Non-T cell activation linker regulates ERK activation in Helicobacter pylori-infected epithelial cells.
It is supposed that human pathogens, e.g. Helicobacter pylori abuse lipid raft domains on the host cell plasma membrane to infect the cell. Investigating DRM-associated molecules we identified the transmembrane adapter proteins (TRAPs), non-T cell activation linker (NTAL) and lymphocyte-specific protein tyrosine kinase (Lck)-interacting membrane protein (LIME) to be regulated by H. pylori in the human epithelial cell line HCA-7. Up to now, raft-associated TRAPs were exclusively described to mediate signal propagation downstream of antigen receptors. Our results posed the question whether these proteins adopt a role in H. pylori-infected epithelial cells too. Our studies revealed that H. pylori induces tyrosine phosphorylation of NTAL as well as LIME within 15 min of infection. We observed that activated NTAL and LIME bind to the Src homology 2 (SH2)-domain of growth factor receptor-bound protein 2 (Grb2) within 15 to 30 min of infection and associate with the c-Met receptor. Further, NTAL has a contributory role in regulating H. pylori-induced extracellular signal-regulated kinase (ERK) activation. After suppression of NTAL protein levels by siRNA, ERK phosphorylation was reduced to approximately 50%. Additionally, the knockdown of NTAL suppressed the phosphorylation of cytosolic phospholipase A2 (cPLA2). Activated cPLA2 catalyzes the release of arachidonic acid (AA), whose metabolites are pivotal mediators in the H. pylori-induced inflammatory response. Thus, we propose that NTAL participates in the activation of the c-Met-Grb2-ERK-cPLA2 signalling cascade at early stages of H. pylori infection.
Rieke
Cornelia
C
Institute of Experimental Internal Medicine, Otto von Guericke University, Magdeburg, Germany.
Kähne
Thilo
T
Schweitzer
Katrin
K
Schraven
Burkhart
B
Wienands
Jürgen
J
Engelke
Michael
M
Naumann
Michael
M
D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000201:enzymology* / Q000382:microbiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D051380:GRB2 Adaptor Protein / Q000378:metabolism; D055785:Gene Knockdown Techniques; D016480:Helicobacter pylori / Q000502:physiology*; D006801:Humans; D054467:Phospholipases A2 / Q000378:metabolism; D010766:Phosphorylation; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C419196:LAT2 protein, human; C545591:LIME1 protein, human; D034741:RNA, Small Interfering; D019859:Proto-Oncogene Proteins c-met; D048049:Extracellular Signal-Regulated MAP Kinases; D054467:Phospholipases A2