title: Biochemical interactions integrating Itk with the T cell receptor-initiated signaling cascade.
abstract: Itk, a Tec family tyrosine kinase, acts downstream of Lck and phosphatidylinositol 3'-kinase to facilitate T cell receptor (TCR)-dependent calcium influxes and increases in extracellular-regulated kinase activity. Here we demonstrate interactions between Itk and crucial components of TCR-dependent signaling pathways. First, the inositide-binding pocket of the Itk pleckstrin homology domain directs the constitutive association of Itk with buoyant membranes that are the primary site of TCR activation and are enriched in both Lck and LAT. This association is required for the transphosphorylation of Itk. Second, the Itk proline-rich region binds to Grb2 and LAT. Third, the Itk Src homology (SH3) 3 and SH2 domains interact cooperatively with Syk-phosphorylated SLP-76. Notably, SLP-76 contains a predicted binding motif for the Itk SH2 domain and binds to full-length Itk in vitro. Finally, we show that kinase-inactive Itk can antagonize the SLP-76-dependent activation of NF-AT. The inhibition of NF-AT activation depends on the Itk pleckstrin homology domain, proline-rich region, and SH2 domain. Together, these observations suggest that multivalent interactions recruit Itk to LAT-nucleated signaling complexes and facilitate the activation of LAT-associated phospholipase Cgamma1 by Itk.
authors.affiliation: Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Bunnell
authors.forename: M
authors.initials: M
authors.lastname: Diehn
authors.forename: M B
authors.initials: MB
authors.lastname: Yaffe
authors.forename: P R
authors.initials: PR
authors.lastname: Findell
authors.forename: L C
authors.initials: LC
authors.lastname: Cantley
authors.forename: L J
authors.initials: LJ
authors.lastname: Berg
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D006801:Humans; D006825:Hybridomas / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D019169:Jurkat Cells; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D003902:Detergents; D007527:Isoenzymes; C110810:LAT protein, human; C491734:Lat protein, mouse; D008565:Membrane Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; C092947:SLP-76 signal Transducing adaptor proteins; D014157:Transcription Factors; D011505:Protein-Tyrosine Kinases; C080813:emt protein-tyrosine kinase; D010738:Type C Phospholipases; D051966:Phospholipase C gamma