Regulatory intramolecular association in a tyrosine kinase of the Tec family

Abstract

The T-cell-specific tyrosine kinase Itk is a member of the Tec family of non-receptor tyrosine kinases, and is required for signalling through the T-cell antigen receptor (TCR). The role of Itk in TCR signalling and the manner in which Itk activity is regulated are not well understood. Substrate binding and enzymatic activity of the structurally related Src kinases are regulated by an intramolecular interaction between the Src-homology-2 (SH2) domain and a phosphotyrosine. Although Itk also contains SH3, SH2 and tyrosine kinase domains, it lacks the corresponding regulatory phosphorylation site, and therefore must be regulated by an alternative mechanism. The proline-rich sequence adjacent to the SH3 domain of Tec family kinases contains an SH3 ligand, potentially allowing a different intramolecular interaction. By using multidimensional nuclear magnetic resonance we have determined the structure of a fragment of Itk, confirming that these domains interact intramolecularly. Formation of this intramolecular SH3-ligand complex prevents the Itk SH3 domain and proline-rich region from interacting with their respective protein ligands, Sam68 and Grb-2. We believe that this structure represents the first example of an intramolecular interaction between an SH3 domain and a proline-rich ligand, and has implications for the regulation of Tec family kinases.

Tec Kinase Itk Forms Membrane Clusters Specifically in the Vicinity of Recruiting Receptors

“…We therefore disrupted the integrity of each of these domains to determine whether they were required for this dimerization. The PRR within the unique TH domain of Itk has been suggested to interact with the SH3 domain of Itk in an intramolecular interaction (31). However, we found that Itk mutants carrying a deletion in the PRR of the TH domain could still form dimers with the WT Itk (Fig.…”

UCS15A, a novel small molecule, SH3 domain-mediated protein–protein interaction blocking drug

“…However, the results of the genome sequencing of Saccharomyces cerivisiae suggest that this organism has only 25 genes that encode for SH3-domain containing proteins (Rubin et al, 2000). Moreover, many SH3 interactions, especially those mediating intramolecular protein ± protein interactions, serve to negatively regulate signal transduction (Franz et al, 1989;Jackson and Baltimore, 1989;Seidel-Dugan et al, 1992;Mayer and Baltimore, 1994;Yamashita et al, 1996;Andreotti et al, 1997;reviewed in Mano, 1999;Kay et al, 2000). Taken together, the current studies suggest that, at least in yeast, SH3-mediated protein ± protein interaction may be dispensable for the viability of the organism.…”

Etk/Bmx Transactivates Vascular Endothelial Growth Factor 2 and Recruits Phosphatidylinositol 3-Kinase to Mediate the Tumor Necrosis Factor-induced Angiogenic Pathway

“…In engagement of integrin, the PH domain of Etk is recruited to the FERM domain of focal adhesion kinase, leading to phosphorylation of Tyr-40, concomitant with the membrane translocation and unfolding the closed conformation of the inactive Etk. Membrane-targeting of Etk will allow Etk to be phosphorylated by Src family kinases at the highly conserved tyrosine residue Tyr-566 in the catalytic domain (29), which is originally masked by the PH domain (38). In TNF signaling, Etk forms a preexisting complex with TNFR2 located in the cytoplasm membrane in a closed inactive form.…”