Interaction of secretin5–27 and its analogues with hormone receptors on pancreatic acini

Gardner, Jerry D.; Rottman, Alvin J.; Natarajan, Sesha; Bodanszky, Miklos

doi:10.1016/0304-4165(79)90066-7

Cited by 57 publications

(37 citation statements)

References 13 publications

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“…At low concentrations (1 nM), the analogue was =50% as active as secretin, and at higher concentrations it was a full agonist. This finding would be consistent with previous reports that the configuration of the NH2-terminal portion of secretin, preserved in the analogues used in the present investigation, is important for stimulation of cAMP formation (21,22 (Table 2). However, VIP does not stimulate InsP3 production at concentrations of 1 MM (Fig.…”

Section: Resultssupporting

confidence: 83%

“…The first was to determine whether the two signal pathways stimulated by secretin are separate at the receptor level. For this purpose, we have utilized secretin analogues with different amino acid substitutions in the middle and COOH-terminal portions of the molecule, regions that are not critical for cAMP generation (21,22). Second, we have investigated whether the two second messenger systems activated by secretin are independent of each other at the postreceptor level.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Secretin stimulates cyclic AMP and inositol trisphosphate production in rat pancreatic acinar tissue by two fully independent mechanisms.

Trimble¹,

Bruzzone²,

Biden³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

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In rat pancreatic acinar tissue adenylate cyclase is stimulated by low concentrations of secretin, while higher concentrations also activate phosphatidylinositol bisphosphate hydrolysis. By the use of the secretin analogues [Tyr'013Jsecretin and [Tyr'0"3,Phe22,Trp25]secretin, we have shown that substitution of tyrosine for leucine at positions 10 and 13 was sufficient to reduce the ability of the peptide to stimulate the production of inositol trisphosphate and the increases in cytosolic free calcium, while the ability to stimulate cAMP is little affected and the peptide remained a full agonist. Incubation with cholera toxin caused increases in cAMP, which were maximal after 30 min. Cholera toxin treatment also resulted in a marked reduction of secretin-stimulated inositol trisphosphate production, but this required a much more prolonged treatment (150-240 min), suggesting that different cholera toxin substrates were involved. Activation of protein kinase C with the phorbol ester phorbol 12-myristate 13-acetate had no effect on secretin-induced cAMP formation, nor was secretin-stimulated inositol trisphosphate formation altered by further increases in cAMP. These results indicate that the mechanisms by which secretin stimulates adenylate cyclase and activates phospholipase C in acinar tissue are completely independent.In the rat exocrine pancreas, binding of low concentrations of secretin to specific high-affinity receptors on acinar tissue leads to activation of adenylate cyclase (1), cAMP accumulation (2), and enzyme secretion (2, 3). However, with increasing concentrations of secretin the rate of cAMP accumulation becomes maximal when the rate of enzyme secretion is only half-maximal, or even less (2, 3). We have recently shown that at these higher concentrations of secretin there is also evidence of phosphatidylinositol bisphosphate (PtdInsP2) hydrolysis with rapid production of inositol trisphosphate (InsP3) and diacylglycerol (3), each of which is believed to play a role in stimulus-secretion coupling (4). These observations argue against the previously held idea that within a single tissue a peptide hormone cannot activate both the adenylate cyclase and the PtdInsP2 systems. It is known that hormones that either stimulate or inhibit the adenylate cyclase system do so through interaction with well-defined GTP-binding proteins, guanine nucleotide stimulatory (G.) and inhibitory (Ga) factors (5). Recent work has shown that in several different cell systems (6-17), including the exocrine pancreas (18)(19)(20), agonists that activate phospholipase C activity and initiate PtdInsP2 hydrolysis also interact with GTP-binding proteins. Although these proteins are not yet as well characterized as those linked to the adenylate cyclase system, they do mark one point where the control mechanisms of the different second messenger pathways are similar.The aim of the present investigation was 2-fold. The first was to determine whether the two signal pathways stimulated by secretin are separate at the receptor leve...

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Section: Resultssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Secretin stimulates cyclic AMP and inositol trisphosphate production in rat pancreatic acinar tissue by two fully independent mechanisms.

Trimble¹,

Bruzzone²,

Biden³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

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“…1). Both Cys 6 -sec and Cys 7 -sec incorporated a tyrosine to replace the leucine in position 10 for radioiodination (8), whereas Cys 10 -sec incorporated a tyrosine to replace Leu 26 for this purpose. All peptides were synthesized by manual solidphase techniques using Pal resin and purified by reversedphase HPLC as described (9) with their identities verified by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry.…”

Section: Methodsmentioning

confidence: 99%

Use of Cysteine Trapping to Map Spatial Approximations between Residues Contributing to the Helix N-capping Motif of Secretin and Distinct Residues within Each of the Extracellular Loops of Its Receptor

Dong

Lam

Orry

et al. 2016

Journal of Biological Chemistry

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Amino-terminal regions of secretin-family peptides contain key determinants for biological activity and binding specificity, although the nature of interactions with receptors is unclear. A helix N-capping motif within this region has been postulated to directly contribute to agonist activity while also stabilizing formation of a helix extending toward the peptide carboxyl terminus and docking within the receptor amino terminus. We used cysteine trapping to systematically explore spatial approximations between cysteines replacing each residue in this motif of secretin (sec), Phe 6 , Thr 7 , and Leu 10 , and cysteines incorporated into the extracellular face of the receptor. Each peptide was a full agonist for cAMP, but had a lower binding affinity than natural hormone. These bound to COS cells expressing 61 receptor constructs incorporating cysteines in every position along each extracellular loop (ECL) and adjacent parts of transmembrane (TM) segments. Patterns of covalent labeling were distinct for each probe, with Cys 6 -sec labeling multiple residues in the carboxyl-terminal half of ECL2 and throughout ECL3, Cys 7 -sec predominantly labeling only single residues in the carboxyl-terminal end of ECL2 and the amino-terminal end of ECL3, and Cys 10 -sec not efficiently labeling any of these residues. These spatial constraints were used to refine our model of secretin bound to its receptor, now bringing ECL3 above the amino terminus of the ligand and revealing possible charge-charge interactions between this part of secretin and receptor residues in TM5, TM6, ECL2, and ECL3, which can orient and stabilize the peptide-receptor complex. This was validated by testing predicted approximations by mutagenesis and residue-residue complementation studies.

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“…The secretin-like probe, (Bpa 5 ,Tyr 10 )rat secretin-27 (Bpa 5 probe), was designed to incorporate a photolabile Bpa in position 5 to replace a threonine located within the aminoterminal half of the ligand and a tyrosine in position 10 to replace a leucine that has previously been shown to be well tolerated (Gardner et al, 1977;Kofod, 1991). This probe and another secretin analog to be used as a radioligand, (Tyr 10 )secretin, were synthesized using the procedures described previously (Powers et al, 1988).…”

Section: Methodsmentioning

confidence: 99%

Spatial Approximation between Secretin Residue Five and the Third Extracellular Loop of Its Receptor Provides New Insight into the Molecular Basis of Natural Agonist Binding

et al. 2008

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The amino terminus of class II G protein-coupled receptors plays an important role in ligand binding and receptor activation. Understanding of the conformation of the amino-terminal domain of these receptors has been substantially advanced with the solution of nuclear magnetic resonance and crystal structures of this region of receptors for corticotrophin-releasing factor, pituitary adenylate cyclase-activating polypeptide, and gastric inhibitory polypeptide. However, the orientation of the amino terminus relative to the receptor core and how the receptor gets activated upon ligand binding remain unclear. In this work, we have used photoaffinity labeling to identify a critical spatial approximation between residue five of secretin and a residue within the proposed third extracellular loop of the secretin receptor.This was achieved by purification, deglycosylation, cyanogen bromide cleavage, and sequencing of labeled wild-type and mutant secretin receptors. This constraint has been used to refine our evolving molecular model of secretin docked at the intact receptor, which for the first time includes refined helical bundle and loop regions and reflects a peptide-binding groove within the receptor amino terminus that directs the amino terminus of the peptide toward the receptor body. This model is fully consistent with the endogenous agonist mechanism for class II G protein-coupled receptor activation, where ligand binding promotes the interaction of a portion of the receptor amino terminus with the receptor body to activate it.Class II guanine nucleotide-binding protein (G protein)-coupled receptors are an important family of potential drug targets that are activated by natural peptide ligands greater than 25 residues in length (Ulrich et al., 1998). All of these agonist ligands possess diffuse pharmacophoric regions, with critical residues spread throughout the length of the peptides. This provides the opportunity to define spatial approximation between such ligand residues and distinct residues within its receptor because ligand and receptor are normally bound to each other. It has been remarkable that probes incorporating photolabile residues throughout the pharmacophore of secretin-27, in positions 6, 12, 13, 14, 18, 21, 22, 23, and 26, each covalently labeled distinct residues that are restricted to the amino-terminal region of the secretin receptor, without labeling the receptor transmembrane core (Dong et al

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Interaction of secretin5–27 and its analogues with hormone receptors on pancreatic acini

Cited by 57 publications

References 13 publications

Secretin stimulates cyclic AMP and inositol trisphosphate production in rat pancreatic acinar tissue by two fully independent mechanisms.

Secretin stimulates cyclic AMP and inositol trisphosphate production in rat pancreatic acinar tissue by two fully independent mechanisms.

Use of Cysteine Trapping to Map Spatial Approximations between Residues Contributing to the Helix N-capping Motif of Secretin and Distinct Residues within Each of the Extracellular Loops of Its Receptor

Spatial Approximation between Secretin Residue Five and the Third Extracellular Loop of Its Receptor Provides New Insight into the Molecular Basis of Natural Agonist Binding

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