An essential role for the MAL protein in targeting Lck to the plasma membrane of human T lymphocytes.
The MAL protein is an essential component of the specialized machinery for apical targeting in epithelial cells. The src family kinase Lck plays a pivotal role in T cell signaling. We show that MAL is required in T cells for efficient expression of Lck at the plasma membrane and activation of IL-2 transcription. To investigate the mechanism by which MAL regulates Lck targeting, we analyzed the dynamics of Lck and found that it travels to the plasma membrane in specific transport carriers containing MAL. Coimmunoprecipitation experiments indicated an association of MAL with Lck. Both carrier formation and partitioning of Lck into detergent-insoluble membranes were ablated in the absence of MAL. Polarization of T cell receptor for antigen (TCR) and microtubule-organizing center to immunological synapse (IS) were also defective. Although partial correction of the latter defects was possible by forced expression of Lck at the plasma membrane, their complete correction, formation of transport vesicles, partitioning of Lck, and restoration of signaling pathways, which are required for IL-2 transcription up-regulation, were achieved by exogenous expression of MAL. We concluded that MAL is required for recruitment of Lck to specialized membranes and formation of specific transport carriers for Lck targeting. This novel transport pathway is crucial for TCR-mediated signaling and IS assembly.
Antón
Olga
O
Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.
Batista
Alicia
A
Millán
Jaime
J
Andrés-Delgado
Laura
L
Puertollano
Rosa
R
Correas
Isabel
I
Alonso
Miguel A
MA
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics / Q000276:immunology; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000276:immunology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000276:immunology*; D022101:Microtubule-Organizing Center / Q000378:metabolism; D009185:Myelin Proteins / Q000235:genetics / Q000276:immunology*; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000378:metabolism; D011510:Proteolipids / Q000235:genetics / Q000276:immunology*; D034622:RNA Interference; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism
D007376:Interleukin-2; C569026:MAL protein, human; D026901:Membrane Transport Proteins; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D011510:Proteolipids; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)