Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of cholecystokinin (CCK) to its receptors on guinea pig gastric chief cell membranes were characterized by the use of 125I-CCK-octapeptide (CCK8). At 30 degrees C optimal binding was obtained at acidic pH in the presence of Mg2+, while Na+ reduced the binding. In contrast to reports on pancreatic and brain CCK receptors, scatchard analysis of CCK binding to chief cell membranes revealed two classes of binding sites. Whereas, in the presence of a non-hydrolyzable GTP analog, GTP gamma S, only a low affinity site of CCK binding was observed. Chief cell receptors recognized CCK analogs, with an order of potency of: CCK8 greater than gastrin-I greater than CCK4. Although all CCK receptor antagonists tested (dibutyryl cyclic GMP, L-364718 and CR1409) inhibited labeled CCK binding to chief cell membranes, the relative potencies of these antagonists in terms of inhibiting labeled CCK binding were different from those observed in either pancreatic membranes or brain membranes. The results indicate, therefore, that on gastric chief cell membranes there exist specific CCK receptors, which are coupled to G protein. Furthermore, chief cell CCK receptors may be distinct from pancreatic or brain type CCK receptors.
...
PMID:Characterization of cholecystokinin receptors on guinea pig gastric chief cell membranes. 199 75

Cholecystokinin (CCK) binding to its receptors on guinea pig gastric chief cell membranes was characterized with 125I-COOH terminal octapeptide of CCK (125I-CCK8). Specific binding of 125I-CCK8 to chief cell membranes was maximal at pH 6.0 and 30 degrees C after 180 min of incubation and reversible upon the addition of 10(-7) M unlabeled CCK8. CCK analogs such as CCK8, gastrin-I, and COOH-terminal tetrapeptide of CCK (CCK4) competitively inhibited the labeled CCK8 binding with the half maximal inhibitory concentration of 10(-10) M, 3 X 10(-7) M and 10(-6) M, respectively. Furthermore, guanine nucleotide analogs such as GTP gamma S and Gpp(NH)p also inhibited the labeled CCK8 binding to chief cell membranes. Scatchard analysis of the binding data at pH 6.0 revealed two orders of the binding sites and GTP gamma S decreased the binding by converting two binding sites of the receptors to only one site of lower affinity. These results suggest that there are specific receptors for CCK, which are coupled to a guanine nucleotide regulatory protein on guiea pig gastric chief cell membranes.
...
PMID:[Cholecystokinin receptors on guinea pig gastric chief cell membranes]. 212 47

Recent studies have demonstrated the presence of both CCKA and CCKB receptors on dog and guinea pig pancreas. Although CCKA receptors are implicated in enzymatic secretion, biological effects of CCKB receptors are still unknown. We have previously found that a rat acinar pancreatic cell line (AR4-2J) possesses both receptor subtypes. In this work we report the ability of various CCK/gastrin agonists and antagonists to bind with these receptors. We found that gastrin, pentagastrin and Gastrin/CCK4 induce ornithine decarboxylase activity, an early event involved in cell proliferation, as well as 3H-thymidine incorporation. Furthermore, these effects occur at doses at which these peptides interact only with the CCKB receptor subtype. In view of these data we propose that modulation of AR4-2J cell growth by gastrin agonists specifically involve occupation of the CCKB receptor.
...
PMID:Gastrin modulates growth of a rat acinar pancreatic cell line: receptor analysis and signal transduction. 226 50

We describe here the properties of tert-butyloxycarbonyl-Trp-Leu-Asp-Phe-NHNH2 (A-57696), a C-terminal hydrazide analogue of tert-butyloxycarbonyl-CCK4 (Boc-Trp-Met-Asp-Phe-NH2), at four cholecystokinin (CCK) receptor-bearing tissues, the guinea pig pancreas and gall bladder (Type A), guinea pig cortex (Type B), and NCI-H345 cells, a human small cell lung cancer cell line that expresses CCK-B/gastrin receptors. Using 125I-Bolton-Hunter-cholecystokinin octapeptide (26-33) (125I-Bolton-Hunter-CCK8) as the radioligand, A-57696 was found to be selective for cortical CCK-B receptors (IC50 = 25 nM), compared with pancreatic CCK-A receptors (IC50 = 15 microM). A-57696 behaved as a competitive antagonist in reversing CCK8-stimulated pancreatic amylase secretion and phosphoinositide breakdown. By Schild analysis, its Kd was determined to be 4.7 and 6.8 microM in amylase and phosphoinositide assays, respectively. A-57696 (100 microM) did not elicit gall bladder contraction, and it inhibited contractions induced by CCK8. The Kd of A-57696 at gall bladder CCK-A receptors was 19 microM. In contrast, A-57696 behaved as a partial agonist (80% of maximal CCK8 response) in stimulating calcium mobilization at CCK-B/gastrin receptors on NCI-H345 cells. A-57696 and CCK8 inhibited each other in calcium mobilization experiments utilizing the fluorescent dye Indo-1. Stimulatory actions of CCK8 and A-57696 were reversed by the CCK-B-selective (R)-L-365,260 (100 nM), whereas at the same concentration, the CCK-A-selective (S)-L-365,260 was ineffective. Binding studies using 125I-Bolton-Hunter-CCK8 and 125I-gastrin indicated that binding sites labeled by these two ligands displayed similar affinities for CCK8, desulfated CCK8, gastrin, A-57696, and both enantiomers of L-365,260. A-57696 represents a new class of CCK-A peptide antagonist at guinea pig pancreas a new class of CCK-A peptide antagonist at guinea pig pancreas and gall bladder. Its contrasting functional activities at guinea pig CCK-A and CCK-B/gastrin receptors in a human tumor cell demonstrate that, in addition to the previously described differences in binding specificity for selective agonists and antagonists, CCK-A receptors and CCK-B/gastrin receptors have different requirements for activation.
...
PMID:Distinct requirements for activation at CCK-A and CCK-B/gastrin receptors: studies with a C-terminal hydrazide analogue of cholecystokinin tetrapeptide (30-33). 260 85

[125I]Bolton Hunter-cholecystokinin octapeptide (BH-CCK8) has been prepared using a modified method and was used to study putative cholecystokinin (CCK) receptor sites in the guinea-pig cerebral cortex. Specific binding of [125I]BH-CCK8, defined as the difference in binding in the absence and presence of 10(-6) M CCK8, was 70% of total binding. In saturation experiments, the apparent dissociation constant (Kd) was 1 nM and total binding capacity was 28 fmol/mg of protein. In association experiments, conducted at 30 degrees C, binding of [125I]BH-CCIK8 reached equilibrium in approximately 150 min. Binding was stable for 4 hr and was reversed by the addition of unlabeled CCK8-sulfated. Dissociation of bound ligand was biphasic and the apparent T1/2 was 45 min. Analyses of kinetic experiments yielded an association rate constant of 0.58 X 10(8) min-1 M-1 and a dissociation rate constant for the slower component of 0.012 min-1. Dithiothreitol increased and N-ethylmaleimide decreased specific binding of [125I]BH-CCK8, indicating that CCK receptor sites involve sulfhydryl groups. In competition experiments, the potency of CCK4 was enhanced 50-fold with addition of protease inhibitors. The rank order of CCK-related peptides was CCK8-sulfated greater than or equal to Gastrin 17 greater than or equal to CCK33 greater than CCK4 greater than or equal to CCK8-desulfated. Proglumide, a proposed CCK antagonist in the periphery and brain, was inactive at 10(-3) M. The specificity of [125I]BH-CCK8 binding sites are similar to that reported for [125I]BH-CCK33.
...
PMID:Characterization of cholecystokinin receptor sites in guinea-pig cortical membranes using [125I]Bolton Hunter-cholecystokinin octapeptide. 298 69

Trophic changes of the exocrine pancreas after in vivo gastrin (G)/CCK treatment are well documented but up to now the study of the mechanisms involved is restricted by the lack of a suitable in vitro model. Nevertheless the in vivo trophic effect induced by gastrin/CCK peptides has been associated with an increase of ornithine decarboxylase (ODC) activity. In the present work, using the AR42J cell line in which CCK receptors and stimulation of amylase release by CCK peptides has already been demonstrated, we investigated the presence of gastrin binding sites and the possible modulation of proliferation by an inhibitor of ODC activity. 125I-BH-G17ns binding is saturable, reversible and specific. Potencies of the different analogues tested are G17ns greater than CCK8 greater than CCK8ns greater than or equal to G6s greater than G/CCK4. Furthermore dBt cGMP, a non-peptide antagonist for CCK receptors, does not compete for gastrin binding. This indicates the existence of a subclass of gastrin binding sites. Difluoromethyl ornithine (DFMO) (1 mM), an irreversible inhibitor of ODC, inhibits cell growth from day 3 up to day 7. This growth inhibition is dose dependent and closely related to an intracellular polyamine modulation. Putrescine and spermidine levels fell under detectable values while spermine levels increased. All these data suggest that this cell line could be a useful in vitro model to study the mechanisms of gastrin induced growth control.
...
PMID:Characterisation of gastrin receptors on a rat pancreatic acinar cell line (AR42J). A possible model for studying gastrin mediated cell growth and proliferation. 312 56

Two major classes of immunoreactive cholecystokinin peptides (iCCK) have been identified in rat and pig brains: (i) large basic peptides (big iCCK) resembling the 33-amino acid porcine cholecystokinin (pCCK33) in size and charge; (ii) small acidic peptides (small iCCK) resembling the COOH-terminal fragments of CCK. Boiling 0.1 M HCl maximally extracts big iCCK; boiling 0.1 M NaOH maximally extracts small iCCK. The differences in hormonal forms removed by these extractants are not likely to be due to enzymatic conversion during the extraction procedures. Fractionation on Sephadex G-50 and starch gel electrophoresis combined with radioimmunoassay using three antisera of different specificities--(i) directed towards the NH2 terminus of pCCK33, (ii) produced by immunization with COOH-terminal fragment CCK8, (iii) produced by immunization with COOH-terminal fragment CCK4--are consistent with the hypothesis that a major fraction of big iCCK may represent intact cholecystokinin with a COOH-terminal extension, as has recently been suggested for gastrin, a molecule having a COOH-terminal pentapeptide identical with that of cholecystokinin.
...
PMID:Extraction and immunochemical characterization of cholecystokinin-like peptides from pig and rat brain. 616 93

Two major classes of immunoreactive cholecystokinin peptides (iCCK) have been identified in rat and pig brains: (1) large basic peptides (Big iCCK) resembling pCCK33 in size and charge; (2) small acidic peptides (Small iCCK) resembling the COOH-terminal fragments of CCK. Boiling 0.1 N HCl maximally extracts Big iCCK; boiling 0.1 N NaOH maximally extracts Small iCCK. The differences in hormonal forms removed by these extractions are not likely to be due to enzymatic conversion during the extraction procedures. Fractionation on Sephadex G50 and starch gel electrophoresis combined with radioimmunoassay using 3 antisera of different specificities: (1) directed towards the NH2-terminus of pCCK33; (2) produced by immunization with CCK8; (3) produced by immunization with CCK4; are consistent with the hypothesis that a major fraction of Big iCCK may represent intact CCK with a COOH-terminus extension as has recently been suggested for gastrin, a molecule having a COOH-terminal pentapeptide identical with that of CCK.
...
PMID:Nature of immunoreactive CCK in rat and pig brain. 617 97

Prior studies have shown that the cerebral cortex cholecystokinin (CCK) receptor can bind CCK and gastrin analogs with high affinity. In the present work the brain CCK receptor had approximately a three times greater affinity for CCK8 than its C-terminal tetrapeptide (CCK4) while the C-terminal tripeptide (CCK3) was 1000-fold less potent than CCK4. Thus the C-terminal tetrapeptide appears to be the minimal C-terminal CCK sequence required for high affinity binding. Since brain membranes degrade various peptides including CCK, we also evaluated the stability of CCK analogs under the conditions used to measure receptor binding by the following three methods: (1) Studies of degradation-resistant analogs in binding assays; (2) analysis of analog degradation by high performance liquid chromatography (HPLC); and (3) determination of the change in potency of CCK analogs in competitive binding studies subsequent to preincubation with brain membranes. These studies indicated that degradation of analogs by the brain membranes although significant did not account for the differences in potency of analogs in competitive binding studies. Therefore, the observed differences in potencies of the analogs tested are due to the receptor affinity and not sensitivity of the analog to degradation.
...
PMID:Binding specificity of the mouse cerebral cortex receptor for small cholecystokinin peptides. 632 3

Serum gastrin I (GLU-GLY-PRO-TRYP-LEU(GLU)6-ALA-[formula, see text]-GLY-TRY-MET-ASP-PHE-CO-NH2) concentrations were investigated by radioimmunoassay in 50 mothers and their newborn infants immediately after birth. The mean serum gastrin concentration in maternal blood was 52.80 +/- 13.37 (SD) pg/ml, and in cord blood 84.12 +/- 42.90 (SD) pg/ml. Both values were significantly higher than serum gastrin levels found in normal, healthy, nonpregnant women (Mean +/- SD = 32.34 +/- 18.35 pg/ml). There were no statistically significant differences in the cord serum gastrin concentrations with respect to sex, weight and length of the infant and age and parity of the mother.
...
PMID:Serum gastrin I concentrations of mother and newborn immediately after birth. 745 1


1 2 3 4 5 6 7 Next >>

---