Differential roles of Lck and Itk in T cell response to antigen recognition revealed by calcium imaging and electron microscopy.
Ag recognition triggered at the interface between a T cell and an APC is conditioned by cell-cell adhesion and cytoskeletal remodeling. The role played in these phenomena by Lck and Itk, two protein tyrosine kinases essential for T cell signaling, was examined. Early T cell responses (membrane ruffling, Ca(2+) response, APC-T cell adhesion) were monitored in T cells overexpressing kinase-defective (KD) Lck and Itk mutants by combining fluorescence imaging and electron microscopy. Neither Lck nor Itk appears to be involved in the Ag-independent formation of a small and labile contact interface between T cells and APCS: By contrast, the Ag-induced Ca(2+) response in a cell population is similarly blunted in both KD transfectants. However, the underlying mechanisms are strikingly different for the two kinases. The major effect of Lck-KD is to reduce the probability of giving rise to quasi-normal Ca(2+) responses, whereas overexpression of Itk-KD results in a tuning down of all single-cell Ca(2+) responses. In addition, Lck, but not Itk, is required for the formation of a stable T/APC conjugate and for T cell polarization after Ag stimulation. Overall, our results lead to a clear distinction between Lck and ITK: Lck plays an ignition role, controlling all the downstream events tested here, whereas Itk amplifies the Ca(2+) response, but is dispensable for APC-induced adhesive and morphological responses.
Donnadieu
E
E
Laboratoire d'Immuno-Pharmacologie, Centre National de la Recherche Scientifique, Paris, France.
Lang
V
V
Bismuth
G
G
Ellmeier
W
W
Acuto
O
O
Michel
F
F
Trautmann
A
A
D000818:Animals; D017951:Antigen Presentation / Q000235:genetics; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000235:genetics / Q000276:immunology; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D048429:Cell Size / Q000235:genetics / Q000276:immunology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006825:Hybridomas; D007739:L Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D018715:Microscopy, Video / Q000379:methods; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000648:ultrastructure; D014162:Transfection
D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); C080813:emt protein-tyrosine kinase; D002118:Calcium