title: MAL protein controls protein sorting at the supramolecular activation cluster of human T lymphocytes.
abstract: T cell membrane receptors and signaling molecules assemble at the immunological synapse (IS) in a supramolecular activation cluster (SMAC), organized into two differentiated subdomains: the central SMAC (cSMAC), with the TCR, Lck, and linker for activation of T cells (LAT), and the peripheral SMAC (pSMAC), with adhesion molecules. The mechanism of protein sorting to the SMAC subdomains is still unknown. MAL forms part of the machinery for protein targeting to the plasma membrane by specialized mechanisms involving condensed membranes or rafts. In this article, we report our investigation of the dynamics of MAL during the formation of the IS and its role in SMAC assembly in the Jurkat T cell line and human primary T cells. We observed that under normal conditions, a pool of MAL rapidly accumulates at the cSMAC, where it colocalized with condensed membranes, as visualized with the membrane fluorescent probe Laurdan. Mislocalization of MAL to the pSMAC greatly reduced membrane condensation at the cSMAC and redistributed machinery involved in docking microtubules or transport vesicles from the cSMAC to the pSMAC. As a consequence of these alterations, the raft-associated molecules Lck and LAT, but not the TCR, were missorted to the pSMAC. MAL, therefore, regulates membrane order and the distribution of microtubule and transport vesicle docking machinery at the IS and, by doing so, ensures correct protein sorting of Lck and LAT to the cSMAC.
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Olga M
authors.initials: OM
authors.lastname: Antón
authors.forename: Laura
authors.initials: L
authors.lastname: Andrés-Delgado
authors.forename: Natalia
authors.initials: N
authors.lastname: Reglero-Real
authors.forename: Alicia
authors.initials: A
authors.lastname: Batista
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alonso
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D011992:Endosomes / Q000276:immunology / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D054992:Immunological Synapses / Q000276:immunology*; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D021962:Membrane Microdomains / Q000276:immunology / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018613:Microscopy, Confocal; D008870:Microtubules / Q000276:immunology / Q000378:metabolism; D018448:Models, Immunological; D009185:Myelin Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D011485:Protein Binding; D021381:Protein Transport; D011510:Proteolipids / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D034622:RNA Interference; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C110810:LAT protein, human; C569026:MAL protein, human; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D011510:Proteolipids; D049452:Green Fluorescent Proteins; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)