7 research outputs found
Neuropeptide Y (18–36) modulates chromaffin cell catecholamine secretion by blocking the nicotinic receptor ion
or Poiuu.cowcy AND ExP iuME rr.u. THERAPEuTIC
UTP and ATP increase extracellular signal-regulated kinase 1/2 phosphorylation in bovine chromaffin cells through epidermal growth factor receptor transactivation
Adenosine triphosphate (ATP) is coreleased with catecholamines from adrenal medullary chromaffin cells in response to sympathetic nervous system stimulation and may regulate these cells in an autocrine or paracrine manner. Increases in extracellular signal-regulated kinase (ERK) 1/2 phosphorylation were observed in response to ATP stimulation of bovine chromaffin cells. The signaling pathway involved in ATP-mediated ERK1/2 phosphorylation was investigated via Western blot analysis. ATP and uridine 5′-triphosphate (UTP) increased ERK1/2 phosphorylation potently, peaking between 5 and 15 min. The mitogen-activated protein kinase (MAPK/ERK)-activating kinase (MEK) inhibitor PD98059 blocked this response. UTP, which is selective for G-protein-coupled P2Y receptors, was the most potent agonist among several nucleotides tested. Adenosine 5′-O-(3-thio) triphosphate (ATPγS) and ATP were also potent agonists, characteristic of the P2Y2 or P2Y4 receptor subtypes, whereas agonists selective for P2X receptors or other P2Y receptor subtypes were weakly effective. The receptor involved was further characterized by the nonspecific P2 antagonists suramin and reactive blue 2, which each partially inhibited ATP-mediated ERK1/2 phosphorylation. Inhibitors of protein kinase C (PKC), protein kinase A (PKA), Ca2+/calmodulin-dependent protein kinase II (CaMKII), and phosphoinositide-3 kinase (PI3K) had no effect on ATP-mediated ERK1/2 phosphorylation. The Src inhibitor PP2, epidermal growth factor receptor (EGFR) inhibitor AG1478, and metalloproteinase inhibitor GM6001 decreased ATP-mediated ERK1/2 phosphorylation. These results suggest nucleotide-mediated ERK1/2 phosphorylation is mediated by a P2Y2 or P2Y4 receptor, which stimulates metalloproteinase-dependent transactivation of the EGFR
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Characterization of neuropeptide Y (NPY) receptors in human hippocampus
We identified a 50 kDa neuropeptide Y (NPY) receptor from human hippocampus by affinity labeling. NPY specific binding and labeling of the receptor were inhibited in parallel by increasing concentrations of unlabeled NPY (IC= 0.27nM and0.18nM, respectively). Peptide YY (PYY), but none of the pancreatic polypeptides, was as effective as NPY in displacing [
125I]NPY. NPY fragments inhibited binding with the rank order of potency: NPY>NPY
13–36 >NPY
20–36≥NPY
18–36 >NPY
1–36free acid≥NPY
26–36. These results demonstrate that the human hippocampal NPY receptor is a 50 kDa protein fitting the classification of a Y
2 receptor subtype
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Cysteamine selectively enhances neuropeptide Y2 receptor binding activity
Affinity labeling of [125I]NPY to the bovine hippocampal NPY receptor has revealed a 50 kDa specific binding protein, the Y2 receptor. Cysteamine (10 μM – 10 mM) specifically enhanced NPY specific labeling of the Y2 receptor without affecting crosslinking effeiciency. Several structurally related agents, including reduced glutathione, cysteine, β-mercaptoethanol and ethanolamine, were without effect on receptor binding. The enhancement of binding by cysteamine could be reversed by washing the membranes. These studies suggest that cysteamine may change the conformation of the NPY Y2 receptor and increase its binding activity