title: The growth determinants and transport properties of tunneling nanotube networks between B lymphocytes.
abstract: Tunneling nanotubes (TNTs) are long intercellular connecting structures providing a special transport route between two neighboring cells. To date TNTs have been reported in different cell types including immune cells such as T-, NK, dendritic cells, or macrophages. Here we report that mature, but not immature, B cells spontaneously form extensive TNT networks under conditions resembling the physiological environment. Live-cell fluorescence, structured illumination, and atomic force microscopic imaging provide new insights into the structure and dynamics of B cell TNTs. Importantly, the selective interaction of cell surface integrins with fibronectin or laminin extracellular matrix proteins proved to be essential for initiating TNT growth in B cells. These TNTs display diversity in length and thickness and contain not only F-actin, but their majority also contain microtubules, which were found, however, not essential for TNT formation. Furthermore, we demonstrate that Ca2+-dependent cortical actin dynamics exert a fundamental control over TNT growth-retraction equilibrium, suggesting that actin filaments form the TNT skeleton. Non-muscle myosin 2 motor activity was shown to provide a negative control limiting the uncontrolled outgrowth of membranous protrusions. Moreover, we also show that spontaneous growth of TNTs is either reduced or increased by B cell receptor- or LPS-mediated activation signals, respectively, thus supporting the critical role of cytoplasmic Ca2+in regulation of TNT formation. Finally, we observed transport of various GM1/GM3+vesicles, lysosomes, and mitochondria inside TNTs, as well as intercellular exchange of MHC-II and B7-2 (CD86) molecules which may represent novel pathways of intercellular communication and immunoregulation.
authors.affiliation: Department of Immunology, Eötvös Loránd University, Budapest, Hungary.
authors.forename: Anikó
authors.initials: A
authors.lastname: Osteikoetxea-Molnár
authors.affiliation: Department of Biophysics, Medical Faculty, University of Pécs, Pecs, Hungary.|MTA-PTE Nuclear-Mitochondrial Interactions Research Group, Pecs, Hungary.
authors.forename: Edina
authors.initials: E
authors.lastname: Szabó-Meleg
authors.affiliation: Department of Immunology, Eötvös Loránd University, Budapest, Hungary.
authors.forename: Eszter Angéla
authors.initials: EA
authors.lastname: Tóth
authors.affiliation: Department of Immunology, Eötvös Loránd University, Budapest, Hungary.
authors.forename: Ádám
authors.initials: Á
authors.lastname: Oszvald
authors.affiliation: Department of Immunology, Eötvös Loránd University, Budapest, Hungary.
authors.forename: Emese
authors.initials: E
authors.lastname: Izsépi
authors.affiliation: Department of Immunology, Eötvös Loránd University, Budapest, Hungary.
authors.forename: Mariann
authors.initials: M
authors.lastname: Kremlitzka
authors.affiliation: Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary.
authors.forename: Beáta
authors.initials: B
authors.lastname: Biri
authors.affiliation: Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Nyitray
authors.affiliation: Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Bozó
authors.affiliation: Environmental Chemistry Research Group, Research Centre for Natural Sciences, Budapest, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Németh
authors.affiliation: Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.|MTA-SE Molecular Biophysics Research Group, Budapest, Hungary.
authors.forename: Miklós
authors.initials: M
authors.lastname: Kellermayer
authors.affiliation: Department of Biophysics, Medical Faculty, University of Pécs, Pecs, Hungary.|MTA-PTE Nuclear-Mitochondrial Interactions Research Group, Pecs, Hungary.
authors.forename: Miklós
authors.initials: M
authors.lastname: Nyitrai
authors.affiliation: Department of Immunology, Eötvös Loránd University, Budapest, Hungary. janos.matko@ttk.elte.hu.
authors.forename: Janos
authors.initials: J
authors.lastname: Matko
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D060833:Cellular Microenvironment; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D009218:Myosins / Q000378:metabolism; D043942:Nanotubes / Q000737:chemistry*
chemical_list: D009218:Myosins; D002118:Calcium
keywords: Fluorescence imaging; Intercellular matter transport; Membrane nanotubes; Membrane protrusion; Superresolution microscopy; Trogocytosis