title: Mechanisms of localized activation of the T cell antigen receptor inside clusters.
abstract: The T cell antigen receptor (TCR) has been shown to cluster both before and upon engagement with cognate antigens. However, the effect of TCR clustering on its activation remains poorly understood. Here, we used two-color photo-activated localization microscopy (PALM) to visualize individual molecules of TCR and ZAP-70, as a marker of TCR activation and phosphorylation, at the plasma membrane of uniformly activated T cells. Imaging and second-order statistics revealed that ZAP-70 recruitment and TCR activation localized inside TCR clusters. Live cell PALM imaging showed that the extent of localized TCR activation decreased, yet remained significant, with cell spreading. Using dynamic modeling and Monte-Carlo simulations we evaluated possible mechanisms of localized TCR activation. Our simulations indicate that localized TCR activation is the result of long-range cooperative interactions between activated TCRs, or localized activation by Lck and Fyn. Our results demonstrate the role of molecular clustering in cell signaling and activation, and are relevant to studying a wide range of multi-molecular complexes. This article is part of a Special Issue entitled: Nanoscale membrane organisation and signalling.
authors.affiliation: Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel.
authors.forename: Yair
authors.initials: Y
authors.lastname: Neve-Oz
authors.affiliation: Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel.
authors.forename: Yair
authors.initials: Y
authors.lastname: Razvag
authors.affiliation: Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel.
authors.forename: Julia
authors.initials: J
authors.lastname: Sajman
authors.affiliation: Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel. Electronic address: sherman@phys.huji.ac.il.
authors.forename: Eilon
authors.initials: E
authors.lastname: Sherman
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D002470:Cell Survival; D016000:Cluster Analysis; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D008213:Lymphocyte Activation / Q000276:immunology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D008853:Microscopy; D018448:Models, Immunological; D010766:Phosphorylation; D011487:Protein Conformation; D021381:Protein Transport; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism
chemical_list: D011948:Receptors, Antigen, T-Cell; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051746:ZAP-70 Protein-Tyrosine Kinase
keywords: Immune synapse; Microcluster; Modeling and simulation; Nanocluster; Photoactivated localization microscopy; Super-resolution light microscopy; T cell activation; T cell receptor