogenesis and increased insulin sensitivity caused by overproduction of prostaglandin D2 in vivo

Lipocalin-type prostaglandin (PG) D synthase is expressed in adipose tissues and involved in the regulation of glucose tolerance and atherosclerosis in type 2 diabetes. However, the physiological roles of PGD(2) in adipogenesis in vivo are not clear, as lipocalin-type prostaglandin D synthase can also act as a transporter for lipophilic molecules, such as retinoids. We generated transgenic (TG) mice overexpressing human hematopoietic PGDS (H-PGDS) and investigated the in vivo functions of PGD(2) in adipogenesis. PGD(2) production in white adipose tissue of H-PGDS TG mice was increased approximately seven-fold as compared with that in wild-type (WT) mice. With a high-fat diet, H-PGDS TG mice gained more body weight than WT mice. Serum leptin and insulin levels were increased in H-PGDS TG mice, and the triglyceride level was decreased by about 50% as compared with WT mice. Furthermore, in the white adipose tissue of H-PGDS TG mice, transcription levels of peroxisome proliferator-activated receptor gamma, fatty acid binding protein 4 and lipoprotein lipase were increased approximately two-fold to five-fold as compared with those of WT mice. Finally, H-PGDS TG mice showed clear hypoglycemia after insulin clamp. These results indicate that TG mice overexpressing H-PGDS abundantly produced PGD(2) in adipose tissues, resulting in pronounced adipogenesis and increased insulin sensitivity. The present study provides the first evidence that PGD(2) participates in the differentiation of adipocytes and in insulin sensitivity in vivo, and the H-PGDS TG mice could constitute a novel model mouse for diabetes studies.

Suppression of adipocyte differentiation by aldo-keto reductase 1B3 acting as prostaglandin F2alpha synthase

Prostaglandin (PG) F(2alpha) suppresses adipocyte differentiation by inhibiting the function of peroxisome proliferator-activated receptor gamma. However, PGF(2alpha) synthase (PGFS) in adipocytes remains to be identified. Here, we studied the expression of members of the aldo-keto reductase (AKR) 1B family acting as PGFS during adipogenesis of mouse 3T3-L1 cells. AKR1B3 mRNA was expressed in preadipocytes, and its level increased about 4-fold at day 1 after initiation of adipocyte differentiation, and then quickly decreased the following day to a level lower than that in the preadipocytes. In contrast, the mRNA levels of Akr1b8 and 1b10 were clearly lower than that level of Akr1b3 in preadipocytes and remained unchanged during adipogenesis. The transient increase in Akr1b3 during adipogenesis was also observed by Western blot analysis. The mRNA for the FP receptor, which is selective for PGF(2alpha), was also expressed in preadipocytes. Its level increased about 2-fold within 1 h after the initiation of adipocyte differentiation and was maintained at almost the same level throughout adipocyte differentiation. The small interfering RNA for Akr1b3, but not for Akr1b8 or 1b10, suppressed PGF(2alpha) production and enhanced the expression of adipogenic genes such as peroxisome proliferator-activated receptor gamma, fatty acid-binding protein 4 (aP2), and stearoyl-CoA desaturase. Moreover, an FP receptor agonist, Fluprostenol, suppressed the expression of those adipogenic genes in 3T3-L1 cells; whereas an FP receptor antagonist, AL-8810, efficiently inhibited the suppression of adipogenesis caused by the endogenous PGF(2alpha). These results indicate that AKR1B3 acts as the PGFS in adipocytes and that AKR1B3-produced PGF(2alpha) suppressed adipocyte differentiation by acting through FP receptors.

Increased expression of lipocalin-type prostaglandin D2 synthase in osteoarthritic cartilage

Introduction

Prostaglandin D synthase (PGDS) is responsible for the biosynthesis of PGD and J series, which have been shown to exhibit anti-inflammatory and anticatabolic effects. Two isoforms have been identified: hematopoietic- and lipocalin-type PGDS (H-PGDS and L-PGDS, respectively). The aims of this study were to investigate the expressions of H-PGDS and L-PGDS in cartilage from healthy donors and from patients with osteoarthritis (OA) and to characterize their regulation by interleukin-1-beta (IL-1β) in cultured OA chondrocytes.

Methods

The expressions of H-PGDS and L-PGDS mRNA and protein in cartilage were analyzed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry, respectively. Chondrocytes were stimulated with IL-1β, and the expression of L-PGDS was evaluated by real-time RT-PCR and Western blotting. The roles of de novo protein synthesis and of the signalling pathways mitogen-activated protein kinases (MAPKs), nuclear factor-kappa-B (NF-κB), and Notch were evaluated using specific pharmacological inhibitors.

Results

L-PGDS and H-PGDS mRNAs were present in both healthy and OA cartilage, with higher levels of L-PGDS than H-PGDS (> 20-fold). The levels of L-PGDS mRNA and protein were increased in OA compared with healthy cartilage. Treatment of chondrocytes with IL-1β upregulated L-PGDS mRNA and protein expressions as well as PGD₂ production in a dose- and time-dependent manner. The upregulation of L-PGDS by IL-1β was blocked by the translational inhibitor cycloheximide, indicating that this effect is indirect, requiring de novo protein synthesis. Specific inhibitors of the MAPK p38 (SB 203580) and c-jun N-terminal kinase (JNK) (SP600125) and of the NF-κB (SN-50) and Notch (DAPT) signalling pathways suppressed IL-1β-induced upregulation of L-PGDS expression. In contrast, an inhibitor of the extracellular signal-regulated kinase (ERK/MAPK) (PD98059) demonstrated no significant influence. We also found that PGD₂ prevented IL-1β-induced upregulation of L-PGDS expression.

Conclusions

This is the first report demonstrating increased levels of L-PGDS in OA cartilage. IL-1β may be responsible for this upregulation through activation of the JNK and p38 MAPK and NF-κB signalling pathways. These data suggest that L-PGDS might have an important role in the pathophysiology of OA.

Enhancement of prostaglandin D(2) production through cyclooxygenase-2 and lipocalin-type prostaglandin D synthase by upstream stimulatory factor 1 in human brain-derived TE671 cells under serum starvation

We found that prostaglandin (PG) D(2) production was induced through transcriptional activation of cyclooxygenase (COX)-2 and lipocalin-type PGD synthase (L-PGDS) genes under serum-starved conditions in human brain-derived TE671 cells. Analysis of promoter and intron regions of the human L-PGDS gene demonstrated that an atypical E-box within intron 4 mediated serum starvation-induced up-regulation of L-PGDS gene expression. The results of electrophoretic mobility shift assay and chromatin immunoprecipitation assay showed that upstream stimulatory factor (USF) 1 bound to this atypical E-box. USF1 gene expression was also enhanced during serum starvation in TE671 cells through activation of p38 mitogen activated protein kinase, and the efficiency of the binding of USF1 to the atypical E-box was clearly increased by serum starvation. Administration of USF1 siRNA suppressed both L-PGDS and COX-2 gene expression and PGD(2) production. Moreover, NS-398, a COX-2 inhibitor and AT-56, an L-PGDS inhibitor, suppressed PGD(2) production in TE671 cells cultured under the serum-starved condition. These results indicate that PGD(2) production stimulated by serum starvation is mediated by both COX-2 and L-PGDS through enhancement of USF1 in TE671 cells.

Increased production of lipocalin-type prostaglandin D synthase in leptomeningeal cells through contact with astrocytes

Lipocalin-type prostaglandin D synthase (L-PGDS) is dominantly expressed in the leptomeninges surrounding the brain and secreted into the cerebrospinal fluid as beta-trace, a major cerebrospinal fluid protein. To examine the interaction between the leptomeninges and the brain parenchyma, we co-cultured rat leptomeningeal cells with cells dissociated from the neonatal rat cortex and found that the production of L-PGDS was remarkably increased after the co-cultivation. A similar increase in L-PGDS production was observed by the co-culturing of the leptomeningeal cells with cells dissociated from astrocyte-rich cultures or with 1321-N1 astrocytoma cells. When a crude membrane fraction prepared from 1321-N1 cells was added to leptomeningeal cell cultures, L-PGDS gene expression was slowly increased up to 48 h after the addition. These results indicate that leptomeningeal cells enhance their L-PGDS production by a slow activation of L-PGDS gene expression through their contact with astrocytes.

Cooperative activation of lipocalin-type prostaglandin D synthase gene expression by activator protein-2beta in proximal promoter and upstream stimulatory factor 1 within intron 4 in human brain-derived TE671 cells

We investigated the activation mechanism of gene expression of lipocalin-type prostaglandin D synthase (L-PGDS) in human brain-derived TE671 cells. Reporter analyses of constructs carrying various lengths of the promoter region and intron 1 to 6, or 3'-untranslated region of the human L-PGDS gene demonstrated that one atypical E-box (aE-box) at +2569 in intron 4 was critical for transactivation of the gene. The aE-box inside the intron 4 functioned as an enhancer element in both directions and in a cell-type specific manner in TE671 cells. Yeast one-hybrid screening revealed that upstream stimulatory factor (USF) 1 bound to the aE-box. Expression of exogenous USF1 induced the endogenous L-PGDS expression in TE671 cells, whereas administration of USF1 siRNA suppressed L-PGDS expression. Binding of USF1 to the aE-box was confirmed by performing electrophoretic mobility shift assay and chromatin immunoprecipitation assay. Furthermore, USF1-mediated transcriptional activation was dependent upon activator protein (AP)-2beta binding to the AP-2 element at position -98 in the proximal promoter region of human L-PGDS gene. These results indicate that L-PGDS gene expression in TE671 cells was activated by USF1 through the aE-box within intron 4 and cooperatively by AP-2beta in the promoter in a cell-type-specific manner.

Different expression of lipocalin-type prostaglandin D synthase in rat epididymidis

This study was designed to explore the different expression of L-PGDS (lipocalin-type prostaglandin D synthase) in rat epididymidis and to gain further insight into the potential function of L-PGDS in male reproduction. The expression of L-PGDS in rat epididymidis was assessed using real-time quantitative PCR and immunoblotting. The distribution of L-PGDS in rat epididymidis was explored by immunohistochemical methods. The result of immunohistochemistry displayed that L-PGDS was mainly distributed in epididymidis and localized within the cytoplasm and the cilia of the epithelial cells. Real-time quantitative PCR and immunoblotting showed that L-PGDS was strikingly expressed in the caput epididymidis, while a moderate to weak expression was observed in the corpus and cauda epididymidis, the level of mRNA was 0.52+/-0.02 in the caput, 0.48+/-0.03 in the corpus and 0.32+/-0.01 in the cauda epididymidis, the level of protein expression in caput, corpus and the cauda groups was 1, 0.89+/-0.03 and 0.62+/-0.01, which suggested that L-PGDS may play certain kind of role during the process of the spermatozoa maturation.

SOX9 Regulates Prostaglandin D Synthase Gene Transcription in Vivo to Ensure Testis Development

In mammals, male sex is determined by the Y-chromosomal gene Sry (sex-determining region of Y chromosome). The expression of Sry and subsequently Sox9 (SRY box containing gene 9) in precursors of the supporting cell lineage results in the differentiation of these cells into Sertoli cells. Sertoli cells in turn orchestrate the development of all other male-specific cell types. To ensure that Sertoli cells differentiate in sufficient numbers to induce normal testis development, the early testis produces prostaglandin D(2) (PGD(2)), which recruits cells of the supporting cell lineage to a Sertoli cell fate. Here we show that the gene encoding prostaglandin D synthase (Pgds), the enzyme that produces PGD(2), is expressed in Sertoli cells immediately after the onset of Sox9 expression. Promoter analysis in silico and in vitro identified a paired SOX/SRY binding site. Interestingly, only SOX9, and not SRY, was able to bind as a dimer to this site and transactivate the Pgds promoter. In line with this, a transgenic mouse model showed that Pgds expression is not affected by ectopic Sry expression. Finally, chromatin immunoprecipitation proved that SOX9 but not SRY binds to the Pgds promoter in vivo.

Post-translational modification regulates prostaglandin D2 synthase apoptotic activity: characterization by site-directed mutagenesis

Lipocalin-type prostaglandin D(2) synthase (L-PGDS) is a highly glycosylated protein found in several body fluids. Elevated L-PGDS levels have been observed in the serum of patients with renal impairment, diabetes mellitus, and hypertension. Recently, we demonstrated the ability of L-PGDS to induce apoptosis in a variety of cell types including epithelial cells, neuronal cells, and vascular smooth muscle cells (VSMCs). The aim of this study was to investigate the effect several site-directed mutations had on L-PGDS-induced apoptosis in order to identify potential sites of regulation. Point mutations created in a glycosylation site (Asn51), a protein kinase C phosphorylation site (Ser106), and the enzymatic active site (Cys65) all inhibited L-PGDS-induced apoptosis as determined by both terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) and caspase3 activity. We also compared the L-PGDS isoforms present in GK rat serum to WKY control serum using two-dimensional gel electrophoresis and observed distinct differences which vanished after PNGase F glycolytic digestion. We conclude that post-translational modification of L-PGDS, by either glycosylation or phosphorylation, enhances its apoptotic activity and inhibits VSMC hyperproliferation and postulate that this process is altered in type 2 diabetes.

Structural and Functional Characterization of HQL-79, an Orally Selective Inhibitor of Human Hematopoietic Prostaglandin D Synthase

We determined the crystal structure of human hematopoietic prostaglandin (PG) D synthase (H-PGDS) as the quaternary complex with glutathione (GSH), Mg2+, and an inhibitor, HQL-79, having anti-inflammatory activities in vivo, at a 1.45-A resolution. In the quaternary complex, HQL-79 was found to reside within the catalytic cleft between Trp104 and GSH. HQL-79 was stabilized by interaction of a phenyl ring of its diphenyl group with Trp104 and by its piperidine group with GSH and Arg14 through water molecules, which form a network with hydrogen bonding and salt bridges linked to Mg2+. HQL-79 inhibited human H-PGDS competitively against the substrate PGH2 and non-competitively against GSH with Ki of 5 and 3 microm, respectively. Surface plasmon resonance analysis revealed that HQL-79 bound to H-PGDS with an affinity that was 12-fold higher in the presence of GSH and Mg2+ (Kd, 0.8 microm) than in their absence. Mutational studies revealed that Arg14 was important for the Mg2+-mediated increase in the binding affinity of H-PGDS for HQL-79, and that Trp104, Lys112, and Lys198 were important for maintaining the HQL-binding pocket. HQL-79 selectively inhibited PGD2 production by H-PGDS-expressing human megakaryocytes and rat mastocytoma cells with an IC50 value of about 100 microm but only marginally affected the production of other prostanoids, suggesting the tight functional engagement between H-PGDS and cyclooxygenase. Orally administered HQL-79 (30 mg/kg body weight) inhibited antigen-induced production of PGD2, without affecting the production of PGE2 and PGF2alpha, and ameliorated airway inflammation in wild-type and human H-PGDS-overexpressing mice. Knowledge about this structure of quaternary complex is useful for understanding the inhibitory mechanism of HQL-79 and should accelerate the structure-based development of novel anti-inflammatory drugs that inhibit PGD2 production specifically.

Zebrafish and chicken lipocalin-type prostaglandin D synthase homologues: Conservation of mammalian gene structure and binding ability for lipophilic molecules, and difference in expression profile and enzyme activity

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is a bifunctional protein possessing both the ability to synthesize PGD(2) and to serve as a carrier protein for lipophilic molecules. L-PGDS has been extensively studied in mammalian species, whereas little is known about non-mammalian forms. Here, we identified and characterized the L-PGDS homologues from non-mammals such as zebrafish and chicken. Phylogenetic analysis revealed that L-PGDSs of mammalian and non-mammalian organisms form a "L-PGDS sub-family" that has been evolutionally separated from other lipocalin gene family proteins. The genes for zebrafish and chicken L-PGDS homologues consisted of 6 exons, and all of the exon/intron boundaries were completely identical to those of mammalian L-PGDS genes. Zebrafish and chicken L-PGDS genes were clustered with several lipocalin genes in the chromosome, as in the case of mouse and human genes. Gene expression profiles were different among chicken, mouse, human, except for conservation of abundant expression in the brain and heart. The chicken L-PGDS homologue carried weak PGDS activity, whereas the zebrafish protein did not show any of the activity. However, when the amino-terminal region of the zebrafish L-PGDS homologue was exchanged for that of mouse L-PGDS carrying the Cys residue essential for PGDS activity, this chimeric protein showed weak PGDS activity. Both zebrafish and chicken L-PGDS homologues bound thyroxine and all-trans retinoic acid, like mammalian L-PGDSs and other lipocalin gene family proteins. These results indicate that non-mammalian and mammalian L-PGDS genes evolved from the same ancestral gene and that the non-mammalian L-PGDS homologue was the primordial form of L-PGDS but whose major function was and is to serve as a carrier protein for lipophilic molecules. During molecular evolution, the mammalian L-PGDS protein might have acquired effective PGDS activity through substitution of several amino acid residues, especially in the amino-terminal region including the Cys residue, which is essential for PGDS activity.