Historical perspectives on cholecystokinin research

CCK1 receptor is involved in the regulation of protein lysine acetylation in GBC-SD cells and gallbladder carcinoma

BACKGROUND

CCK1 (cholecystokinin receptor 1) and protein lysine acetylation were associated with several cancers, respectively. However, whether they are involved in the alternation of gallbladder carcinoma is unknown.

AIMS

This study investigated the characteristics of CCK1 and protein lysine acetylation in GBC-SD cells and carcinoma of gallbladder.

METHODS

The expression and localization of CCK1 were detected by western blot analysis and indirect immunofluorescence. GBC-SD cells were treated with CCK-8 and CCK-8+CCK1 inhibitor. The protein lysine acetylation from cells, as well as tissues of gallbladder carcinoma, was examined by western blotting.

RESULTS

CCK1 receptor was expressed and localized in the GBC-SD cells. The synthetic octapeptide of CCK (CCK-8) could accelerate the lysine acetylation of a subset of proteins in dose-dependent manners in GBC-SD cells. Further investigation demonstrated that the specific inhibitor (CR1409) of CCK1 receptor could attenuate the CCK8-induced increase of protein lysine acetylation. In addition, we revealed that the rise of CCK1 receptor expression is associated with the increase of protein lysine acetylation in tissues from carcinoma of gallbladder.

CONCLUSIONS

CCK might regulate protein lysine acetylation via CCK1 receptor.

Cholecystokinin receptors regulate sperm protein tyrosine phosphorylation via uptake of HCO3-

Cholecystokinin (CCK), a peptide hormone and a neurotransmitter, was detected in mature sperm two decades ago. However, the exact role of CCK and the types of CCK receptors (now termed CCK1 and CCK2) in sperm have not been identified. Here, we find that CCK1 and CCK2 receptors are immunolocalized to the acrosomal region of mature sperm. The antagonist of CCK1 or CCK2 receptor strongly activated the soluble adenylyl cyclase/cAMP/protein kinase A signaling pathway that drives sperm capacitation-associated protein tyrosine phosphorylation in dose- and time-dependent manners. But these actions of stimulation were abolished when sperm were incubated in the medium in the absence of HCO3-. Further investigation demonstrated that the inhibitor of CCK1 or CCK2 receptor could accelerate the uptake of HCO3- and significantly elevate the intracellular pH of sperm. Interestingly, the synthetic octapeptide of CCK (CCK8) showed the same action and mechanism as antagonists of CCK receptors. Moreover, CCK8 and the antagonist of CCK1 or CCK2 receptor were also able to accelerate human sperm capacitation-associated protein tyrosine phosphorylation by stimulating the influx of HCO3-. Thus, the present results suggest that CCK and its receptors may regulate sperm capacitation-associated protein tyrosine phosphorylation by modulating the uptake of HCO3-.

Gastrointestinal hormone research - with a Scandinavian annotation

Gastrointestinal hormones are peptides released from neuroendocrine cells in the digestive tract. More than 30 hormone genes are currently known to be expressed in the gut, which makes it the largest hormone-producing organ in the body. Modern biology makes it feasible to conceive the hormones under five headings: The structural homology groups a majority of the hormones into nine families, each of which is assumed to originate from one ancestral gene. The individual hormone gene often has multiple phenotypes due to alternative splicing, tandem organization or differentiated posttranslational maturation of the prohormone. By a combination of these mechanisms, more than 100 different hormonally active peptides are released from the gut. Gut hormone genes are also widely expressed outside the gut, some only in extraintestinal endocrine cells and cerebral or peripheral neurons but others also in other cell types. The extraintestinal cells may release different bioactive fragments of the same prohormone due to cell-specific processing pathways. Moreover, endocrine cells, neurons, cancer cells and, for instance, spermatozoa secrete gut peptides in different ways, so the same peptide may act as a blood-borne hormone, a neurotransmitter, a local growth factor or a fertility factor. The targets of gastrointestinal hormones are specific G-protein-coupled receptors that are expressed in the cell membranes also outside the digestive tract. Thus, gut hormones not only regulate digestive functions, but also constitute regulatory systems operating in the whole organism. This overview of gut hormone biology is supplemented with an annotation on some Scandinavian contributions to gastrointestinal hormone research.

Development of eating behavior: biology and context

Eating is necessary for survival, gives great pleasure, and can be perturbed leading to undernutrition, overnutrition, and eating disorders. The development of feeding in humans relies on complex interplay between homeostatic mechanisms; neural reward systems; and child motor, sensory, and socioemotional capability. Furthermore, parenting, social influences, and the food environment influence the development of eating behavior. The rapid expansion of new knowledge in this field, from basic science to clinical and community-based research, is expected to lead to urgently needed research in support of effective, evidence-based prevention and treatment strategies for undernutrition, overnutrition, and eating disorders in early childhood. Using a biopsychosocial approach, this review covers current knowledge of the development of eating behavior from the brain to the individual child, taking into account important contextual influences.

Acute pancreatitis: a historical perspective

Among the various pancreatic disorders, the pace of scientific discovery in acute pancreatitis has been particularly slow. The objective of this paper was to briefly review the history of scientific discovery of the clinical features, pathophysiology, and treatment of acute pancreatitis. A clinical description of acute pancreatitis was first presented in 1652 by the Dutch anatomist Nicholas Tulp, and despite the nearly 350 years that have passed, there continue to be many unanswered questions. In the late 19th and early 20th century, Reginald Fitz, Nicholas Senn, Eugene Opie, and others made seminal contributions that continue to influence our present understanding of acute pancreatitis. Despite remarkable progress in the past 6 decades, our ability to accurately diagnose and estimate the severity of acute pancreatitis remains limited. History provides multiple examples of empiric remedies and surgical interventions based on the prevailing theories and opinions of the scientific luminaries du jour, and indeed, after 3 centuries of inquiry, the most effective interventions for acute pancreatitis are purely supportive in nature and not specific to the pancreas. However, the perseverance of successive generations of the finest scientific minds provides hope that we will unravel the many mysteries of this enigmatic gland.

Distribution and colocalization of cholecystokinin with the prohormone convertase enzymes PC1, PC2, and PC5 in rat brain

During posttranslational processing to generate CCK 8, pro-cholecystokinin (CCK) undergoes endoproteolytic cleavage at three sites. Several studies using endocrine and neuronal tumor cells in culture and recombinant enzymes and synthetic substrates in vitro have pointed to the subtilisin/kexin-like enzymes prohormone convertase (PC) 1, PC2, and PC5 as potential candidates for these endoproteolytic cleavages. In these experimental models, they all appear to be able to cleave pro-CCK to make the correct products. One rodent model has provided information about the role of PC2. PC2 knockout mouse brains had less CCK 8 than wild-type, although a substantial amount of CCK was still present. The degree to which CCK levels were reduced in these mice was regionally specific. These data indicated that PC2 is important for normal production of CCK but that it is not the only endoprotease that is involved in CCK processing. To evaluate whether PC1 and PC5 are possible candidates for the other enzymes involved in CCK processing, the distribution of PC1, PC2, and PC5 mRNA was studied in rat brain. Their colocalization with CCK mRNA was examined using double-label in situ hybridization. PC2 was the most abundant of these enzymes in terms of the intensity and number of cells labeled. It was widely colocalized with CCK. PC1 and PC5 mRNA-positive cells were less abundant, but they were also widely distributed and strongly colocalized with CCK in the cerebral cortex, hippocampus, amygdala, ventral tegmental area, and substantia nigra zona compacta. The degree of colocalization of the enzymes with CCK was regionally specific. It is clear that PC1 and PC5 are extensively colocalized with CCK and could be participating in CCK processing in the rat brain and may be able to substitute for PC2 in its absence. These three enzymes may represent a redundant system to ensure production of biologically active CCK.

Biosynthesis and processing of pro CCK: recent progress and future challenges

Pro Cholecystokinin (CCK) like other prohormones that pass through the regulated secretory pathway, undergoes a number of post-translational modifications during its biosynthesis including tyrosine sulfation, endoproteolytic cleavages, trimming by carboxypeptidase and c-terminal amidation. This minireview summarizes what is known about this process, what specific enzymes are involved in endocrine and neuronal tumor cells and in mutant and knockout mouse strains. It also points out the major challenges that remain for future research.

Isolation and characterization of sulphated and nonsulphated forms of cholecystokinin-58 and their action on gallbladder contraction

Cholecystokinin (CCK) exists in multiple molecular forms with different polypeptide lengths and the absence or presence of sulphation. We have isolated sulphated and nonsulphated forms of CCK-58 from porcine intestine and have determined their bioactivities in a guinea-pig gallbladder contraction assay. Both forms co-eluted in cation-exchange chromatography and in several rounds of reverse-phase (RP)-HPLC, but separated upon RP-HPLC using a water/acetonitrile system with heptafluorobutyric acid as counter ion. Nonsulphated CCK-58 was the form detected by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry because of desulphation in that process. The biological activity of CCK-58 and CCK-33 is equipotent, although the kinetics of the response differ. Sulphated CCK-58 was found to be 35 times more potent than nonsulphated CCK-58. In contrast, sulphated CCK-8 is 150 times more potent than nonsulphated CCK-8, and for sulphated and nonsulphated CCK-33, the activities differ by a factor of 100. This type of correlation indicates that the N-terminal end of CCK-58 partially compensates for the decrease in activity arising from the lack of sulphated tyrosine. Given its fairly high bioactivity, nonsulphated CCK-58 may have a physiological significance.

Effect of some gastrointestinal hormones on antral, small intestinal and caecal myoelectrical activity in the conscious miniature pig

The effect of i.v. infusion of gastrin (CCK-4), cholecystokinin (CCK-8) and pancreatic polypeptide (PP), 20 and 200 ng/kg/min for 1 h, on gastrointestinal electrical activity and arterial pressure was studied in conscious miniature pigs. During infusion of CCK-8 a transient hypertension was observed. In the antrum, the 3 peptides provoked an increase in slow wave activity and a decrease in spike activity. In the intestine, CCK-8 induced an increase in ileal spiking activity, whereas infusion of PP resulted in an increased frequency of long spike bursts in the caecum.

G protein-coupled cholecystokinin-B/gastrin receptors are responsible for physiological cell growth of the stomach mucosa in vivo

Many peptide hormone and neurotransmitter receptors belonging to the seven membrane-spanning G protein-coupled receptor family have been shown to transmit ligand-dependent mitogenic signals in vitro. However, the physiological roles of the mitogenic activity through G protein-coupled receptors in vivo remain to be elucidated. Here we have generated G protein-coupled cholecystokinin (CCK)-B/gastrin receptor deficient-mice by gene targeting. The homozygous mice showed a remarkable atrophy of the gastric mucosa macroscopically, even in the presence of severe hypergastrinemia. The atrophy was due to a decrease in parietal cells and chromogranin A-positive enterochromaffin-like cells expressing the H+,K(+)-ATPase and histidine decarboxylase genes, respectively. Oral administration of a proton pump inhibitor, omeprazole, which induced hypertrophy of the gastric mucosa with hypergastrinemia in wild-type littermates, did not eliminate the gastric atrophy of the homozygotes. These results clearly demonstrated that the G protein-coupled CCK-B/gastrin receptor is essential for the physiological as well as pathological proliferation of gastric mucosal cells in vivo.