Early and dynamic polarization of T cell membrane rafts and constituents prior to TCR stop signals.
Polarization of membrane rafts and signaling proteins to form an immunological synapse is a hallmark of T cell stimulation. However, the kinetics of raft polarization and associated proteins in relation to the initial contact of the T cell with the APC are poorly defined. We addressed this question by measuring the distribution of membrane-targeted fluorescent protein markers during initial T cell interactions with B cell APCs. Experiments with unpulsed B cells lacking cognate Ag demonstrated an MHC class II-independent capping that was specific to membrane raft markers and required actin rearrangements and signals from Src kinases and PI3K. By live cell imaging experiments, we identified a similar specific polarization of membrane raft markers before TCR-dependent stop signals, and which occurred independently of cognate peptide-MHC class II. T cells conjugated to unpulsed B cells exhibited capping of CD4 and microclusters of the TCR zeta-chain, but only the CD4 enrichment was cholesterol dependent. Furthermore, raft association of CD4 was necessary for its efficient targeting to the Ag-independent caps. Interestingly, anergic Vbeta8(+) T cells isolated from staphylococcal enterotoxin B-injected mice did not exhibit Ag-independent capping of membrane rafts, showing that inhibition of these early, Ag-independent events is a property associated with tolerance. Altogether, these data show that membrane raft capping is one of the earliest events in T cell activation and represents one avenue for promoting and regulating downstream peptide-MHC-dependent signaling within the T cell.
Van Komen
Jeffrey S
JS
Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
Mishra
Sudha
S
Byrum
Jennifer
J
Chichili
Gurunadh R
GR
Yaciuk
Jane C
JC
Farris
A Darise
AD
Rodgers
William
W
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D000941:Antigens / Q000276:immunology / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D015704:CD4 Antigens / Q000276:immunology / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D016764:Cell Polarity / Q000276:immunology*; D002784:Cholesterol / Q000276:immunology / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism; D007108:Immune Tolerance / Q000276:immunology; D007152:Immunologic Capping; D008213:Lymphocyte Activation / Q000276:immunology*; D021962:Membrane Microdomains / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D010455:Peptides / Q000276:immunology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology / Q000378:metabolism; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology*; D019061:src-Family Kinases / Q000276:immunology / Q000378:metabolism
D000941:Antigens; D015704:CD4 Antigens; D000949:Histocompatibility Antigens Class II; D010455:Peptides; D016693:Receptors, Antigen, T-Cell, alpha-beta; D002784:Cholesterol; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases