Peptides (v.26, #4)
IFC (editorial board) (CO2).
Stereoselective differentiation in the Salt-induced Peptide Formation reaction and its relevance for the origin of life by Kristof Plankensteiner; Hannes Reiner; Bernd M. Rode (535-541).
All living organisms on earth are almost totally made up of biomolecules of only one chiral form. For example, proteins are built almost exclusively of l-amino acids, and sugars are composed of d-saccharides, a fact that is usually referred to as biohomochirality. Its origin is the center of numerous investigations and theories but is not really elucidated yet. The results of experimental investigations of peptide formation in a prebiotically relevant scenario, as described in this paper, give indications on a possible pathway for the synthesis of homochiral l-peptides in the course of the Salt-induced Peptide Formation (SIPF) reaction.
Keywords: Prebiotic peptide formation; Stereoselectivity; Origin of life; Origin of biohomochirality; Amino acid complexes; Copper complexes;
pH- and thermal-dependent conformational transition of PGAIPG, a repeated hexapeptide sequence from tropoelastin by Shan-Yang Lin; Tzu-Feng Hsieh; Yen-Shan Wei (543-549).
The secondary structure of PGAIPG (Pro–Gly–Ala–IIe–Pro–Gly), a repeated hexapeptide of tropoelastin, in buffer solution of different pH was determined by using attenuated total reflection-Fourier transform infrared (ATR–FTIR) spectroscopy. The thermal-dependent structural change of PGAIPG in aqueous solution or in solid state was also examined by thermal FTIR microspectroscopy. The conformation of PGAIPG in aqueous solution exhibited a pH-dependent structural characterization. A predominant peak at 1614 cm−1 (aggregated β-sheet) with a shoulder near 1560 cm−1 (β-sheet) appeared in pH 5.5–8.5 buffer solutions. A new broad shoulder at 1651 cm−1 (random coil and/or α-helix) with 1614 cm−1 was observed in the pH 4.5 buffer solution. However, the broad shoulder at 1651 cm−1 was converted to a maximum peak at 1679 cm−1 (β-turn/antiparallel β-sheet) when the pH shifted from 4.5 to 3.5, but the original pronounced peak at 1614 cm−1 became a shoulder. Once the pH was lowered to 2.5, the IR spectrum of PGAIPG was dominated by major absorption at 1679 cm−1 with a minor peak at 1552 cm−1 (α-helix/random coil). The result indicates that the pH was a predominant factor to transform PGAIPG structure from aggregated β-sheet (pH 8.5) to β-turn/intermolecular antiparallel β-sheet (pH 2.5). Moreover, a partial conformation of PGAIPG with minor α-helix/random coil structures was also explored in the lower pH buffer solution. There was no thermal-dependent structural change for solid-state PGAIPG. The thermal-induced formation of aggregated β-sheet for PGAIPG in aqueous solution was found from 28 to 30 °C, however, which might be correlated with the formation of an opaque gel that turned from clear solution. The formation of aggregated β-sheet structure for PGAIPG beyond 30 °C might be due to the intermolecular hydrogen bonded interaction between the hydrophobic PGAIPG fragments induced by coacervation.
Keywords: Tropoelastin; PGAIPG; Secondary conformation; pH; Temperature; ATR–FTIR; Coacervation;
3D molecular modeling, free radical modulating and immune cells signaling activities of the novel peptidomimetic l-glutamyl-histamine: possible immunostimulating role by Mark A. Babizhayev; Yuri A. Semiletov; Yuri A. Lul’kin; Natalia L. Sakina; Ekaterina L. Savel’yeva; Ludmila M. Alimbarova; Igor Ph. Barinskii (551-563).
An original representative of the patented by author family of histamine-containing peptidomimetics l-glutamyl-histamine (l-Glu-Hist) was synthesized and characterized as a biologically active compound with a role of cytokine mimic leading to cellular responses of improved specificity. The study assesses the ability of l-Glu-Hist to affect molecular modeling, modulate free radical activity and influence immune cell signaling. The energy-minimized 3D conformations of l-Glu-Hist derived from its chemical structure resulted in stabilization for Fe2+ chelating complexes. l-Glu-Hist accelerated the decrease of ferrous iron in the ferrous sulfate solution in a concentration-dependent mode and showed the ferroxidase-like activity at concentrations less than 3 mM in the phenanthroline assay, whereas in the concentration range 3–20 mM l-Glu-Hist restricted the availability of Fe2+ to phenanthroline due to binding of ferrous ions in chelating complexes. l-Glu-Hist showed stimulatory effect on phosphatidylcholine liposomal peroxidation (LPO) catalyzed by the superoxide anion radical (O2 • − )-generating system (Fe2+ + ascorbate) at low (less or about 1 mM) l-Glu-Hist concentrations and both revealed the inhibitory effect on LPO in this system of high (∼10 mM) l-Glu-Hist concentration. The stimulation of LPO by l-Glu-Hist was related to the ability of peptidomimetic in small (∼0.05 mM) concentrations to release O2 • − free radicals as determined by the superoxide dismutase-inhibitable cytochrome c reduction assay. O2 • − release by l-Glu-Hist might result from its ferroxidase-like activity, while inhibition of LPO by l-Glu-Hist was caused by its chelating activity to Fe2+ ions, prevention of free radical generation and lipid hydroperoxide-degrading ability of 5–20 mM l-Glu-Hist. l-Glu-Hist released O2 • − in concentrations which stimulated [3H]-thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and mononuclear cells from human blood. l-Glu-Hist modulates the ability of oxygen free radicals to act as signaling agents at low concentrations, influencing gene expression. The structural peptide-like analogues of l-Glu-Hist such as l-Glu-Trp, carcinine (β-alanylhistamine), but not l-Pro-Glu-Trp were active in stimulating thymidine incorporation and in inducing proliferation of mononuclear cells as compared to mitogen concanavalin A at doses 2.5–25.0 μg/ml. Our data provide evidence that l-Glu-Hist may act as a very fast, specific and sensitive trigger for lymphocyte proliferation and immunoregulation. The cited abilities and further obtained in vivo results make Immudilin® ((INCI: glutamylamidoethyl imidazole, aqueous solution), l-Glu-Hist) a useful immunoregulatory agent.
Keywords: l-Glutamyl-histamine; l-Glutamyl-tryptophan; Peptidomimetics; Free radical oxygen species; Superoxide radical; Iron chelating and ferroxidase activities; Immune cells signaling; Spleen lymphocytes; Blood mononuclear cells; Immunostimulating activities; Lymphocyte proliferation;
Phylloseptins: a novel class of anti-bacterial and anti-protozoan peptides from the Phyllomedusa genus by José Roberto S.A. Leite; Luciano P. Silva; Maria Izabel S. Rodrigues; Maura V. Prates; Guilherme D. Brand; Bruno M. Lacava; Ricardo B. Azevedo; Anamélia L. Bocca; Sergio Albuquerque; Carlos Bloch (565-573).
Six novel peptides called phylloseptins (PS-1, -2, -3, -4, -5, and -6) showing anti-bacterial (PS-1) and anti-protozoan (PS-4 and -5) activities were isolated from the skin secretion of the Brazilian tree-frogs, Phyllomedusa hypochondrialis and Phyllomedusa oreades. Phylloseptins have a primary structure consisting of 19–21 amino acid residues (1.7–2.1 kDa). They have common structural features, such as a highly conserved N-terminal region and C-terminal amidation. Phylloseptin-1 (FLSLIPHAINAVSAIAKHN-NH2) demonstrated a strong effect against Gram-positive and Gram-negative bacteria (MICs ranging from 3 to 7.9 μM), without showing significant hemolytic activity (<0.6% at the MIC range) towards mammalian cells. Atomic force microscopy experiments indicated that the bacteriolytic properties of these peptides might be related to their disruptive action on the cell membrane, characterized by a number of bubble-like formations, preceding every cell lysis. PS-4 and PS-5 showed anti-protozoan activity with IC50 at about 5 μM for Trypanossoma cruzi.
Keywords: Antimicrobial peptides; Phylloseptin; Phyllomedusa oreades; Phyllomedusa hypochondrialis; Atomic force microscopy; Trypanocidal activity;
Isolation of trichogin, an antifungal protein from fresh fruiting bodies of the edible mushroom Tricholoma giganteum by Yongxia Guo; Hexiang Wang; T.B. Ng (575-580).
An antifungal protein was isolated from the mushroom Tricholoma giganteum var. golden blessings. The protocol included ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on CM-cellulose, and gel filtration by fast protein liquid chromatography on Superdex 75. The antifungal protein, designated trichogin, was unadsorbed on DEAE-cellulose but was adsorbed on Affi-gel blue gel and CM-cellulose. It exhibited antifungal activity against Fusarium oxysporum, Mycosphaerella arachidicola and Physalospora piricola. Trichogin inhibited HIV-1 reverse transcriptase with an IC50 of 83 nM.
Keywords: Antifungal protein; Fusarium oxysporum; Reverse transcriptase; Tricholoma giganteum;
Kenojeinin I, antimicrobial peptide isolated from the skin of the fermented skate, Raja kenojei by Soung-Hun Cho; Byung-Doo Lee; Haejung An; Jong-Bang Eun (581-587).
An antimicrobial peptide was purified from fermented skate skin extract using the solid-phase extraction and separation on HPLC reversed-phase chromatography. Amino acid sequence of the purified peptide (Peak A) having an antimicrobial activity revealed the presence of many cationic residues of the total 28 amino acids. Its molecular mass was found to be 3059 Da. This result was in excellent agreement with the theoretical molecular mass calculated from the amino acid sequence. The synthetic kenojeinin I had inhibitory effects on B. subtilis (MIC, 12 μg/ml), E. coli (28 μg/ml), and S. cerevisiae (12 μg/ml). These results indicate that fermented skate skin is potentially antimicrobial.
Keywords: Antimicrobial peptide; Kenojeinin I; Raja kenojei; Skate skin;
Aplysia capsulin is localized to egg capsules and egg cordon sheaths and shares sequence homology with Drosophila dec-1 gene products by Scott F. Cummins; Gregg T. Nagle (589-596).
Differential library screening of an albumen gland cDNA library, Western blot analysis, protein expression, immunolocalization studies, comparative genomics, and secretion assays identified a major Aplysia californica albumen gland protein (‘capsulin’) that is localized to egg capsules and to the sheaths of the egg cordon. Capsulin shared sequence homology with eggshell proteins encoded by the Drosophila dec-1 gene. The 1790-amino acid A. californica precursor contains 17 repeat sequences that are flanked by basic residue processing sites. The numerous proteolytic processing sites may facilitate the breakdown of capsulin prior to when veliger larvae break out of egg capsules as free-swimming larvae. An Aplysia brasiliana capsulin repeat sequence was 97% identical to its A. californica homolog. Capsulin fragments were not detected in the eluates of egg cordons, suggesting that capsulin is not a candidate water-borne pheromone precursor.
Keywords: Aplysia; Capsulin; Egg capsule protein;
Characterization of a peptide from skin secretions of male specimens of the frog, Leptodactylus fallax that stimulates aggression in male frogs by Jay D. King; Louise A. Rollins-Smith; Per F. Nielsen; Anne John; J. Michael Conlon (597-601).
During the breeding season of the mountain chicken frog Leptodactylus fallax, fighting between males results in the emergence of dominant animals that subsequently attract females to nesting sites. A peptide, termed Leptodactylus aggression-stimulating peptide (LASP), was isolated from norepinephrine-stimulated skin secretions from male specimens of L. fallax that was not present in skin secretions obtained from females. The primary structure of the peptide was established as: Gly-Leu-Trp-Asp-Asp-Leu-Lys-Ala-Ala-Ala-Lys-Lys-Val-Val-Ser-Ser-Leu-Ala-Ser-Ala-Ala-Ile-Glu-Lys-Leu NH2. LASP had no pheromone-like action on females but had a chemoattractive effect on males and stimulated aggressive behaviors, such as rearing and leaping. It is suggested that this peptide may play an important role in initiating the competitive male–male interactions that are associated with the onset of reproductive behavior in L. fallax.
Keywords: Frog skin; Peptide purification; Pheromone; Fallaxin; Reproductive behavior;
An opioid peptide from synganglia of the tick, Amblyomma testindinarium by Jian-guo Liang; Jie Zhang; Ren Lai; Huw H. Rees (603-606).
An opioid peptide, which shares similarity with mammalian hemorphins, has been identified from the synganglia (central nervous system) of the hard tick, Amblyomma testindiarium. Its primary sequence was established as LVVYPWTKM that contains a tetrapeptide sequence Tyr-Pro-Trp-Thr of hemorphin-like opioid peptides. By hot-plate bioassay, the purified peptide and synthetic peptide displayed dose-related antinociceptive effect in mice, as observed for other hemorphin-like opioid peptides. This is the first opioid peptide identified from ticks. Ticks may utilize the opioid peptide in their strategy to escape host immuno-surveillance as well as in inhibiting responses directed against themselves.
Keywords: Ticks; Synganglia; Opioid peptides; Defensive reaction;
Cardiovascular effects of endomorphins in alloxan-induced diabetic rats by Jing Liu; Ye Yu; Ying-zhe Fan; Hui Chang; Hong-mei Liu; Yun Cui; Qiang Chen; Rui Wang (607-614).
Endomorphins, the endogenous, potent and selective μ-opioid receptor agonists, have been shown to decrease systemic arterial pressure (SAP) in rats. In the present study, responses to endomorphins were investigated in systemic vascular bed of alloxan-induced diabetic rats and in non-diabetic rats. Diabetes was induced by alloxan (220 mg/kg, i.p.) in male Wistar rats. At 4–5 weeks after the onset of diabetes, intravenous injections of endomorphins (1–30 nmol/kg) led to an increase of SAP and heart rate (HR) consistently and dosed-dependently. SAP increased 7.68 ± 3.73, 11.19 ± 4.55, 21.19 ± 2.94 and 27.48 ± 6.21% from the baseline at the 1, 3, 10 and 30 nmol/kg dose, respectively, of endomorphin 1 (n = 4; p < 0.05), and similar changes were observed in response to endomorphin 2. The hypertension could be antagonized markedly by i.p. 2 mg/kg of naloxone. On the other hand, bilateral vagotomy would attenuate the effects of hypertension and diminished the changes of HR in response to endomorphins. With diabetic rats, 6–10 weeks after the induction of diabetes, intravenous injections of endomorphins produced non-dose-related various changes in SAP, such as a single decrease, or a single increase, or biphasic changes characterized by an initial decrease followed by a secondary increase, or no change at all. These results suggest that diabetes may lead to the dysfunction of the cardiovascular system in response to endomorphins. Furthermore, the diabetic rats of 4–5 weeks after alloxan-treatment, the increase in SAP and HR caused by i.v. endomorphins might be explained by a changed effect of vagus and by a naloxone-sensitive mechanism.
Keywords: Endomorphins; Alloxan-induced diabetic rats; Systemic arterial pressure; Heart rate; Naloxone; Vagal afferent;
Antinociceptive and antipyretic effects of a derivatized tetrapeptide from lactoferrin in rats by K.V.S. Narayana Raju; Dilly Ashok Kumar; N. Arutselvan; P. Thejomoorthy; R. Puvanakrishnan (615-619).
PEP1261, a tetrapeptide derivative used in this study, corresponds to residues 39–42 of human lactoferrin. The parent protein lactoferrin is known to exhibit antinociceptive activity and it regulates many aspects of inflammation. This study is aimed to evaluate the antinociceptive and antipyretic activities of PEP1261 in rats. PEP1261 exhibits a significant dose dependent antinociceptive activity with optimal effect at 40 mg/kg body weight (b.w.) (i.p.) in both tail-flick model and acetic acid induced writhing in rats. PEP1261 at the doses of 20 and 40 mg/kg b.w. (i.p.) is also observed to exhibit notable antipyretic effect in lipopolysaccharide-induced pyrexia in rats. In conclusion, the results suggest that PEP1261 possesses antinociceptive and antipyretic activities better than the control peptide KRDS.
Keywords: Lactoferrin; Tetrapeptide; Antinociceptive; Antipyretic; Rats;
Reciprocal opioid–opioid interactions between the ventral tegmental area and nucleus accumbens regions in mediating μ agonist-induced feeding in rats by Richard J. Bodnar; Nicole Lamonte; Yuriy Israel; Yakov Kandov; Tsippa F. Ackerman; Eleonora Khaimova (621-629).
Feeding elicited by the μ-selective agonist, [d-Ala2, M-Phe4, Gly-ol5]-encephalin administered into the nucleus accumbens is blocked by accumbal pre-treatment with μ, δ1, δ2 and κ, but not μ1 opioid antagonists. Correspondingly, μ-agonist-induced feeding elicited from the ventral tegmental area is blocked by ventral tegmental area pre-treatment with μ and κ, but not δ opioid antagonists. A bi-directional opioid–opioid feeding interaction has been firmly established such that μ-agonist-induced feeding elicited from the ventral tegmental area is blocked by accumbal naltrexone, and that accumbal μ-agonist-induced feeding is blocked by naltrexone pre-treatment in the ventral tegmental area. To determine which opioid receptor subtypes mediate the regional bi-directional opioid–opioid feeding interactions between these two sites, the present study examined the dose-dependent ability of either general (naltrexone), μ (β-funaltrexamine), κ (nor-binaltorphamine) or δ (naltrindole) opioid antagonists administered into one site to block μ-agonist-induced feeding elicited from the other site. General, μ and κ, but not δ opioid receptor antagonist pre-treatment in the ventral tegmental area dose-dependently reduced μ-agonist-induced feeding elicited from the nucleus accumbens. General, μ and δ, and to a lesser degree κ, opioid receptor antagonist pre-treatment in the nucleus accumbens dose-dependently reduced μ-agonist-induced feeding elicited from the ventral tegmental area. Thus, multiple, but different opioid receptor subtypes are involved in mediating opioid–opioid feeding interactions between the nucleus accumbens and ventral tegmental area regions.
Keywords: [d-Ala2, M-Phe4, Gly-ol5]-encephalin; Naltrexone; β-funaltrexamine; Nor-binaltorphamine; Naltrindole;
High Fos expression during the active phase in orexin neurons of a diurnal rodent, Tamias sibiricus barberi by Tohru Kodama; Setsuo Usui; Yoshiko Honda; Mayumi Kimura (631-638).
To investigate whether a diurnal animal possesses the orexinergic system implicating vigilance and behavior, we examined Fos immunoreactivity (IR) in orexinergic neurons of Korean chipmunks raised under 12 h light–dark cycles. Brain tissue, collected at four different zeitgeber times (ZT), was double-labeled with Fos and orexin-A antibodies. There was no difference in the number of orexin-IR neurons in the hypothalamus across all ZTs. However, more orexin-IR neurons expressing Fos-IR were found at ZTs 3 and 9 than ZTs 15 and 21. The results demonstrate circadian variations in the activation of orexin neurons corresponding with locomotor cycles, similarly seen in nocturnal rodents.
Keywords: cFos reactivity; Diurnal rodent; Tamias sibiricus barberi; Circadian; Orexin; Hypocretin;
CRF receptor type 1 mediates continual hypoxia-induced CRF peptide and CRF mRNA expression increase in hypothalamic PVN of rats by Jian-Fen Xu; Xue-Qun Chen; Ji-Zeng Du; Tong-Ying Wang (639-646).
We demonstrated previously that hypoxia activated CRF and CRF mRNA in PVN, and CRF receptor 1 (CRFR1) mRNA in rat pituitary. The aim of the study is to test whether the hypoxia-activated CRF and CRF mRNA is associated with triggering CRFR1. Rats were exposed to hypobaric hypoxia at altitude of 2 and 5 km. CRF and CRF mRNA were assayed by immunostaining and in situ hybridization. CRFR1 mRNA was assayed by RT-PCR. Results showed that 5 km continual hypoxia increased CRF and CRF mRNA in PVN, CRFR1 mRNA in pituitary, and plasma corticosterone. The hypoxia-increased CRF, CRF mRNA, CRFR1 mRNA, and corticosterone were blocked by CRFR1 antagonist (CP-154,526), suggesting that CRFR1 in PVN and pituitary are responsible for the hypoxia-increased CRF and CRF mRNA in PVN.
Keywords: Corticotropin-releasing factor (CRF); CRF mRNA; CRFR1; CRFR1 mRNA; Hypoxia; Stress;
A comparison of leptin and ghrelin levels in plasma and saliva of young healthy subjects by Suleyman Aydin; İhsan Halifeoglu; İbrahim H. Ozercan; Fazilet Erman; Nermin Kilic; Suna Aydin; Nevin İlhan; Necip İlhan; Yusuf Ozkan; Nusret Akpolat; Levent Sert; Emrah Caylak (647-652).
In the last 10 years, saliva has been increasingly used as a diagnostic fluid and in predictions of disease progression. Leptin and ghrelin are synthesized in several tissues including the salivary glands. The action of ghrelin is antagonistic to that of leptin. This study was undertaken to measure and compare the saliva ghrelin–leptin and plasma ghrelin–leptin levels in healthy young subjects. In 30 healthy subjects, after an overnight fast, saliva and plasma leptin levels were measured using the ELISA method while saliva and plasma immunoreactive ghrelin levels were measured using a commercial radioimmunoassay (RIA). The latter uses 125I-labeled bioactive ghrelin as a tracer and a rabbit polyclonal antibody raised against full-length octanoylated human ghrelin (Phoenix, Europe, Karlsruhe, Germany). The results of this investigation revealed that saliva leptin levels (6.19 ± 2.10 μg/l) were lower than plasma levels (7.39 ± 3.23 μg/l) while saliva ghrelin levels (188.5 ± 84.7 pg/ml) were higher than plasma levels (126.4 ± 38.5 pg/ml), when male and female subjects were considered together. Saliva leptin levels (5.93 ± 1.94 μg/l) were lower than plasma levels (6.22 ± 2.92 pg/ml) while saliva ghrelin levels (190.3 ± 80.2 pg/ml) were higher than plasma levels (120.4 ± 35.7 pg/ml) in young males. Saliva leptin levels (6.47 ± 2.29 μg/l) were lower than plasma levels (8.73 ± 3.14 μg/l) while saliva ghrelin levels (183.2 ± 90.2 pg/ml) were higher than plasma levels (129.3 ± 42.8 pg/ml) in young females, and both saliva and plasma leptin levels were slightly lower in male subjects in comparison with female subjects. Also, Immunohistochemistry study indicated that ghrelin positivity was found in ductus epithelium of salivary gland. We have demonstrated for the first time that saliva ghrelin levels were higher than in plasma while saliva leptin levels were almost the same as in plasma. Measurements of ghrelin and leptin in saliva is non-invasive, simple, and generally much preferred by patients and thus may be an acceptable alternative to plasma sampling.
Keywords: Ghrelin; Leptin; Saliva; Plasma; Immunohistochemistry;
Central vagal stimulation activates enteric cholinergic neurons in the stomach and VIP neurons in the duodenum in conscious rats by Pu-Qing Yuan; Hiroshi Kimura; Mulugeta Million; Jean-Pierre Bellier; Lixin Wang; Gordon V. Ohning; Yvette Taché (653-664).
The influence of central vagal stimulation induced by 2 h cold exposure or intracisternal injection of thyrotropin-releasing hormone (TRH) analog, RX-77368, on gastro-duodenal enteric cholinergic neuronal activity was assessed in conscious rats with Fos and peripheral choline acetyltransferase (pChAT) immunoreactivity (IR). pChAT-IR was detected in 68%, 70% and 73% of corpus, antrum and duodenum submucosal neurons, respectively, and in 65% of gastric and 46% of duodenal myenteric neurons. Cold and RX-77368 induced Fos-IR in over 90% of gastric submucosal and myenteric neurons, while in duodenum only 25–27% of submucosal and 50–51% myenteric duodenal neurons were Fos positive. In the stomach, cold induced Fos-IR in 93% of submucosal and 97% of myenteric pChAT-IR neurons, while in the duodenum only 7% submucosal and 5% myenteric pChAT-IR neurons were Fos positive. In the duodenum, cold induced Fos in 91% of submucosal and 99% of myenteric VIP-IR neurons. RX-77368 induces similar percentages of Fos/pChAT-IR and Fos/VIP-IR neurons. These results indicate that increased central vagal outflow activates cholinergic neurons in the stomach while in the duodenum, VIP neurons are preferentially stimulated.
Keywords: Peripheral choline acetyltransferase; Vagus; Enteric nervous system; Cold; Duodenum; Vasoactive intestinal peptide;
Neurotoxicity and oxidative stress in D1M-substituted Alzheimer's Aβ(1-42): relevance to N-terminal methionine chemistry in small model peptides by Debra Boyd-Kimball; Rukhsana Sultana; Hafiz Mohmmad-Abdul; D. Allan Butterfield (665-673).
Small model peptides containing N-terminal methionine are reported to form sulfur-centered-free radicals that are stabilized by the terminal N atom. To test whether a similar chemistry would apply to a disease-relevant longer peptide, Alzheimer's disease (AD)-associated amyloid beta-peptide 1-42 was employed. Methionine at residue 35 of this 42-mer has been shown to be a key amino acid residue involved in amyloid beta-peptide 1-42 [Aβ1-42]-mediated toxicity and therefore, the pathogenesis of AD. Previous studies have shown that mutation of the methionine residue to norleucine abrogates the oxidative stress and neurotoxic properties of Aβ(1-42). In the current study, we examined if the position of methionine at residue 35 is a criterion for toxicity. In doing so, we tested the effects of moving methionine to the N-terminus of the peptide in a synthetic peptide, Aβ(1-42)D1M, in which methionine was substituted for aspartic acid at the N-terminus of the peptide and all subsequent residues from D1 to L34 were shifted one position towards the carboxy-terminus. Aβ(1-42)D1M exhibited oxidative stress and neurotoxicity properties similar to those of the native peptide, Aβ(1-42), all of which are inhibited by the free radical scavenger Vitamin E, suggesting that reactive oxygen species may play a role in the Aβ-mediated toxicity. Additionally, substitution of methionine at the N-terminus by norleucine, Aβ(1-42)D1Nle, completely abrograted the oxidative stress and neurotoxicity associated with the Aβ(1-42)D1M peptide. The results of this study validate the chemistry reported for short peptides with N-terminal methionines in a disease-relevant peptide.
Keywords: Amyloid beta-peptide; Methionine; Free radicals; Neurotoxicity;
Characterization of a naturally-occurring polymorphism in the UHR-1 gene encoding the putative rat prolactin-releasing peptide receptor by Kate L.J. Ellacott; Emma L. Donald; Paul Clarkson; John Morten; Dave Masters; John Brennand; Simon M. Luckman (675-681).
The rat orphan receptor UHR-1 and its human orthologue, GPR10, were first isolated in 1995. The ligand for this receptor, prolactin-releasing peptide (PrRP), was identified in 1998 by reverse pharmacology and has subsequently been implicated in a number of physiological processes. As supported by its localization and regulation in the hypothalamus and brainstem, we have shown previously that PrRP is involved in energy homeostasis. Here we describe a naturally occurring polymorphism in the UHR-1 gene that results in an ATG to ATA change at the putative translational initiation site. The presence of the polymorphism abolished the binding of 125I PrRP in rat brain slices but did not affect the ability of PrRP to reduce fast-induced food intake. Together this data suggest that PrRP may be exerting its feeding effects through a receptor other than UHR-1.
Keywords: UHR-1; PrRP; Food intake; Receptor autoradiography; Genetic variation;
Characterization of functional urotensin II receptors in human skeletal muscle myoblasts: comparison with angiotensin II receptors by Jian-shen Qi; Lisa K. Minor; Charles Smith; Bing Hu; Jing Yang; Patricia Andrade-Gordon; Bruce Damiano (683-690).
The properties of urotensin II (U-II) receptor (UT receptor) and angiotensin II (ANG II) receptor (AT receptor) in primary human skeletal myoblasts (HSMM) and differentiated skeletal myotubes (HSMMT) were characterized. Radiolabeled U-II and ANG II bound specifically to HSMM with K d's of 0.31 nM (2311 receptors/cell) and 0.61 nM (18,257 receptors/cell), respectively. The cyclic segment of U-II peptide, CFWKYC, was the minimal sequence required for binding, with the WKY residues essential. Inhibitor studies suggested AT1 is the predominant ANG II receptor. After radioligand binding, under conditions designed to minimize receptor internalization, half the bound U-II was resistant to acid washing suggesting that U-II binds tightly to its receptor in a qusai-irreversible fashion. The AT1 receptor-bound radioligand was completely removed under the same conditions. RT-PCR detected the expression of mRNAs for UT and AT1 receptors. Western blotting showed that U-II and ANG II signaled via ERK1/2 kinase. UT receptor was not lost upon differentiation into myotubes since both mRNA for UT receptor and U-II binding were still present. ANG II receptors were also present as shown by ANG II-induced calcium mobilization.
Keywords: Urotensin II receptor; Urotensin II; Urotensin II-related peptide; Human skeletal muscle myoblasts; Qusai-irreversible binding; Angiotensin II receptor; Human skeletal muscle myotubes;
Distribution of atrial natriuretic peptide and its effects on contraction and intracellular calcium in ventricular myocytes from streptozotocin-induced diabetic rat by F.C. Howarth; A. Adem; E.A. Adeghate; N.A. Al Ali; A.M. Al Bastaki; F.R. Sorour; R.O. Hammoudi; N.A. Ghaleb; N.J. Chandler; H. Dobrzynski (691-700).
The distribution of atrial natriuretic peptide (ANP) in blood plasma and cardiac muscle and its effects on ventricular myocyte contraction and intracellular free calcium concentration [Ca2+]i in the streptozotocin (STZ)-induced diabetic rat have been investigated. Blood plasma concentration and heart atrial and ventricular contents of ANP were significantly increased in STZ-treated rats compared to age-matched controls. STZ treatment increased the number of ventricular myocytes immunolabeled with antibodies against ANP. In control myocytes the percentage of cells that labeled positively and negatively were 17% versus 83%, respectively. However, in myocytes from STZ-treated rat the percentages were 52% versus 53%. Time to peak (TPK) shortening was significantly and characteristically prolonged in myocytes from STZ-treated rats (360 ± 5 ms) compared to controls (305 ± 5 ms). Amplitude of the Ca2+ transient was significantly increased in myocytes from STZ-treated rats compared to controls (0.39 ± 0.02 versus 0.29 ± 0.02 fura-2 RU in controls) and treatment with ANP reduced the amplitude of the Ca2+ transient to control levels. ANP may have a protective role in STZ-induced diabetic rat heart.
Keywords: Atrial natriuretic peptide; Diabetes; Ventricular myocytes; Calcium;
Deficit in beta-endorphin peptide and tendency to alcohol abuse by Jadwiga Zalewska-Kaszubska; Elżbieta Czarnecka (701-705).
Human and animal studies suggest that there is a correlation between endogenous opioid peptides, especially beta-endorphin, and alcohol abuse. It has been proven that the consumption of alcohol activates the endogenous opioid system. Consumption of alcohol results in an increase in beta-endorphin level in those regions of the human brain, which are associated with a reward system. However, it has also been observed that habitual alcohol consumption leads to a beta-endorphin deficiency. It is a well-documented phenomenon that people with a genetic deficit of beta-endorphin peptide are particularly susceptible to alcoholism. The plasma level of beta-endorphin in subjects genetically at high risk of excessive alcohol consumption shows lower basal activity of this peptide. Its release increases significantly after alcohol consumption. Clinical and laboratory studies confirm that certain genetically determined factors might increase the individual's vulnerability to alcohol abuse.
Keywords: Alcohol abuse; Beta-endorphin; Genetic factors;