Mammalian Peptides Research Articles

Digesting New Elements in Peptide Transport

In this issue of Structure, Beale et al. (2015) define structurally and functionally a large extracellular domain unique to mammalian peptide transporters and its implications for the transport of basic di- and tri-peptides (Beale et al., 2015).

Investigations into the Use of a Protein Sensor Assay for Metabolite Analysis.

Rapid and definitive classification of biological samples has application in industrial, agricultural, and clinical settings. Considerable effort has been given to analytical methods to address such applications over the past 50 years, with the majority of successful solutions focusing on a single molecular target. However, in many cases, a single or even a few features are insufficient for accurate characterization or classification. Serum albumin (SA) proteins are a class of cargo-carrying proteins in blood that have evolved to transport a wide variety of metabolites and peptides in mammals. These proteins have up to seven binding sites which communicate allosterically to orchestrate a complex pick-up and delivery system involving a large number of different molecules at any time. The ability of SA proteins to bind multiple molecular species in a sophisticated manner inspired the development of assays to differentiate complex biological solutions. The combination of SA and high-resolution liquid chromatography mass spectrometry (LC-MS) is showing exciting promise as a protein sensor assay (PSA) for classification of complex biological samples. In this study, the PSA has been applied to cells undergoing and recovering from mild oxidative stress. Analysis using traditional LC-MS-based metabolomics failed to differentiate samples into treatment or temporal groups, whereas samples first treated with the PSA were cleanly classified into both correct treatment and temporal groups. The success of the PSA could be attributed to selective binding of metabolites, leading to a reduction in sample complexity and a general reduction in chemical noise. Metabolites important to successful sample classification were often enriched by 100-fold or more yet displayed a wide range of affinities for SA. The end result of PSA treatment is better classification of samples with a reduction in the number of features seen overall. Together, these results demonstrate how the use of a protein-based assay before LC-MS analysis can greatly improve separation and lead to more accurate and successful tracking of the metabolic state in an organism, suggesting potential application in a wide range of fields.

Sensing and responding to energetic stress: The role of the AMPK-PGC1α-NRF1 axis in control of mitochondrial biogenesis in fish

Remodeling the muscle metabolic machinery in mammals in response to energetic challenges depends on the energy sensor AMP-activated protein kinase (AMPK) and its ability to phosphorylate PPAR γ coactivator 1 α (PGC1α), which in turn coactivates metabolic genes through direct and indirect association with DNA-binding proteins such as the nuclear respiratory factor 1 (NRF1) (Wu et al., 1999). The integrity of this axis in fish is uncertain because PGC1α i) lacks the critical Thr177 targeted by AMPK and ii) has mutations that may preclude binding NRF1. In this study we found no evidence that AMPK regulates mitochondrial gene expression through PGC1α in zebrafish and goldfish. AICAR treatment of zebrafish blastula cells increased phosphorylation of AMPK and led to changes in transcript levels of the AMPK targets mTOR and hexokinase 2. However, we saw no increases in mRNA levels for genes associated with mitochondrial biogenesis, including PGC1α, NRF1, and COX7C, a cytochrome c oxidase subunit. Further, AMPK phosphorylated mammalian peptides of PGC1α but not the corresponding region of zebrafish or goldfish in vitro. In vivo cold acclimation of goldfish caused an increase in mitochondrial enzymes, AMP and ADP levels, however AMPK phosphorylation decreased. In fish, the NRF1-PGC1α axis may be disrupted due to insertions in fish PGC1α orthologs within the region that serves as NRF1 binding domain in mammals. Immunocopurification showed that recombinant NRF1 protein binds mammalian but not fish PGC1α. Collectively, our studies suggest that fish have a disruption in the AMPK-PGC1α-NRF1 pathway due to structural differences between fish and mammalian PGC1α.

Crystal Structures of the Extracellular Domain from PepT1 and PepT2 Provide Novel Insights into Mammalian Peptide Transport

SummaryMammals obtain nitrogen via the uptake of di- and tri-peptides in the gastrointestinal tract through the action of PepT1 and PepT2, which are members of the POT family of proton-coupled oligopeptide transporters. PepT1 and PepT2 also play an important role in drug transport in the human body. Recent crystal structures of bacterial homologs revealed a conserved peptide-binding site and mechanism of transport. However, a key structural difference exists between bacterial and mammalian homologs with only the latter containing a large extracellular domain, the function of which is currently unknown. Here, we present the crystal structure of the extracellular domain from both PepT1 and PepT2 that reveal two immunoglobulin-like folds connected in tandem, providing structural insight into mammalian peptide transport. Functional and biophysical studies demonstrate that these domains interact with the intestinal protease trypsin, suggesting a role in clustering proteolytic activity to the site of peptide transport in eukaryotic cells.

Manipulators live better, but are they always parasites?

A recent study reports partner manipulation for an interaction that was considered a reward-for-defence mutualism. Secretions of lycaenid caterpillars altered ant locomotion and aggressiveness, likely by manipulating dopaminergic signalling. This study opens the question whether such manipulation is common and whether manipulation necessarily characterises an interaction as parasitism.

Effects of systematic N-terminus deletions and benzoylations of endogenous RF-amide peptides on NPFF1R, NPFF2R, GPR10, GPR54 and GPR103

Mammalian RF-amide peptides including RF-amide-related peptides-1 and -3, neuropeptides AF and FF, Prolactin releasing peptides, Kisspeptins and RFa peptides are currently considered endogenous peptides for the GPCRs NPFF1R, NPFF2R, GPR10, GPR54 and GPR103, respectively. While NPFF1R and NPFF2R displayed high affinity for all the RF-amide peptides, GPR10, GPR54 and GPR103 only bind their cognate ligands. Through a systematic and sequential N-terminus deletion and benzoylation of either RF-amide neuropeptide (RFRP-3, NPFF, Kp-10, PrRP20, and 26RFa), we report the corresponding impact on affinity and activity towards all the RF-amide receptors (NPFF1R, NPFF2R, GPR10, GPR54 and GPR103). Our results highlight the difficulty to develop selective peptide ligands for GPR10, GPR54 or GPR103 without a modification of the C-terminus RF-amide signature, but open the door to the design of new RF-amide peptides acting as agonist for one receptor and antagonist for another one.

Endomorphin-1 analogues (MELs) penetrate the blood–brain barrier and exhibit good analgesic effects with minimal side effects

Endomorphins are endogenous opioid peptides in mammals and display a strong antinociceptive effect after central administration. However, the clinical usage of these peptides is limited because of their diminished analgesic effect following systemic injection and their inability to cross the blood−brain barrier. In this study, we characterized the in vivo effects of four novel endomorphin-1 analogues (termed MELs), which previously showed potential as highly potent analgesics with a good pharmacological profile in vitro. The analogues were administered intravenously to several rodent pain models to examine their antinociception and blood−brain barrier permeability. The tested peptides, especially MEL1214, showed good analgesic activity and blood−brain barrier permeability. Behavioral studies showed dose-dependent analgesic effect after systematic administration of MEL1214 in the tested pain models. Pre-treatment of subcutaneous administration of naloxone methiodide did not affect the antinociception of these peptides. As compared to morphine, MEL1214 was less prone to induce tolerance after consecutive intravenous administration for 5 days. Gastrointestinal transit was evaluated by the isolated colon response and bead expulsion to determine the potential constipation effect. In contrast to morphine, MEL1214 produced no significant constipation effect at an equivalent dose. MEL1214 shows promise as a suitable compound to treat pain with reduced side effects, and exhibits good potential to be further developed as a novel opioid analgesic in pain treatment.

Molecular cloning of a proglucagon in a cyprinid fish (Schizothorax prenanti): mRNA tissue distribution and quantification during periprandial changes and fasting

Abstract Proglucagon is the precursor for several peptides: glucagon, glicentin, oxyntomodulin and at least one glucagon-like peptide. Previous reports indicated that proglucagon-derived peptides are important in regulating feeding and energy homeostasis in both mammals and fish. In the present study, a 504 bp cDNA fragment encoding a highly conserved proglucagon in a cyprinid fish ( Schizothorax prenanti ) was amplified by homologous cloning. Tissue expression profiles of proglucagon showed that S. prenanti proglucagon had a broad tissue distribution, but was expressed primarily in the intestine and brain. Proglucagon mRNA levels significantly increased after feeding in the hypothalamus and intestine, while levels were dramatically reduced during a week of food deprivation and increased upon refeeding. Proglucagon mRNA expression changes in the hypothalamus and intestine responded to the altered feeding status and suggest that proglucagon is involved in the regulation of feeding and energy in S. prenanti . Statement of relevance In the present study, we deal with the molecular, distribution expressions and mRNA quantification during periprandial, fasting and refeeding in lower vertebrate Ya-fish ( S. prenanti ). S. prenanti is an endemic cold temperate fish in the southwest of China valuable in both aquaculture and research. However, slow growth rate has been recognized as a major problem in S. prenanti farming, increasing the final production cost. Studies concerning the expression of genes related to feeding and growth regulation have been conducted for this species in our laboratory. Recently, a growing number of homologues of mammalian appetite-regulating peptides and their receptors have been characterized in fish. Proglucagon is the precursor for several peptides: glucagon, glicentin, oxyntomodulin and at least one glucagon-like peptide. These peptides are derived in a tissue-specific manner via post-translational proteolytic processing. Previous reports in mammals indicated that proglucagon-derived peptides are important in regulating feeding and energy homeostasis. However, there is scarce information about their physiological roles in fish. Here, we cloned a 504 bp cDNA fragment of a single proglucagon gene, that is mainly expressed in the intestine and brain and responded to changes of feeding status. These suggest that proglucagon acts as a satiety factor involved in the regulation of food intake in S. prenanti . Our findings of this study provide a basis for future research to better understand the functions and mechanisms of actions of proglucagon and will be helpful in dealing with feeding and growth issues in fishes. We believe that something in this manuscript would be of interest to the journal's readers and hope that this paper is suitable for publication in Aquaculture (Physiology and Endocrinology: Fish).

Identification of snake bradykinin-potentiating peptides (BPPs)-simile sequences in rat brain – Potential BPP-like precursor protein?

Bradykinin-potentiating peptides (BPPs) from the South American pit viper snake venom were the first natural inhibitors of the human angiotensin I-converting enzyme (ACE) described. The pioneer characterization of the BPPs precursor from the snake venom glands by our group showed for the first time the presence of the C-type natriuretic peptide (CNP) in this same viper precursor protein. The confirmation of the BPP/CNP expression in snake brain regions correlated with neuroendocrine functions stimulated us to pursue the physiological correlates of these vasoactive peptides in mammals. Notably, several snake toxins were shown to have endogenous physiological correlates in mammals. In the present work, we expressed in bacteria the BPPs domain of the snake venom gland precursor protein, and this purified recombinant protein was used to raise specific polyclonal anti-BPPs antibodies. The correspondent single protein band immune-recognized in adult rat brain cytosol was isolated by 2D-SDS/PAGE and/or HPLC, before characterization by MS fingerprint analysis, which identified this protein as superoxide dismutase (SOD, EC 1.15.1.1), a classically known enzyme with antioxidant activity and important roles in the blood pressure modulation. In silico analysis showed the exposition of the BPP-like peptide sequences on the surface of the 3D structure of rat SOD. These peptides were chemically synthesized to show the BPP-like biological activities in ex vivo and in vivo pharmacological bioassays. Taken together, our data suggest that SOD protein have the potential to be a source for putative BPP-like bioactive peptides, which once released may contribute to the blood pressure control in mammals.

Hemokinin-1-derived peptides have antipruritic effects in rats

Substance P (SP) is a member of the tachykinin peptide family. Hemokinin-1 (HK-1) was recently identified as a new mammalian tachykinin peptide. SP and HK-1 consist of undecapeptides and share a common carboxyl-terminal (C-terminal), Phe-Xaa-Gly-Leu-Met-amide motif, and more varied amino-terminals (N-terminal). The function of SP in the pain system of the spinal cord has been examined in detail, whereas that of HK-1 remains unclear. Therefore, the effects of [Leu 11 ]-HK-1 on the induction of scratching behavior by the intrathecal administration of HK-1 or SP and scratching behavior by a subcutaneous injection of histamine and serotonin were examined in order to elucidate the function of HK-1. The pretreatment with [Leu 11 ]-HK-1 decreased the induction of scratching behavior by HK-1, but not by SP, while the pretreatment with [Leu 11 ]-SP decreased the induction of scratching behavior by SP, but not by HK-1. Furthermore, the pretreatments with [Leu 11 ]-HK-1 and [Leu 11 ]-SP decreased the frequency of scratching following an intradermal injection of pruritogens, such as serotonin (5-HT) and histamine, into the nape of the neck. The effects of the pretreatment with HK-1 (1-5), an N-terminal fragment peptide, were also examined to determine the function of HK-1. The pretreatment with HK-1 (1-5) attenuated the induction of scratching behavior by HK-1 and SP. In addition, the pretreatment with HK-1 (1-5) attenuated the induction of scratching behavior by a subcutaneous injection of histamine and 5-HT, while the pretreatment with SP (1-5) had a negligible effect on the scratching behavior induced by these compounds. Collectively, these results indicated that HK-1 was involved in pruritic processing because the pretreatment with [Leu 11 ]-HK-1 and HK-1 (1-5) attenuated the induction of scratching behavior by an injection of histamine and 5-HT. Peptide-derived antagonists, such as [Leu 11 ]-HK-1 and HK-1 (1-5), may be unsuitable for the treatment of pruritus because of the difficulties associated with penetrating the blood brain barrier. Therefore, the discovery of chemical compounds that function as antagonists to the HK-1-preferred receptor will become more important in the treatment of pruritic diseases.

Characterization of a Pachymedusa dacnicolor-Sauvagine analog as a new high-affinity radioligand for corticotropin-releasing factor receptor studies.

The corticotropin-releasing factor (CRF) peptide family comprises the mammalian peptides CRF and the urocortins as well as frog skin sauvagine and fish urophyseal urotensin. Advances in understanding the roles of the CRF ligand family and associated receptors have often relied on radioreceptor assays using labeled CRF ligands. These assays depend on stable, high-affinity CRF analogs that can be labeled, purified, and chemically characterized. Analogs of several of the native peptides have been used in this context, most prominently including sauvagine from the frog Phyllomedusa sauvageii (PS-Svg). Because each of these affords both advantages and disadvantages, new analogs with superior properties would be welcome. We find that a sauvagine-like peptide recently isolated from a different frog species, Pachymedusa dacnicolor (PD-Svg), is a high-affinity agonist whose radioiodinated analog, [(125)ITyr(0)-Glu(1), Nle(17)]-PD-Svg, exhibits improved biochemical properties over those of earlier iodinated agonists. Specifically, the PD-Svg radioligand binds both CRF receptors with comparably high affinity as its PS-Svg counterpart, but detects a greater number of sites on both type 1 and type 2 receptors. PD-Svg is also ∼10 times more potent at stimulating cAMP accumulation in cells expressing the native receptors. Autoradiographic localization using the PD-Svg radioligand shows robust specific binding to rodent brain and peripheral tissues that identifies consensus CRF receptor-expressing sites in a greater number and/or with greater sensitivity than its PS-Svg counterpart. We suggest that labeled analogs of PD-Svg may be useful tools for biochemical, structural, pharmacological, and anatomic studies of CRF receptors.

Recognition of Bacterial Signal Peptides by Mammalian Formyl Peptide Receptors: A NEW MECHANISM FOR SENSING PATHOGENS

Formyl peptide receptors (FPRs) are G-protein-coupled receptors that function as chemoattractant receptors in innate immune responses. Here we perform systematic structure-function analyses of FPRs from six mammalian species using structurally diverse FPR peptide agonists and identify a common set of conserved agonist properties with typical features of pathogen-associated molecular patterns. Guided by these results, we discover that bacterial signal peptides, normally used to translocate proteins across cytoplasmic membranes, are a vast family of natural FPR agonists. N-terminally formylated signal peptide fragments with variable sequence and length activate human and mouse FPR1 and FPR2 at low nanomolar concentrations, thus establishing FPR1 and FPR2 as sensitive and broad signal peptide receptors. The vomeronasal receptor mFpr-rs1 and its sequence orthologue hFPR3 also react to signal peptides but are much more narrowly tuned in signal peptide recognition. Furthermore, all signal peptides examined here function as potent activators of the innate immune system. They elicit robust, FPR-dependent calcium mobilization in human and mouse leukocytes and trigger a range of classical innate defense mechanisms, such as the production of reactive oxygen species, metalloprotease release, and chemotaxis. Thus, bacterial signal peptides constitute a novel class of immune activators that are likely to contribute to mammalian immune defense against bacteria. This evolutionarily conserved detection mechanism combines structural promiscuity with high specificity and enables discrimination between bacterial and eukaryotic signal sequences. With at least 175,542 predicted sequences, bacterial signal peptides represent the largest and structurally most heterogeneous class of G-protein-coupled receptor agonists currently known for the innate immune system.

Insights into the molecular flexibility of θ-defensins by NMR relaxation analysis.

θ-Defensins are mammalian cyclic peptides that have antimicrobial activity and show potential as stable scaffolds for peptide-based drug design. The cyclic cystine ladder structural motif of θ-defensins has been characterized using NMR spectroscopy and is important for their structure and stability. However, the effect of the pronounced elongated topology of θ-defensins on their molecular motion is not yet understood. Studies of molecular motion by NMR relaxation measurements have been facilitated by the recent development of a semirecombinant method for producing cyclic peptides that allows for isotopic labeling. Here we have undertaken a multifield (15)N NMR relaxation analysis of the anti-HIV θ-defensin, HTD-2, and interpreted the experimental data using various models of overall and internal molecular motion. We found that it was necessary to apply a model that includes internal motion to account for the variations in the experimental T1 and NOE data at different backbone amide sites in the peptide. Although an isotropic model with internal motion was the simplest model that provided a satisfactory fit with the experimental data, we cannot exclude the possibility that overall motion is anisotropic, especially considering the strikingly elongated topology of θ-defensins. The presence of flexible side chains, self-association, interactions with solvent, and internal motions are all potential contributors to the observed relaxation data. Internal motion consistent with the constraints imposed by the cyclic cystine ladder was observed in that the order parameters, S(2), show that residues in the turns are more flexible than those in the β-sheet. This study provides insights into the dynamics of θ-defensins and information that might be useful in their application as scaffolds in drug design.

Involvement of Mammalian RF-Amide Peptides and Their Receptors in the Modulation of Nociception in Rodents.

Mammalian RF-amide peptides, which all share a conserved carboxyl-terminal Arg–Phe–NH2 sequence, constitute a family of five groups of neuropeptides that are encoded by five different genes. They act through five G-protein-coupled receptors and each group of peptide binds to and activates mostly one receptor: RF-amide related peptide group binds to NPFFR1, neuropeptide FF group to NPFFR2, pyroglutamylated RF-amide peptide group to QRFPR, prolactin-releasing peptide group to prolactin-releasing peptide receptor, and kisspeptin group to Kiss1R. These peptides and their receptors have been involved in the modulation of several functions including reproduction, feeding, and cardiovascular regulation. Data from the literature now provide emerging evidence that all RF-amide peptides and their receptors are also involved in the modulation of nociception. This review will present the current knowledge on the involvement in rodents of the different mammalian RF-amide peptides and their receptors in the modulation of nociception in basal and chronic pain conditions as well as their modulatory effects on the analgesic effects of opiates.

Structure and function of a peptide pheromone family that stimulate the vomeronasal sensory system in mice.

Mammals use pheromones to communicate with other animals of the same species. In mice, the VNO (vomeronasal organ) has a pivotal role in pheromone detection. We discovered a 7 kDa peptide, ESP1 (exocrine-gland-secreting peptide 1), in tear fluids from male mice that enhances the sexual behaviour of female mice via the VNO. NMR studies demonstrate that ESP1 adopts a compact structure with a helical fold stabilized by an intramolecular disulfide bridge. Functional analysis in combination with docking simulation indicates that ESP1 is recognized by a specific G-protein-coupled vomeronasal receptor, V2Rp5, via charge-charge interactions in the large extracellular region of the receptor. ESP1 is a member of the ESP family, which comprises 38 homologous genes in mice, and some of these genes are expressed in a sex- or age-dependent manner. Most recently, ESP22 was found to be released specifically in juvenile tear fluids and to inhibit the sexual behaviour of adult male mice. These studies demonstrate that peptide pheromones are used for chemical communication in mice, and they indicate a structural basis for the narrowly tuned perception of mammalian peptide pheromones by vomeronasal receptors.

Hemokinin-1 mediates pruriceptive processing in the rat spinal cord

Hemokinin-1 (HK-1) is a new mammalian tachykinin peptide consisting of the amino acid sequence similar to substance P (SP). Although the function of SP, a representative tachykinin peptide, has been well established in the pain system, that of HK-1 has not yet been elucidated. [Leu11]-SP had an antagonistic effect on SP-induced scratching behavior, suggesting that [Leu11]-HK-1 may also attenuate the induction of scratching behavior by HK-1. Thus, the effects of a pretreatment with [Leu11]-HK-1 were evaluated to clarify the function of HK-1. The intrathecal administration of [Leu11]-HK-1 attenuated the induction of scratching by HK-1, but not SP, while [Leu11]-SP reduced the induction of scratching by SP, but not HK-1. These results indicated that [Leu11]-HK-1 may be a more specific antagonist of HK-1-preferred receptors and [Leu11]-SP has an antagonistic effect on the SP-preferred receptor, the neurokinin 1 receptor. In the formalin test for examining noxious response, the intrathecal administration of [Leu11]-SP, but not [Leu11]-HK-1, reduced the number of flinchings and c-Fos-positive cells in the spinal dorsal horn following formalin injection into the plantar region of the hind paw. These results indicated that SP, but not HK-1, is involved in nociceptive processing at the spinal level. To evaluate the involvement of HK-1 and SP in pruritic processing, the effect of [Leu11]-HK-1 and [Leu11]-SP on the induction of scratching behavior and c-Fos expression by serotonin (5-HT) and histamine was evaluated. The increased induction of scratching behavior and c-Fos expression by 5-HT and histamine was markedly attenuated by pretreatment with both [Leu11]-HK-1 and [Leu11]-SP, suggesting that HK-1 and SP may be involved in pruritic processing. These results indicate that HK-1 is involved in pruritic processing and [Leu11]-HK-1 is a valuable tool for clarifying the mechanisms underlying pruritic processing.

Structural basis for polyspecificity in the POT family of proton-coupled oligopeptide transporters.

An enigma in the field of peptide transport is the structural basis for ligand promiscuity, as exemplified by PepT1, the mammalian plasma membrane peptide transporter. Here, we present crystal structures of di- and tripeptide-bound complexes of a bacterial homologue of PepT1, which reveal at least two mechanisms for peptide recognition that operate within a single, centrally located binding site. The dipeptide was orientated laterally in the binding site, whereas the tripeptide revealed an alternative vertical binding mode. The co-crystal structures combined with functional studies reveal that biochemically distinct peptide-binding sites likely operate within the POT/PTR family of proton-coupled symporters and suggest that transport promiscuity has arisen in part through the ability of the binding site to accommodate peptides in multiple orientations for transport.

Plasma neutrophil gelatinase-associated lipocalin levels are markedly increased in patients with non-transfusion-dependent thalassemia: Lack of association with markers of erythropoiesis, iron metabolism and renal function

BackgroundNeutrophil Gelatinase-Associated Lipocalin (NGAL) (known as NGAL, Lipocalin 2, Siderocalin, Uterocalin, proteinase-3 and 24p3) is a mammalian small 25-kD peptide that belongs to the lipocalin superfamily, which consists of about 20 small lipoproteins. NGAL was initially discovered as an antibacterial factor of natural immunity and an acute-phase protein. NGAL is also an iron trafficking protein, a member of the non-transferrin-bound iron (NTBI) pool and an alternative to the transferrin-mediated iron-delivery pathway. Of note, NTBI, which is elevated in thalassemic patients, induces cellular toxicity. In this study we investigated the possible association of NGAL with parameters of erythropoiesis, iron metabolism and renal injury in patients with non-transfusion-dependent thalassemia (thalassemia intermedia or TI). Patients and methodsThirty-five patients with TI, 13 men and 22 women, aged 8–63years, were included in the study, while, 20 healthy individuals served as controls. Plasma NGAL levels were determined using an immunoenzymatic technique. Erythroid marrow activity was estimated by measuring soluble transferrin receptors (sTfR) levels with a turbidimetric technique. NTBI levels were determined using electrothermal atomic absorption spectrometry. Cystatin C, β2-microglobulin and hs-CRP concentrations were measured by means of immunonephelometric techniques. ResultsThe main results of the study showed: a) NGAL levels were significantly higher in patients with TI compared to controls (139.1±86.1 vs 51.2±11.8μg/L, p<0.0001), without significant effect of splenectomy or hydroxyurea on NGAL levels. Only 4 patients had NGAL levels within the control group range, b) no correlation was found between NGAL levels and either the parameters of erythropoiesis Hb, Hb F, reticulocytes and sTfR (p>0.66, p>0.67, p>0.63 and p>0.81 respectively), or with those of iron metabolism ferritin and NTBI (p>0.90 and p>0.95 respectively). ConclusionsThe increased NGAL levels reported for the first time in TI patients in this study are in agreement with the elevated expression of NGAL observed in TI mouse models. We postulate that the induction of NGAL in these patients may represent either a survival response, facilitating the survival of the less damaged thalassemic erythroid precursors, or a consequence of the abnormal iron regulation in TI.

An amino-terminal fragment of hemokinin-1 has an inhibitory effect on pruritic processing in rats

Hemokinin-1 (HK-1) is a peptide encoded by the preprotachykinin gene, TAC-4, and shares the hydrophobic carboxyl-terminal (C-terminal) region common to mammalian tachykinin peptides, such as substance P (SP). It is generally believed that C-terminal fragments of SP elicit an excitatory effect, while pretreatment with amino-terminal (N-terminal) fragments of SP inhibits the function of SP; however, there is no available information on HK-1. Therefore, to clarify the characteristics of C-terminal and N-terminal fragments of HK-1, HK-1 was divided into HK-1 (1–5) as the N-terminal fragment and HK-1 (6–11) as the C-terminal fragment based on the similarity of amino acids between HK-1 and SP. Intrathecal administration of HK-1 (6–11) induced scratching behavior similar to HK-1, while HK-1 (1–5) hardly induced scratching. Pretreatment with HK-1 (1–5), however, attenuated scratching induced by HK-1 and SP, whereas pretreatment with SP (1–5) attenuated SP-induced scratching, but not HK-1. Furthermore, intrathecal administration of HK-1 (1–5) and SP (1–5) markedly attenuated the induction of flinching and enhancement of c-Fos expression in the spinal cord following the intradermal administration of formalin, a noxious stimulant, while pretreatment with HK-1 (1–5), but not SP (1–5), markedly attenuated the induction of scratching behavior by subcutaneous administration of pruritic agents, such as serotonin or histamine. Taken together, these findings indicate that HK-1 (1–5) suppresses pruritic and nociceptive processing, while SP (1–5) suppresses nociceptive processing. Therefore, it is suggested that HK-1 (1–5) may be a useful tool for revealing pruritic processing and HK-1 may play a crucial role in pruritic processing.

A structural and biophysical comparison between the extra-cellular domains from the mammalian peptide transporters, PepT1 and PepT2

A structural and biophysical comparison between the extra-cellular domains from the mammalian peptide transporters, PepT1 and PepT2