title: Formin INF2 regulates MAL-mediated transport of Lck to the plasma membrane of human T lymphocytes.
abstract: Expression of the src-family kinase lymphocyte-specific protein tyrosine kinase (Lck) at the plasma membrane is essential for it to fulfill its pivotal role in signal transduction in T lymphocytes. MAL, an integral membrane protein expressed in specific types of lymphoma, has been shown to play an important role in targeting Lck to the plasma membrane. Here we report that MAL interacts with Inverted Formin2 (INF2), a formin with the atypical property of promoting not only actin polymerization but also its depolymerization. In Jurkat T cells, INF2 colocalizes with MAL at the cell periphery and pericentriolar endosomes and along microtubules. Videomicroscopic analysis revealed that the MAL(+) vesicles transporting Lck to the plasma membrane move along microtubule tracks. Knockdown of INF2 greatly reduced the formation of MAL(+) transport vesicles and the levels of Lck at the plasma membrane and impaired formation of a normal immunologic synapse. The actin polymerization and depolymerization activities of INF2 were both required for efficient Lck targeting. Cdc42 and Rac1, which bind to INF2, regulate Lck transport in both Jurkat and primary human T cells. Thus, INF2 collaborates with MAL in the formation of specific carriers for targeting Lck to the plasma membrane in a process regulated by Cdc42 and Rac1.
authors.affiliation: Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Cantoblanco, Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Andrés-Delgado
authors.forename: Olga M
authors.initials: OM
authors.lastname: Antón
authors.forename: Ricardo
authors.initials: R
authors.lastname: Madrid
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Byrne
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alonso
mesh_terms: D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D000080865:Formins; D006801:Humans; D047468:Immunoprecipitation; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008840:Microfilament Proteins / Q000494:pharmacology*; D009185:Myelin Proteins / Q000378:metabolism*; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D021381:Protein Transport; D011510:Proteolipids / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000080865:Formins; C546959:INF2 protein, human; C569026:MAL protein, human; D026901:Membrane Transport Proteins; D008840:Microfilament Proteins; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D011510:Proteolipids; C107953:RAC1 protein, human; D033921:Vesicular Transport Proteins; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein