Ubc9 Binds to ADAP and Is Required for Rap1 Membrane Recruitment, Rac1 Activation, and Integrin-Mediated T Cell Adhesion.
Although the immune adaptor adhesion and degranulation-promoting adaptor protein (ADAP) acts as a key mediator of integrin inside-out signaling leading to T cell adhesion, the regulation of this adaptor during integrin activation and clustering remains unclear. We now identify Ubc9, the sole small ubiquitin-related modifier E2 conjugase, as an essential ... regulator of ADAP where it is required for TCR-induced membrane recruitment of the small GTPase Rap1 and its effector protein RapL and for activation of the small GTPase Rac1 in T cell adhesion. We show that Ubc9 interacted directly with ADAP in vitro and in vivo, and the association was increased in response to anti-CD3 stimulation. The Ubc9-binding domain on ADAP was mapped to a nuclear localization sequence (aa 674-700) within ADAP. Knockdown of Ubc9 by short hairpin RNA or expression of the Ubc9-binding-deficient ADAP mutant significantly decreased TCR-induced integrin adhesion to ICAM-1 and fibronectin, as well as LFA-1 clustering, although it had little effect on the TCR proximal signaling responses and TCR-induced IL-2 transcription. Furthermore, downregulation of Ubc9 impaired TCR-mediated Rac1 activation and attenuated the membrane targeting of Rap1 and RapL, but not Rap1-interacting adaptor molecule. Taken together, our data demonstrate for the first time, to our knowledge, that Ubc9 acts as a functional binding partner of ADAP and plays a selective role in integrin-mediated T cell adhesion via modulation of Rap1-RapL membrane recruitment and Rac1 activation.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Animals, COS Cells, Cell Adhesion, Cell Membrane, Cercopithecus aethiops, Enzyme Activation, Gene Knockdown Techniques, Humans, Integrins, Jurkat Cells, Lymphocyte Function-Associated Antigen-1, Mice, Models, Immunological, Monomeric GTP-Binding Proteins, Phosphoproteins, Phosphorylation, Protein Binding, Protein Processing, Post-Translational, RNA, Small Interfering, Receptors, Antigen, T-Cell, Recombinant Fusion Proteins, Signal Transduction, T-Lymphocytes, Ubiquitin-Conjugating Enzymes, rac1 GTP-Binding Protein, rap1 GTP-Binding Proteins
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Animals, COS Cells, Cell Adhesion, Cell Membrane, Cercopithecus aethiops, Enzyme Activation, Gene Knockdown Techniques, Humans, Integrins, Jurkat Cells, Lymphocyte Function-Associated Antigen-1, Mice, Models, Immunological, Monomeric GTP-Binding Proteins, Phosphoproteins, Phosphorylation, Protein Binding, Protein Processing, Post-Translational, RNA, Small Interfering, Receptors, Antigen, T-Cell, Recombinant Fusion Proteins, Signal Transduction, T-Lymphocytes, Ubiquitin-Conjugating Enzymes, rac1 GTP-Binding Protein, rap1 GTP-Binding Proteins
J. Immunol.
Date: Dec. 15, 2016
PubMed ID: 29127148
View in: Pubmed Google Scholar
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