Contributions to the physiological effects of peptone when injected into the circulation: Part V. The influence of peptone and albumoses on the urinary secretion.
Explore the source record for details and available documents.
Journal Article↗
SEARCH · PubMed Health
Results for “PEPTONES”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Gastric acid secretion in dogs in response to combinations of beer, ethanol and peptone meal--the role of endogenous gastrin.
AIM: To examine the effects of beer, ethanol, peptone meal and combinations of either peptone meal and beer or peptone meal and ethanol on gastric acid secretion in vagally denervated pouch dogs. METHODS AND RESULTS: The oral administration of either 200 mL of beer, 5% ethanol or 10% peptone meal significantly stimulated gastric acid secretion for 60-90 min in these dogs. With 5% ethanol the plasma gastrin concentration was not affected for 90 min. Combinations of 10% peptone and beer (peptone-beer) or 10% peptone and 5% ethanol (peptone-ethanol) potentiated the acid secretion and increased the plasma gastrin level. While a selective cholecystokinin-B/gastrin receptor antagonist, S-0509, had no effect on ethanol-stimulated acid secretion, the compound markedly inhibited both peptone-beer-stimulated and peptone-ethanol-stimulated gastric acid secretion. Famotidine and atropine significantly inhibited gastric acid secretion stimulated by 5% ethanol, peptone-beer and peptone-ethanol. CONCLUSIONS: The mechanisms by which peptone-beer and peptone-ethanol stimulate gastric acid secretion may be mediated not only by increased plasma gastrin, but also by the action of histamine and acetylcholine coupled with the increased plasma gastrin. Ethanol-stimulated secretion appears to be unrelated to circulating gastrin, yet may be related to the acid regulatory mechanism involving histamine and acetylcholine.
Administration, Oral↗
Role of endogenous CCK in the inhibition of gastric emptying by peptone and Intralipid in rats.
To assess the role of endogenous cholecystokinin in the control of gastric emptying of peptone solutions and Intralipid suspensions, we examined the ability of a dose range of the CCK-A antagonist, devazepide to accelerate the gastric emptying of various caloric concentrations of peptone and Intralipid in rats. In the absence of devazepide, both peptone and Intralipid emptying slowed with increasing concentration. Devazepide's effect on peptone gastric emptying diminished with increasing peptone concentration. The threshold dose for accelerating the emptying of 0.2 kcal/ml peptone was lower than the threshold dose for affecting 0.5 kcal/ml peptone and devazepide had no effect on the gastric emptying of 1.0 kcal/ml peptone. In contrast, devazepide affected Intralipid gastric emptying at all three Intralipid concentrations and the threshold dose decreased with increasing Intralipid concentration. However, the magnitude of the effect of devazepide on peptone or Intralipid gastric emptying was partial and did not increase as a function of concentration. These data demonstrate a role for endogenous CCK in the emptying of peptone and Intralipid but suggest that endogenous CCK does not account for the increased slowing of gastric emptying evident with increased caloric concentration.
Animals↗
Intragastric CO2 and nitric oxide participate in the regulation of peptone-induced gastrin release in humans.
BACKGROUND: Moderate acidification of the gastric lumen inhibits peptone-induced gastrin release. The aim of the present study was to investigate if the gastric acid neutralization products CO2 (from secreted HCO3) and NO (from reduced salivary nitrite) could act as intermediate messengers between luminal acidity and the inhibition of peptone-induced gastrin release. METHODS: Fourteen healthy volunteers (mean age, 27 years; range, 20-39 years; 3 women) participated in the study. Intragastric perfusion with saline or peptone was performed on the healthy volunteers. Venous blood samples were analyzed for serum gastrin concentrations. Intragastric NO was measured by chemiluminescence. RESULTS: Basal serum gastrin ranged between 11 and 23 pmol/l. Peptone in Sörensen's phosphated buffer (pH 6.9, PCO2 0 mmHg) increased serum gastrin by 83% +/- 23%, whereas acidified peptone (pH 2.0) did not stimulate gastrin release. Acidified peptone buffered with NaHCO3 to neutrality (pH 6.9, PCO2 approximately 600 mmHg) increased serum gastrin by 166% +/- 29%. Low intragastric NO levels were obtained by deviation of saliva. During such salivary depletion, acidified peptone (pH 2.0) stimulated gastrin release to a level of about 40% of the control response (pH 6.9). This peptone-induced gastrin response during salivary deviation was inhibited by addition of nitrite to the perfusate. CONCLUSIONS: Acid-induced inhibition of peptone-stimulated gastrin release is partly dependent on intraluminal NO formed in the reaction between salivary nitrite and gastric acid. In addition, the gastric acid neutralization product CO2 seems to potentiate the effect of peptone on gastrin release.
Adult↗
Peptones stimulate cholecystokinin secretion and gene transcription in the intestinal cell line STC-1.
In rats, protein hydrolysates (peptones) stimulate cholecystokinin (CCK) release both in vivo and in a model of isolated vascularly perfused duodeno-jejunum. However, the mechanisms involved in peptone-induced stimulation of CCK cells are not well understood. In particular, the possibility that peptones may directly interact with CCK-producing cells to stimulate CCK release and gene transcription has not yet been examined. To test this hypothesis, we used the enteroendocrine cell line STC-1. Incubation of STC-1 cells for 2 h with albumin egg hydrolysate over the concentration range 0.01-1% (wt/ vol) caused a dose-dependent release of CCK, with a maximal increase at 1420% of the control value. In contrast, BSA (1%, wt/vol) or a mixture of amino acids (1%, wt/vol) induced a modest rise in CCK secretion. A dose-dependent, hydrolysate-specific, increase in the CCK steady state RNA level was also observed. It was detectable by 2-4 h of peptone treatment and sustained until 24-48 h. Peptones did not increase the CCK RNA level in the colonic CCK-producing cell line GLUTag or in nonintestinal CCK-expressing cell lines, namely the pancreatic cell line RINm5F and the medullar thyroid carcinoma cell line CA77. The peptone-induced increase in the CCK RNA level resulted from enhanced gene transcription, because labeled CCK transcripts from nuclear run-on incubations increased 3-fold when cells were incubated with peptones, whereas the level of beta-actin transcripts was not modified. Finally, peptones dose-dependently stimulated the transcriptional activity of an 800-bp fragment of CCK gene promoter transfected in STC-1 cells. These studies indicate that peptones specifically stimulate CCK secretion and gene transcription in the intestinal cell line STC-1, and that cis-acting elements conferring peptone inducibility are located in the first 800 bp of the 5'-flanking region of the CCK gene.
Animals↗
Soybean beta-conglycinin peptone suppresses food intake and gastric emptying by increasing plasma cholecystokinin levels in rats.
Cholecystokinin (CCK) is an important physiologic mediator that regulates satiety and gastric emptying. We demonstrated previously that soybean peptone acts directly on rat small intestinal mucosal cells to stimulate CCK release. In the present study, we examined the effects of beta-conglycinin, a major component of soy protein, and its peptone on food intake and gastric emptying after an intraduodenal infusion of beta-conglycinin peptone in relation to CCK release and interaction with the mucosal cell membrane. Intraduodenal infusion of beta-conglycinin peptone inhibited food intake in a dose-dependent manner, but that of whole soy peptone or camostat did not. The suppression of food intake by beta-conglycinin peptone was abolished by an intravenous injection of devazepide, a selective peripheral CCK receptor antagonist. The beta-conglycinin peptone infusion strongly suppressed gastric emptying with marked increases in portal CCK levels. We also observed that the beta-conglycinin peptone dose dependently and more potently stimulated CCK release from isolated dispersed mucosal cells of the rat jejunum than did beta-conglycinin itself. This stimulation corresponded to the binding activity of the peptide or protein to solubilized components of the rat jejunum membrane as evaluated by surface plasmon biosensor. These results indicate that beta-conglycinin peptone suppresses food intake, and this effect may be due to beta-conglycinin peptone in the lumen stimulating endogenous CCK release with direct acceptance to the intestinal cells.
Animals↗
Asymptomatic H. pylori infection impairs pH inhibition of gastrin and acid secretion during second hour of peptone meal stimulation.
H. pylori infection is associated with acid-peptic disease, although its role in the pathogenesis is unclear. The purpose of this study was to determine if chronic infection in asymptomatic subjects impairs the inhibition of meal-stimulated gastrin and acid secretion that is observed normally at low intragastric pH. Presence of infection was determined by both C-14 urea breath test and serology. Acid secretion was measured under basal conditions and in response to peptone meal stimulation and pentagastrin. Plasma gastrin concentrations were determined by radioimmunoassay under basal conditions and during peptone meal stimulation. Intragastric titration with 1% peptone during the first hour, and 8% peptone during the second hour, was performed at both pH 7.0 and 2.5 on different days to compare the inhibition of gastrin and acid secretion. Compared to noninfected subjects, asymptomatic individuals infected with H. pylori had significantly increased: (1) basal gastrin values (P < 0.005); (2) 8% peptone-stimulated gastrin responses at both pH 7.0 and 2.5 (P < 0.05); and (3) 8% peptone-stimulated acid output at pH 2.5 (P = 0.01). During the second hour of peptone-stimulation, subjects infected with H. pylori had significantly decreased inhibition of gastrin (52% vs 95%) (P = 0.002) and acid (30% vs 81%) (P = 0.01) secretion from pH 7.0 to 2.5. Thus, chronic infection with H. pylori results in impaired inhibition of gastrin and acid secretion at low intragastric pH during the second hour of peptone meal stimulation. These defects may be unrelated to the pathogenesis of acid-peptic disease, since they occur in asymptomatic subjects infected with H. pylori.
Adult↗
Mechanisms of increased lower esophageal sphincter pressure following intraduodenal peptone infusion in dogs.
Peptone perfusion of the excluded duodenum in dogs is associated with an increase in lower esophageal sphincter pressure (LESP). This study investigates the role of cholinergic, adrenergic, and hormonal mediators in the response of the LES to intraduodenal peptone infusion. Adult dogs underwent duodenal exclusion via a Roux-en-Y pylorojejunostomy with formation of a mucocutaneous fistula. Manometric measurements of LESP and radioimmunoassay determinations of gastrin and pancreatic polypeptide (PP) blood levels were made at rest and at 15-min intervals following peptone infusion of the excluded duodenum. In control experiments, peptone infusion resulted in an increase in mean LESP at all time intervals (P less than 0.05). PP blood levels increased significantly, while gastrin levels remained unchanged. Both truncal vagotomy and pretreatment with atropine blocked the changes in LESP. PP release in response to peptone was accentuated in vagotomized dogs, while atropine suppressed the release of PP following peptone infusion. Treatment with 6-hydroxydopamine did not affect the increase in either LESP or PP blood levels observed in controls. Intravenous somatostatin suppressed the release of PP following intraduodenal peptone, but did not block the lower esophageal sphincter response. This data indicates that the increase in LESP seen following intraduodenal peptone infusion is centrally mediated and dependent on vagal innervation and cholinergic neurotransmission.
Animals↗
The ontogeny of the postingestive inhibitory effect of peptone in rats.
The ontogeny of the postingestive inhibitory control of intake by protein digestion products was investigated by administering gastric preloads of a peptone that was a hydrolysate of meat and that decreased intake in adult rats [Am. J. Physiol., Regul. Integr. Comp. Physiol. 276 (1999) R1623; Am. J. Physiol., Regul. Integr. Comp. Physiol. 277 (1999) R1144]. Gastric preloads of saline or peptone, or sham preloads were given 5 min before a 30-min, independent ingestion test in which pups had access to a sweet, high-fat milk diet. Preloads of isotonic peptone reduced intake significantly more than preloads of isotonic saline on postnatal day (P) 18, but not on P12. Pretreatment with the CCKA receptor antagonist devazepide (600 microg/kg ip) did not change the inhibitory effect of isotonic peptone. Thus, the inhibitory effect of peptone on P18 was apparently not mediated by endogenous CCK acting at CCKA receptors. In contrast to isotonic peptone, preloads of hypertonic peptone did not decrease intake more than preloads of hypertonic saline on P12, P18, or P24. We conclude that if the isotonic peptone used in these experiments is an adequate model of the digestion products of dietary protein at these postnatal ages, then the postingestive inhibitory control of intake by digestion products of dietary protein during independent ingestion appears between P13 and P18.
Age Factors↗
The role of cholecystokinin in inhibition of gastric emptying by peptone in the rat.
It is clear that the intestinal hormone cholecystokinin (CCK) inhibits gastric emptying, but doubts remain about the physiological significance of this action. Evaluation of the apparently conflicting data is complicated by the fact that little is known of the duration of action of CCK-releasing meals in delaying emptying. We have studied this issue by following the emptying of the second of two successive liquid test meals instilled into the stomach in conscious gastric fistula rats. Prior administration of peptone, but not saline, delayed the emptying of subsequently administered saline and delayed still further the emptying of subsequently administered peptone. The action of isotonic peptone lasted about 10 min from the initial instillation into the stomach. Radioimmunoassay of plasma CCK indicated a significant increase 5 min after intragastric peptone, and a still further rise occurred 5 min after administration of the second of two consecutive peptone meals; 21 min after the first meal, plasma CCK had returned to basal levels. Intravenous infusion of CCK in a dose that matched the inhibition of gastric emptying caused by peptone gave plasma concentrations about 35% higher than those seen 5 min after the second of two consecutive peptone meals. It is concluded that a liquid test meal of peptone delays gastric emptying in part through release of CCK and that the response lasts 10 min or less. The relatively short duration of action of endogenous CCK released by a single protein-rich meal in the rat should be kept in mind in interpreting the significance of studies on the physiology of CCK.
Animals↗
Regulation of cholecystokinin secretion by peptones and peptidomimetic antibiotics in STC-1 cells.
Peptones are potent stimulants of cholecystokinin (CCK) release in rats, both in vivo and ex vivo in a model of isolated vascularly perfused duodeno-jejunum preparation and in vitro in the intestinal CCK-producing cell line STC-1. The underlying mechanisms were here investigated with this cell line. Protein hydrolysates from various origins (meat, casein, soybean, and ovalbumin; 0.5-1%, wt/vol) dose dependently increased CCK release. Cephalosporin antibiotics, which mimic tripeptides, also stimulated the release of CCK over the concentration range 1-20 mM. The study of concentration dependence of cephalosporin uptake indicated a passive diffusion process at either pH 7.4 or pH 6.0, thus arguing against the involvement of a peptide transporter in CCK secretion. After pertussis toxin treatment (200 ng/ml; 5 h), the peptone- and cephalexin-induced CCK secretion was significantly reduced, suggesting the involvement of pertussis toxin-sensitive heterotrimeric G protein(s) in the secretory activity of STC-1 cells. Consistent with this was the identification by Western blot of G(i2)alpha, G(i3)alpha, and G(o)alpha immunoreactivities in STC-1 cell extracts. Additionally, peptones and cephalexin increased the cellular content in inositol phosphates, whereas a mild increase in cAMP content was restricted to peptone-treated cells. Protein kinase A or C inhibition did not modify peptone- or antibiotic drug-evoked CCK release. The extracellular Ca2+ chelator EGTA (500 microM) and the intracellular Ca2+ chelator BAPTA-AM [1,2-bis-(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester; 20 microM] abolished the peptone- and antibiotic drug-induced CCK release. Nifedipine and verapamil (10 microM) reduced by about 50% the CCK secretion evoked by these two secretagogues. In conclusion, peptones and some cephalosporins are potent stimulants of CCK release in the STC-1 cell line. The cellular mechanisms involve pertussis toxin-sensitive G protein(s) and are dependent on Ca2+ availability. We suggest that the STC-1 cell line is a useful model to study the molecular basis of peptone-induced CCK secretion.
Animals↗
Peptones stimulate both the secretion of the incretin hormone glucagon-like peptide 1 and the transcription of the proglucagon gene.
Truncated glucagon-like peptide (GLP)-1 is a potent incretin. Its synthesis and secretion are modulated by food, but the influence of individual nutrients remains to be established. The hypothesis that protein hydrolysates (peptones) can directly regulate both GLP-1 secretion and proglucagon (PG) gene transcription was tested in this study, ex vivo in the isolated vascularly perfused rat intestine and in vitro in the murine enteroendocrine cell line STC-1. Peptones were albumin egg hydrolysate (AEH) and meat hydrolysate (MH). We demonstrate in these two models that peptones dose-dependently stimulate GLP-1 release, whereas isocaloric quantities of bovine serum albumin or of an amino acid mixture had no stimulatory effect. A strong and rapid increase of PG RNA level was observed in STC-1 cells treated with peptones (14-fold and 7-fold increase after 4 h of incubation with 3% wt/vol MH and AEH, respectively). Peptones also increased the PG RNA level in the colonic PG-expressing cell line GLUTag. In contrast, peptones did not modify the PG RNA level in two pancreatic glucagon-producing cell lines, namely, the RINm5F and INR1G9 cells. The peptone effect in STC-1 cells was completely abolished by blocking transcription before MH treatment. The stability of proglugacon transcripts was not modified by MH treatment, but nascent transcripts were more abundant in STC-1 cells preincubated with MH. Finally, MH treatment strongly stimulated (15-fold stimulation) the transcriptional activity of two PG gene promoter fragments (-1100 and -350 base pair) linked to the CAT reporter gene transiently transfected in STC-1 cells. Overall, peptones evoke an as yet undescribed release of GLP-1 when brought into contact with native intestinal L-cells or with STC-1 enteroendocrine cells. The increased transcription of the glucagon gene in the latter system suggests an important role of protein hydrolysates in the control of not only the secretion but also the synthesis of the incretin hormone.
Animals↗
Peptone, a low-cost growth-promoting nutrient for intensive animal cell culture.
The effect of addition of peptone to serum-free and serum supplemented media for the growth of hybridoma cells in various systems was studied. Supplementation of defined medium with either proteose peptone or meat peptone resulted in significant increases in cell number and specific monoclonal antibody production in batch culture system. Other peptones were either inactive or less effective. In continuous culture, using medium supplemented with new born calf serum, the addition of peptone resulted in 125% and 150% increases in cell and antibody concentrations respectively. Similar increase in cell number (128%) was also obtained in spin-filter perfusion culture when medium was supplemented with peptone. By comparison, the substitution of a defined 1 x MEM amino acids mixture resulted in only a 50% increase. At higher perfusion rates the cell number maintained in steady state using peptone supplement could be increased to 1.3 x 10(7) cells ml-1 while the serum concentration was reduced from 5% to 1% at a perfusion rate of 2.5 volumes per day.
Animals↗
Effects of lorglumide on gastrin- and peptone-stimulated gastric acid secretion in rats.
This study in rats demonstrates that gastric acid secretion stimulated by infusion of gastrin 17-I yielding plasma concentrations in the physiological range is almost abolished by the cholecystokinin-receptor antagonist lorglumide. Furthermore, lorglumide also inhibited intragastric peptone stimulated gastric acid secretion by 43%. When compared to peptone stimulation with a saline background infusion, lorglumide infusion inhibited peptone stimulated gastric acid secretion only significantly in the late (20 to 30 minutes) part of stimulation, while the initial part (0 to 10 and 10 to 20 minutes) was not significantly inhibited by lorglumide. Both peptone stimulation and gastrin infusion significantly augmented serum gastrin concentrations, which were not significantly influenced by lorglumide. The serum gastrin concentrations achieved during gastrin infusion were higher than during peptone stimulation, however the differences were not statistically significant. It is concluded that lorglumide abolishes gastrin stimulated gastric acid secretion in rats, but only partly (43%) inhibits peptone-meal stimulated gastric acid secretion. In contrast to the gastrin infusion experiments, where lorglumide abolishes acid secretion during the entire study period, the compound inhibits gastric acid secretion more effectively towards the end of peptone stimulation than in the beginning.
Animals↗
Peptones and mycological reproducibility.
The pH reactions, ultraviolet spectra and phosphorus content of solutions of a variety of commercially available peptones all indicated, predictably, considerable differences in the chemical composition of the peptones. The effects of these differences on the outcome of experiments with Candida albicans grown in different peptone media was investigated. The fungus produced germ tubes equally effectively on all such media provided that the inoculum was kept to 10(6) blastospores/ml or less. However, expression of inducible enzyme activities in C. albicans varied extensively from peptone to peptone; there was, for example, an inverse relationship between the inorganic phosphorus content of peptones and the amount of acid phosphomonoesterase detectable in intact blastospores. The results indicated that use of different peptones in "Sabouraud's" media by different laboratories may account for some, but not all, published instances of irreproducibility of experiments with C. albicans.
Acid Phosphatase↗
Osmoprotection of Escherichia coli by peptone is mediated by the uptake and accumulation of free proline but not of proline-containing peptides.
The effect of meat peptone type I (Sigma) on the growth of Escherichia coli cells under hyperosmotic stress has been investigated. Peptone is a complex mixture of peptides with a small content of free amino acids, which resembles nutrients found in natural environments. Our data showed that peptone enhances the growth of E. coli cells in high-osmolarity medium to levels higher than those achieved with the main compatible solute in bacteria, glycine betaine. The mechanism of osmoprotection by peptone comprises the uptake and accumulation of the compatible solute, proline. The main role of the peptides contained in peptone is the provision of nutrients rather than the intracellular accumulation of osmolytes. In contrast to Listeria monocytogenes (M. R. Amezaga, I. Davidson, D. McLaggan, A. Verheul, T. Abee, and I. R. Booth, Microbiology 141:41-49, 1995), E. coli does not accumulate exogenous peptides for osmoprotection and peptides containing proline do not lead to the accumulation of proline as a compatible solute. In late-logarithmic-phase cultures of E. coli growing at high osmolarity plus peptone, proline becomes the limiting factor for growth, and the intracellular pools of proline are not maintained. This is a consequence of the low concentration of free proline in peptone, the catabolism of proline by E. coli, and the inability of E. coli to utilize proline-containing peptides as a source of compatible solutes. Our data highlight the role that natural components in food such as peptides play in undermining food preservation regimes, such as high osmolarity, and also that the specific mechanisms of osmoprotection by these compounds differ according to the organism.
Amino Acids↗
Peptone induction and rifampin-insensitive collagenase production by Vibrio alginolyticus.
Vibrio alginolyticus produces an extracellular collagenase which requires specific induction by collagen or its high-molecular-weight fragments. Peptone also induces collagenase during the late exponential and early stationary growth phases. The peptone inducers have been shown to have a broad molecular weight range between 1,000 and 60,000. The peptone inducers supported slow growth of V. alginolyticus when supplied as the sole nitrogen source in minimal medium. Digestion of the peptone inducers with purified V. alginolyticus collagenase resulted in a decrease in their inducing ability, whereas digestion with trypsin or alpha-chymotrypsin did not. This indicated that induction by the inducers required the presence of collagenase-sensitive bonds. Prolonged digestion of the inducers with collagenase did not completely eliminate the inducing ability of the inducers. The peptone inducers acted as inhibitors of collagenase. A minimal medium induction system has been developed which involves resuspending cells at high density in a medium containing succinate, (NH(4))(2)SO(4), KH(2)PO(4), and the peptone inducer. Cells grown in minimal medium induce earlier than cells grown on peptone, Casamino Acids, or tryptone. Collagenase production was shown to occur for 30 to 60 min in the presence of rifampin at levels which completely inhibit the incorporation of [(3)H]uracil into trichloroacetic acid-precipitable material. Chloramphenicol completely and immediately abolished collagenase production, which together with labeling studies has confirmed that collagenase production involves de novo synthesis of the enzyme. Both glucose and Casamino Acids repressed collagenase production, although synthesis of the enzyme continued for 30 to 60 min after their addition. The repression of collagenase production by glucose and Casamino Acids was more severe than the inhibition of enzyme formation due to addition of rifampin.
Amino Acids↗
Peptones stimulate intestinal cholecystokinin gene transcription via cyclic adenosine monophosphate response element-binding factors.
Cholecystokinin (CCK) is a potent intestinal hormone that regulates several digestive functions. Despite the physiological importance of CCK, the cellular and molecular mechanisms that govern its synthesis and secretion are not completely identified. Peptones, which are fair counterparts of the protein fraction in the intestinal lumen, are good stimulants of CCK secretion. We have previously shown that peptones activate CCK gene transcription in STC-1 enteroendocrine cells. The DNA element(s) necessary to induce the transcriptional stimulation was preliminary, localized in the first 800 bp of the CCK gene promoter. In the present study, we identify a DNA element [peptone-response element (PepRE)] essential to confer peptone-responsiveness to the CCK promoter, and we characterize the transcription factors implicated. Localization of the PepRE between -93 and -70 bp of the promoter was established using serial 5'-3'deletions. Systematic site-directed mutagenesis demonstrated that the core PepRE sequence, spanning from nucleotide -72 to -83, overlapped with the putative AP-1/CRE site. Mutations in the core sequence dramatically decreased peptone-responsiveness of CCK promoter fragments. The PepRE functioned as a low-affinity CRE consensus site, binding only transcription factors of the CREB family. Overexpression, in STC-1 cells, of a dominant-negative protein (A-CREB), that prevented the binding of CREB factors to DNA, completely abolished the peptone-induced transcriptional stimulation. Peptone treatment did not modify the nature and the abundance of proteins bound to the PepRE but led to increased phosphorylation of the CREB factors. In conclusion, the present study first demonstrates that CCK gene expression is under the control of protein-derived nutrients in the STC-1 enteroendocrine cell line.
Animals↗