- Open Open Peer Review
A hypothesis of couplet molecules and couplet cells in gastric function and an association with Helicobacter pylori
BMC Gastroenterologyvolume 16, Article number: 16 (2016)
Gastrin, from G-cells, and histamine, from enterochromaffin-like (ECL) cells, are two of the hormones that regulate gastric activity.
It is proposed that the G-cells and the ECL cells are coupled by the couplet molecules gastrin and histamine and by a prior asymmetrical cell division. The gastrin (from G-cells) stimulates the ECL cells to produce and secrete histamine while, in a reciprocal way, this histamine (from ECL cells), stimulates the G-cells to produce and secrete gastrin. These molecules would also stimulate cell division – the gastrin would stimulate cell division of ECL cells while histamine would stimulate that of G-cells. A chemical complex of gastrin and histamine is postulated as is also the asymmetric cell divisions of precursor cells to produce the coupled G-cells and ECL cells.
There is sufficient evidence to support the feasibility of the model in general, but more direct experimental evidence is required to validate the model as applied here to gastric function.
Gastric activity is regulated by various hormones including gastrin and histamine. The hypothesis offered here will tie together the activities of these two hormones and the specific cells that produce them, namely G-cells and enterochromaffin-like (ECL) cells, respectively.
Gastrin is a hormone that is secreted from G-cells which are mainly in the antrum of the stomach and the duodenum, and it stimulates acid secretion by the parietal cells. There are a number of forms of gastrin including ones with 14, 17 or 34 amino acids, perhaps sulphated, amidated or with an additional glycine at the C-terminus. There are a number of potential receptors for gastrin and its related molecules – cholecystokinin (CCK) A, B and C receptors plus other high-affinity receptors. Of these, CCKB binds sulphated gastrin; CCKC is a low-affinity gastrin binding protein; and there are high-affinity receptors selective particularly for amidated gastrin . The major gastrin receptor (CCKB) is a G-protein coupled receptor and is also found in the CNS.
Histamine also acts as a hormone and neurotransmitter. It is produced by enterochromaffin-like (ECL) cells and exerts hormonal control of gastric acidity. It is also produced by mast cells and basophils and triggers an inflammatory response to foreign pathogens. There are four specific types of histamine receptors (H1, H2, H3, H4) and they are 7-transmembrane G-protein coupled receptors . The H2 receptor functions to stimulate gastric acid production by parietal cells.
The model proposed here is an example of a more generic model that has already been proposed as a basis towards an understanding of multicellular organisation and cellular interactions within tissue cells . The base of this model is an initial asymmetric cell division of precursor cells to produce two cell types which share inherent specific cellular communications. Symmetric cell divisions of the two types of cells will produce a mixed cluster of cells with an equilibrium of metabolic processes maintained by control of individual cell activity and of cell numbers. The cell communications are reciprocal and one of the couplet molecules, produced by one cell type, stimulates the growth of the other cell type via a cell receptor. The type and number of cell divisions will be controlled by the levels of the individual molecules and by the level of the complex formed by the couplet molecules. This generic model has been described with specific reference to various diseases including that associated with Helicobacter pylori .
The model has already been further elaborated on for insulin and glucagon as couplet molecules, derived from the beta- and alpha-cells of the pancreas . The model is here specifically interpreted to the G-cells and the neighbouring ECL cells and their stimulation by histamine and gastrin respectively where these coupled molecules are produced by the couplet cells reciprocally. The model requires that a special molecule (a Trefone) will be both a proliferator and a secretagogue of the same cell type. For example, gastrin may be such a molecule as it is a potent gastrointestinal trophic agent acting as a growth factor to induce cell proliferation and is also a histamine secretory agent .
Evidence required to support the model in gastric function
The model proposed in reference  has Couplet molecules (“Trefones”) produced by couplet Cells and is referred to as the CTC model. The couplet cells produced by the asymmetric cell division of a precursor cell are referred to as the a-Cell and the i-Cell. Gastrin and histamine would be Trefone couplets - two interacting, cell-stimulating molecules produced by couplet cells that form a complex described in the generic model as a “Trefone Couplet Complex” This couplet complex (TCC), together with the individual molecules, control cell division. The G-Cell and the ECL cell are the cell couplets and, arbitrarily in this proposal, the G-cell is the a-Cell which produces gastrin (aT) and the ECL cell is the i-Cell which produces histamine (iT). Reciprocal receptors are indicated in Fig. 1.
Thus for the proposed couplet cells (G-cells and ECL cells) with a molecular couplet of gastrin and histamine, the following would be expected:-
Gastrin binds histamine to form a complex.
G-cells have receptors for histamine.
Histamine normally stimulates proliferation of G-cells.
Histamine inhibits proliferation of G-cells when both histamine and gastrin are high.
Histamine stimulates production/secretion of gastrin by G-cells.
ECL cells have receptors for gastrin.
Gastrin normally stimulates proliferation of ECL cells.
Gastrin inhibits proliferation of ECL cells when both gastrin and histamine are high.
Gastrin stimulates production/secretion of histamine by ECL cells.
G-cells and ECL cells each have a receptor for the gastrin: histamine complex.
Evidence to support this model is offered.
(1) Gastrin (GAS) binds Histamine (HTM)
There is no evidence for this, known to be recorded. Were studies to be conducted to assess this potential binding, all of the five active forms of gastrin would need to be considered to discover the actual couplet of histamine (ie. the Trefone). Progastrin, the C-terminal Gly-extended gastrins (G34-Gly and G17-Gly) and the C-terminal amidated gastrins (G34 and G17), all have some biological activity .
(2) (i) G-Cells have receptors for Histamine
Rabbit G-cells have HTM H2-receptors  and the cells release gastrin upon HTM stimulation. This receptor would function in a different way in G-cells compared to H2-receptors in parietal cells where the receptor, with HTM bound, stimulates acid production.
(ii) Histamine stimulates proliferation of G-Cells
HTM stimulates proliferation of a human gastric adenocarcinoma subline (MKN45G) which itself produces GAS and which therefore could be a model for G-cells . HTM also increased the proliferation of grafted MKN45G tumour tissue in nude mice . HTM it is also known to be a proliferative stimulant for some other cells (eg. airway smooth muscle cells , cultured rat thymic epithelium cells  and a Leydig cancer cell line ).
(iii) Histamine inhibits proliferation of G-Cells
HTM is not known to be an inhibitor of G-cells but it is an inhibitor for other cells (eg. colorectal , pancreatic carcinoma cells ). For the latter, HTM concentrations higher than 1 μmol · L−1 inhibited clonogenic growth but nanomolar HTM doses stimulated cell proliferation  Within the CTC model, HTM would inhibit proliferation of G-cells when both HTM and gastrin are high but such experiments have not been reported for G-cells.
(iv) Histamine stimulates production of Gastrin by G-Cells
HTM stimulates release of GAS from G-cells via H2-receptors, as was previously noted .
(3) (i) ECL cells have receptors for Gastrin
(ii) Gastrin stimulates proliferation of ECL Cells
GAS stimulates the proliferation rate of both ECL cells and of stem cells in the oxyntic mucosal progenitor zone of the rat stomach [17, 18]. GAS also induces ECL cell proliferation in cell culture  and it has a specific proliferative effect on rat ECL cells . Amidated gastrin causes increased proliferation of ECL cells in the oxyntic mucosa of the stomach of mice . Antrectomy in rats causes atrophy of the oxyntic gland mucosa .
(iii) Gastrin inhibits proliferation of ECL cells when [GAS] and (HTM] are high
GAS inhibition of ECL cells is not recorded but GAS does inhibit proliferation of colon cancer cells  although the level of HTM is not known here.
(iv) Gastrin stimulates production of HTM by ECL Cells
Gastrin stimulates the synthesis of HTM [24, 25] and GAS stimulates the release of histamine from gastric ECL cells in cell culture  and from rabbit fundic mucosal cells enriched in ECL cells . (That GAS stimulates acid production by parietal cells is independent of the proposed model.)
(4) The G-cells and ECL cells would each have a receptor for the gastrin:histamine complex.
GAS has four cell receptors with variable binding to gastrin variants  and one could possibly bind a gastrin:histamine complex (TCC). Similarly, HTM also has four (H1, H2, H3 and H4) receptors  and one could possibly bind the TCC.
In this model, gastrin and histamine are stimulants (Trefones) of the ECL cells and the G-cells, respectively. Each cell, via the Trefone it produces, has a stimulating effect on the cell activity and on the cell division of the couplet cell. For example, gastrin stimulates the activity of the ECL cells and stimulates the proliferation rate of both ECL cells and stem cells . An activated ECL cell becomes a hypertrophic cell within a week of exposure to high levels of gastrin and the cell division rate is maximal after about 10 days of hypergastrinemia . Indeed, the histamine-releasing and the trophic effects of gastrin may be mediated via the same gastrin receptor .
With adequate nutrients, each Trefone will initially stimulate the recipient cells to produce more of the couplet stimulant and grow in size if necessary. Further, each cell, sustained with adequate nutrients and other growth enhancers will gain competence to progress to cell division and to divide symmetrically or asymmetrically, dependent on the level of the Trefones. In the current model, whether a cell divides and the type of division is contingent on the concentration of the gastrin:histamine complex. The calculated data relevant to this contingency is tabulated in Additional File Six of reference . As an example, if the ECL cell detects a low level of free gastrin, then the response depends on the concentration of the complex of gastrin:histamine. A low, medium or high concentration of complex would signal underactive, duly active or overactive status of the ECL cell itself which has produced low, medium and high levels of total histamine respectively. The cell then has a measure of the amount of histamine relative to the amount of gastrin to allow a decision on whether the two hormones (and their source cells) are in harmony or not. If there is a sustained imbalance, a cellular decision, for each cell type, may then be to divide symmetrically, asymmetrically or with dedifferentiation or with transdifferentiation, as appropriate to bring the G-cells and ECL cells back into harmony. Apoptosis is also possible . Gastrin can induce apoptosis in gastric epithelial cells and this contributes to the development of gastric carcinogenesis .
One possible means by which the cells could measure the gastrin:histamine complex would be to have cell membrane receptors for the complex. This is illustrated in Fig. 2 . The existence of a membrane receptor is not integral to this hypothesis but there needs to be some intracellular mechanism to measure the level of complex .
Once internalised, a component or a signal derived from (i) the gastrin, its receptor and/or the couplet complex in ECL cells or (ii) the histamine, its receptor and/or the couplet complex in G-cells would need to localise to the nucleus to affect gene expression and cell division.
Note that these simple reciprocal interactions are seen to be just a part of a number of potential cellular interactions that produce the complexity of this gastric area.
The binding of gastrin and histamine to produce a complex – for investigation
A metal ion may be involved in the binding of gastrin and histamine.
Zinc forms a complex with histamine and zinc-histamine-aspartate and zinc-histamine-glutamate complexes are formed with the respective dicarboxylic acids . Within gastrin (of perhaps 17 amino-acid residues), there are five glutamate residues, in positions 6 to 10, so that a zinc complex with histamine and gastrin is conceivable, given that gastrin binds both divalent and trivalent metal ions . Further, gastrin forms a ternary complex with albumin and various metal ions, and the highest association constant is with zinc .
Iron could also be involved in a ternary complex. Ferric ions are essential for the biological activity of gastrin (glycine-extended) . Indeed, gastrin binds two ferric ions with high affinity and the glutamate residues of gastrin are involved in the binding of both of these atoms of iron . That it is this ferric complex which is active as a stimulant to proliferation of colonic mucosa , may need to be considered. In addition, histamine binds FeIII heme proteins, in particular nitrophorin , wherein an aspartate stabilises the complex .
Location of cells and paracrine or endocrine communication
It is generally considered that the ECL cells have no close contact with G-cells. The usual description of the location of these cells is that G-cells are in the antrum and ECL cells are in the corpus/body of the stomach (but accepted to be in the lower third of this area close to the G-cells).
But there is unlikely to be a sharply-defined boundary between the cells in these areas and there is evidence for an overlap or mixed zone of ECL cells and G-cells. G-cells have been mmunocytochemically identified in the antral zone of the rat  and gastrin expression has been co-localized with the expression of histidine decarboxylase, an ECL cell marker, in a subset of histaminergic gastric mucosal cells .
Gastrin and histamine could interact with the coupling cell via a short diffusion if the cells shared a common location or by more direct cellular contact possibly via cytoplasmic processes [39, 40]. Over larger separatory distances, diffusion directed by microanatomy  or either microcirculatory or endocrine transport allow interaction of the molecules with the cells.
The relationship of this model of gastric function to Helicobacter pylori
H. pylori could be involved in gastric function in two ways which are compatible with the proposed model. One could be by (a) an oncoprotein virulence factor (CagA), the other by (b) a histamine receptor agonist (methyl histamine).
One virulence factor of H. pylori is the oncoprotein cytotoxin-associated antigen A (CagA). Overexpressed CagA affects various intracellular pathways and is sufficient by itself to induce gastric cancer and other malignancies in transgenic mice .
One mechanism of tumour initiation could involve the specific interaction of CagA with PAR1/MARK kinase . This binding inhibits the kinase activity which is necessary for microtubule stabilisation and consequent epithelial cell polarity  and also deregulates SHP-2 phosphatase, an oncoprotein associated with growth regulation and malignancies . Thus CagA affects polarity and subsequent intercellular interactions and alters kinase/phosphatase reactions which could alter cell growth. Gastric carcinogenesis could be due to abnormal proliferation of epithelial cells associated with earlier CagA-induced abnormal intestinal transdifferentiation of cells to produce intestinal metaplasia as an early stage of gastric cancer  In addition, PAR1/MARK kinase is one of the six par genes necessary for the asymmetric division of the zygote of C. Elegans  and these protein kinases are evolutionarily conserved from yeast to humans. If CagA-induced kinase inhibition prevents asymmetric cell division (AsCD) or causes an aberrant AsCD, then the homeostasis of the couplet cells (G-cells and ECL cells) could be disrupted and abnormal proliferation could ensue. In addition, epigenetic alterations (DNA methylations and histone modifications) induced by H. pylori, could contribute to cancer development . However, although this relationship between H. pylori infection and gastric cancer is established, knowledge of the exact mechanism of tumor initiation is lacking .
Within the model proposed here, the mechanism of metaplasia and cancer would be via abnormal AsCD of precursor cells producing abnormal types and/or numbers of G-cells and/or ECL cells. Excess of histamine and/or gastrin or the presence of aberrant/mutated receptor molecules or of molecules which translate the messages of the couplet molecules, would be part of the mechanism.
In addition to CagA, H. Pylori produces N-alpha-methyl histamine (NAMH) , which stimulates H3-histamine receptors in gastric mucosa [7, 50] and which stimulates gastrin release from rabbit G-cells via H2- histamine receptors .
Within the model proposed here, there are two possibilities:-
If NAMH forms a complex with gastrin, then, with an unregulated supply of NAMH from H.pylori, there would be maximal continuous stimulation of gastrin release and of G-cell proliferation. Because of the high level of NAMH, there would be little local free gastrin to stimulate ECL cells. In summary there would be a large numbers of G-cells but few ECL cells. The G-cells may be abnormal if the cell divisions, especially transdifferentiations, are affected by CagA. Gastrin that enters the blood may stimulate hyperacidity of the stomach via the parietal cells.
If NAMH does not form a complex with gastrin, then there would be a large production of gastrin initially with an associated strong stimulation of histamine release and of ECL cell proliferation. But with a high level of the gastrin:histamine complex, then both cell types would tend to reduce secretion and cell division except that the NAMH would still stimulate the G-cells. Again, CagA may adversely affect cell divisions and transdifferentiation. Histamine, released from mast cells recruited by the H. pylori infection , may exacerbate this disturbance from normal cell divisions.
A model is proposed involving asymmetric cell division which produces G-cells and ECL cells which communicate to each other via the secreted couplet molecules of gastrin and histamine. Each will stimulate the cell that it is not secreted from, to stimulate the other cell to secrete more of the couplet molecule and, if this response is inadequate, to stimulate cell division in order to maintain a fixed ratio of gastrin:histamine as assessed by the level of the complex formed by the couplet molecules. Abnormal cell division in Helicobacter infection could be part of the cause of cancer in some cases of this infection.
Couplet Complex of Gastrin and Histamine
Couplet Trefones and Cells
Yassin RR. Signaling pathways mediating gastrin’s growth-promoting effects. Peptides. 1999;20(7):885–98.
Panula P, Chazot PL, Cowart M, Gutzmer R, Leurs R, Liu WL, et al. International union of basic and clinical pharmacology. XCVIII. Histamine receptors. Pharmacol Rev. 2015;67(3):601–55.
Craven CJ. A model to explain specific cellular communications and cellular harmony:- a hypothesis of coupled cells and interactive coupling molecules. Theor Biol Med Model. 2014;11:40.
Craven CJ. Alpha- and beta-cell proliferation and extracellular signaling - a hypothesis. Int J Diabetes Clin Res. 2015;2(2):6.
Kidd M, Modlin IM, Tang LH. Gastrin and the enterochromaffin-like cell: an acid update. Dig Surg. 1998;15(3):209–17.
Dockray GJ, Varro A, Dimaline R, Wang T. The gastrins: their production and biological activities. Annu Rev Physiol. 2001;63:119–39.
Bliss PW, Healey ZV, Arebi N, Calam J. Nalpha-methyl histamine and histamine stimulate gastrin release from rabbit G-cells via histamine H2-receptors. Aliment Pharmacol Ther. 1999;13(12):1669–74.
Watson SA, Wilkinson LJ, Robertson JF, Hardcastle JD. Effect of histamine on the growth of human gastrointestinal tumours: reversal by cimetidine. Gut. 1993;34(8):1091–6.
Panettieri RA, Yadvish PA, Kelly AM, Rubinstein NA, Kotlikoff MI. Histamine stimulates proliferation of airway smooth muscle and induces c-fos expression. Am J Physiol. 1990;259(6 Pt 1):L365–371.
Head GM, Mentlein R, von Patay B, Downing JE, Kendall MD. Neuropeptides exert direct effects on rat thymic epithelial cells in culture. Dev Immunol. 1998;6(1-2):95–104.
Pagotto RM, Monzon C, Moreno MB, Pignataro OP, Mondillo C. Proliferative effect of histamine on MA-10 Leydig tumor cells mediated through HRH2 activation, transient elevation in cAMP production, and increased extracellular signal-regulated kinase phosphorylation levels. Biol Reprod. 2012;87(6):150.
Suonio E, Tuomisto L, Alhava E. Effects of histamine, H1, H2 and Hic receptor antagonists and alpha-fluoromethylhistidine on the growth of human colorectal cancer in the subrenal capsule assay. Agents Actions. 1994;41 Spec No:C118–120.
Cricco G, Martin G, Labombarda F, Cocca C, Bergoc R, Rivera E. Human pancreatic carcinoma cell line Panc-I and the role of histamine in growth regulation. Inflamm Res. 2000;49 Suppl 1:S68–69.
Medina VA, Rivera ES. Histamine receptors and cancer pharmacology. Br J Pharmacol. 2010;161(4):755–67.
Modlin IM, Tang LH. The gastric enterochromaffin-like cell: an enigmatic cellular link. Gastroenterology. 1996;111(3):783–810.
Kulaksiz H, Arnold R, Goke B, Maronde E, Meyer M, Fahrenholz F, et al. Expression and cell-specific localization of the cholecystokinin B/gastrin receptor in the human stomach. Cell Tissue Res. 2000;299(2):289–98.
Ryberg B, Tielemans Y, Axelson J, Carlsson E, Hakanson R, Mattson H, et al. Gastrin stimulates the self-replication rate of enterochromaffinlike cells in the rat stomach. Effects of omeprazole, ranitidine, and gastrin-17 in intact and antrectomized rats. Gastroenterology. 1990;99(4):935–42.
Brenna E, Waldum HL. Trophic effect of gastrin on the enterochromaffin like cells of the rat stomach: establishment of a dose response relationship. Gut. 1992;33(10):1303–6.
Prinz C, Scott DR, Hurwitz D, Helander HF, Sachs G. Gastrin effects on isolated rat enterochromaffin-like cells in primary culture. Am J Physiol. 1994;267(4 Pt 1):G663–675.
Bakke I, Qvigstad G, Brenna E, Sandvik AK, Waldum HL. Gastrin has a specific proliferative effect on the rat enterochromaffin-like cell, but not on the parietal cell: a study by elutriation centrifugation. Acta Physiol Scand. 2000;169(1):29–37.
Koh TJ, Chen D. Gastrin as a growth factor in the gastrointestinal tract. Regul Pept. 2000;93(1-3):37–44.
Dembinski AB, Johnson LR. Role of gastrin in gastrointestinal adaptation after small bowel resection. Am J Physiol. 1982;243(1):G16–20.
Song LJ, Liu RJ, Zeng Z, Alper SL, Cui HJ, Lu Y, et al. Gastrin inhibits a novel, pathological colon cancer signaling pathway involving EGR1, AE2, and P-ERK. J Mol Med (Berl). 2012;90(6):707–18.
Dimaline R, Sandvik AK. Histidine decarboxylase gene expression in rat fundus is regulated by gastrin. FEBS Lett. 1991;281(1-2):20–2.
Sandvik AK, Dimaline R, Marvik R, Brenna E, Waldum HL. Gastrin regulates histidine decarboxylase activity and mRNA abundance in rat oxyntic mucosa. Am J Physiol. 1994;267(2 Pt 1):G254–258.
Hollande F, Combettes S, Bali JP, Magous R. Gastrin stimulation of histamine synthesis in enterochromaffin-like cells from rabbit fundic mucosa. Am J Physiol. 1996;270(3 Pt 1):G463–469.
Hakanson R, Chen D, Andersson K, Monstein HJ, Zhao CM, Ryberg B, et al. The biology and physiology of the ECL cell. Yale J Biol Med. 1994;67(3-4):123–34.
Cui G, Takaishi S, Ai W, Betz KS, Florholmen J, Koh TJ, et al. Gastrin-induced apoptosis contributes to carcinogenesis in the stomach. Lab Invest. 2006;86(10):1037–51.
Berthon G, Germonneau P. Histamine as a ligand in blood plasma. Part 6. Aspartate and glutamate as possible partner ligands for zinc and histamine to favour histamine catabolism. Agents Actions. 1982;12(5-6):619–29.
Baldwin GS. A new role for an old hormone: is gastrin a cofactor for dietary metal ion uptake? Med Hypotheses. 1992;38(1):70–4.
Mann RJ, Howlett GJ, Baldwin GS. Metal ion-dependent binding of gastrin to albumin. Arch Biochem Biophys. 1991;291(2):311–5.
Baldwin GS, Curtain CC, Sawyer WH. Selective, high-affinity binding of ferric ions by glycine-extended gastrin(17). Biochemistry. 2001;40(36):10741–6.
Pannequin J, Barnham KJ, Hollande F, Shulkes A, Norton RS, Baldwin GS. Ferric ions are essential for the biological activity of the hormone glycine-extended gastrin. J Biol Chem. 2002;277(50):48602–9.
Koh TJ, Dockray GJ, Varro A, Cahill RJ, Dangler CA, Fox JG, Wang TC. Overexpression of glycine-extended gastrin in transgenic mice results in increased colonic proliferation. J Clin Invest. 1999;103(8):1119–26.
Ribeiro JM, Walker FA. High affinity histamine-binding and antihistaminic activity of the salivary nitric oxide-carrying heme protein (nitrophorin) of Rhodnius prolixus. J Exp Med. 1994;180(6):2251–7.
Weichsel A, Andersen JF, Champagne DE, Walker FA, Montfort WR. Crystal structures of a nitric oxide transport protein from a blood-sucking insect. Nat Struct Biol. 1998;5(4):304–9.
Hunyady B, Zolyomi A, Hoffman BJ, Mezey E. Gastrin-producing endocrine cells: a novel source of histamine in the rat stomach. Endocrinology. 1998;139(10):4404–15.
Walker AK, Park WM, Chuang JC, Perello M, Sakata I, Osborne-Lawrence S, et al. Characterization of gastric and neuronal histaminergic populations using a transgenic mouse model. PLoS One. 2013;8(3):e60276.
Larsson LI, Goltermann N, de Magistris L, Rehfeld JF, Schwartz TW. Somatostatin cell processes as pathways for paracrine secretion. Science. 1979;205(4413):1393–5.
Bohorquez DV, Liddle RA. Axon-like basal processes in enteroendocrine cells: characteristics and potential targets. Clin Transl Sci. 2011;4(5):387–91.
Denef C. Paracrinicity: the story of 30 years of cellular pituitary crosstalk. J Neuroendocrinol. 2008;20(1):1–70.
Ohnishi N, Yuasa H, Tanaka S, Sawa H, Miura M, Matsui A, et al. Transgenic expression of Helicobacter pylori CagA induces gastrointestinal and hematopoietic neoplasms in mouse. Proc Natl Acad Sci U S A. 2008;105(3):1003–8.
Saadat I, Higashi H, Obuse C, Umeda M, Murata-Kamiya N, Saito Y, et al. Helicobacter pylori CagA targets PAR1/MARK kinase to disrupt epithelial cell polarity. Nature. 2007;447(7142):330–3.
Lu H, Murata-Kamiya N, Saito Y, Hatakeyama M. Role of partitioning-defective 1/microtubule affinity-regulating kinases in the morphogenetic activity of Helicobacter pylori CagA. J Biol Chem. 2009;284(34):23024–36.
Hatakeyama M. Linking epithelial polarity and carcinogenesis by multitasking Helicobacter pylori virulence factor CagA. Oncogene. 2008;27(55):7047–54.
Suzuki A, Ohno S. The PAR-aPKC system: lessons in polarity. J Cell Sci. 2006;119(Pt 6):979–87.
Ding SZ, Goldberg JB, Hatakeyama M. Helicobacter pylori infection, oncogenic pathways and epigenetic mechanisms in gastric carcinogenesis. Future Oncol. 2010;6(5):851–62.
Ding SZ, Zheng PY. Helicobacter pylori infection induced gastric cancer; advance in gastric stem cell research and the remaining challenges. Gut Pathog. 2012;4(1):18.
Courillon-Mallet A, Launay JM, Roucayrol AM, Callebert J, Emond JP, Tabuteau F, et al. Helicobacter pylori infection: physiopathologic implication of N alpha-methyl histamine. Gastroenterology. 1995;108(4):959–66.
Saitoh T, Fukushima Y, Otsuka H, Ishikawa M, Tamai M, Takahashi H, et al. Effects of N-alpha-methyl-histamine on human H(2) receptors expressed in CHO cells. Gut. 2002;50(6):786–9.
The author declares that he has no competing interests.
Retired Lecturer/Scientist from the Queensland University of Technology, Brisbane. Australia.