Distribution and regulation of natriuretic factor-R1C receptor subtypes in mammalian cell lines

The differential distribution of natriuretic peptide receptor subtypes and their distinct properties were assessed in mammalian cellular models which were screened for their ability to produce cGMP upon stimulation by different natriuretic peptides. The ANF-R_1A receptor subtype was distinguished by its selective activation by atrial natriuretic factor (ANF) while the ANF-R_1C was characterized by preferential stimulation by C-type natriuretic peptide (CNP). AT-t20 pituitary cells, bovine adrenal chromaffin cells, and NIH-3T3 fibroblasts mainly express the ANF-R_1C receptor subtype. Other cell lines such as PC12, RASM and GH3 express significant but varying amounts of both ANF-R_1A and ANF-R_1C subtypes. A10 and NIH cells which express high density of ANF-R₂ receptor subtype, also demonstrate a higher sensitivity to CNP over ANF suggesting that they express significant amounts of ANF-R_1C. Studies of the regulation by ATP of guanylyl cyclase activity indicate that both ANF-R_1A and ANF-R_1C subtypes are modulated in the same manner. In the presence of Mn²⁺, ATP inhibits the CNP-stimulated guanylyl cyclase activity while in the presence of Mg²⁺ adenine nucleotides potentiate the stimulation by CNP. In addition, we show that like the ANF-R_1A, the ANF-R_1C guanylyl cyclase activity can be regulated by phosphorylation since preincubation with TPA or FKL attenuates the subsequent stimulation by CNP in cultured cells. The results presented demonstrate that specific cell types express distinct natriuretic peptide receptor subtypes and also that the newly characterized ANF-R_1C subtype is regulated by ATP and serine/threonine kinases in the same way as the ANF-R_1A subtype.Abbreviation ANF atrial natriuretic factor - BNP brain natriuretic peptide - CNP C-type natriuretic peptide - ATP adenosine-5-triphosphate - IBMX 3-isobutyl-1-methylxanthine - TPA 12-O-tetradecanoyl-phorbol-13-acetate - FKL forskolin - PKC calcium-phospholipid-dependent protein kinase - PKA cAMP-dependent protein kinase - PKG cGMP-dependent protein kinase - C-ANF [Cys¹¹⁶]-ANF-(102-116)-NH₂ - CC chromaffin cells     

Localization of neuropeptide Y and atrial natriuretic peptide in the endothelial cells of human umibilical blood vessels

The localization of neuropeptide Y (NPY) and atrial natriuretic peptide (ANP) in the endothelial cells of human umbilical blood vessels was studied using the pre-embedding peroxidase-antiperoxidase (PAP) technique for electron microscopy and avidin-biotin-complex (ABC) immunostaining for endothelial cells cultured from umbilical vein. Subpopulations of NPY- and ANP-immunoreactive endothelial cells were present in term umbilical vein and artery. The umbilical vein contained more positive cells than the artery. The percentage of NPY- and ANP-immunoreactive umbilical vein cells in culture was 32% and 44%, respectively, out of a total of 3013 cells examined. The possibility that these potent vasoactive substances located in the endothelial cells of the non-innervated umbilical vessels are involved in the local regulation of blood flow is discussed.     

Localization of corazonin in the nervous system of the cockroach Periplaneta americana

Antisera raised to the cardioactive peptide corazonin were used to localize immunoreactive cells in the nervous system of the American cockroach. Sera obtained after the seventh booster injection were sufficiently specific to be used for immunocytology. They recognized a subset of 10 lateral neurosecretory cells in the protocerebrum that project to, and arborize and terminate in the ipsilateral corpus cardiacum. They also reacted with bilateral neurons in each of the thoracic and abdominal neuromeres, a single dorsal unpaired median neuron in the suboesophageal ganglion, an interneuron in each optic lobe, and other neurons at the base of the optic lobe, in the tritocerebrum and deutocerebrum. The presence of corazonin in the abdominal neurons and the lateral neurosecretory cells was confirmed by HPLC fractionation of extracts of the abdominal ganglia, brains and retrocerebral complexes, followed by determination of corazonin by ELISA, which revealed in each tissue a single immunoreactive peak co-eluting with corazonin in two different HPLC systems. Antisera obtained after the first three booster injections recognized a large number of neuroendocrine cells and neurons in the brain and the abdominal nerve cord. However, the sera from the two rabbits reacted largely with different cells, indicating that the majority of this immunoreactivity was due to cross-reactivity. These results indicate that the production of highly specific antisera to some neuropeptides may require a considerable number of booster injections.     

Synthetic glycosylation of peptides using unprotected saccharide β-glycosylamines

Glycopeptides can be valuable tools in determining the influence of carbohydrate moieties on the intrinsic properties of glycoproteins. However, glycopeptides of sufficient quantity and purity are as yet not readily available from biological sources. The chemical coupling of a -glycosylamino group of an unprotected carbohydrate with an activated aspartic acid residue of an unprotected peptide is a simple method for synthesizing asparagine-linked glycopeptides. In this report we demonstrate that the use of this method is not restricted to -glycosylamines of simple monosaccharides or short aspartic acid-containing pentapeptides. This is illustrated by the syntheses of several glycopentapeptides containingN,N-diacetylchitobiose, a glutamine-linked glycopentapeptide containing a biantennary complex oligosaccharide, and glycosylated variants of two analogs of a polypeptide hormone, atriopeptin, containingN,N-diacetylchitobiose.Abbreviations Ac acetyl - Bzl benzyl - DMF dimethylformamide - Fmoc 9-fluorenylmethoxycarbonyl - Fuc fucose - Gal galactose - GlcNAc N-acetylglucosamine - HBTU O-benzotriazol-1-yl-N,N,N,N-tetramethyluroniumhexa-fluorophosphate - HOBt 1-hydroxybenzotriazole - Man mannose - m/z mass/charge - NMR nuclear magnetic resonance - Xyl xylose - Z benzyloxycarbonyl; unless otherwise specified, amino acids are abbreviated using their one-letter codes.     

乙型肝炎病毒表面抗原preS1在大肠杆菌中的表达与鉴定

本文报告利用pWR590质粒为载体,构建了含1ac启动子、β-半乳糖苷酶(1—590)基因、Xa因子的四肽识别位点和HBV preS1、preS2编码序列的表达质粒,并成功地在大肠杆菌中获得稳定表达。融合蛋白经Xa因子消化和高效液相层析,得到了preS1(1—91)纯肽。此肽特异性地与人肝细胞质膜结合,从而为肝细胞上存在preS1受体提供了直接的实验依据,也为分离和鉴定肝细胞上preS1受体打下了良好的基础。     

EFFECTS OF VASOACTIVE INTESTINAL PEPTIDE ON ACTIVITIES OF SUCCINIC DEHYDROGENASE AND ALKALINE PHOSPHATASE IN RAT HEPATOMA CELLS

Using cytochemical method,microspectrophotometry and image analysis,effects of va-soactive intestinal peptide(VIP)on activities of succinic dehydrogenase(SDH)and alkalinephosphatase(ALP)in rat hepatoma cells were studied in vitro.The results showed that thehepatoma cell expressed potent positive reactions of SDH and ALP,the positive positionswere located at the cell membranes and/or cytoplasm.Having been treated with VIP,ALPdecreased obviously in activity(P<0. 01,compared with hepatoma cells untreated by VIP).The sites of ALP activty were chiefly located at the cell membranes,particularly at the cell-cell contacts.Cultured rat hepatoma cells had intensive SDH activity in their cytoplasm.Compared with untreated eclls,there was no marked difference in the intensity of SDH activ-ity in VIP-treated hepatoma cells(P>0.05).     

Synthesis and characterization of two potential impurities (des-ethyl-Ganirelix) generated in the Ganirelix manufacturing process

Controlling certain diseases using peptide drugs has remarkably increased in the past two decades. In this regard, a generic formulation is an upfront solution to fulfill market demands. Ganirelix, a leading peptide active pharmaceutical ingredient (API) primarily used as a gonadotropin-releasing hormone antagonist (GnRH), has established a potential market value worldwide. But its generic formulation mandates detailed impurity profiles from a synthetic source and contemplates the sameness of a reference-listed drug (RLD). Post-chemical synthesis and processing of Ganirelix, some commercial sources have revealed two new potential impurities among many known, which show the deletion of an ethyl group from the hArg(Et)₂ residue at the sixth and eighth positions, named des-ethyl-Ganirelix. These impurities are unprecedented in traditional peptide chemistry, and such monoethylated-hArg building blocks are not easily accessible commercially to synthesize these two impurities. Here, we have outlined the synthesis, purification, and enantiomeric purity characterization of the amino acids and their incorporation in the Ganirelix peptide sequence to synthesize these potential peptide impurities. This methodology will enable the convenient synthesis of side-chain substituted Arg and hArg derivatives in peptide drug discovery platforms.     

Conjugates of adenosine mimetics and arginine-rich peptides serve as inhibitors and fluorescent probes but not as long-lifetime photoluminescent probes for protein arginine methyltransferases

The conjugates of an adenosine mimetic and oligo-l -arginine or oligo-d -arginine (ARCs) were initially designed in our research group as inhibitors and photoluminescent probes targeting basophilic protein kinases. Here, we explored a panel of ARCs and their fluorescent derivatives in biochemical assays with members of the protein arginine methyltransferase (PRMT) family, focusing specifically on PRMT1. In the binding/displacement assay with detection of fluorescence anisotropy, we found that ARCs and arginine-rich peptides could serve as high-affinity ligands for PRMT1, whereas the equilibrium dissociation constant values depended dramatically on the number of arginine residues within the compounds. The fluorescently labeled probe ARC-1081 was displaced from its complex with PRMT1 by both S-adenosyl-l -methionine (SAM) and S-adenosyl-l -homocysteine (SAH), indicating binding of the adenosine mimetic of ARCs to the SAM/SAH-binding site within PRMT1. The ARCs that had previously shown microsecond-lifetime photoluminescence in complex with protein kinases did not feature such property in complex with PRMT1, demonstrating the selectivity of the time-resolved readout format. When tested against a panel of PRMT family members in single-dose inhibition experiments, a micromolar concentration of ARC-902 was required for the inhibition of PRMT1 and PRMT7. Overall, our results suggest that the compounds containing multiple arginine residues (including the well-known cell-penetrating peptides) are likely to inhibit PRMT and thus interfere with the epigenetic modification status in complex biological systems, which should be taken into consideration during interpretation of the experimental data.     

New method for peptide purification based on selective removal of truncation peptide impurities after SPPS with orthogonal capping

Peptide purification by high-performance liquid chromatography (HPLC) is associated with high solvent consumption, relatively large effort and lack of efficient parallelization. As an alternative, many catch-and-release (c&r) purification methods have been developed over the last decades to enable the efficient parallel purification of peptides originating from solid-phase peptide synthesis (SPPS). However, with one exception, none of the c&r systems has been widely established in industry and academia until today. Herein, we present an entirely new chromatography-free purification concept for peptides synthesized on a solid support, termed reactive capping purification (RCP). The RCP method relies on the capping of truncation peptides arising from incomplete coupling of amino acids during SPPS with a reactive tag. The reactive tag contains a masked functionality that, upon liberation during cleavage from the resin, enables straightforward purification of the peptide by incubation with a resin-bound reactive moiety. In this work, two different reactive tags based on masked thiols were developed. Capping with these reactive tags during SPPS led to effective modification of truncated sequences and subsequent removal of the latter by chemoselective reaction with a maleimide-functionalized solid support. By introducing a suitable protecting group strategy, the thiol-based RCP method described here could also be successfully applied to a thiol-containing peptide. Finally, the purification of a 15-meric peptide by the RCP method was demonstrated. The developed method has low solvent consumption, has the potential for efficient parallelization, uses readily available reagents, and is experimentally simple to perform.     

Successful synthesis of a glial-specific blood–brain barrier shuttle peptide following a fragment condensation approach on a solid-phase resin

Successful manual synthesis of the TD2.2 peptide acting as a blood–brain barrier shuttle was achieved. TD2.2 was successfully synthesised by sequential condensation of four protected peptide fragments on solid-phase settings, after several unsuccessful attempts using the stepwise approach. These fragments were chosen to minimise the number of demanding amino acids (in terms of coupling, Fmoc removal) in each fragment that are expected to hamper the overall synthetic process. Thus, the hydrophobic amino acids as well as Arg(Pbf) were strategically spread over multiple fragments rather than having them congested in one fragment. This study shows how a peptide that shows big challenges in the synthesis using the common stepwise elongation methodology can be synthesised with an acceptable purity. It also emphasises that choosing the right fragment with certain amino acid constituents is key for a successful synthesis. It is worth highlighting that lower amounts of reagents were required to synthesise the final peptide with an identical purity to that obtained by the automatic synthesiser.