-
Edwige Roy,
Dieudonnée Togbe, Amy D Holdorf,
Dmitry Trubetskoy,
Sabrina Nabti,
Günter Küblbeck,
Alexandra Klevenz,
Annette Kopp-Schneider,
Frank Leithäuser,
Peter Möller,
Friedhelm Bladt,
Günter Hämmerling,
Bernd Arnold,
Tony Pawson,
Anna Tafuri
[show abstract]
[hide abstract]
ABSTRACT: The size and sensitivity of the T-cell repertoire governs the effectiveness of immune responses against invading pathogens. Both are modulated by T-cell receptor (TCR) activity through molecular mechanisms, which remain unclear. Here, we provide genetic evidence that the SH2/SH3 domain containing proteins Nck lower the threshold of T-cell responsiveness. The hallmarks of Nck deletion were T-cell lymphopenia and hyporeactivity to TCR-mediated stimulation. In the absence of the Nck adaptors, peripheral T cells expressing a TCR with low avidity for self-antigens were strongly reduced, whereas an overall impairment of T-cell activation by weak antigenic stimulation was observed. Mechanistically, Nck deletion resulted in a significant decrease in calcium mobilization and ERK phosphorylation upon TCR engagement. Taken together, our findings unveil a crucial role for the Nck adaptors in shaping the T-cell repertoire to ensure maximal antigenic coverage and optimal T cell excitability.
Proceedings of the National Academy of Sciences 08/2010; 107(35):15529-34. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The evolutionarily conserved proteins Par-6, atypical protein kinase C (aPKC), Cdc42 and Par-3 associate to regulate cell polarity and asymmetric cell division, but the downstream targets of this complex are largely unknown. Here we identify direct physiological interactions between mammalian aPKC, murine Par-6C (mPar-6C) and Mlgl, the mammalian orthologue of the Drosophila melanogaster tumour suppressor Lethal (2) giant larvae. In cultured cell lines and in mouse brain, aPKC, mPar-6C and Mlgl form a multiprotein complex in which Mlgl is targeted for phosphorylation on conserved serine residues. These phosphorylation sites are important for embryonic fibroblasts to polarize correctly in response to wounding and may regulate the ability of Mlgl to direct protein trafficking. Our data provide a direct physical and regulatory link between proteins of distinct polarity complexes, identify Mlgl as a functional substrate for aPKC in cell polarization and indicate that aPKC is directed to cell polarity substrates through a network of protein-protein interactions.
Nature Cell Biology 05/2003; 5(4):301-8. · 19.49 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The evolutionarily conserved proteins Par-6, atypical protein kinase C (aPKC), Cdc42 and Par-3 associate to regulate cell polarity and asymmetric cell division, but the downstream targets of this complex are largely unknown. Here we identify direct physiological interactions between mammalian aPKC, murine Par-6C (mPar-6C) and Mlgl, the mammalian orthologue of the Drosophila melanogaster tumour suppressor Lethal (2) giant larvae. In cultured cell lines and in mouse brain, aPKC, mPar-6C and Mlgl form a multiprotein complex in which Mlgl is targeted for phosphorylation on conserved serine residues. These phosphorylation sites are important for embryonic fibroblasts to polarize correctly in response to wounding and may regulate the ability of Mlgl to direct protein trafficking. Our data provide a direct physical and regulatory link between proteins of distinct polarity complexes, identify Mlgl as a functional substrate for aPKC in cell polarization and indicate that aPKC is directed to cell polarity substrates through a network of protein–protein interactions.
Nature Cell Biology 03/2003; 5(4):301-308. · 19.49 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Although the accumulation of lipid rafts at the immunological synapse is now well accepted, the degree of the accumulation, the localization within the fine structure of the immunological synapse, and the region from which lipid rafts are recruited have not been defined. In this work we show that lipid rafts preferentially accumulate in the central zone of the immunological synapse, the central supramolecular activation complex (C-SMAC). However, quantitative analyses indicate that the level of recruitment of lipid rafts to the C-SMAC is relatively small and suggests that rearrangement of lipid rafts from the peripheral zone of the synapse into the C-SMAC can account for this accumulation. We also assessed the effects of CD28 deficiency on lipid raft recruitment to the immunological synapse. The accumulation of lipid occurred independently of the CD28/B7 system and was not measurably altered by CD28.
The Journal of Immunology 10/2002; 169(6):2837-41. · 5.79 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Although the Src family tyrosine kinase Lck is essential for T cell receptor (TCR) signaling, whether or how Lck is activated is unknown. Using a phosphospecific antiserum to Lck, we show here that Lck becomes autophosphorylated when T cells are stimulated by antigen-presenting cells (APCs). We found that TCR cross-linking alone could not stimulate Lck autophosphorylation and CD45 was not required for this process. Instead, the T cell accessory molecules CD4 and CD28 cooperated to induce autophosphorylation of Lck. CD4 recruited Lck to the T cell--APC interface, whereas CD28 sustained Lck activation. These data show how the multiple interactions afforded by the immunological synapse drive efficient and highly specific signaling.
Nature Immunology 04/2002; 3(3):259-64. · 26.01 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The area of contact between a T cell and an antigen-presenting cell (APC) is known as the immunological synapse. Although its exact function is unknown, one model suggests that it allows for T cell receptor (TCR) clustering and for sustained signaling in T cells for many hours. Here we demonstrate that TCR-mediated tyrosine kinase signaling in naïve T cells occurred primarily at the periphery of the synapse and was largely abated before mature immunological synapses had formed. These data suggest that many hours of TCR signaling are not required for T cell activation. These observations challenge current ideas about the role of immunological synapses in T cell activation.
Science 03/2002; 295(5559):1539-42. · 31.20 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The Src family tyrosine kinases Lck and Fyn are critical for signaling via the T cell receptor. However, the exact mechanism
of their activation is unknown. Recent crystal structures of Src kinases suggest that an important mechanism of kinase activation
is via engagement of the Src homology (SH)3 domain by proline-containing sequences. To test this hypothesis, we identified
several T cell membrane proteins that contain potential SH3 ligands. Here we demonstrate that Lck and Fyn can be activated
by proline motifs in the CD28 and CD2 proteins, respectively. Supporting a role for Lck in CD28 signaling, we demonstrate
that CD28 signaling in both transformed and primary T cells requires Lck as well as proline residues in CD28. These data suggest
that Lck plays an essential role in CD28 costimulation.
Journal of Experimental Medicine 08/1999; 190(3):375-384. · 13.85 Impact Factor
