Glutamine Stimulates Biosynthesis and Secretion of Insulin-like Growth Factor 2 (IGF2), an Autocrine Regulator of Beta Cell Mass and Function.

IGF2 is an autocrine ligand for the beta cell IGF1R receptor and GLP-1 increases the activity of this autocrine loop by enhancing IGF1R expression, a mechanism that mediates the trophic effects of GLP-1 on beta cell mass and function. Here, we investigated the regulation of IGF2 biosynthesis and secretion. We showed that glutamine rapidly and strongly induced IGF2 mRNA translation using reporter constructs transduced in MIN6 cells and primary islet cells. This was followed by rapid secretion of IGF2 via the regulated pathway, as revealed by the presence of mature IGF2 in insulin granule fractions and by inhibition of secretion by nimodipine and diazoxide. When maximally stimulated by glutamine, the amount of secreted IGF2 rapidly exceeded its initial intracellular pool and tolbutamide, and high K(+) increased IGF2 secretion only marginally. This indicates that the intracellular pool of IGF2 is small and that sustained secretion requires de novo synthesis. The stimulatory effect of glutamine necessitates its metabolism but not mTOR activation. Finally, exposure of insulinomas or beta cells to glutamine induced Akt phosphorylation, an effect that was dependent on IGF2 secretion, and reduced cytokine-induced apoptosis. Thus, glutamine controls the activity of the beta cell IGF2/IGF1R autocrine loop by increasing the biosynthesis and secretion of IGF2. This autocrine loop can thus integrate changes in feeding and metabolic state to adapt beta cell mass and function.

Effect of a novel beta-adrenoceptor agonist (Ro 40-2148) on resting energy expenditure in obese women.

The aim of this single-blind, placebo-controlled study was to investigate the effects of the new beta-adrenergic compound Ro 40-2148 on resting energy expenditure (REE) at rest and after an oral glucose load in non-diabetic obese women before and after two weeks of treatment. After one week of placebo administration and after an overnight fast and one hour rest, REE and glucose and lipid oxidation rates were measured by indirect calorimetry (hood system) before and for 6 h after a single dose of placebo solution. A 75 g oral glucose tolerance test (OGTT) was performed during this period starting 90 min after the placebo administration. During the following two weeks, using a randomization design, six patients received Ro 40-2148 at a dose of 400 mg diluted in 100 ml water twice a day (i.e. 800 mg per day), while six others continued with the placebo administration. The same tests and measurements were repeated after two weeks, except for the treatment group which received the drug instead of the placebo. The 14-day period of drug administration did not increase REE measured in post-absorptive conditions. Similarly, there was no acute effect on REE of a 400 mg dose of Ro 40-2148. In contrast, glucose-induced thermogenesis was significantly increased after two weeks in the treatment group (means +/- s.e.m.: 3.7 +/- 1.3%, P = 0.047), while no change was observed in the placebo group (-0.8 +/- 0.7%, not significant). Since there was no significant change in the respiratory quotient, the increase in energy expenditure observed in the treatment group was due to stimulation of both lipid and glucose oxidation. The drug induced no variations in heart rate, blood pressure, axillary temperature or in plasma glucose, insulin and free fatty acid levels. In conclusion, this study shows that Ro 40-2148 activates glucose-induced thermogenesis in obese non-diabetic patients.

Characterization and detection of naturally occurring antibodies against IL-1 alpha and IL-1 beta in normal human plasma.

During the development and testing of a radioreceptor assay (RRA) for human IL-1, we have detected and identified the presence of auto-antibodies to IL-1 in normal human plasma (NHP). The RRA is based on the competition between human 125I-labeled rIL-1 alpha and standard or unknown quantities of IL-1 alpha or IL-1 beta for binding to a limited amounts of IL-1 receptor (IL-1R) isolated from the EL4 mouse thymoma cell line. NHP from 20 out of 100 unselected blood donors were found to completely inhibit the binding of 125I-labeled IL-1 alpha to its receptor, suggesting the presence in these NHP samples of either abnormal amounts of IL-1 or of a factor binding to the 125I-labeled IL-1 alpha. Special care was taken to ascertain that the inhibitory factors were antibodies and not soluble IL-1 receptor antagonist. When plasma samples with inhibiting activity were incubated with labeled IL-1 alpha and chromatographed on a Sephadex G200 column, they were found to contain 125I-labeled complexes with an apparent molecular weight of 150-200kD. The IL-1 binding factor could be eliminated from plasma by incubation with protein A-Sepharose, suggesting that it consisted in IgG antibodies directed against IL-1. Furthermore, the antibody nature of the inhibiting factor was confirmed by its binding to purified rIL-1 coupled to Sepharose. Screening of 200 NHP samples by incubation with 100 pg of 125I-labeled IL-1 followed by precipitation with 12% of polyethylene glycol (PEG) confirmed that about 25% of NHP contain detectable IgG antibodies to IL-1 alpha, while only 2% of NHP contain antibodies to IL-1 beta. No correlation between the presence of these anti-IL-1 antibodies and any particular major histocompatibility complex or any pathological conditions was detected. We suggest that all serum samples assayed for IL-1 alpha or IL-1 beta content should be pretested with the PEG precipitation assay described here.

Protection of pancreatic beta-cells by high density lipoproteins

SUMMARYThe incidence of type 2 diabetes (T2D) is increasing worldwide and is linked to the enhancement of obesity. The principal cause of T2D development is insulin resistance, which lead to the increase of insulin production by the pancreatic beta-cells. In a pathological environment, namely dyslipidaemia, hyperglycaemia and inflammation, beta-cell compensation will fail in more vulnerable cells and diabetes will occur. High Density Lipoproteins (HDLs), commonly named "good cholesterol" are known to be atheroprotective. Low levels of HDLs are associated with increased prevalence of cardiovascular disease but are also an independent risk factor for the development of T2D. HDLs were demonstrated to protect pancreatic beta-cells against several stresses. However the molecular mechanisms of the protection are unknown and the objectives of this work were to try to elucidate the way how HDLs protect. The first approach was a broad screening of genes regulated by the stress and HDLs. A microarray analysis was performed on beta-cells stressed by serum deprivation and rescued by HDLs. Among the genes regulated, we focused on 4E-BP1, a cap-dependent translational inhibitor. In addition, HDLs were also found to protect against several other stresses.Endoplasmic reticulum (ER) stress is a mechanism that may play a role in the onset of T2D. The unfolded protein response (UPR) is a physiological process that aims at maintaining ER homeostasis in conditions where the protein folding and secretion is perturbed. Specific signalling pathways are involved in the increase of folding, export and degradation capacity of the ER. However, in case where the stress is prolonged, this mechanism turns to be pathological, by inducing cell death effector pathways, leading to beta-cell apoptosis. In our study, we discovered that HDLs were protective against ER stress induced by drugs and physiological stresses such as saturated free fatty acids. HDLs protected beta-cells by promoting ER homeostasis via the improvement of the folding and trafficking od proteins from the ER to the Golgi apparatus.Altogether our results suggest that HDLs are important for beta-cell function and survival, by protecting them from several stresses and acting on ER homeostasis. This suggests that attempt in keeping normal HDLs levels or function in patients is crucial to lessen the development of T2D.RÉSUMÉL'incidence du diabète de type 2 est en constante augmentation et est fortement liée à l'accroissement du taux d'obésité. La cause principale du diabète de type 2 est la résistance à l'insuline, qui entraîne une surproduction d'insuline par les cellules bêta pancréatiques. Dans un environnement pathologique associé à l'obésité (dyslipidémie, hyperglycémie et inflammation), les cellules bêta les plus vulnérables ne sont plus capables de compenser en augmentant leur production d'insuline, dysfonctionnent, ce qui conduit à leur mort par apoptose. Les lipoprotéines de hautes densités (HDLs), communément appelées (( bon cholestérol », sont connues pour leurs propriétés protectrices contre l'athérosclérose. Des niveaux bas de HDLs sanguins sont associés au risque de développer un diabète de type 2. Les HDLs ont également montré des propriétés protectrices contre divers stresses dans la cellule bêta. Cependant, les mécanismes de protection restent encore inconnus et l'objectif de ce travail a été d'investiguer les mécanismes moléculaires de protection des HDLs. La première approche choisie a été une étude du profil d'expression génique par puce à ADN afin d'identifier les gènes régulés par le stress et les HDLs. Parmi les gènes régulés, notre intérêt s'est porté sur 4E-BP1, un inhibiteur de la traduction coiffe- dépendante, dont l'induction par le stress était corrélée avec une augmentation de l'apoptose. Suite à cette étude, les HDLs ont également montrés un rôle protecteur contre d'autres stresses. Il s'agit particulièrement du stress du réticulum endoplasmique (RE), qui est un mécanisme qui semble jouer un rôle clé dans le développement du diabète. L'UPR (« Unfolded Protein Response ») est un processus physiologique tendant à maintenir l'homéostasie du réticulum endoplasmique, organelle prépondérante pour la fonction des cellules sécrétrices, notamment lorsqu'elle est soumise à des conditions extrêmes telles que des perturbations de la conformation tertiaire des protéines ou de la sécrétion. Dans ces cas, des voies de signalisation moléculaires sont activées, ce qui mène à l'exportation des protéines mal repliées, à leur dégradation et à l'augmentation de l'expression de chaperonnes capables d'améliorer le repliement des protéines mal formées. Toutefois, en cas de stress persistant, ce mécanisme de protection s'avère être pathologique. En induisant des voies de signalisation effectrices de l'apoptose, il conduit finalement au développement du diabète. Dans cette étude, nous avons démontré que les HDLs étaient capables de protéger la cellule bêta contre le stress du RE induits par des inhibiteurs (thapsigargine, tunicamycine) ou des stresses physiologiques tels que les acides gras libres. Les HDLs ont la capacité d'améliorer l'homéostasie du RE, notamment en favorisant le repliement et le transfert des protéines du RE à l'appareil de Golgi.En résumé, ces données suggèrent que les HDLs sont bénéfiques pour la survie des cellules bêta soumises à des stresses impliqués dans le développement du diabète, notamment en restaurant l'homéostasie du RE. Ces résultats conduisent à soutenir que le maintien des taux de cholestérol joue un rôle important dans la limitation de l'incidence du diabète.

Spine Bone Texture Assessed by Trabecular Bone Score (TBS) to Evaluate Bone Health in Thalassemia Major.

Due to the increasing survival of thalassemic patients, osteopathy is a mounting clinical problem. Low bone mass alone cannot account for the high fracture risk described; impaired bone quality has been speculated but so far it cannot be demonstrated noninvasively. We studied bone quality in thalassemia major using trabecular bone score (TBS), a novel texture measurement extracted from spine dual-energy X-ray absorptiometry (DXA), proposed in postmenopausal and secondary osteoporosis as an indirect index of microarchitecture. TBS was evaluated in 124 adult thalassemics (age range 19-56 years), followed-up with optimal transfusional and therapeutical regimens, and in 65 non-thalassemic patients (22-52 years) undergoing DXA for different bone diseases. TBS was lower in thalassemic patients (1.04 ± 0.12 [range 0.80-1.30]) versus controls (1.34 ± 0.11 [1.06-1.52]) (p < 0.001), and correlated with BMD. TBS and BMD values correlated with age, indicating that thalassemia negatively affects both bone quality and quantity, especially as the patient gets older. TBS was 1.02 ± 0.11 [0.80-1.28] in the osteoporotic thalassemic patients, 1.08 ± 0.12 [0.82-1.30] in the osteopenic ones and 1.15 ± 0.10 [0.96-1.26] in those with normal BMD. No gender differences were found (males: 1.02 ± 0.13 [0.80-1.30], females 1.05 ± 0.11 [0.80-1.30]), nor between patients with and without endocrine-metabolic disorders affecting bone metabolism. Our findings from a large population with thalassemia major show that TBS is a valuable tool to assess noninvasively bone quality, and it may be related to fragility fracture risk in thalassemic osteopathy.

Liddle's syndrome caused by a novel missense mutation (P617L) of the epithelial sodium channel beta subunit.

OBJECTIVE: The aim of the study was to search for mutations of SCNN1B and SCNN1G in an Italian family with apparently dominant autosomal transmission of a clinical phenotype consistent with Liddle's syndrome. METHODS: Genetic analysis was performed in the proband, his relatives, and 100 control subjects. To determine the functional role of the mutation identified in the proband, we expressed the mutant or wild-type epithelial sodium channel in Xenopus laevis oocytes. RESULTS: A novel point mutation, causing an expected substitution of a leucine residue for the second proline residue of the conserved PY motif (PPP x Y) of the beta subunit was identified in the proband. The functional expression of the mutant epithelial sodium channel in X. laevis oocytes showed a three-fold increase in the amiloride-sensitive current as compared with that of the wild-type channel. CONCLUSION: This newly identified mutation adds to other missense mutations of the PY motif of the beta subunit of the epithelial sodium channel, thus confirming its crucial role in the regulation of the epithelial sodium channel. To our knowledge, this is the first report of Liddle's syndrome in the Italian population, confirmed by genetic and functional analysis, with the identification of a gain-of-function mutation not previously reported.

Homologous DNA pairing domain peptides of RecA protein: intrinsic propensity to form beta-structures and filaments.

The 20 amino acid residue peptides derived from RecA loop L2 have been shown to be the pairing domain of RecA. The peptides bind to ss- and dsDNA, unstack ssDNA, and pair the ssDNA to its homologous target in a duplex DNA. As shown by circular dichroism, upon binding to DNA the disordered peptides adopt a beta-structure conformation. Here we show that the conformational change of the peptide from random coil to beta-structure is important in binding ss- and dsDNA. The beta-structure in the DNA pairing peptides can be induced by many environmental conditions such as high pH, high concentration, and non-micellar sodium dodecyl sulfate (6 mM). This behavior indicates an intrinsic property of these peptides to form a beta-structure. A beta-structure model for the loop L2 of RecA protein when bound to DNA is thus proposed. The fact that aromatic residues at the central position 203 strongly modulate the peptide binding to DNA and subsequent biochemical activities can be accounted for by the direct effect of the aromatic amino acids on the peptide conformational change. The DNA-pairing domain of RecA visualized by electron microscopy self-assembles into a filamentous structure like RecA. The relevance of such a peptide filamentous structure to the structure of RecA when bound to DNA is discussed.

Mécanisme moléculaire de protection des HDLs contre le stress du réticulum endoplasmique dans la cellule beta pancréatique. [Molecular mechanisms of HDLs to protect against the endoplasmic reticulum stress in pancreatic beta cell.]

Introduction: Les particules de HDL (High Density Lipoproteins) ont des fonctions très diverses notamment anti-inflamatoires, anti-apoptotiques ou anti-oxydatives. Chez les patients diabétiques, les niveaux de HDLs sont bas, les prédisposants ainsi à un risque élévé à développer une maladie cardiovasculaire. Sachant que le s HDLs ont également un effet protecteur sur la cellule beta, le but de cette étude est dinvestigué les mécanismes moléculaires de cette protection contre le stress du réticulum, stress qui contriubue au développement du diabéte de type 2. Résultats: La thapsigargine et la tunicamycine induisent lapoptose en induisant un stress dans le réticulum endoplasmique (RE) par un mauvais repliement des protéines dans le RE, ainsi que l'activation de l'UPR (Unfolded Protein Respons) avec trois voies communes de signalisation intracellulaire (IRE1, PREK et ATF6). Ces voix veillent tout d'abord à augmenter la capacité de repliement des protéines et le cas échéant à lapoptose. Nos résultats montrent que les HDLs sont capable d'inhuber lapoptose induite par la thapsigargine et la tunicamycine dans les MIN6. Dans le cas du traitement avec la thapsigargine, plusieurs marqueurs des voix UPR sont bloqués en présence des HDLs, suggérant que l'effet anti-apoptotiques des HDLs s'exerce au niveau ou en amont du RE. Les HDLS par contre ne bloquent par la sortie de calcium du RE induite par la thapsigargine ce qui indique que les HDLs n'interfèrent pas avec l'action de cette drogue sur sa cible (SERCA). Dans le cas de la la tunicamycine, les HDLs ne bloquent pas, ou très légèrement, l'activation des voix de l'UPR. La protection induite par les HDLs contre la mort engendrée par la tunicamycine s'sexerce dont apparement en aval de l'UPR et reste à être déterminer. Conclusions: Nos données suggérent que les HDLs sont capable de protéger la cellule beta contre le stress du réticulum mais apparement de façon différente selon les modalités d'inductions de ce stress.

The complete amino acid sequence for brain beta spectrin (beta fodrin): relationship to globin sequences.

The amino acid sequence of mouse brain beta spectrin (beta fodrin), deduced from the nucleotide sequence of complementary DNA clones, reveals that this non-erythroid beta spectrin comprises 2363 residues, with a molecular weight of 274,449 Da. Brain beta spectrin contains three structural domains and we suggest the position of several functional domains including f-actin, synapsin I, ankyrin and spectrin self association sites. Analysis of deduced amino acid sequences indicated striking homology and similar structural characteristics of brain beta spectrin repeats beta 11 and beta 12 to globins. In vitro analysis has demonstrated that heme is capable of specific attachment to brain spectrin, suggesting possible new functions in electron transfer, oxygen binding, nitric oxide binding or heme scavenging.

Transcriptional activation of the GLUT2 gene by the IPF-1/STF-1/IDX-1 homeobox factor.

The homeodomain protein PDX-1, referred as IPF-1/STF-1/IDX-1, is a transcriptional factor that plays a critical role in the control of several genes expressed in the pancreatic islet. PDX-1 gene expression has been previously shown to be reduced in cultured beta-cell lines chronically exposed to high glucose concentrations. As the glucose transporter type 2 (GLUT2) gene expression is selectively decreased in the beta-pancreatic cells of experimental models of diabetes, we postulated that the loss of GLUT2 gene expression in the pancreatic islets of diabetic animals may be due to the loss of PDX-1 transacting function on the GLUT2 gene. We, therefore, investigated the potential role of PDX-1 in the transcriptional control of GLUT2. We have identified a repeat of a TAAT motif (5'-TAATA-ATAACA-3') conserved in the sequence of the human and murine GLUT2 promoters. Recombinant PDX-1 binds to this GLUT2TAAT motif in electrophoretic mobility shift experiments. PDX-1 antiserum detects the formation of the complex of PDX-1 with the GLUT2TAAT motif in nuclear extracts from the pancreatic insulin-secreting cell line, beta TC3. The GLUT2TAAT motif was mutated in the murine GLUT2 promoter (-1308/+49 bp) linked to a luciferase reporter gene and transfected into beta TC3 cells. Compared with the transcriptional activity of the wild type promoter, that of the mutated promoter decreases by 41%. Multiple copies of the GLUT2TAAT motif were ligated 5' to a heterologous promoter and transfected into a PDX-1-expressing cell line (beta TC3) and into cell lines lacking the homeobox factor (InR1-G9 and JEG-3). The GLUT2TAAT motif mediates the activation of the heterologous promoter in the PDX-1-expressing cell line but not in InR1-G9 or JEG-3 cell lines. Furthermore, cotransfection in a PDX-1-deficient cell line with the expression vector encoding PDX-1 transactivates specifically the heterologous promoter containing the multimerized GLUT2TAAT motif. These data demonstrate that the murine GLUT2 promoter is controlled by the PDX-1 homeobox factor through the identified GLUT2TAAT motif.

Manganese-induced integrin affinity maturation promotes recruitment of alpha V beta 3 integrin to focal adhesions in endothelial cells: evidence for a role of phosphatidylinositol 3-kinase and Src.

Integrin activity is controlled by changes in affinity (i.e. ligand binding) and avidity (i.e. receptor clustering). Little is known, however, about the effect of affinity maturation on integrin avidity and on the associated signaling pathways. To study the effect of affinity maturation on integrin avidity, we stimulated human umbilical vein endothelial cells (HUVEC) with MnCl(2) to increase integrin affinity and monitored clustering of beta 1 and beta 3 integrins. In unstimulated HUVEC, beta 1 integrins were present in fibrillar adhesions, while alpha V beta 3 was detected in peripheral focal adhesions. Clustered beta 1 and beta 3 integrins expressed high affinity/ligand-induced binding site (LIBS) epitopes. MnCl(2)-stimulation promoted focal adhesion and actin stress fiber formation at the basal surface of the cells, and strongly enhanced mAb LM609 staining and expression of beta 3 high affinity/LIBS epitopes at focal adhesions. MnCl(2)-induced alpha V beta 3 clustering was blocked by a soluble RGD peptide, by wortmannin and LY294002, two pharmacological inhibitors of phosphatidylinositol 3-kinase (PI 3-K), and by over-expressing a dominant negative PI 3-K mutant protein. Conversely, over-expression of active PI 3-K and pharmacological inhibiton of Src with PP2 and CGP77675, enhanced basal and manganese-induced alpha V beta 3 clustering. Transient increased phosphorylation of protein kinase B/Akt, a direct target of PI 3K, occurred upon manganese stimulation. MnCl(2) did not alter beta 1 integrin distribution or beta1 high-affinity/LIBS epitope expression. Based on these results, we conclude that MnCl(2)-induced alpha V beta 3 integrin affinity maturation stimulates focal adhesion and actin stress fiber formation, and promotes recruitment of high affinity alpha V beta 3 to focal adhesions. Affinity-modulated alpha V beta 3 clustering requires PI3-K signaling and is negatively regulate by Src.

Beta-ionone attracts Euglossa mandibularis(Hymenoptera, Apidae) males in western Paraná forests

ABSTRACTMales of Euglossa mandibularis were consistently captured in scent traps baited with β-ionone in areas of Mixed Ombrophylous Forests or transition between this latter physiognomy and Montane Semideciduous Forest at Parque Nacional do Iguaçu, Paraná state, Brazil. Geographic records for the species and sampling effort (including or not β-ionone among the offered compounds) along Atlantic Forest biome are presented and discussed. We also discuss seasonal and geographic variation in collection of scents by orchid bees.

Setting in motion the immune mechanisms underlying genetically determined resistance and susceptibility to infection with Leishmania major.

The murine model of infection with Leishmania major has allowed the demonstration of a causal relationship between, on the one hand, genetically determined resistance to infection and the development of a Th1 CD4+ cell response, and on the other hand, genetically determined susceptibility and Th2 cell maturation. Using this murine model of infection, the role of cytokines in directing the functional differentiation pathway of CD4+ T cell precursors, has been demonstrated in vivo. Thus, IL-12 and IFN-gamma have been shown to favour Th1 cell development and IL-4 is crucial for the differentiation of Th2 responses. Maturation of a Th2 response in susceptible BALB/c mice following infection with L. major is triggered by the IL-4 produced during the first two days after parasite inoculation. This IL-4 rapidly renders parasite specific CD4+ T cells precursors unresponsive to IL-12. A restricted population of CD4+ T cells expressing the V beta 4V alpha 8 TCR heterodimer and recognizing a single epitope on the LACK (Leishmania Activated C-Kinase) antigen of L. major is responsible for this rapid production of IL-4, instructing subsequent differentiation towards the Th2 phenotype of CD4+ T cells specific for several parasite antigens.

Hierarchal utilization of different T-cell receptor Vbeta gene segments in the CD8(+)-T-cell response to an immunodominant Moloney leukemia virus-encoded epitope in vivo.

The CD8(+)-T-cell response to Moloney murine leukemia virus (M-MuLV)-associated antigens in C57BL/6 mice is directed against an immunodominant gag-encoded epitope (CCLCLTVFL) presented in the context of H-2D(b) and is restricted primarily to cytotoxic T lymphocytes (CTL) expressing the Valpha3.2 and Vbeta5.2 gene segments. We decided to examine the M-MuLV response in congenic C57BL/6 Vbeta(a) mice which are unable to express the dominant Valpha3.2(+) Vbeta5.2(+) T-cell receptor (TCR) due to a large deletion at the TCR locus that includes the Vbeta5.2 gene segment. Interestingly, M-MuLV-immune C57BL/6 Vbeta(a) mice were still able to reject M-MuLV-infected tumor cells and direct ex vivo analysis of peripheral blood lymphocytes from these immune mice revealed a dramatic increase in CD8(+) cells utilizing the same Valpha3.2 gene segment in association with two different Vbeta segments (Vbeta3 and Vbeta17). Surprisingly, all these CTL recognized the same immunodominant M-MuLV gag epitope. Analysis of the TCR repertoire of individual M-MuLV-immune (C57BL/6 x C57BL/6 Vbeta(a))F(1) mice revealed a clear hierarchy in Vbeta utilization, with a preferential usage of the Vbeta17 gene segment, whereas Vbeta3 and especially Vbeta5.2 were used to much lesser extents. Sequencing of TCRalpha- and -beta-chain junctional regions of CTL clones specific for the M-MuLV gag epitope revealed a diverse repertoire of TCRbeta chains in Vbeta(a) mice and a highly restricted TCRbeta-chain repertoire in Vbeta(b) mice, whereas TCRalpha-chain sequences were highly conserved in both cases. Collectively, our data indicate that the H-2D(b)-restricted M-MuLV gag epitope can be recognized in a hierarchal fashion by different Vbeta domains and that the degree of beta-chain diversity varies according to Vbeta utilization.

Differentiation of trophoblast giant cells and their metabolic functions are dependent on peroxisome proliferator-activated receptor beta/delta.

Mutation of the nuclear receptor peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) severely affects placenta development, leading to embryonic death at embryonic day 9.5 (E9.5) to E10.5 of most, but not all, PPARbeta/delta-null mutant embryos. While very little is known at present about the pathway governed by PPARbeta/delta in the developing placenta, this paper demonstrates that the main alteration of the placenta of PPARbeta/delta-null embryos is found in the giant cell layer. PPARbeta/delta activity is in fact essential for the differentiation of the Rcho-1 cells in giant cells, as shown by the severe inhibition of differentiation once PPARbeta/delta is silenced. Conversely, exposure of Rcho-1 cells to a PPARbeta/delta agonist triggers a massive differentiation via increased expression of 3-phosphoinositide-dependent kinase 1 and integrin-linked kinase and subsequent phosphorylation of Akt. The links between PPARbeta/delta activity in giant cells and its role on Akt activity are further strengthened by the remarkable pattern of phospho-Akt expression in vivo at E9.5, specifically in the nucleus of the giant cells. In addition to this phosphatidylinositol 3-kinase/Akt main pathway, PPARbeta/delta also induced giant cell differentiation via increased expression of I-mfa, an inhibitor of Mash-2 activity. Finally, giant cell differentiation at E9.5 is accompanied by a PPARbeta/delta-dependent accumulation of lipid droplets and an increased expression of the adipose differentiation-related protein (also called adipophilin), which may participate to lipid metabolism and/or steroidogenesis. Altogether, this important role of PPARbeta/delta in placenta development and giant cell differentiation should be considered when contemplating the potency of PPARbeta/delta agonist as therapeutic agents of broad application.