Dynamics of Subsynaptic Vesicles and Surface Microclusters at the Immunological Synapse

Purbhoo, Marco A.; Liu, Hebin; Oddos, Stéphane; Owen, Dylan M.; Neil, Mark A. A.; Pageon, Sophie V.; French, Paul M. W.; Rudd, Christopher E.; Davis, Daniel M.

doi:10.1126/scisignal.2000645

Cited by 123 publications

(154 citation statements)

References 36 publications

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“…Conceivably, the retargeting of LAT to intracellular compartments and thus away from sites of TCR engagement at the plasma membrane in Nef-expressing cells significantly limits its availability for LAT phosphorylation by ZAP70, causing the prominent defect in assembly of SLP-76 MCs. According to an emerging concept, signaling competent MCs depend on the de novo recruitment of LAT from intracellular pools to TCR-proximal sites, where it is activated by phosphorylation, whereas pre-existing LAT MCs at the plasma membrane are largely devoid of pLAT and thus signaling incompetent (57,58). The LAT MCs observed in Nef-or Nef F195I-expressing cells most likely represent such pre-existing, inactive MCs.…”

Section: Discussionmentioning

confidence: 99%

HIV-1 Nef Limits Communication between Linker of Activated T Cells and SLP-76 To Reduce Formation of SLP-76–Signaling Microclusters following TCR Stimulation

Abraham

Bankhead

Pan

et al. 2012

The Journal of Immunology

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Signal initiation by engagement of the TCR triggers actin rearrangements, receptor clustering, and dynamic organization of signaling complexes to elicit and sustain downstream signaling. Nef, a pathogenicity factor of HIV, disrupts early TCR signaling in target T cells. To define the mechanism underlying this Nef-mediated signal disruption, we employed quantitative single-cell microscopy following surface-mediated TCR stimulation that allows for dynamic visualization of distinct signaling complexes as microclusters (MCs). Despite marked inhibition of actin remodeling and cell spreading, the induction of MCs containing TCR-CD3 or ZAP70 was not affected significantly by Nef. However, Nef potently inhibited the subsequent formation of MCs positive for the signaling adaptor Src homology-2 domain-containing leukocyte protein of 76 kDa (SLP-76) to reduce MC density in Nef-expressing and HIV-1–infected T cells. Further analyses suggested that Nef prevents formation of SLP-76 MCs at the level of the upstream adaptor protein, linker of activated T cells (LAT), that couples ZAP70 to SLP-76. Nef did not disrupt pre-existing MCs positive for LAT. However, the presence of the viral protein prevented de novo recruitment of active LAT into MCs due to retargeting of LAT to an intracellular compartment. These modulations in MC formation and composition depended on Nef’s ability to simultaneously disrupt both actin remodeling and subcellular localization of TCR-proximal machinery. Nef thus employs a dual mechanism to disturb early TCR signaling by limiting the communication between LAT and SLP-76 and preventing the dynamic formation of SLP-76–signaling MCs.

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Section: Discussionmentioning

confidence: 99%

HIV-1 Nef Limits Communication between Linker of Activated T Cells and SLP-76 To Reduce Formation of SLP-76–Signaling Microclusters following TCR Stimulation

Abraham

Bankhead

Pan

et al. 2012

The Journal of Immunology

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“…The initial TCR signal is amplified after CD3 and LAT signalosomes localize to their corresponding microclusters at the plasma membrane [32], as well as after their recycling and sorting from intracellular stores. Indeed, the synchronized traffic of LAT-enriched vesicles and plasma membrane LAT clusters has been detected by total internal reflexion fluorescence microscopy (TIRFM) and linked to sustained TCR signaling [33]. However, a recent study describes that LAT remains unphosphorylated at pre-existing clusters at the plasma membrane, suggesting T cell activation depends on intracellular traffic [34].…”

Section: The Centrosome Marks the Waymentioning

confidence: 99%

Immune synapse: conductor of orchestrated organelle movement

Martín-Cófreces¹,

Baixauli²,

Sánchez-Madrid³

2014

Trends in Cell Biology

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SummaryTo ensure proper cell function, intracellular organelles are not randomly distributed within the cell, but polarized and highly constrained by the cytoskeleton and associated adaptor proteins. This relationship between distribution and function was originally found in neurons and epithelial cells; however, recent evidence suggests that it is a more general phenomenon that occurs in many highly specialized cells including the immune T cells. Recent studies reveal that the orchestrated redistribution of organelles is dependent on antigen specific activation and immune-synapse formation of T cells. This review highlights the functional implications of organelle polarization in early T cell activation and examines recent findings on how the immune synapse sets the rhythm of organelle motion and the spread of the activation signal to the nucleus. KeywordsImmune synapse; microcluster; signalosome; mitochondria; vesicle; microtubule Overview of the immune synapseT cell activation starts with an initial wave of signalling that depends on the activation of surface receptors, but subsequent propagation of the signal appears to depend on intracellular compartments, in a sequence driven by the actin and tubulin cytoskeletons [1]. The study of neural synapses highlighted the importance of cell polarity and the specific localization of organelles and clusters of receptors at the pre-and post-synaptic terminals. Despite its transient nature, recent evidence shows that the immune synapse (IS) shares these same neuronal features.The IS is the interface between a T lymphocyte and an antigen presenting cell (APC). During the formation and stabilization of the IS, membrane microdomains and the cytoskeleton reorganize and promote the segregation of membrane and intracellular signaling proteins within the T cell, such as the T cell receptor (TCR), integrins, tyrosine Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts kinases and scaffold proteins such as Linker for activation of T cells (LAT) (Figure 1 and Glossary). The TCR and associated molecules (TCR signalosomes) form microclusters that move to congregate in the central area (central supramolecular activation cluster; cSMAC) of the IS, whereas adhesion receptors such as integrins reorganize in a surrounding external ring called the peripheral or pSMAC ( Figure 2) [2]. In addition, phosphorylation and dephosphorylation, protein-protein interactions and degradation of important molecules such as the TCR-accompanying CD3 complex, tyrosine kinases, phosphatases and adaptor molecules also control receptor activation [3,4]. The polarization of several organelles occurs during T cell stimulation with important roles, such as the centrosome, Golgi apparatus, mitochondria, endoplasmic reticulum and the multivesicular bodies (MVB) [5][6][7][8][9][10]. These rearrangements at the IS promote the activation of signaling pathways that propagate to the nucleus. Signals activating nuclear transcription factors in combination with polarity proteins, such as partit...

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“…The same proteins, or different splice variants thereof, can therefore appear in several distinct sub-cellular compartments and engage in very different types of activities [16,17]. Many aspects of this cellular organization are still unknown.…”

Section: Introductionmentioning

confidence: 99%

Beyond ‘furballs’ and ‘dumpling soups’ – towards a molecular architecture of signaling complexes and networks

2012

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a b s t r a c tThe molecular architectures of intracellular signaling networks are largely unknown. Understanding their design principles and mechanisms of processing information is essential to grasp the molecular basis of virtually all biological processes. This is particularly challenging for human pathologies like cancers, as essentially each tumor is a unique disease with vastly deranged signaling networks. However, even in normal cells we know almost nothing. A few 'signalosomes', like the COP9 and the TCR signaling complexes have been described, but detailed structural information on their architectures is largely lacking. Similarly, many growth factor receptors, for example EGF receptor, insulin receptor and c-Met, signal via huge protein complexes built on large platform proteins (Gab, Irs/Dok, p130Cas[BCAR1], Frs families etc.), which are structurally not well understood. Subsequent higher order processing events remain even more enigmatic. We discuss here methods that can be employed to study signaling architectures, and the importance of too often neglected features like macromolecular crowding, intrinsic disorder in proteins and the sophisticated cellular infrastructures, which need to be carefully considered in order to develop a more mature understanding of cellular signal processing.

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Dynamics of Subsynaptic Vesicles and Surface Microclusters at the Immunological Synapse

Abstract: Word count: 7316 One sentence summary:Movement of sub-synaptic vesicles rich in LAT is constrained by protein microclusters at T cell immune synapses, dependent on LAT residues important for its binding to SLP-76 and consistent with a role for vesicular LAT in T cell signal transduction.

Cited by 123 publications

References 36 publications

HIV-1 Nef Limits Communication between Linker of Activated T Cells and SLP-76 To Reduce Formation of SLP-76–Signaling Microclusters following TCR Stimulation

HIV-1 Nef Limits Communication between Linker of Activated T Cells and SLP-76 To Reduce Formation of SLP-76–Signaling Microclusters following TCR Stimulation

Immune synapse: conductor of orchestrated organelle movement

Beyond ‘furballs’ and ‘dumpling soups’ – towards a molecular architecture of signaling complexes and networks

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