SLAMF7 is a single-pass type I membrane protein and contains 1 Ig-like C2-type (immunoglobulin-like) domain. SLAMF7 is expressed in NK cells, activated B-cells, NK-cell line but not in promyelocytic, B-cell lines, or T-cell lines. Although the cytoplasmic domain of CS1 contains immunoreceptor tyrosine-based switch motifs (ITSM), which enables to recruite signaling lymphocyte activation molecule (SLAM)-associated protein (SAP/SH2D1A), it activates NK cells in the absence of a functional SAP. SLAMF7 positively regulated natural killer cell functions by a mechanism dependent on the adaptor EAT-2 but not the related adaptor SAP. However, in the absence of EAT-2, CRACC potently inhibited natural killer cell function. It was also inhibitory in T cells, which are typically devoid of EAT-2. Thus, SLAMF7 can exert activating or inhibitory influences on cells of the immune system depending on cellular context and the availability of effector proteins.
SLAM family member 7 (SLAMF7), also known as CRACC, CD319, CD2-like receptor-activating cytotoxic cells, and CS1, is a single-pass type I membrane protein and a member of the CD2 family of cell surface receptors. SLAMF7 is expressed in NK cells, activated B-cells, NK-cell line but not in promyelocytic, B-cell lines, or T-cell lines. Although the cytoplasmic domain of CS1 contains immunoreceptor tyrosine-based switch motifs (ITSM), which enables to recruite signaling lymphocyte activation molecule (SLAM)-associated protein (SAP/SH2D1A), it activates NK cells in the absence of a functional SAP. CS1 is a self ligand and homophilic interaction of CS1 regulates NK cell cytolytic activity. CRACC positively regulated natural killer cell functions by a mechanism dependent on the adaptor EAT-2 but not the related adaptor SAP. However, in the absence of EAT-2, CRACC potently inhibited natural killer cell function. It was also inhibitory in T cells, which are typically devoid of EAT-2. Thus, CRACC can exert activating or inhibitory influences on cells of the immune system depending on cellular context and the availability of effector proteins.
SLAM family member 8 (SLAMF8) is a single-pass type I membrane protein and contains 1 Ig-like C2-type domain. SLAMF8 is a member of the CD2 family of cell surface proteins involved in lymphocyte activation. These proteins are characterized by Ig domains and studies of a similar protein in mouse suggest that it may function during B cell lineage commitment. SLAMF8 is expressed in lymph node, spleen, thymus and bone marrow. It may play a role in B-lineage commitment and/or modulation of signaling through the B-cell receptor.
SLAM-induced signal-transduction events in T-lymphocytes are different from those in B-cells. Two modes of SLAM signaling are likely to exist: one in which the inhibitor SH2D1A acts as a negative regulator and another in which protein-tyrosine phosphatase 2C (PTPN11)-dependent signal transduction operates.
SLAM family member 5 (SLAMF5/CD84) is a type I transmembrane protein in the SLAM subgroup of the CD2 family. SLAM family proteins regulate multiple aspects of immune system function. Mature human CD84 consists of a 204 amino acid (aa) extracellular domain (ECD) with two Iglike domains,a 21 aa transmembrane segment, and a 99 aa cytoplasmic domain with two immunoreceptor tyrosinebased switch motifs (ITSMs). CD84 exhibits homophilic binding which is mediated by the N-terminal Ig-like domain. Ligation induces tyrosine phosphorylation in the cytoplasmic ITSMs which then recruit the signaling adaptor molecules SAP (SLAM-associated protein) and EAT-2(EWS/Fli1-activated transcript 2).CD84 signaling inhibits Fc epsilon RI-induced mast cell activation but enhances platelet activation. LPS-induced macrophage activation,T cell proliferation and IFN-γproduction, and the interactions between T cells and B cells that are required for germinal center formation.
SLAM Family Member 6 (SLAMF6) is a 60 kD single-pass type I membrane protein that belongs to the SLAM subgroup of the CD2 family. Human SLAMF6/ NTB-A contains a 205 amino acid extracellular domain (ECD) with one Ig-like V-set and one Ig-like C2-set domain, a 21 amino acid transmembrane segment and an 84 amino acid cytoplasmic domain, with two immunoreceptor tyrosine-based switch motifs. SLAMF6 is a homodimer. SLAMF6 can interact with PTN6 and, upon phosphorylation, with PTN11 and SH2D1A/SAP. Phosphorylation-dependent NTB-A association with SAP is required for full production of IFN-γ by NK cells and independent of EAT-2 binding. It Triggers cytolytic activity only in natural killer cells (NK) expressing high surface densities of natural cytotoxicity receptors. On B cells, NTB-A modulates immunoglobulin class switching and the balance between tolerance and autoimmunity.
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