SLAMF3 (CD229) is a type I transmembrane glycoprotein in the SLAM subgroup of the CD2 family. Mature human SLAMF3 consists of a 407 amino acid (aa) extracellular domain (ECD) with two Ig-like V-set and two Ig-like truncated C2-set domains. The ECD of human SLAMF3 shares 57% - 59% aa sequence identity with mouse and rat SLAMF3. Within the first two Ig-like domains that are common to all SLAM proteins, human SLAMF3 shares 24% - 39% aa sequence identity with human 2B4, BLAME, CD2F-10, CD84, CRACC, NTB-A, and SLAM. It is expressed on T and B cells, thymocytes, and more weakly on NK cells. It may participate in adhesion reactions between T lymphocytes and accessory cells by homophilic interaction. Promotes T-cell differentiation into a helper T-cell Th17 phenotype leading to increased IL-17 secretion; the costimulatory activity requires SH2D1A. SLAMF3 may be involved in the maintenance of peripheral cell tolerance by serving as a negative regulator of the immune response. It also disable autoantibody responses and inhibit IFN-gamma secretion by CD4+ T-cells and negatively regulate the size of thymic innate CD8+ T-cells and the development of invariant natural killer T (iNKT) cells.
The CD2 family receptors are type I transmembrane glycoproteins belonging to immunoglobulin (Ig) superfamily characterized by a membrane-proximal Ig constant 2 (C2) domain and a membrane-distal variable (V) domain that is responsible for ligand recognition. CD84, also known as LY9B and SLAMF5, is a homophilic member of the SLAM (signaling lymphocyte activation molecule) subfamily of the CD2 family. The SLAM family receptorsmediate signal transduction through the interaction of its ITSM (immunoreceptor tyrosine-based switch motifs) in the intracellular region and the SH2 domain of adaptor molecules SAP (SLAM-associated protein) and EAT-2 (EWS-activated transcript 2), and accordingly modulate both adaptive and innate immune responses. The CD84-CD84 interaction was independent of its cytoplasmic tail. Thus, CD84 is its own ligand and acts as a costimulatory molecule. CD84 is expressed on cells from almost all hematopoietic lineages and on CD34+ hematopoietic progenitor cells, suggesting that CD84 serves as a marker for committed hematopoietic progenitor cells.
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; also known as Activating NK receptor; NK-T-B-antigen; NTB-A; SLAMF6; KALI and Ly108; is a single-pass type I membrane protein which belongs to the CD2 subfamily of the immunoglobulin superfamily. SLAMF6 / Ly108 contains one Ig-like (immunoglobulin-like) domain. It is expressed by all (resting and activated) natural killer cells (NK); T- and B-lymphocytes. SLAMF6 / Ly108 triggers cytolytic activity only in natural killer cells (NK) expressing high surface densities of natural cytotoxicity receptors. SLAMF6 / Ly108 is a homodimer. It interacts with PTN6 and; upon phosphorylation; with PTN11 and SH2D1A/SAP. SLAMF6 / Ly108 undergoes tyrosine phosphorylation and associates with the Src homology 2 domain-containing protein (SH2D1A) as well as with SH2 domain-containing phosphatases (SHPs). It may function as a coreceptor in the process of NK cell activation. SLAMF6 / Ly108 can also mediate inhibitory signals in NK cells from X-linked lymphoproliferative patients.
SLAM Family Member 6 (SLAMF6) is a 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.
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.
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.
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