Studies On Polymorphism In Carboxy-Terminal Sequence Of Helicobacter Pylori CagA And IL-8 Expressions Of The Co-Cultured AGS Cells

Helicobacter pylori(H.pylori) is the main pathogenic factor of chronic gastritis, peptic ulcer and gastric cancer.Patients with serious gastric diseases are usually infected by H.pylori containing cag PAI,Cytotoxin-associated protein A(CagA) coded by cagA participates in a series of signal transductions in host cells and results in inflammatory damage of tissues even canceration on different levels.Patients in the western who suffer from serious gastric disorders are infected by cagA⁺ H.pylori, while 90%patients in East Asian are infected by cagA⁺ HP,the polymorphism of CagA carboxy-terminal sequence among various strains in East Asian leads to diverse clinical endings.The phosphorylation site of CagA exists in the Tyr locating in EPIYA (Glu-Pro-â…¡e-Tyr-Ala) motif,and mainly shows in surrounding sequences and the repetition of EPIYA.Based on the surrounding sequences of EPIYA,H.pylori,all over the world,are divided into Western and East Asian types.The East Asian-type CagA binds to SHP-2 more strongly than the Western-type because of the East Asian SHP-2-binding sequence(ESS),which activates effectively the phosphorylation kinase system in cells.The Western-type CagA contains WSS and shows weak pathogenicity.These facts indicate the function of CagA is different between H.pylori strains in East Asian and Western.Due to largely recombination and variation of H. pylori,conservative regions used by classical typing theory appear deletion and mutation in some cases partially or integrally,which make a challenge to current recognitions about structural characteristics of CagA and the correlative pathogenicity. EPIYA-A and B motifs act inverse feedback to the phosphorylation through suppressant phosphorylated motifs.Certain investigation indicated that the completed EPIYA-B is essential during the expression of pro-inflammator IL-8 in infected host cells.Therefore,the relationship between the polymorphism of H.pylori CagA Cterminal characters and pathogenicity is intricate,expecially among East Asian strains which almost all carry with the CagA.100 C-sequences of H.pylori CagA amplified from Zhejiang strains and other 287 strains submitted in NCBI from all over the world participated in the study,and were implemented the multiple sequence alignment.The result indicated a new potential oligopeptide biomarker which contained 6 to 19 residues,located around the 840^th amino acid residue of CagA and possessed highly conservative surrounding sequences could enhance the validity of H.pylori identification from 80.10%used by classical method to 98.45%,the consistency of two methods reached to 99.44%,and it may be as a characteristic marker in further study of cagA⁺ H.pylori pathogenicity.Furthermore,a Chinese H.pylori isolate carrying EPIYA-A-D,which naturally EPIYA-B absence but showed stronger activity in stimulation of IL-8 expression compared to other Chinese strains and Western 26695,both after co-culture with AGS 4h and 36h.This suggested the IL-8 expression in host cells was independent of EPIYA-B in Chinese H.pylori,which was significantly different from Western strains' correlative mechanism.The Alignment results also indicated CagA multimerization(CM) sequence appeared different characteristics between Western and East Asian H.pylori.