title: Paxillin phosphorylation by JNK and p38 is required for NFAT activation.
abstract: Paxillin is an adaptor protein associated with focal adhesion complex, and is activated by tyrosine phosphorylation through focal adhesion kinase (FAK) and Src kinase. Recent studies reveal that serine phosphorylation of paxillin by JNK and p38 MAPK is essential for cell migration or neurite extension, but their cellular targets remain unclear. In this study, we examined the requirement of paxillin phosphorylation by p38 MAPK or JNK in T-cell motility and activation using paxillin mutants at the respective phosphorylation sites, Ser85, and Ser178. (S85A)-paxillin, (S178A)-paxillin, or (S85A/S178A)-paxillin inhibited the motility of NIH/3T3 fibroblasts, but did not interfere with T-cell migration and integrin-mediated T-cell adhesion. In contrast, activation of T cells was effectively suppressed by (S85A/S178A)-paxillin. Transgenic (S85A/S178A)-paxillin expression inhibited T-cell proliferation and reduced the production of IL-2, IFN-γ, and IL-4. In searching for signals modulated by (S85A/S178A)-paxillin, we found that NFAT activation was specifically blocked by (S85A/S178A)-paxillin. This could be partly attributed to diminished stromal interaction molecule 1 (STIM1) expression and attenuated TCR-induced Ca(2+)  influx. Our results demonstrate that dual phosphorylation of paxillin by JNK and p38 MAPK is essential for T-cell activation and suggest that NFAT is a functional target of the JNK/p38 phosphorylated paxillin.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan ROC.
authors.forename: Yu-Chi
authors.initials: YC
authors.lastname: Lee
authors.forename: An-Yun
authors.initials: AY
authors.lastname: Chang
authors.forename: Ming-Hsien
authors.initials: MH
authors.lastname: Lin-Feng
authors.forename: Wen-I
authors.initials: WI
authors.lastname: Tsou
authors.forename: I-Hsuan
authors.initials: IH
authors.lastname: Chiang
authors.forename: Ming-Zong
authors.initials: MZ
authors.lastname: Lai
mesh_terms: D016475:3T3 Cells; D000818:Animals; D015220:Calcium Channels; D002448:Cell Adhesion / Q000276:immunology; D002460:Cell Line; D002634:Chemotaxis, Leukocyte; D016023:Integrins / Q000378:metabolism; D007371:Interferon-gamma / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D015847:Interleukin-4 / Q000096:biosynthesis; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D051379:Mice; D050778:NFATC Transcription Factors / Q000096:biosynthesis / Q000378:metabolism*; D051419:Paxillin / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D000071737:Stromal Interaction Molecule 1; D013601:T-Lymphocytes / Q000276:immunology* / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D016023:Integrins; D007376:Interleukin-2; D008562:Membrane Glycoproteins; D050778:NFATC Transcription Factors; D051419:Paxillin; C100757:Stim1 protein, mouse; D000071737:Stromal Interaction Molecule 1; D015847:Interleukin-4; D007371:Interferon-gamma; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases