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.
Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Yuzuru
Y
Ikehara
Sanae Kabata
SK
Ikehara
James C
JC
Paulson
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