Interestingly, GST-CagY, but not the other GST fusion proteins, bound more efficiently when the integrins were activated by Mn2+
Interestingly, GST-CagY, but not the other GST fusion proteins, bound more efficiently when the integrins were activated by Mn2+. gastric pathologies is the CagA protein. This protein is directly injected into host cells through the Cag Type IV Secretion System ((that have been associated with disease induction are the vacuolating cytotoxin (VacA) and the cytotoxin-associated antigen A (CagA), both of which are delivered into eukaryotic target cells. VacA, a secreted multifunctional protein toxin, induces intracellular vacuoles in epithelial cells, inhibits T lymphocyte proliferation and modulates T cell function [reviewed in 2]. Using the 2 2 integrin subunit CD18 as a cellular receptor for uptake , VacA efficiently down-regulates transcription of several cytokines or chemokines in T cells . CagA, an immunodominant protein of 120C170 kDa, is usually encoded around the pathogenicity island (strains is usually their ability to induce the secretion of chemokines upon contact with epithelial cells, such as interleukin-8 (IL-8) . The function of each strains harbour membrane protrusions consisting of a central filament, carrying on its surface the pilus-associated adhesin CagL . Integrins represent a family of about 24 different heterodimeric receptors that mediate cell-cell, cell-extracellular matrix and cell-pathogen interactions and govern migration and anchorage of almost all kinds of cells. Each of the non-covalently associated subunits contains a large N-terminal extracellular domain name, a transmembrane segment and a short C-terminal cytoplasmic tail. Affinity for biological ligands is regulated by inside-out and outside-in signalling. The bent conformation of the integrin heterodimer represents the physiological low-affinity state, whereas insideCout signalling and ligand binding induces a large-scale conformational rearrangement, in which the integrin extends from the bent into an extended, open conformation . T4SS-pilus-associated CagL was suggested to bind via its arginine-glycine-aspartate (RGD) motif to 51 integrin, a process described as essential for CagA translocation and activation of focal adhesion kinase (FAK) and Src kinase . In the present study we show that further components of the translocates its effector protein CagA via the T4SS-pilus-associated protein CagL, binding in an RGD-dependent way to 51 integrin around the host cell . However, nothing is known about the mechanism of CagA translocation and the involvement of other T4SS components in this process. Using a different approach, we also identified 1 integrin as a cellular receptor for the strains (P12, P145, P217) were applied Senktide to study host cell requirements for CagA translocation using several human and animal cell lines (data not shown). Of special interest were human promyelocytic leukaemia (HL60) cells, which were fully qualified for CagA translocation (Physique 1A, lanes 1C3 and 7), whereas, HL60 cells differentiated to a granulocyte-like phenotype (dHL60 cells) revealed only a very weak CagA-P signal (Physique 1A, lanes 4C6 and 8). Thus, the capacity of to translocate CagA varies considerably, even for the same type Senktide of cell, dependent on its cellular differentiation stage. Flow cytometry revealed elevated 2, but significantly reduced 1 integrin levels on the surface of dHL60, as compared to HL60 cells (Physique 1C). We therefore concentrated on 1 integrin as a potential receptor for the T4SS. CagA translocation was completely absent for epithelial (GE11) or fibroblast-like (GD25) 1 integrin knockout cells, but was functional in genetically complemented GE11 or GD25 cells (Physique 1B) . In agreement with Kwok et Nkx1-2 al. , these data independently confirmed the important finding that 1 integrin is essential for CagA translocation. Open in a separate window Physique 1 Host cell 1 Senktide integrin is essential for to translocate and tyrosine-phosphorylate CagA in different cell lines.(A) Immunoblots to determine translocation of CagA in HL60 versus dHL60 cells. (B) Immunoblots of 1 1 integrin knockout fibroblasts (GD25), epithelial cells (GE11) or 1 gene-complemented cells (GD25, GE11) infected with strains or media (control). The upper panel shows CagA translocation Senktide using a phosphotyrosine-specific antibody (mAb PY99), the lower panel shows CagA production by wt, P12-wt (upper panel) or P12PAI (lower panel) and 1-integrin-labelled AGS cells (4B7-AlexaFluor568) and areas of co-localization of and 1 integrin (arrows). CagA, CagY and CagI are 1 Integrin Conversation Partners CagL is the only protein encoded around the.