Recruitment of Grb2 and SHIP1 by the ITT-like motif of TIGIT suppresses granule polarization and cytotoxicity of NK cells

Abstract

Activating and inhibitory receptors control natural killer (NK) cell activity. T-cell immunoglobulin and ITIM (immunoreceptor tyrosine-based inhibition motif) domain (TIGIT) was recently identified as a new inhibitory receptor on T and NK cells that suppressed their effector functions. TIGIT harbors the immunoreceptor tail tyrosine (ITT)-like and ITIM motifs in its cytoplasmic tail. However, how its ITT-like motif functions in TIGIT-mediated negative signaling is still unclear. Here, we show that TIGIT/PVR (poliovirus receptor) engagement disrupts granule polarization leading to loss of killing activity of NK cells. The ITT-like motif of TIGIT has a major role in its negative signaling. After TIGIT/PVR ligation, the ITT-like motif is phosphorylated at Tyr225 and binds to cytosolic adapter Grb2, which can recruit SHIP1 to prematurely terminate phosphatidylinositol 3-kinase (PI3K) and MAPK signaling, leading to downregulation of NK cell function. In support of this, Tyr225 or Asn227 mutation leads to restoration of TIGIT/PVR-mediated cytotoxicity, and SHIP1 silencing can dramatically abolish TIGIT/PVR-mediated killing inhibition. Meanwhile, normal cells are kept away from their cytotoxicity. Therefore, the discrimination between 'self' normal cells and 'nonself' abnormal cells has to be precisely recognized by NK cells. [5][6][7] A very large repertoire of receptors, both activating and inhibitory, is proved to be critical in NK cell function. The best-known inhibitory receptors of NK cells are the killer-cell immunoglobulin-like receptor family, whose physical ligands are MHC-I molecules that are expressed on self normal cells to protect them from NK cell lysis. 8 Other non-MHC-I inhibitory receptors, which do not associate with MHC-I molecules, are also expressed on NK cells. 9 However, their physiological and pathological significances have not been defined yet.T-cell immunoglobulin and ITIM domain (TIGIT) was recently identified as an inhibitory receptor that is expressed mainly on NK cells, activated CD4 and CD8 T cells. 10-12 TIGIT harbors one extracellular immunoglobulin domain, a type 1 transmembrane region, and an immunoglobulin tail tyrosine (ITT)-like phosphorylation motif followed by an ITIM (immunoreceptor tyrosine-based inhibition motif) of the cytoplasmic tail. 13 The physical ligands of TIGIT were identified as the poliovirus receptor (PVR, or CD155) and the PVRL2 (Nectin2, or CD112). 10,12 TIGIT can bind to PVR of human dendritic cells to enhance interleukin 10 (IL-10) production, which inhibits T-cell activation. 10 Kuchroo et al. 14 showed that TIGIT harbors a T-cell-intrinsic inhibitory function to suppress T-cell activation.Moreover, TIGIT can inhibit NK cell cytolysis through engagement with PVR or PVRL2. 11 TIGIT-deficient mice are more susceptible to autoimmune diseases. 14,15 However, the inhibitory mechanism mediated by TIGIT has not been elucidated.TIGIT contains a classical ITIM motif, which recruits either Src homology (SH) 2 domain-containing protein tyrosine phosphatases SHP1 and SHP...

T-cell Immunoglobulin and ITIM Domain (TIGIT) Receptor/Poliovirus Receptor (PVR) Ligand Engagement Suppresses Interferon-γ Production of Natural Killer Cells via β-Arrestin 2-mediated Negative Signaling

“…YTS-TIGIT cells, its mutants, and 721.221-PVR cells were maintained with additional 0.5 g/ml of puromycin (Sigma) as described (15). HEK293T cells were grown in DMEM supplemented with 10% (v/v) heat-inactivated FBS (Invitrogen), 50 M ␤-mercaptoethanol, 100 units/ml of penicillin, and 100 g/ml of streptomycin.…”

“…TIGIT/PVR signaling can also downregulate both human and mouse NK cell cytotoxicity (10,14). We have defined that the ITT-like motif of TIGIT recruits Grb2 and SHIP1 to initiate negative signaling, leading to suppression of granule polarization and cytotoxicity of NK cells (15). However, whether and how TIGIT/PVR signaling regulates cytokine secretion of NK cells remains elusive.…”

CD155 on HIV-Infected Cells Is Not Modulated by HIV-1 Vpu and Nef but Synergizes with NKG2D Ligands to Trigger NK Cell Lysis of Autologous Primary HIV-Infected Cells

“…29,30 TIGIT is an immune cell-specific immunoglobulin superfamily receptor of the CD28 family, which is present on the cell surface of 20%-90% of human NK cells with a median of 64%. 31 Similar to DNAM-1, TIGIT binds to CD112 and CD155; however, TIGIT affinity for CD112 and CD155 is higher compared with DNAM-1.…”

TIGIT Enhances Antigen-Specific Th2 Recall Responses and Allergic Disease

“…In addition to TIGIT expressed on T cells, TIGIT Ab blocks TIGIT on other cell types that mediate allergic responses (37). For example, TIGIT is highly expressed on NK cells and is an inhibitor of NK cell cytotoxicity (3,38,39). However, the role of TIGIT in NK2 cells that mediate asthma is unknown and merits investigation (40).…”