Galectin-1 is a protein that in humans is encoded by the LGALS1 gene. [5] [6]
Galectin-1 is a protein that in humans is encoded by the LGALS1 gene. [5] [6]
LGALS1 contains four exons. The galectin-1 protein is 135 amino acids in length and highly conserved across species. It can be found in the nucleus, the cytoplasm, the cell surface and in the extracellular space. Galectins in general lack a traditional signal sequence, but are still secreted across the plasma membrane. This non-traditional secretion requires a functional glycan binding site. Galectin 1 contains a single carbohydrate recognition domain through which it can bind glycans both as a monomer and as a homodimer. Dimers are non-covalently bound and will spontaneously disassociate in low concentration. [7] Galectin 1 does not bind glycans when oxidized. [8] Having 6 cysteine residues, the oxidation state has a significant effect on the protein structure. The oxidized form is reported to have alternative functions not involving carbohydrate binding. [9]
The galectins are a family of beta-galactoside-binding proteins implicated in modulating cell-cell and cell-matrix interactions. Galectin-1 may act as an autocrine negative growth factor that regulates cell proliferation. [10] Galectin-1 expression in Hodgkin Lymphoma has also been shown to mediate immunosuppression of CD8+ T-cells. [11]
It has been linked to the inflammatory process in HIV individuals, and some research suggest that Gal-1 could be related to the HIV-1 latency. [12]
Galectin-1 is thought to play a role in creating immune tolerance in pregnancy. [13] Galectin-1 is expressed by the endometrial stromal cells throughout the menstrual cycle, however significantly increases during implantation. Galectin-1 induces the differentiation of Dendritic cells towards a phenotype which dampens T helper 1 cells and T helper 17 cells and dampens inflammation via interleukin-10 and interleukin-27. [14] It also plays a role in the formation and expression of HLA-G in the syncytium. [15]
LGALS1 has been shown to interact with GEMIN4 [16] HRAS. [17]
The Consortium for Functional Glycomics (CFG) is a large research initiative funded in 2001 by a glue grant from the National Institute of General Medical Sciences (NIGMS) to “define paradigms by which protein-carbohydrate interactions mediate cell communication”. To achieve this goal, the CFG studies the functions of:
Lectins are carbohydrate-binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides. Lectins have a role in recognition at the cellular and molecular level and play numerous roles in biological recognition phenomena involving cells, carbohydrates, and proteins. Lectins also mediate attachment and binding of bacteria, viruses, and fungi to their intended targets.
DC-SIGN also known as CD209 is a protein which in humans is encoded by the CD209 gene.
Mannose-binding lectin (MBL), also called mannan-binding lectin or mannan-binding protein (MBP), is a lectin that is instrumental in innate immunity as an opsonin and via the lectin pathway.
Siglecs(Sialic acid-binding immunoglobulin-type lectins) are cell surface proteins that bind sialic acid. They are found primarily on the surface of immune cells and are a subset of the I-type lectins. There are 14 different mammalian Siglecs, providing an array of different functions based on cell surface receptor-ligand interactions.
Galectins are a class of proteins that bind specifically to β-galactoside sugars, such as N-acetyllactosamine, which can be bound to proteins by either N-linked or O-linked glycosylation. They are also termed S-type lectins due to their dependency on disulphide bonds for stability and carbohydrate binding. There have been about 15 galectins discovered in mammals, encoded by the LGALS genes, which are numbered in a consecutive manner. Only galectin-1, -2, -3, -4, -7, -7B, -8, -9, -9B, 9C, -10, -12, -13, -14, and -16 have been identified in humans. Galectin-5 and -6 are found in rodents, whereas galectin-11 and -15 are uniquely found in sheep and goats. Members of the galectin family have also been discovered in other mammals, birds, amphibians, fish, nematodes, sponges, and some fungi. Unlike the majority of lectins they are not membrane bound, but soluble proteins with both intra- and extracellular functions. They have distinct but overlapping distributions but found primarily in the cytosol, nucleus, extracellular matrix or in circulation. Although many galectins must be secreted, they do not have a typical signal peptide required for classical secretion. The mechanism and reason for this non-classical secretion pathway is unknown.
Langerin (CD207) is a type II transmembrane protein which is encoded by the CD207 gene in humans. It was discovered by scientists Sem Saeland and Jenny Valladeau as a main part of Birbeck granules. Langerin is C-type lectin receptor on Langerhans cells (LCs) and in mice also on dermal interstitial CD103+ dendritic cells (DC) and on resident CD8+ DC in lymph nodes.
C-type lectin domain family 4 member M is a protein that in humans is encoded by the CLEC4M gene. CLEC4M has also been designated as CD299.
Galectin-3-binding protein is a protein that in humans is encoded by the LGALS3BP gene.
Gem-associated protein 2 (GEMIN2), also called survival of motor neuron protein-interacting protein 1 (SIP1), is a protein that in humans is encoded by the GEMIN2 gene.
Galectin-8 is a protein of the galectin family that in humans is encoded by the LGALS8 gene.
Galectin-2 is a protein that in humans is encoded by the LGALS2 gene.
Gem-associated protein 4 is a protein that in humans is encoded by the GEMIN4 gene.
Hepatitis A virus cellular receptor 2 (HAVCR2), also known as T-cell immunoglobulin and mucin-domain containing-3 (TIM-3), is a protein that in humans is encoded by the HAVCR2 (TIM-3)gene. HAVCR2 was first described in 2002 as a cell surface molecule expressed on IFNγ producing CD4+ Th1 and CD8+ Tc1 cells. Later, the expression was detected in Th17 cells, regulatory T-cells, and innate immune cells. HAVCR2 receptor is a regulator of the immune response.
Galectin-7 is a protein that in humans is encoded by the LGALS7 gene.
Placental protein 13 (PP13) is a protein that in humans is encoded by the LGALS13 gene.
Galectin-4 is a protein that in humans is encoded by the LGALS4 gene.
C-type lectin domain family 10 member A (CLEC10A) also designated as CD301 is a protein that in humans is encoded by the CLEC10A gene. CLEC10A is part of the C-type lectin superfamily and binds to N-Acetylgalactosamine (GalNAc). It is mainly expressed on myeloid cells and also on oocytes and very early stages of embryogenesis. CLEC10A is used as a marker of the CD1c+ dendritic cell subgroup, also called cDC2. The actions of CLEC10A are diverse, depending on the ligand and environment.
Galectin-3 is a protein that in humans is encoded by the LGALS3 gene. Galectin-3 is a member of the lectin family, of which 14 mammalian galectins have been identified.
Glycan-Protein interactions represent a class of biomolecular interactions that occur between free or protein-bound glycans and their cognate binding partners. Intramolecular glycan-protein (protein-glycan) interactions occur between glycans and proteins that they are covalently attached to. Together with protein-protein interactions, they form a mechanistic basis for many essential cell processes, especially for cell-cell interactions and host-cell interactions. For instance, SARS-CoV-2, the causative agent of COVID-19, employs its extensively glycosylated spike (S) protein to bind to the ACE2 receptor, allowing it to enter host cells. The spike protein is a trimeric structure, with each subunit containing 22 N-glycosylation sites, making it an attractive target for vaccine search.
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