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Helicobacter Pylori CagA (helicobacter + pylori_caga)
Selected AbstractsHelicobacter pylori CagA: Analysis of Sequence Diversity in Relation to Phosphorylation Motifs and Implications for the Role of CagA as a Virulence FactorHELICOBACTER, Issue 3 2001Doyle J. Evans Jr Abstract CagA is transported into host target cells and subsequently phosphorylated. Clearly this is a mechanism by which Helicobacter pylori could take control of one or more host cell signal transduction pathways. Presumably the end result of this interaction favors survival of H. pylori, irrespective of eventual damage to the host cell. CagA is noted for its amino acid (AA) sequence diversity, both within and outside the variable region of the molecule. The primary purpose of this review is to examine how variation in the type and number of CagA phosphorylation sites might determine the outcome of infection by different strains of H. pylori. The answer to this question could help to explain the widely disparate results obtained when H. pylori CagA status has been compared to type and severity of disease outcome in different populations, that is in different countries. Analysis of all available CagA sequences revealed that CagA contains both tyrosine phosphorylation motifs (TPMs) and cyclic-AMP-dependent phosphorylation motifs (CPMs). There are two potential CPMs near the N-terminus of CagA and at least two in the repeat region; these are not all equally well conserved. We also defined a 48-residue AA sequence, which includes the N-terminal TPM at tyrosine (Y)-122, which distinguishes between Eastern (Hong Kong-Taiwan-Japan-Thailand) H. pylori isolates and those from the West (Europe-Africa-the Americas-Australia). All 28 of the Eastern type CagA proteins have a functional N-terminal TPM whereas 11 of 47 (23.4%) of the Western type contain an inactive motif, with threonine (T) replacing the critical aspartic acid (D) residue. Only 13 of 24 (54%) known CagA sequences have an active TPM in the repeat region and only one has two TPMs in this region. The potential TPM near the C-terminus of CagA is not likely to be important since only 3 of 24 (12.5%) sequences were found to be intact. Protein database searches revealed that the AA sequence immediately following the TPM at Y-122 in CagA is homologous with a pair of PDZ domains which are common in signal transducing proteins, particularly tyrosine phosphatases. This provides a theoretical link between CagA and many of the observed responses of host cells to H. pylori. In summary, not all CagA proteins are equal in their potential for initiating host cell responses via signal transduction pathways. The degree of functional diversity of this protein depends upon which phosphorylation motifs are critical to the biological activity of CagA. [source] A novel diagnostic monoclonal antibody specific for Helicobacter pylori CagA of East Asian typeAPMIS, Issue 12 2009AIKO YASUDA Molecular biological and epidemiological studies have suggested that Helicobacter pylori producing East Asian CagA protein variant is more virulent than that producing Western CagA. In the present study, we developed and validated an enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody specifically recognizing East Asian CagA-positive H. pylori. A total of 32 H. pylori strains were tested and the data were subjected to receiver-operator characteristic (ROC) curve analysis. The accuracy of the test, determined by calculating the area under the curve, was 0.96, which indicated a high level of accuracy. At the ROC optimized cutoff, the sensitivity and specificity of our ELISA method were 88.0% and 100%, respectively. The validated ELISA showed good performance in terms of sensitivity and specificity. These results suggest that this test is suitable for the diagnostic detection of East Asian CagA carrying strains. We also analyzed the localization of the CagA protein in H. pylori -infected gastric mucosa with fluorescence immunohistochemistry, and found that CagA protein expression was up-regulated by adhesion to epithelial cells. [source] Structural and functional diversity in the PAR1b/MARK2-binding region of Helicobacter pylori CagACANCER SCIENCE, Issue 10 2008Huai-Sheng Lu Helicobacter pylori (H. pylori) cagA -positive strains are associated with gastritis, peptic ulcerations, and gastric adenocarcinoma. Upon delivery into gastric epithelial cells, the cagA -encoded CagA protein specifically binds and aberrantly activates SHP-2 oncoprotein in a manner that is dependent on CagA tyrosine phosphorylation. CagA-deregulated SHP-2 then elicits aberrant Erk activation while causing an elongated cell shape known as the hummingbird phenotype. In polarized epithelial cells, CagA also binds to PAR1b/MARK2 and inhibits the PAR1b kinase activity, thereby disrupting tight junctions and epithelial cell polarity independent of CagA tyrosine phosphorylation. We show here that the CagA-multimerization (CM) sequence that mediates interaction of CagA with PAR1b is not only essential for the CagA-triggered junctional defects but also plays an important role in induction of the hummingbird phenotype by potentiating CagA-SHP-2 complex formation. We also show that the CM sequence of CagA isolated from East Asian H. pylori (referred to as the E-CM sequence) binds PAR1b more strongly than that of CagA isolated from Western H. pylori (referred to as the W-CM sequence). Within Western CagA species, the ability to bind PAR1b is proportional to the number of W-CM sequences. Furthermore, the level of PAR1b-binding activity of CagA correlates with the magnitude of junctional defects and the degree of hummingbird phenotype induction. Our findings reveal that structural diversity in the CM sequence is an important determinant for the degree of virulence of CagA, a bacterial oncoprotein that is associated with gastric carcinogenesis. (Cancer Sci 2008; 99: 2004,2011) [source] Identification of the repeated number of C and D regions of tyrosine phosphorylation motifs in Helicobacter pylori cagA using multiplex PCRMICROBIOLOGY AND IMMUNOLOGY, Issue 10 2008Byungrak An ABSTRACT Various tyrosine phosphorylation motif regions of H. pylori cagA exist. The number of these regions was found to have some influence on cell signaling, which was found to be more pronounced when in D (ESS) region than in C (WSS) region. A molecular biological method with multiplex PCR was developed to distinguish C and D regions, and to identify the repetition number of tyrosine phosphorylation of the cagA gene. Multiplex PCR using novel primer sets was performed on 73 strains of H. pylori isolated from Korean patients with upper gastrointestinal diseases. The Western cagA was identified in only 3 strains (4.1%) whereas East Asia cagA was identified in 69 strains (94.5%). These results were reconfirmed through a sequencing analysis. The method developed in this study would be useful for monitoring the repeated number of C and D regions of tyrosine phosphorylation motifs in H. pylori cagA. [source] | ||||||||||