title: The adaptor protein Lad associates with the G protein beta subunit and mediates chemokine-dependent T-cell migration.
abstract: Lck-interacting adaptor protein/Rlk/Itk-binding protein (Lad/RIBP) was previously identified as an adaptor protein involved in TCR-mediated T-cell activation. To elucidate the functions of Lad further, we here performed yeast 2-hybrid screening using Lad as bait and discovered that the G protein beta subunit (G beta) is a Lad-binding partner. Since the most well-known G protein-coupled receptor in T cells is the chemokine receptor, we investigated whether Lad is involved in chemokine signaling. We found that, upon chemokine treatment, Lad associated with G beta in Jurkat T cells. Furthermore, ectopic expression of dominant-negative Lad or the reduction of endogenous Lad expression by siRNA impaired the chemokine-induced migration of T cells, indicating that Lad is required for chemokine-induced T-cell migration. Subsequent investigation of the signaling pathways revealed that, in response to chemokine, Lad associated with the tyrosine kinases Lck and Zap-70 and that Lad was essential for the activation of Zap-70. Moreover, Lad was required for the chemokine-dependent tyrosine phosphorylation of focal adhesion molecules that included Pyk2 and paxillin. Taken together, these data show that, upon chemokine stimulation, Lad acts as an adaptor protein that links the G protein beta subunit to the tyrosine kinases Lck and Zap-70, thereby mediating T-cell migration.
authors.affiliation: Department of Life Science, Ewha Woman's University, Seoul, Korea.
authors.forename: Dongsu
authors.initials: D
authors.lastname: Park
authors.forename: Inyoung
authors.initials: I
authors.lastname: Park
authors.forename: Deogwon
authors.initials: D
authors.lastname: Lee
authors.forename: Young Bong
authors.initials: YB
authors.lastname: Choi
authors.forename: Hyunsook
authors.initials: H
authors.lastname: Lee
authors.forename: Yungdae
authors.initials: Y
authors.lastname: Yun
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism / Q000502:physiology*; D018925:Chemokines / Q000494:pharmacology*; D002634:Chemotaxis, Leukocyte; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018925:Chemokines; D044387:GTP-Binding Protein beta Subunits; C405691:SH2D2A protein, human; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051746:ZAP-70 Protein-Tyrosine Kinase