Negative regulation of T cell receptor signaling by Siglec-7 (p70/AIRM) and Siglec-9.
Siglec-7 (p70/AIRM) and Siglec-9 are "CD33"-related siglecs expressed on natural killer (NK) cells and subsets of peripheral T cells. Like other inhibitory NK cell receptors, they contain immunoglobulin receptor family tyrosine-based inhibitory motifs in their cytoplasmic domains, and Siglec-7 has been demonstrated to negatively regulate NK cell activation. Based on reports of the presence of these siglecs on T cells, we sought to determine if they are capable of modulating T cell receptor (TCR) signaling using Jurkat T cells stably and transiently transfected with Siglec-7 or Siglec-9. Following either pervanadate stimulation or TCR engagement, both Siglecs exhibited increased tyrosine phosphorylation and recruitment of SHP-1. Effects of Siglec-7 and -9 were also evident in downstream events in the signaling pathway. Both siglecs reduced phosphorylation of Tyr319 on ZAP-70, known to play a pivotal role in up-regulation of gene transcription following TCR stimulation. There was also a corresponding decreased transcriptional activity of nuclear factor of activated T cells (NFAT) as determined using a luciferase reporter gene. Like all siglecs, Siglec-7 and -9 recognize sialic acid-containing glycans of glycoproteins and glycolipids as ligands. Mutation of the conserved Arg in the ligand binding site of Siglec-7 (Arg124) or Siglec-9 (Arg120) resulted in reduced inhibitory function in the NFAT/luciferase transcription assay, suggesting that ligand binding is required for optimal inhibition of TCR signaling. The combined results demonstrate that both Siglec-7 and Siglec-9 are capable of negative regulation of TCR signaling and that ligand binding is required for optimal activity.
Ikehara
Yuzuru
Y
Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Ikehara
Sanae Kabata
SK
Paulson
James C
JC
D020816:Amino Acid Motifs; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D015214:Antigens, Differentiation, Myelomonocytic / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D015153:Blotting, Western; D002469:Cell Separation; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D017930:Genes, Reporter; D006801:Humans; D047468:Immunoprecipitation; D019169:Jurkat Cells; D037102:Lectins / Q000378:metabolism / Q000502:physiology*; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry; D063268:Sialic Acid Binding Ig-like Lectin 3; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry; D014638:Vanadates / Q000737:chemistry; D051746:ZAP-70 Protein-Tyrosine Kinase
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C571163:CD33 protein, human; D004791:Enzyme Inhibitors; D037102:Lectins; D008024:Ligands; C402206:SIGLEC7 protein, human; C412227:SIGLEC9 protein, human; D063268:Sialic Acid Binding Ig-like Lectin 3; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; C076715:pervanadate; D014638:Vanadates; D014443:Tyrosine; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human