Modulation of the cleavage of the gastrin precursor by prohormone phosphorylation

Bishop, L.A.; Dimaline, R.; Blackmore, Colin G.; Deavall, Damian G.; Dockray, Graham J.; Varró, Andrea

doi:10.1016/s0016-5085(98)70086-1

Cited by 29 publications

(20 citation statements)

References 37 publications

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“…Thirdly, the Ca 2ϩ ion might enhance the solubility of progastrin, as has been reported previously for the binding of Zn 2ϩ ions to proinsulin (32). Fourthly, the Ca 2ϩ ion might redirect the processing of progastrin by preventing cleavage at some dibasic sites, in the same way that phosphorylation of Ser 75 prevents cleavage of the Arg 73 -Ser 74 bond (33). The observation that the calcium remained bound to progastrin even after extensive dialysis at pH 5.5 (data not shown), which is the pH within the secretory granule where processing occurs (34), is consistent with a role in processing.…”

Section: Discussionmentioning

confidence: 69%

Biologically Active Recombinant Human Progastrin6–80Contains a Tightly Bound Calcium Ion

Baldwin

Hollande

Yang

et al. 2001

Journal of Biological Chemistry

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Evidence is accumulating that gastrin precursors may act as growth factors for the colonic mucosa in vivo. The aims of this study were to prepare recombinant human progastrin 6 -80 and to investigate its structure and biological activities in vitro. Human progastrin 6 -80 was expressed in Escherichia coli as a glutathione S-transferase fusion protein. After thrombin cleavage progastrin 6 -80 was purified by reverse phase high pressure liquid chromatography and characterized by radioimmunoassay, amino acid sequencing, and mass spectrometry. Assays for metal ions by atomic emission spectroscopy revealed the presence of a single tightly bound calcium ion. Progastrin 6 -80 at concentrations in the pM to nM range stimulated proliferation of the conditionally transformed mouse colon cell line YAMC. The observations that progastrin 6 -80 did not bind to either the cholecystokinin (CCK)-A or the gastrin/CCK-B receptor expressed in COS cells and that antagonists selective for either receptor did not reverse the proliferative effects of progastrin 6 -80 suggested that progastrin 6 -80 stimulated proliferation independently of either the CCK-A or the gastrin/CCK-B receptor. We conclude that recombinant human progastrin 6 -80 is biologically active and contains a single calcium ion. With the exception of the well known zinc-dependent polymerization of insulin and proinsulin, this is the first report of selective, high affinity binding of metal ions to a prohormone.

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Section: Discussionmentioning

confidence: 69%

Biologically Active Recombinant Human Progastrin6–80Contains a Tightly Bound Calcium Ion

Baldwin

Hollande

Yang

et al. 2001

Journal of Biological Chemistry

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“…Phosphorylation of ACTH in primary anterior pituitary lobe cultures is unaffected by cell stimulation (47). Phosphorylation of a gastrin precursor has been shown to modulate its rate of cleavage (56); in this peptide, the phosphoserine is present in close proximity to a known convertase cleavage site. A similar situation may apply to the 7B2 C-terminal peptide, although, in this instance, the phosphoserine is located six residues C-terminal to the known furin cleavage site (46).…”

Section: Discussionmentioning

confidence: 99%

Neuroendocrine Protein 7B2 Can Be Inactivated by Phosphorylation within the Secretory Pathway

Lee

Hwang

Lindberg

2006

Journal of Biological Chemistry

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The prohormone convertases play important roles in the maturation of neuropeptides and peptide hormone precursors. Prohormone convertase-2 (PC2) is the only convertase that requires the expression of another neuroendocrine protein, 7B2, for expression of enzyme activity. In this study, we determined that 7B2 can be phosphorylated in Rin cells (a rat insulinoma cell line) and cultured chromaffin cells, but not in AtT-20 cells (derived from mouse anterior pituitary). Phosphoamino acid analysis of Rin cell 7B2 indicated the presence of phosphorylated serine and threonine. Phosphorylation of Ser 115 (located within the minimally active 36-residue peptide) was confirmed by mutagenesis, although Ser 115 did not represent the sole residue phosphorylated. Two independent assays were used to investigate the effect of phosphorylated 7B2 on PC2 activation: the ability of 7B2 to bind to pro-PC2 was assessed by co-immunoprecipitation, and activation of pro-PC2 was assessed in a cell-free assay. Phosphorylated 7B2 was unable to bind pro-PC2, and the phosphorylated 7B2 peptide (residues 86 -121, known to be the minimally active peptide for pro-PC2 activation) was impaired in its ability to facilitate the generation of PC2 activity in membrane fractions containing pro-PC2. In vitro phosphorylation experiments using Golgi membrane fractions showed that 7B2 could be phosphorylated by endogenous Golgi kinases. Golgi kinase activity was strongly inhibited by the broad-range kinase inhibitor staurosporine and partially inhibited by the protein kinase C inhibitor bisindolylmaleimide I, but not by the other protein kinase A, Ca 2؉ /calmodulin-dependent kinase II, myosin light chain kinase, and protein kinase G inhibitors tested. We conclude that phosphorylation of 7B2 functionally inactivates this protein and suggest that this may be analogous to the phosphorylating inactivation of BiP, which impairs its ability to bind substrate.Prohormone convertase-2 (PC2), 2 a member of the family of eukaryotic subtilisins, exhibits an interesting but atypical cell biology compared with other convertases. The PC2 zymogen spends an unusually long time in the endoplasmic reticulum (ER) compared with other convertases and then binds to a partner protein, 7B2, which escorts it to the Golgi (1, 2). In the Golgi, a 7B2-mediated "capacitation" process renders pro-PC2 capable of autoactivation to an active enzyme molecule (reviewed in Ref. 3). Pro-PC2 expressed in cells lacking 7B2 (such as Chinese hamster ovary (CHO) cells) may still undergo propeptide cleavage, but in this case, propeptide removal does not result in the production of enzymatically active species (4). The biochemical mechanism underlying the 7B2 capacitation effect is still enigmatic: however, it can be reproduced in a cell-free environment using Golgi membranes (5). Our current hypothesis is that 7B2 prevents pro-PC2 aggregation and/or facilitates its binding to membranes during intracellular transit. Structure-function studies have revealed that the minimal portion of 7B2 required to e...

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“…Another cleavage by prohormone convertases at Lys 74 -Lys 75 gives G17-Gly [39–41]. Various factors within the secretory vesicles modify these cleavages, including the differential expression of PC1/3 and PC2 and the pH of the vesicle interior (pH > 5.5 may inhibit the maturation of prohormone convertases) [41, 44–46]. …”

Section: Gastrin Processing In the Gi Tractmentioning

confidence: 99%

“…Sulfation and phosphorylation may both increase processing of progastrin [44, 46], while phosphorylation may also affect the conversion of glycine-extended gastrin intermediates to mature gastrins [47]. …”

Section: Gastrin Processing In the Gi Tractmentioning

confidence: 99%

The Production and Role of Gastrin-17 and Gastrin-17-Gly in Gastrointestinal Cancers

Copps

Murphy

Lovas³

2009

PPL

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The gastrointestinal peptide hormone gastrin is responsible for initiating the release of gastric acid in the stomach in response to the presence of food and/or humoral factors such as gastrin releasing peptide. However, it has a role in the growth and maintenance of the gastric epithelium, and has been implicated in the formation and growth of gastric cancers. Hypergastrinemia resulting from atrophic gastritis and pernicious anemia leads to hyperplasia and carcinoid formation in rats, and contributes to tumor formation in humans. Additionally, gastrin has been suspected to play a role in the formation and growth of cancers of the colon, but recent studies have instead implicated gastrin processing intermediates, such as gastrin-17-Gly, acting upon a putative, non-cholecystokinin receptor. This review summarizes the production and chemical structures of gastrin and the processing intermediate gastrin-17-Gly, as well as their activities in the gastrointestinal tract, particularly the promotion of colon cancers. Gastrin processing in the GI tractJohn Sydney Edkins postulated in 1905 [1][2] that the acid secretory activity of the stomach could be attributed to the agent gastrin. The gastrin gene is expressed and gastrin secreted in a variety of cells in the body, among them those of the small and large intestine (duodenal, jejunal, ileal, and colonic mucosas), the pancreas, neuroendocrine tissue (the pituitary and hypothalamus, cerebellum, vagal nerve, and adrenal medulla), the genitals and the respiratory tract, where it serves a variety of purposes [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, "mature" gastrin is predominantly manufactured by the antral mucosa of the stomach, where G endocrine cells secrete the peptide in response to the presence of amino acids, dietary amines, and calcium in the stomach, for the purpose of stimulating gastric acid secretion [19-25, reviewed in 26]. Neutralization of acid or inhibition of acid secretion also stimulates gastrin release [27][28][29][30][31][32][33]. In addition to luminal stimuli, basolateral stimuli of the G cells by GRP or Ach from nerve fibers, or by humoral factors such as EGF, also cause the expression and secretion of gastrin in some species [34][35]. In response to increased acid levels or VIP, D endocrine cells, in turn, secrete somatostatin, which acts to inhibit the secretion of gastrin.The expression of the gastrin gene and the processing of its polypeptide product in the gastrointestinal tract have been gradually revealed through extraction from gastrin-producing tissues and characterization of its processing intermediates with antibodies, chromatography and peptide analysis tools such as mass spectrometry. Genomic DNA information revealed the gastrin gene structure. The mRNA of the 101-residue gastrin precursor preprogastrin is translated at the endoplasmic reticulum, where an N-terminal signaling sequence is cleaved *Corresponding author: Sándor Lovas, Department of Biomedical Sciences, Creighton University School of Medi...

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Modulation of the cleavage of the gastrin precursor by prohormone phosphorylation

Cited by 29 publications

References 37 publications

Biologically Active Recombinant Human Progastrin6–80Contains a Tightly Bound Calcium Ion

Biologically Active Recombinant Human Progastrin6–80Contains a Tightly Bound Calcium Ion

Neuroendocrine Protein 7B2 Can Be Inactivated by Phosphorylation within the Secretory Pathway

The Production and Role of Gastrin-17 and Gastrin-17-Gly in Gastrointestinal Cancers

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