The study objective was to evaluate the interaction between corticotrophin releasing factor () receptor signaling and prophylactic antibiotic administration on intestinal physiology in newly weaned and transported pigs. Pigs (n = 56; 5.70 ± 1.
View Article and Find Full Text PDFThe corticotropin-releasing factor (CRF) family of peptides includes CRF and three urocortins, which signal through two distinct G-protein coupled receptors, CRF and CRF . Although the cellular distribution of CRF receptor expression has been well characterized at the mRNA level, the localization of receptor protein, and, by inference, of functional receptors, has been limited by a lack of reliable immunohistochemical evidence. Recently, a CRF-related peptide, termed PD-sauvagine, was isolated from the skin of the frog, Pachymedusa dacnicolor, and validated as a high-affinity ligand for CRF receptor studies.
View Article and Find Full Text PDFIt is noteworthy that thirty three years of efforts in corticotropin releasing factor (CRF) research by academia and the pharmaceutical industry resulted in several thousand papers and patents, yet little progress has been made to identify and market diagnostic or therapeutic CRF peptides and small molecule ligands. We document the potential relevance of CRF peptide antagonists to reinvigorate stress/anxiety affected "anatomy systems" in order to boost their efficacy.
View Article and Find Full Text PDFInsulins in the venom of certain fish-hunting cone snails facilitate prey capture by rapidly inducing hypoglycemic shock. One such insulin, Conus geographus G1 (Con-Ins G1), is the smallest known insulin found in nature and lacks the C-terminal segment of the B chain that, in human insulin, mediates engagement of the insulin receptor and assembly of the hormone's hexameric storage form. Removal of this segment (residues B23-B30) in human insulin results in substantial loss of receptor affinity.
View Article and Find Full Text PDFCone snail toxins are well known blockers of voltage-gated sodium channels, a property that is of broad interest in biology and therapeutically in treating neuropathic pain and neurological disorders. Although most conotoxin channel blockers function by direct binding to a channel and disrupting its normal ion movement, conotoxin μO§-GVIIJ channel blocking is unique, using both favorable binding interactions with the channel and a direct tether via an intermolecular disulfide bond. Disulfide exchange is possible because conotoxin μO§-GVIIJ contains anS-cysteinylated Cys-24 residue that is capable of exchanging with a free cysteine thiol on the channel surface.
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFWe investigated the identities of the isoforms of the α (NaV1)- and β (NaVβ)-subunits of voltage-gated sodium channels, including those responsible for action potentials in rodent sciatic nerves. To examine α-subunits, we used seven μ-conotoxins, which target site 1 of the channel. With the use of exogenously expressed channels, we show that two of the μ-conotoxins, μ-BuIIIB and μ-SxIIIA, are 50-fold more potent in blocking NaV1.
View Article and Find Full Text PDFUnlabelled: Preclinical and clinical studies have indicated that somatostatin receptor (sst)-expressing tumors demonstrate higher uptake of radiolabeled sst antagonists than of sst agonists. In 4 consecutive patients with advanced neuroendocrine tumors, we evaluated whether treatment with (177)Lu-labeled sst antagonists is feasible.
Methods: After injection of approximately 1 GBq of (177)Lu-DOTA-[Cpa-c(DCys-Aph(Hor)-DAph(Cbm)-Lys-Thr-Cys)-DTyr-NH2] ((177)Lu-DOTA-JR11) and (177)Lu-DOTATATE, 3-dimensional voxel dosimetry analysis based on SPECT/CT was performed.
Corticotropin-Releasing Factor Receptors (CRFRs) are class B1 G-protein-coupled receptors, which bind peptides of the corticotropin releasing factor family and are key mediators in the stress response. In order to dissect the receptors' binding specificity and enable structural studies, full-length human CRFR1α and mouse CRFR2β as well as fragments lacking the N-terminal extracellular domain, were overproduced in E. coli.
View Article and Find Full Text PDFElusive for more than half a century, corticotropin-releasing factor (CRF) was finally isolated and characterized in 1981 from ovine hypothalami and shortly thereafter, from rat brains. Thirty years later, much has been learned about the function and localization of CRF and related family members (Urocortins 1, 2 and 3) and their 2 receptors, CRF receptor type 1 (CRFR1) and CRF receptor type 2 (CRFR2). Here, we report the stepwise development of peptide CRF agonists and antagonists, which led to the CRFR1 agonist Stressin1; the long-acting antagonists Astressin2-B which is specific for CRFR2; and Astressin B, which binds to both CRFR1 and CRFR2.
View Article and Find Full Text PDFThe role of brain corticotropin-releasing factor type 2 (CRF2) receptors in behavioral stress responses remains controversial. Conflicting findings suggest pro-stress, anti-stress or no effects of impeding CRF2 signaling. Previous studies have used antisauvagine-30 as a selective CRF2 antagonist.
View Article and Find Full Text PDFAmong the μ-conotoxins that block vertebrate voltage-gated sodium channels (VGSCs), some have been shown to be potent analgesics following systemic administration in mice. We have determined the solution structure of a new representative of this family, μ-BuIIIB, and established its disulfide connectivities by direct mass spectrometric collision induced dissociation fragmentation of the peptide with disulfides intact. The major oxidative folding product adopts a 1-4/2-5/3-6 pattern with the following disulfide bridges: Cys5-Cys17, Cys6-Cys23, and Cys13-Cys24.
View Article and Find Full Text PDFMouse (m) and human (h) urocortin 2 (Ucn 2) were identified by molecular cloning strategies and the primary sequence of their mature forms postulated by analogy to closely related members of the corticotropin-releasing factor (CRF) neuropeptide family. Because of the paucity of Ucn 2 proteins in native tissues, skin, muscle, and pancreatic cell lines were transduced with lentiviral constructs and secretion media were used to isolate and characterize Ucn 2 products and study processing. Primary structures were assigned using a combination of Edman degradation sequencing and mass spectrometry.
View Article and Find Full Text PDFBackground And Purpose: Adult rat dorsal root ganglion (DRG) neurons normally express transcripts for five isoforms of the α-subunit of voltage-gated sodium channels: NaV 1.1, 1.6, 1.
View Article and Find Full Text PDFBackground And Purpose: Voltage-gated sodium channels (VGSCs) are assembled from two classes of subunits, a pore-bearing α-subunit (NaV 1) and one or two accessory β-subunits (NaV βs). Neurons in mammals can express one or more of seven isoforms of NaV 1 and one or more of four isoforms of NaV β. The peptide μ-conotoxins, like the guanidinium alkaloids tetrodotoxin (TTX) and saxitoxin (STX), inhibit VGSCs by blocking the pore in NaV 1.
View Article and Find Full Text PDFChelated somatostatin agonists have been shown to be sensitive to N-terminal radiometal modifications, with Ga-DOTA agonists having significantly higher binding affinity than their Lu-, In-, and Y-DOTA correlates. Recently, somatostatin antagonists have been successfully developed as alternative tracers to agonists. The aim of this study was to evaluate whether chelated somatostatin antagonists are also sensitive to radiometal modifications and how.
View Article and Find Full Text PDFDifferent types of neurons diverge in function because they express their own unique set or constellation of signaling molecules, including receptors and ion channels that work in concert. We describe an approach to identify functionally divergent neurons within a large, heterogeneous neuronal population while simultaneously investigating specific isoforms of signaling molecules expressed in each. In this study we characterized two subclasses of menthol-sensitive neurons from cultures of dissociated mouse dorsal-root ganglia.
View Article and Find Full Text PDFBackground And Aims: Psychological stress is a predisposing factor in the onset and exacerbation of important gastrointestinal diseases including irritable bowel syndrome (IBS) and the inflammatory bowel diseases (IBD). The pathophysiology of stress-induced intestinal disturbances is known to be mediated by corticotropin releasing factor (CRF) but the precise signaling pathways remain poorly understood. Utilizing a porcine ex vivo intestinal model, the aim of this study was to investigate the mechanisms by which CRF mediates intestinal epithelial barrier disturbances.
View Article and Find Full Text PDFBackground: Several peptide hormone receptors were identified that are specifically over-expressed on the cell surface of certain human tumors. For example, high incidence and density of the Y1 subtype of neuropeptide Y (NPY) receptors are found in breast tumors. Recently, we demonstrated that the use of potent radiolabeled somatostatin or bombesin receptor antagonists considerably improved the sensitivity of in vivo imaging when compared to agonists.
View Article and Find Full Text PDFμ-Conotoxin KIIIA (μ-KIIIA) blocks mammalian voltage-gated sodium channels (VGSCs) and is a potent analgesic following systemic administration in mice. Previous structure-activity studies of μ-KIIIA identified a helical pharmacophore for VGSC blockade. This suggested a route for designing truncated analogues of μ-KIIIA by incorporating the key residues into an α-helical scaffold.
View Article and Find Full Text PDFUnlabelled: Preclinical studies have indicated that somatostatin receptor (sst)-expressing tumors demonstrate higher uptake of radiolabeled sst antagonists than of sst agonists. In this study, we evaluated whether imaging with sst antagonists was feasible in patients.
Methods: Biodistribution and tumor uptake of the sst antagonist (111)In-DOTA-pNO(2)-Phe-c(DCys-Tyr-DTrp-Lys-Thr-Cys)DTyrNH(2) ((111)In-DOTA-BASS) were studied in 5 patients with metastatic thyroid carcinoma or neuroendocrine tumors.
Despite 3 decades of focused chemical, biological, structural, and clinical developments, unusual properties of somatostatin (SRIF, 1) analogues are still being uncovered. Here we report the unexpected functional properties of 1 and the octapeptide cyclo(3-14)H-Cys-Phe-Phe-Trp(8)-Lys-Thr-Phe-Cys-OH (somatostatin numbering; OLT-8, 9) substituted by imBzl-l- or -d-His at position 8. These analogues were tested for their binding affinity to the five human somatostatin receptors (sst(1-5)), as well as for their functional properties (or functionalities) in an sst(3) internalization assay and in an sst(3) luciferase reporter gene assay.
View Article and Find Full Text PDFThe corticotropin-releasing factor (CRF) peptide hormone family members coordinate endocrine, behavioral, autonomic, and metabolic responses to stress and play important roles within the cardiovascular, gastrointestinal, and central nervous systems, among others. The actions of the peptides are mediated by activation of two G-protein-coupled receptors of the B1 family, CRF receptors 1 and 2 (CRF-R1 and CRF-R2α,β). The recently reported three-dimensional structures of the first extracellular domain (ECD1) of both CRF-R1 and CRF-R2β (Pioszak, A.
View Article and Find Full Text PDFEur J Nucl Med Mol Imaging
August 2010
Purpose: Peptide receptor targeting has become an increasingly attractive method to target tumors diagnostically and radiotherapeutically. Peptides linked to a variety of chelators have been developed for this purpose. They have, however, rarely been tested for their agonistic or antagonistic properties.
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