Human Siglec-5 are Itype(Igtype) lectins belonging to the Ig superfamily;They are characterized by an N terminal Ig-like V type domain which mediates sialic acid binding; followed by varying numbers of Ig-like C2 type domains. SIGLEC5 has also been designated CD170; they are expressed by monocytic or myeloid lineage cells; and also found at high levels in peripheral blood leukocytes; spleen; bone marrow and at lower levels in lymph node; lung; appendix; placenta; pancreas and thymus. SIGLEC5 are expressed by monocytes and neutrophils but absent from leukemic cell lines representing early stages of myelomonocytic differentiation. Siglec5 to 11 share a high degree of sequence similarity with CD33/Siglec3 both in their extracellular and intracellular regions. They are collectively referred to as CD33 related Siglecs. One remarkable feature of the CD33 related Siglecs is their differential expression pattern within the hematopoietic system This fact; together with the presence of two conserved immunoreceptor tyrosinebased inhibition motifs (ITIMs) in their cytoplasma tails; suggests that CD33 related Siglecs are involved in the regulation of cellular activation within the immune system.
SIGLEC6, also known as CD327, belongs to the immunoglobulin superfamily, SIGLEC (sialic acid binding Ig-like lectin) family. SIGLEC6 is a sialic acid recognizing protein expressed at high levels in placenta (cyto- and syncytiotrophoblastic cells) and at lower levels in spleen, peripheral blood leukocytes (predominantly B-cells) and small intestine. SIGLEC6 localizes in various compartments such as membrane fraction, extracellular region and so on. SIGLEC6 may show increasing expression human labor and following childbirth, it has been speculated that this expression helps to slow the tempo of human labor. Interestingly, expression of SIGLEC6 is further upregulated in pre-eclampsia, which appears to be a uniquely human disease.
Siglecs (sialic acid binding Ig-like lectins) are I-type (Ig-type) lectins belonging to the Ig superfamily. They are characterized by an N-terminal Ig-like V-type domain which mediates sialic acid binding, followed by varying numbers of Ig-like C2-type domains. Eleven human Siglecs have been cloned and characterized. Human Siglec-7 encodes a 467 amino acid (aa) polypeptide with a hydrophobic signal peptide, an N-terminal Ig-like V-type domain, two Ig-like C2-type domains, a transmembrane region and a cytoplasmic tail. Siglec-7 exists as a monomer on the cell surface and is expressed on natural killer cells, CD8+ T cells and monocytes. It binds equally well to both alpha 2,3- and alpha 2,6-linked sialic acid. The gene encoding Siglec-7 was mapped to chromosome 19q13.3.
Siglec-8 is also known as SIGLEC8, SAF2, SIGLEC-8, SIGLEC8L and sialic acid binding Ig like lectin 8, is an approximately 75 kDa transmembrane glycoprotein in the Siglec family of sialic acid-binding immune regulatory molecules. Siglec-8 is expressed on eosinophils, basophils, and mast cells, and it shows a binding preference for the carbohydrate 6-O sulfated sLex. At the tissue level, Siglec-8 mRNA was found to be most highly expressed in lung, PBMCs, spleen, and kidney. Mature human Siglec-8 consists of a 347 amino acid (aa) extracellular domain (ECD) with three Ig-like domains, a 21 aa transmembrane segment, and a 115 aa cytoplasmic domain with two tyrosine based signaling motifs. Alternative splicing generates additional isoforms that either lack most of the second Ig-like domain or have a substituted cytoplasmic domain without the signaling motifs. Cross-linking of Siglec-8 inhibits Fc epsilon RI alpha induced mast cell degranulation (9). It also induces eosinophil apoptosis, an effect which is enhanced by the eosinophil-activating cytokines IL-5, IL-33, and GM-CSF.
Siglec-8 is also known as SIGLEC8, SAF2, SIGLEC-8, SIGLEC8L and sialic acid binding Ig like lectin 8, is an approximately 75 kDa transmembrane glycoprotein in the Siglec family of sialic acid-binding immune regulatory molecules. Siglec-8 is expressed on eosinophils, basophils, and mast cells, and it shows a binding preference for the carbohydrate 6-O sulfated sLex. At the tissue level, Siglec-8 mRNA was found to be most highly expressed in lung, PBMCs, spleen, and kidney. Mature human Siglec-8 consists of a 347 amino acid (aa) extracellular domain (ECD) with three Ig-like domains, a 21 aa transmembrane segment, and a 115 aa cytoplasmic domain with two tyrosine based signaling motifs. Alternative splicing generates additional isoforms that either lack most of the second Ig-like domain or have a substituted cytoplasmic domain without the signaling motifs. Cross-linking of Siglec-8 inhibits Fc epsilon RI alpha induced mast cell degranulation. It also induces eosinophil apoptosis, an effect which is enhanced by the eosinophil-activating cytokines IL-5, IL-33, and GM-CSF.
Sialic acid-binding Ig-like lectin 9(Siglec 9) is expressed by peripheral blood leukocytes (neutrophils and monocytes but not eosinophils); and found in liver; fetal liver; bone marrow; placenta; spleen and in lower levels in skeletal muscle; fetal brain and so on. It is a putative adhesion molecule that mediates sialic-acid dependent binding to cells. It also binds to alpha-2;3- or alpha-2;6-linked sialic acid. The sialic acid recognition site may be masked by cis interactions with sialic acids on the same cell surface.
Inserisci la tua e-mail e seleziona le aree di interesse per ricevere le ultime novità, approfondimenti e promozioni.
Seleziona uno o più ambiti di interesse per ricevere comunicazioni più utili e mirate.
2025 TEMA Ricerca - All Rights Reserved.
