Actin assembly and inward flow in the plane of the immunological synapse (IS) drives the centralization of T cell receptor microclusters (TCR MCs) and the integrin LFA-1. Using structured-illumination microscopy (SIM), we show that actin arcs populating the medial, lamella-like region of the IS arise from linear actin filaments generated by one or more formins present at the IS distal edge. After traversing the outer, Arp2/3-generated, lamellipodia-like region of the IS, these linear filaments are organized by myosin II into anti-parallel concentric arcs. 3D-SIM shows that active LFA-1 often aligns with arcs while TCR MCs commonly reside between arcs, and TIRF-SIM shows TCR MCs being swept inward by arcs. Consistently, disrupting actin arc formation via formin inhibition results in less centralized TCR MCs, miss-segregated integrin clusters, decreased T: B cell adhesion, and diminished TCR signaling. Together, our results define the origin, organization, and functional significance of a major actomyosin contractile structure at the IS that directly propels TCR MC transport. T cell receptor (TCR) mechano-transduction is an emerging but poorly understood component of T cell activation. To define the contribution made by the cytoskeleton to TCR mechano-transduction, we investigated the role played by contractile actomyosin II arcs populating the pSMAC region of the immunological synapse (IS) in ligand discrimination. Using super resolution microscopy, we show that the generation of organized actomyosin arcs depends on ligand potency and the ability of myosin II to contract actin filaments. While weak ligands induce disorganized actomyosin arcs, strong ligands result in organized actomyosin arcs that correlate well with tension-sensitive CasL phosphorylation and with ligand accumulation at the IS center. Furthermore, the presence of ligand-dependent actomyosin arcs allows for a broad dynamic range in the phosphorylation of the early signaling molecules. Taken together, our correlative study implicates ligand-dependent actomyosin arc formation and contraction in a mechano-chemical feedback mechanism that amplifies the accumulation of critical signaling molecules at the IS.

Project Start
Project End
Budget Start
Budget End
Support Year
6
Fiscal Year
2016
Total Cost
Indirect Cost
Name
U.S. National Heart Lung and Blood Inst
Department
Type
DUNS #
City
State
Country
Zip Code
Hammer, John A (2018) Immunology: Is Actin at the Lytic Synapse a Friend or a Foe? Curr Biol 28:R155-R157
Rout, Ashok K; Wu, Xufeng; Starich, Mary R et al. (2018) The Structure of Melanoregulin Reveals a Role for Cholesterol Recognition in the Protein's Ability to Promote Dynein Function. Structure 26:1373-1383.e4
Varadarajan, Ramya; Hammer, John A; Rusan, Nasser M (2017) A centrosomal scaffold shows some self-control. J Biol Chem 292:20410-20411
Alexander, C J; Hammer 3rd, J A (2016) Optimization of cerebellar purkinje neuron cultures and development of a plasmid-based method for purkinje neuron-specific, miRNA-mediated protein knockdown. Methods Cell Biol 131:177-97
Murugesan, Sricharan; Hong, Jinsung; Yi, Jason et al. (2016) Formin-generated actomyosin arcs propel T cell receptor microcluster movement at the immune synapse. J Cell Biol 215:383-399
Yi, Jason; Wu, Xufeng; Chung, Andrew H et al. (2013) Centrosome repositioning in T cells is biphasic and driven by microtubule end-on capture-shrinkage. J Cell Biol 202:779-92
Hammer 3rd, John A; Burkhardt, Janis K (2013) Controversy and consensus regarding myosin II function at the immunological synapse. Curr Opin Immunol 25:300-6
Chen, Yu; Wang, Yan; Zhang, Jinzhong et al. (2012) Rab10 and myosin-Va mediate insulin-stimulated GLUT4 storage vesicle translocation in adipocytes. J Cell Biol 198:545-60
Yi, Jason; Wu, Xufeng S; Crites, Travis et al. (2012) Actin retrograde flow and actomyosin II arc contraction drive receptor cluster dynamics at the immunological synapse in Jurkat T cells. Mol Biol Cell 23:834-52
Martina, Jose A; Wu, Xufeng S; Catalfamo, Marta et al. (2011) Imaging of lytic granule exocytosis in CD8+ cytotoxic T lymphocytes reveals a modified form of full fusion. Cell Immunol 271:267-79

Showing the most recent 10 out of 11 publications