Differently phosphorylated forms of the cortactin homolog HS1 mediate distinct functions in natural killer cells

Department of Cell Biology and Physiology, Washington University, Saint Louis, Missouri 63110, USA.
Nature Immunology (Impact Factor: 20). 07/2008; 9(8):887-97. DOI: 10.1038/ni.1630
Source: PubMed


Here we investigated the involvement of HS1, the hematopoietic cell-specific homolog of cortactin, in the actin-based functions of natural killer cells. Involvement of HS1 in T cell regulation has been established, as HS1 is required for the formation of immune synapses. 'Knockdown' of HS1 in natural killer cells resulted in defective lysis of target cells, cell adhesion, chemotaxis and actin assembly at the lytic synapse. Phosphorylation of the tyrosine residue at position 397 (Tyr397) was required for adhesion to the integrin ligand ICAM-1 and for cytolysis, whereas phosphorylation of Tyr378 was required for chemotaxis. Phosphorylation of Tyr397 was also required for integrin signaling and recruitment of integrins, adaptors and actin to the lytic synapse. Thus, HS1 is essential for signaling and actin assembly in natural killer cells, and the functions of the two phosphorylated tyrosine residues are distinct and separable.

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    • "Since phosphorylation of HS1 has been implicated in the signal transduction of the chemokine receptor CXCR4 in NK cells [25], we tested whether the stimulation of T cells with the CXCR4 ligand SDF1α induces HS1 phosphorylation at Y 378 . Therefore human Jurkat cells were incubated with SDF1α for different time periods, lysed and HS1 Y 378 phosphorylation was assessed via Western blot employing a phospho-specific antibody. "
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    ABSTRACT: Nck is an adapter protein that comprises one SH2 domain and three SH3 domains. Nck links receptors and receptor-associated tyrosine kinases or adapter proteins to proteins that regulate the actin cytoskeleton. Whereas the SH2 domain binds to phosphorylated receptors or associated phosphoproteins, individual interactions of the SH3 domains with proline-based recognition motifs result in the formation of larger protein complexes. In T cells, changes in cell polarity and morphology during T-cell activation and effector function require the T-cell receptor-mediated recruitment and activation of actin-regulatory proteins to initiate cytoskeletal reorganization at the immunological synapse. We previously identified the adapter protein HS1 as a putative Nck-interacting protein. We now demonstrate that the SH2 domain of Nck specifically interacts with HS1 upon phosphorylation of its tyrosine residue 378. We report that in human T cells, ligation of the chemokine receptor CXCR4 by SDF1α induces a rapid and transient phosphorylation of tyrosine 378 of HS1 resulting in an increased association with Nck. Consequently, siRNA-mediated downregulation of HS1 and/or Nck impairs SDF1α-induced actin polymerization and T-cell migration.This article is protected by copyright. All rights reserved
    European Journal of Immunology 02/2015; 45(2). DOI:10.1002/eji.201444473 · 4.03 Impact Factor
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    • "Following the dynamic rearrangement of the actin cytoskeleton, microtubule dynamics result in a dramatic reorientation of the MTOC and associated lytic granules toward the synapse (Figure 1j). Requirements for centrosome polarization include LFA-1, Pyk2, ERK2, CIP4, the formin hDia and Vav1.54, 76, 104, 105, 106, 107 However, it is important to note that F-actin polymerization is required for MTOC polarization;46, 53, 54, 58, 108, 109 therefore, any interference with F-actin dynamics will subsequently impair MTOC and granule polarization. "
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    ABSTRACT: Natural killer (NK) cell-mediated cytotoxicity is governed by the formation of a lytic immune synapse in discrete regulated steps, which give rise to an extensive array of cellular checkpoints in accessing NK cell-mediated cytolytic defense. Appropriate progression through these cell biological steps is critical for the directed secretion of specialized secretory lysosomes and subsequent target cell death. Here we highlight recent discoveries in the formation of the NK cell cytolytic synapse as well as the molecular steps and cell biological checkpoints required for this essential host defense process.Immunology and Cell Biology advance online publication, 21 January 2014; doi:10.1038/icb.2013.96.
    Immunology and Cell Biology 01/2014; 92(3). DOI:10.1038/icb.2013.96 · 4.15 Impact Factor
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    • "Thus, it was surprising that lytic granule convergence still occurred in cells treated with cytochalasin D or latrunculin A. This suggests that signals required for lytic granule convergence, while downstream of activating receptors, are at least partially independent of those requiring significant actin reorganization at the IS. Thus far, few signaling events upstream of F-actin reorganization in NK cells have been defined at a cellular level (Riteau et al., 2003; Butler et al., 2008). These include LFA-1 signaling (Riteau et al., 2003), which was defined as required for granule convergence in noncytolytic conjugates (Figure 7) where the lytic granule convergence was typically present (Figure 2), but the MTOC did not polarize (Figure 1). "
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    ABSTRACT: Natural killer cells are lymphocytes specialized to participate in host defense through their innate ability to mediate cytotoxicity by secreting the contents of preformed secretory lysosomes (lytic granules) directly onto a target cell. This form of directed secretion requires the formation of an immunological synapse and occurs stepwise with actin reorganization preceding microtubule-organizing center (MTOC) polarization to the synapse. Because MTOC polarization to the synapse is required for polarization of lytic granules, we attempted to define their interrelationship. We found that compared with the time required for MTOC polarization, lytic granules converged to the MTOC rapidly. The MTOC-directed movement of lytic granules was independent of actin and microtubule reorganization, dependent on dynein motor function, occurred before MTOC polarization, and did not require a commitment to cytotoxicity. This defines a novel paradigm for rapid MTOC-directed transport as a prerequisite for directed secretion, one that may prepare, but not commit cells for precision secretory function.
    Molecular biology of the cell 05/2010; 21(13):2241-56. DOI:10.1091/mbc.E09-11-0930 · 4.47 Impact Factor
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