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Tissue specific expression of rat peptidylglycine alpha-amidating monooxygenase activity and mRNA.

The tissue specific expression of peptidylglycine alpha-amidating monooxygenase [(PAM) EC 1.14.17.3], an enzyme which catalyzes the formation of amidated bioactive peptides from their glycine-extended precursors, was examined in adult rat. Soluble and membrane-associated PAM enzymatic activities were determined, and the levels and size classes of PAM mRNA were examined by Northern blot analysis. PAM specific activity varied 1000-fold in the tissues examined, with highest levels in heart atrium, pituitary and salivary glands, and hypothalamus. The fraction of total PAM activity that was membrane associated varied from approximately 70% in heart atrium to 10% in neurointermediate pituitary lobe and thyroid gland. Levels of PAM mRNA varied over 300-fold. In the heart atrium, PAM mRNA accounts for more than 0.1% of the mRNA. For many tissues the ratio of total PAM specific activity to PAM mRNA levels was similar; however, PAM activity was higher than expected from mRNA levels in the salivary glands and lower than expected in several tissues, including heart ventricle. Three major size classes of PAM mRNA were identified among the tissues. Use of RNAse H indicated that differences in size were not due to the length of the poly(A) tail. The heart and central nervous system expressed PAM mRNA of the 4.2 kilobase (kb) and 3.8 kb size classes, while the remaining tissues expressed predominantly 3.8 kb and 3.6 kb classes; few tissues contained only one size class of PAM mRNA. The two major forms of PAM mRNA in adult heart atrium differ by the presence or absence of a 315 nucleotide segment in the protein coding region. Using a cDNA probe from within this segment, the 4.2 kb and 3.8 kb size classes of PAM mRNA in the central nervous system appeared to resemble those in the heart atrium. In the remaining tissues, a subset of PAM mRNAs in the 3.8 kb and 3.6 kb size classes hybridized with this probe, suggesting that additional forms of PAM mRNA are present.

Adrenal Glands↗

Thyroid hormone regulation of peptidylglycine alpha-amidating monooxygenase expression in anterior pituitary gland.

Peptidylglycine alpha-amidating monooxygenase (PAM; EC 1.14.17.3) is a copper-, molecular oxygen-, and ascorbate-dependent enzyme which catalyzes the COOH-terminal amidation of bioactive peptides. Expression of PAM in the adult male rat anterior pituitary was evaluated after experimental manipulation of thyroid status. Levels of PAM mRNA increased 4- to 7-fold in animals made hypothyroid by treatment with 6-n-propyl-2-thiouracil or thyroidectomy and were not diminished below control levels in animals made hyperthyroid by treatment with T4. Treatment of thyroidectomized animals with T4 prevented the increase in PAM mRNA levels; similar doses of T4 returned serum TSH and anterior pituitary PAM mRNA to euthyroid values. Based on Northern blot analysis and amplification of fragments derived from rat PAM-1 by reverse transcription and the polymerase chain reaction, thyroid status did not affect the distribution of PAM mRNA among its various alternatively spliced forms. The specific activity of PAM in the anterior pituitary was increased slightly in both the soluble and particulate fractions from chemically hypothyroid rats; the majority of the PAM activity in the rat anterior pituitary was soluble, and increased secretion of enzyme may account for the lesser effect of chemical thyroidectomy on specific activity compared to mRNA levels. Western blot analysis demonstrated a 104-kDa PAM protein in particulate fractions prepared from control, PTU-treated, and T4-treated animals. The soluble fraction contained major PAM proteins of 95 and 75 kDa, and PTU treatment brought about an increase in the prevalence of the 75-kDa form of PAM protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

The yeast KEX-2-processing endoprotease is active in the Golgi apparatus of transfected NIH 3T3 fibroblasts.

Proteolytic processing of polyprotein precursors at pairs of basic amino acids is a prerequisite for the generation of bioactive peptide hormones. While the mammalian endoproteases responsible for these cleavages are yet to be identified, this function has been unequivocally assigned in yeast to the product of the KEX-2 gene. To study the molecular mechanisms involved in polyprotein processing, we have transfected the yeast KEX-2 gene into mouse NIH 3T3 fibroblasts and established a new cell line (called 2N-DK) where the KEX-2 endoprotease is permanently expressed. Immunofluorescence studies show that the KEX-2 enzyme is retained within the Golgi of the 2N-DK cells. The evidence for this cellular location is supported by measurement of intracellular and extracellular KEX-2 enzyme activity. In this permanently transfected cell line, KEX-2 activity is exclusively intracellular, in contrast to the situation previously described in transiently infected cell lines, where extracellular KEX-2 activity was detected. Furthermore, infection of 2N-DK cells with a recombinant retrovirus expressing a cDNA coding for porcine proopiomelanocortin (POMC) resulted in the synthesis of POMC and its efficient processing into beta-lipotropin and beta-endorphin, two of its physiologically authentic maturation products. These results suggest that in the fibroblast cell line 2N-DK, proteolytic processing of POMC by KEX-2 endoprotease occurs in the Golgi apparatus.

Amino Acid Sequence↗

Distribution of, and a putative role for, the cell-surface neutral metallo-endopeptidases during mammalian craniofacial development.

Endopeptidase-24.11 (neutral endopeptidase, neprilysin, 'enkephalinase', EC 3.4.24.11) and endopeptidase-24.18 (endopeptidase-2, meprin, EC 3.4.24.18) are cell-surface zinc-dependent metallo-endopeptidases able to cleave a variety of bioactive peptides including growth factors. We report the first study of the cellular and tissue distribution of both enzymes and of the mRNA for NEP during embryonic development in the rat. Endopeptidase-24.11 protein was first detected at E10 in the lining of the gut and, at E12, the enzyme was present on the notochord, medial and lateral nasal processes, otocyst, mesonephros, heart and neuroepithelium. In contrast, at this time endopeptidase-24.18 was present only on the apical surface of the neuroepithelial cells. By E14 and E16, NEP was also detected in a wide range of craniofacial structures, notably the palatal mesenchyme, the choroid plexus, tongue and perichondrium. The distribution of endopeptidase-24.18 at these stages was restricted to the inner ear, the nasal conchae, and ependymal layer of the brain ventricles and the choroid plexus. Although endopeptidase-24.11 had been detectable in the craniofacial vasculature at E12 and E14, this was no longer apparent at E16. Significantly, the distribution of endopeptidase-24.11 mRNA closely matched the immunolocalization of the protein at all stages investigated. In order to explore the functional role of these enzymes, inhibition studies were carried out using two selective inhibitors of endopeptidase-24.11, phosphoramidon and thiorphan. E9.5 and E10.5 embryos exposed to either inhibitor displayed a characteristic, asymmetric abnormality consisting of a spherical swelling, possibly associated with a haematoma, predominantly on the left side of the prosencephalon, and the severity of this defect appeared to be a dose-dependent phenomenon. This study suggests that these enzymes play previously unrecognized roles during mammalian embryonic development.

Animals↗

Improved preparation of an amino acid type poly(ethylene glycol) derivative.

An amino acid type poly(ethylene glycol) is a useful tool for preparation of a bi- or multivalent poly(ethylene glycol) hybrid of bioactive peptides, but synthesis is problematic. The amino acid type poly(ethylene glycol) was prepared from poly(oxyethylene)diglycolic acid followed by introduction of a fluorenylmethyloxycarbonyl group. The resulting product could be purified easily by LH-20 column chromatography and HPLC.

Amino Acids↗

[The role of tachykinin NK-1 receptors in emetic action in the area postrema of ferrets].

Substance P (SP) is a member of the tachykinin family of bioactive peptides and has highest affinity for the NK-1 receptor. We have developed the non-peptide compound HSP-117 as a selective antagonist of the NK-1 receptor. Binding of 3H-SP to the membranes of IM-9 cells was inhibited by the antagonists HSP-117 and CP-99,994, the inhibitory activity of HSP-117 being 50-fold that of CP-99,994. The SP-induced firing responses of single neuron activity in slices of the nucleus tractus solitarius of ferrets were inhibited by 10 microM HSP-117. Intracerebroventricular injection of HSP-117 significantly inhibited retching and vomiting induced by copper sulphate and morphine and the inhibitory effect of HSP-117 on emesis was greater than that of CP-99,994. Moreover, emesis induced by copper sulphate and morphine were inhibited by the microinjection of HSP-117 and CP-99,994 into the area postrema and by lesion of the area postrema. These results indicate that HSP-117 is a potent anti-emetic agent, blocking NK-1 receptors in the area postrema and that NK-1 receptors in the area postrema play an important role in emesis induced by broad-spectrum emetic stimuli.

Animals↗

[Regulation of brain microvessel function].

The brain microvessels are formed by a specialized endothelium and regulate the movement of solutes between blood and brain. The endothelial cells are sealed together by tight junctions and play a role as the blood-brain barrier. The brain microvessels express GLUT1 as the major form of glucose transporter, aquaporin-4 as a water channel, and p-glycoprotein as a xenobiotic transporter. Occludin and claudin-5 have been identified as the components of tight junction. Increasing evidence suggests that the activities of the transporters are regulated by adrenergic nerve activity as well as by bioactive peptides such as adrenomedullin. The regulation of the activity as well as expression of these transporters may become a strategy for prophylaxis and treatment of not only cerebral vascular diseases but also neurodegenerative disorders, developmental abnormalities and aging of the brain.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Effect of endothelin-1 (1-31) on human mesangial cell proliferation.

It was previously found that human chymase cleaves big endothelins (ETs) at the Tyr31-Gly32 bond and produces 31-amino acid ETs (1-31). In the present study, human plasma concentrations of ET-1 (1-31) and ET-1 were examined and the effect of synthetic ET-1 (1-31) on the proliferation of cultured human mesangial cells (HMCs) was investigated. The proliferative effect of ET-1 (1-31) was evaluated from the [3H]-thymidine uptake. The activity of extracellular signal-regulated kinase (ERK) and DNA binding activity of activator protein-1 were determined by using an in-gel kinase assay and gel mobility shift assay, respectively. Immunoreactive ET-1 (1-31) was detectable in plasma, but the level was slightly lower than that of ET-1. ET-1 (1-31) increased [3H]-thymidine incorporation in HMCs to a degree similar to that induced by ET-1. ET-1 (1-31) also activated ERK1/2. Inhibition of protein kinase C and ERK kinase caused a reduction of ET-1 (1-31)-induced ERK1/2 activation. The ERK1/2 activation was followed by an increase in transcription factor activator protein-1 DNA binding activity. These findings suggest that ET-1 (1-31) is a bioactive peptide in humans and ET-1 (1-31) itself stimulates HMC proliferation.

Adult↗

CD10 immunohistochemical staining in urothelial neoplasms.

CD10, or common acute lymphoblastic leukemia antigen, is a cell surface neutral endopeptidase that inactivates various bioactive peptides. It is expressed by hematopoietic cells and their neoplasms and in a variety of nonhematopoietic tissues and neoplasms. CD10 has been suggested as a useful marker for urothelial carcinoma, but the few studies of CD10 in urothelial tissues have shown varying results; a comparative study of the CD10 immunoprofile in a range of urothelial tumors has not been performed. We report the CD10 immunoprofile of 70 cases representing urothelial lesions as defined by the World Health Organization Classification (2004) of urothelial neoplasia. We demonstrated moderate to strong CD10 immunohistochemical staining in 67% (40/60) of urothelial neoplasms, with a predominantly cytoplasmic staining pattern. We found a statistically significant difference in staining intensity (scale, 0-3) between high-grade neoplasms (mean, 2.5), dysplasia (mean, 1.7), and low-grade lesions (mean, 1.3), with the high-grade group showing a propensity for a more diffuse staining distribution than the low-grade group. Larger studies incorporating molecular genetic techniques should help better define the role of CD10 in urothelial tumorigenesis.

Humans↗

Drugs to interfere with orexins (hypocretins).

Orexins (hypocretins) are bioactive peptides linking arousal, appetite and neuroendocrine-autonomic control. Dysfunction of the orexin system is associated with narcolepsy-cataplexy. Here, we review drugs interfering with orexins directly such as novel selective orexin receptor agonists and antagonists, as well as drugs interfering with orexins indirectly such as those used for the treatment of narcolepsy-cataplexy, and pharmacological targets within the complex network of endogenous neurohumoral signals integrated and relayed by the orexin system. These include amines, acetylcholine, purines, GABA and glutamate, as well as nutritional-metabolic, circadian-photic, immunological and neuroendocrine-peptidergic influences. Basic and clinical evaluation of drugs interfering with the orexin system will lead to a better understanding of the molecular prerequisites that control behavioral state, stress responses, energy homeo- stasis and survival, and yield therapeutic advances for the treatment of narcolepsy and other disorders of sleep, eating, mood and memory.

Animals↗

Adiponectin and other adipocytokines as predictors of markers of triglyceride-rich lipoprotein metabolism.

BACKGROUND: Adipocytokines are bioactive peptides that may play an important role in the regulation of glucose and lipid metabolism. In this study, we investigated the association of plasma adipocytokine concentrations with markers of triglyceride-rich lipoprotein (TRL) metabolism in men. METHODS: Fasting adiponectin, leptin, resistin, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), apolipoprotein (apo) B-48, apo C-III, and remnant-like particle (RLP)-cholesterol concentrations were measured by immunoassays and insulin resistance by homeostasis assessment (HOMA) score in 41 nondiabetic men with a body mass index of 22-35 kg/m2. Visceral and subcutaneous adipose tissue masses (ATMs) were determined by magnetic resonance imaging and total ATM by bioelectrical impedance. RESULTS: In univariate regression, plasma adiponectin and leptin concentrations were inversely and directly associated with plasma apoB-48, apoC-III, RLP-cholesterol, triglycerides, VLDL-apoB, and VLDL-triglycerides (P <0.05). Resistin, IL-6, and TNF-alpha were not significantly associated with any of these variables, except for a direct correction between apoC-III and IL-6 (P <0.05). In multivariate regression including HOMA, age, nonesterified fatty acids, and adipose tissue compartment, adiponectin was an independent predictor of plasma apoB-48 (beta coefficient = -0.354; P = 0.048), apoC-III (beta coefficient = -0.406; P = 0.012), RLP-cholesterol (beta coefficient = -0.377; P = 0.016), and triglycerides (beta coefficient = -0.374; P = 0.013). By contrast, leptin was not an independent predictor of these TRL markers. Plasma apoB-48, apoC-III, RLP-cholesterol, and triglycerides were all significantly and positively associated with plasma insulin, HOMA, and visceral, subcutaneous, and total ATMs (P <0.05). CONCLUSIONS: These data suggest that the plasma adiponectin concentration may not only link abdominal fat, insulin resistance, and dyslipidemia, but may also exert an independent role in regulating TRL metabolism.

Adiponectin↗

Prolactin and 16K prolactin stimulate release of vasopressin by a direct effect on hypothalamo-neurohypophyseal system.

Activity of the magnocellular neurons that synthesize vasopressin and oxytocin in the paraventricular and supraoptic nuclei of the hypothalamus can be modulated by local release of neuromediators within the nuclei. Among the bioactive peptides that may play autocrine or paracrine roles in this system is prolactin (PRL). Paraventricular and supraoptic neurons express PRL mRNA and contain and secrete PRL-like proteins of 23 and 14 kDa. We investigated the localization of PRL receptors in vasopressinergic and oxytocinergic magnocellular neurons using dual-label immunofluorescence. The results demonstrate that both vasopressin- and oxytocin-immunoreactive cells of the paraventricular and supraoptic nuclei contain the PRL receptor. In addition, we investigated the possible regulation of vasopressin secretion by PRL using hypothalamo-neurohypophyseal explants in culture. The results show that PRL and a 16 kDa N-terminal fragment of the hormone that is analogous to the neurohypophyseal 14-kDa PRL fragment stimulate the release of vasopressin. Together, these findings support the hypothesis that vasopressinergic and oxytocinergic neurons of the magnocellular secretory system are regulated directly by various isoforms of PRL via autocrine/paracrine mechanisms.

Animals↗

[The effects of cholera toxin in the release of beta-endorphin from the dispersed cells of the rat neurointermediate lobe].

The intermediate lobe cells of pituitary gland synthesize and secrete bioactive peptides derived from proopiomelanocortin. In the present study, we investigated the effects of cholera toxin on the release of beta-endorphin (beta-Ep) from dispersed-intermediate lobe cells of rats. Cholera toxin added into culture medium, enhanced the intracellular accumulation of adenosine 3', 5'-monophosphate (cAMP) and the release of beta-endorphin like immunoreactive substance (beta-END-LIS). A positive dose-response relationship existed between the concentration of cholera toxin and the release of beta-END-LIS or the accumulation of cAMP. Maximal response was obtained with approximately 3 X 10(-10) M (in beta-END-LIS release) and 1 X 10(-9) M (in cAMP accumulation) concentration of cholera toxin. Incubation with cholera toxin (3 X 10(-8) M) resulted in a significant rise of cAMP accumulation after 20-30 min, and a 2-2.5 fold increase of beta-END-LIS release occurred after 60 min in comparison with nontreated cells. cAMP analog and phosphodiesterase inhibitor also increased the beta-END-LIS release). These results suggested the close relationship between cAMP accumulation and its biological effect (i.e. beta-END-LIS release).

Animals↗

Not more than three tissue kallikreins identified from organs of the guinea pig.

The large and varied multigene families of tissue kallikreins of rat and mouse are considered to selectively release as many bioactive peptides. In order to determine whether a similar family of enzymes is expressed in the organs of the guinea pig purification studies were performed. Tissue kallikreins from the submandibular gland, coagulating gland/prostate complex and the pancreas were separated by affinity chromatography on benzamidine-Sepharose. Amino-terminal sequences, the patterns of hydrolysis rates of a number of peptide p-nitroanilides, inactivation rates by active site-directed irreversible inhibitors, specific kininogenase activities and types of kinin released were used to probe the identity of the isolated enzymes. Guinea pig tissue kallikreins 1 and 2 have been reported previously. In the present study we have identified a third type, designated tissue kallikrein 1a because of its sequence similarity to kallikrein 1, which differs from the latter in the catalytic properties. The inferred occurrence of not more than two or three independent tissue kallikrein genes in the guinea pig contrasts with the varied family of enzymes expressed by the large number of such genes present in rats and mice. Expression in the guinea pig (and also in humans) of only a small number of tissue kallikreins makes specific processing of a multitude of biologically active peptides by such enzymes unlikely.

Amino Acid Sequence↗

Regulatory role of membrane-bound peptidases in the progression of gynecologic malignancies.

Membrane-bound peptidases play a key role in the control of growth, differentiation, and signal transduction of many cellular systems by degrading bioactive peptides. Thus, abnormal changes in their expression pattern and catalytic function result in altered peptide activation, which contributes to neoplastic transformation or progression. In this review, we describe our recent findings along with work from other groups on the expression and biological functions of membrane-bound peptidases in cancer, focusing on the regulatory roles of three peptidases, aminopeptidase A (APA), neutral endopeptidase (NEP) and placental leucine aminopeptidase (P-LAP), in the progression of gynecologic malignancies. APA, NEP and P-LAP are differentially expressed and localized in various gynecologic malignancies including cervical cancer, endometrial cancer, ovarian cancer and choriocarcinoma in a tumor-type specific pattern. The expression levels are up- or down-regulated depending on histological grade or disease progression. These peptidases play regulatory roles in tumor cell proliferation, invasion or angiogenesis via degradation/inactivation of target peptides such as angiotensin II, endothelin-1 and oxytocin, which act on cancer cells as stimulatory or inhibitory factors. Thus, membrane-bound peptidases may become not only a new diagnostic/prognostic marker, but also a novel molecular target for the treatment of gynecologic malignancies.

Disease Progression↗

Papaya glutamine cyclotransferase shows a singular five-fold beta-propeller architecture that suggests a novel reaction mechanism.

Cyclisation of N-terminal glutamine and/or glutamate to yield pyroglutamate is an essential posttranslational event affecting a plethora of bioactive peptides and proteins. It is directly linked with pathologies ranging from neurodegenerative diseases to inflammation and several types of cancers. The reaction is catalysed by ubiquitous glutaminyl cyclotransferases (QCs), which present two distinct prototypes. Mammalian QCs are zinc-dependent enzymes with an alpha/beta-hydrolase fold. Here we present the 1.6-A-resolution structure of the other prototype, the plant analogue from Carica papaya (PQC). The hatbox-shaped molecule consists of an unusual five-fold beta-propeller traversed by a central channel, a topology that has hitherto been described only for some sugar-binding proteins and an extracellular nucleotidase. The high resistance of the enzyme to denaturation and proteolytic degradation is explained by its architecture, which is uniquely stabilised by a series of tethering elements that confer rigidity. Strikingly, the N-terminus of PQC specifically interacts with residues around the entrance to the central channel of a symmetry-related molecule, suggesting that this location is the putative active site. Cyclisation would follow a novel general-acid/base working mechanism, pivoting around a strictly conserved glutamate. This study provides a lead structure not only for plant QC orthologues, but also for bacteria, including potential human pathogens causing diphtheria, plague and malaria.

Amino Acid Sequence↗

Species specificity of thimet oligopeptidase (EC 3.4.24.15).

The recombinant rat testes metallo-endooligopeptidase (EC 3.4.24.15) and the rabbit brain endooligopeptidase A (formerly EC 3.4.22.19) were compared, side-by-side, in view of their striking similarities in both the physicochemical features and the specificities for oligopeptides. Concerning the tissue distribution in rat and rabbit, no relation between the levels of enzyme activity in cytosol and the levels of metallo-endooligopeptidase 24.15 mRNA could be established. The results suggest that the predominant neuropeptide-metabolizing activity attributed to the metallo-endooligopeptidase 24.15 is performed by, at least, two distinct cytosolic enzymes, one predominant in rat testes and the other in rabbit brain and testes, and possibly also in rat brain. Both enzymes are activated by dithiothreitol and irreversibly inhibited by a SH-affinity labeling dynorphin-related compound, but they are not inhibited by EDTA in a concentration dependent manner. Both enzymes exhibit the same specificity toward several bioactive peptides, except for LH-RH and substance P, which are only hydrolysed by the rat testes enzyme. Taken together, these results lead us to conclude that it is unlikely that the recombinant rat testes metallo-endooligopeptidase 24.15 and the rabbit brain endooligopeptidase A are the same molecule although they might belong to the same family of oligopeptidases.

Amino Acid Sequence↗

Cell-surface actin binds plasminogen and modulates neurotransmitter release from catecholaminergic cells.

An emerging area of research has documented a novel role for the plasminogen activation system in the regulation of neurotransmitter release. Prohormones, secreted by cells within the sympathoadrenal system, are processed by plasmin to bioactive peptides that feed back to inhibit secretagogue-stimulated release. Catecholaminergic cells of the sympathoadrenal system are prototypic prohormone-secreting cells. Processing of prohormones by plasmin is enhanced in the presence of catecholaminergic cells, and the enhancement requires binding of plasmin(ogen) to cellular receptors. Consequently, modulation of the local cellular fibrinolytic system of catecholaminergic cells results in substantial changes in catecholamine release. However, mechanisms for enhancing prohormone processing and cell-surface molecules mediating the enhancement on catecholaminergic cells have not been investigated. Here we show that plasminogen activation was enhanced >6.5-fold on catecholaminergic cells. Carboxypeptidase B treatment decreased cell-dependent plasminogen activation by approximately 90%, suggesting that the binding of plasminogen to proteins exposing C-terminal lysines on the cell surface is required to promote plasminogen activation. We identified catecholaminergic plasminogen receptors required for enhancing plasminogen activation, using a novel strategy combining targeted specific proteolysis using carboxypeptidase B with a proteomics approach using two-dimensional gel electrophoresis, radioligand blotting, and tandem mass spectrometry. Two major plasminogen-binding proteins that exposed C-terminal lysines on the cell surface contained amino acid sequences corresponding to beta/gamma-actin. An anti-actin monoclonal antibody inhibited cell-dependent plasminogen activation and also enhanced nicotine-dependent catecholamine release. Our results suggest that cell-surface-expressed forms of actin bind plasminogen, thereby promoting plasminogen activation and increased prohormone processing leading to inhibition of neurotransmitter release.

Actins↗