Emt/Itk associates with activated TCR complexes: role of the pleckstrin homology domain.
Expressed in mast and T-cells/inducible T cell tyrosine kinase (Emt/Itk) is a protein tyrosine kinase required for T cell Ag receptor (TCR)-induced activation and development. A physical interaction between Emt/Itk and TCR has not been described previously. Here, we have utilized laser scanning confocal microscopy to demonstrate that Ab-mediated engagement of the CD3epsilon chain induces the membrane colocalization of Emt/Itk with TCR/CD3. Removal of the Emt/Itk pleckstrin homology domain (DeltaPH-Emt/Itk) abrogates the association of the kinase with the cell membrane, as well as its activation-induced colocalization with the TCR complex and subsequent tyrosine phosphorylation. The addition of a membrane localization sequence to DeltaPH-Emt/Itk from Lck restores all of these deficiencies except the activation-induced tyrosine phosphorylation. Our data suggest that the PH domain of Emt/Itk can be replaced with another membrane localization signal without affecting the membrane targeting and activation-induced colocalization of the kinase with the TCR. However, the PH domain is indispensable for the activation-induced tyrosine phosphorylation of the kinase.
Ching
K A
KA
Department of Biology and Molecular Biology Institute, San Diego State University, San Diego, CA 92182, USA.
Kawakami
Y
Y
Kawakami
T
T
Tsoukas
C D
CD
D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins; D017252:CD3 Complex / Q000378:metabolism*; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D010446:Peptide Fragments / Q000378:metabolism; D010750:Phosphoproteins; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
D001798:Blood Proteins; D017252:CD3 Complex; D010446:Peptide Fragments; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; C039077:platelet protein P47; D011505:Protein-Tyrosine Kinases; C080813:emt protein-tyrosine kinase