CSF2RA | |||||||||||||||||||||||||||||||
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Aliases | CSF2RA , CD116, CDw116, CSF2R, CSF2RAX, CSF2RAY, CSF2RX, CSF2RY, GM-CSF-R-alpha, GMCSFR, GMR, SMDP4, colony stimulating factor 2 receptor alpha subunit, alphaGMR, colony stimulating factor 2 receptor subunit alpha, GMR-alpha, GMCSFR-alpha, granulocyte-macrophage colony-stimulating factor receptor | ||||||||||||||||||||||||||||||
External IDs | OMIM: 425000, 306250 MGI: 1339754 HomoloGene: 48406 GeneCards: CSF2RA | ||||||||||||||||||||||||||||||
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The granulocyte-macrophage colony-stimulating factor receptor, also known as CD116 (Cluster of Differentiation 116), is a receptor for granulocyte-macrophage colony-stimulating factor, which stimulates the production of white blood cells. [5] In contrast to M-CSF and G-CSF which are lineage specific, GM-CSF and its receptor play a role in earlier stages of development. The receptor is primarily located on neutrophils, eosinophils and monocytes/macrophages, it is also on CD34+ progenitor cells (myeloblasts) and precursors for erythroid and megakaryocytic lineages, but only in the beginning of their development. [5] [6]
It is associated with Surfactant metabolism dysfunction type 4.
The granulocyte-macrophage colony-stimulating factor receptor is a heterodimer composed of at least two different subunits; an α chain, and a β chain which is also present in the receptors for IL-3 and IL-5. The α subunit contains a binding site for granulocyte macrophage colony-stimulating factor, but associates with the ligand only with low affinity. [6] [7] The β chain is involved in signal transduction and formation of high affinity receptor complex together with α chain. Furthermore association of the α and β subunits results in receptor activation. [8]
Gene for α chain is in pseudoautosomal region (PAR) of X and Y chromosomes at the very tip of the chromosomes, near telomere regions and also genes encoding IL-3α with which they share some similarities. [9] Along the gene are several transcription regulatory binding sites with common binding motifs for such transcription factors as GATA, C/EBP or NF-κB. [6]
α chain is 80kDa type I transmembrane protein composed of 3 domains: extracellular, transmembrane and cytoplasmic. Mature polypeptide contains 378 amino acids - 298 amino acids in extracellular domain, 26 in transmembrane domain, 54 in short cytoplasmic tail, plus 22 amino acid long signal peptide, which is cleaved off during translation. [6] Extracellular domain contains cytokine receptor domain for binding its cognate ligand with conserved cysteine residues, WSXWS motif and 11 potential N-glycosylation sites for oligosaccharides, which are important for ligand binding and signalling. Cytoplasmic domain is made of short proline-rich motif and has no intrinsic enzymatic activity. [6] [9] [10] Similar to such motif is also Box1 sequence in β chain.
β chain is crucial for enhancement of binding affinity to the ligand and transduces signal of the activated receptor complex. It is shared with other cytokine receptors IL-3 and IL-5. [9] Its location is on chromosome 22. Surrounding sequences provide binding sites for several regulatory transcription factors similar to those for α chain (GATA, C/EBP, NF-κB). [6] [11] β subunit forms mature 95kDa 800 amino acid long polypeptide with 3 domains: extracellular, transmembrane and cytoplasmic. Extracellular domain contains haematopoietin domains, also known as cytokine receptor modules, which can be found in other cytokine receptors (growth hormone receptor, erythropoietin receptor). In the membrane distant part are typically cysteine residues forming disulphide bonds, proline pair, which devies the extracellular domain into two fibronectin type III-like subdomains in seven stranded β-barrel structure. In the membrane proximal region is then a WSXWS motif as is in α chain. [6] Cytoplasmic domain serves as a signal transducer. [9] [10]
α chain can be modified in post-transcriptional manner by alternative splicing creating different variant of mRNA. Splicing on 3´end produces transcript where 25 amino acids in C-terminal region are completely replaced by 35 new amino acids. Such protein is functional, but 10 times less abundant. Another splicing variant lacks both transmembrane and cytoplasmic domains. Remaining extracellular domain acts as a soluble GM-CSFRα and have been identified in bone marrow, monocytes and macrophages, placenta and chorio-carcinoma cells. Splicing products on the 5´end were found in primary haematopoietic cells and acute myeloid leukemia blasts. [6] [12]
β subunit can be found in two distinct isoforms: classical full-length protein and alternative form with deletions in transmembrane domain. Deletions results in truncated peptide with 23 original amino acids in the membrane proximal cytoplasmic region and 23 new ones in C-terminal tail. This shorter isoform is unable to transduce any signals, thus acts as a negative inhibitor. Significantly upregulated production is in blasts from acute myeloid leukemia patients. [6] [12]
Upon dimerisation of the α and β subunits the β subunit becomes phosphorylated on tyrosine residues in its cytoplasmic domain, where are many regions participating in different cell signalling mechanisms for proliferation, differentiation and survival. Formation of high affinity receptor complex includes specific interactions between both subunits and ligand. Interactions then mediate conformational changes and subsequent receptor activation. Receptor is either functional in single heterodimer α1β1 or in dimerised complexes α2β2 joined by intermolecular disulphide bonds. [6] [7] [9] For full activation oligomerization of the receptor is crucial, it is formed into hexamer composed of two GM-CSF, two α and two β subunits or dodecamer which is composed of two hexamers. [11]
Phosphorylation is mediated by tyrosine kinases, members of the Janus kinase (JAK) family, which are constitutively associated with cytoplasmic domain. [8] Activated kinases then phosphorylate tyrosine residues on cytoplasmic domain of β subunit, thus creating docking sites for Src homology 2 (SH2) domain-containing signalling proteins like Shc and STATs. [6] [11] [13] These interactions trigger downstream signalling pathways, depending on the location of phosphorylated tyrosine residues in the chain. Membrane proximal section is known to be responsible for proliferation by activating STAT5 and c-myc. [6] Membrane distal section is then required for differentiation and survival by prevention of apoptosis and activation of MAPK and PI3K pathways. [10] [11] [13]
Simultaneously with receptor activation goes hand in hand its downregulation, that prevents unwanted overactivation. Controlling mechanisms are mainly aimed at inhibition of JAK kinase activity by SHP-1 tyrosine phosphatase with SH2 binding domain or by members of SOCS family which also possess SH2 domain. After direct ligation with JAK kinase, they mediate degradation in proteasome. [11] Other possibility of downregulation is degradation of phosphorylated β subunit and subsequent internalization of the receptor/ligand complex. Rate of such process positively correlates with amount of ligand/receptor complexes. In addition, after stimulation of β subunit mRNA levels coding α chain decrease and on the contrary expression of soluble α subunit is upregulated. Soluble GM-CSFRα then clutches free ligands with similar affinity as membrane receptor and prevents binding of GM-CSF to the cell surface. GM-CSFRα can be also cleaved off of the membrane receptor. [6] [8]
Different expression of GM-CSFR subunits on hematopoietic cells mediates maturation of various lineages. For example in quiescent hematopoietic stem cells the β chain is expressed at very low levels and the amount increases along initial differentiation of erythroid, megakaryocytic, granulocytic and monocytic lineages. In the first two mentioned lineages the expression eventually vanishes completely, in granulocytes and monocytes persists and continues to grow during their differentiation. In monocytes and mainly neutrophils receptor regulates proliferation, maturation and overall survival. [6] [11]
Kinetics of the receptor in immature and mature myeloid cells in response to GM-CSF is readily regulated by internalization or just by above mentioned degradation and desensitization of β subunit (mainly in the earlier hematopoietic development). [6]
It was shown that defective dendritic cell (DC) differentiation in malaria at least partially caused by GM-CSFR dysregulation and GM-CSFR modification by lipoperoxidation product 4-HNE via direct interaction with its CD116 subunit. [14] [15]
A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation. Usually it is a secreted protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes.
Integrins are transmembrane receptors that help cell-cell and cell-extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle, organization of the intracellular cytoskeleton, and movement of new receptors to the cell membrane. The presence of integrins allows rapid and flexible responses to events at the cell surface.
Cytokines are a broad and loose category of small proteins important in cell signaling. Due to their size, cytokines cannot cross the lipid bilayer of cells to enter the cytoplasm and therefore typically exert their functions by interacting with specific cytokine receptors on the target cell surface. Cytokines have been shown to be involved in autocrine, paracrine and endocrine signaling as immunomodulating agents.
Granulocyte colony-stimulating factor, also known as colony-stimulating factor 3, is a glycoprotein that stimulates the bone marrow to produce granulocytes and stem cells and release them into the bloodstream.
Granulocyte-macrophage colony-stimulating factor (GM-CSF), also known as colony-stimulating factor 2 (CSF2), is a monomeric glycoprotein secreted by macrophages, T cells, mast cells, natural killer cells, endothelial cells and fibroblasts that functions as a cytokine. The pharmaceutical analogs of naturally occurring GM-CSF are called sargramostim and molgramostim.
Interleukin 3 (IL-3) is a protein that in humans is encoded by the IL3 gene localized on chromosome 5q31.1. Sometimes also called colony-stimulating factor, multi-CSF, mast cell growth factor, MULTI-CSF, MCGF; MGC79398, MGC79399: the protein contains 152 amino acids and its molecular weight is 17 kDa. IL-3 is produced as a monomer by activated T cells, monocytes/macrophages and stroma cells. The major function of IL-3 cytokine is to regulate the concentrations of various blood-cell types. It induces proliferation and differentiation in both early pluripotent stem cells and committed progenitors. It also has many more specific effects like the regeneration of platelets and potentially aids in early antibody isotype switching.
Interleukin 5 (IL-5) is an interleukin produced by type-2 T helper cells and mast cells.
Integrin alpha M (ITGAM) is one protein subunit that forms heterodimeric integrin alpha-M beta-2 (αMβ2) molecule, also known as macrophage-1 antigen (Mac-1) or complement receptor 3 (CR3). ITGAM is also known as CR3A, and cluster of differentiation molecule 11B (CD11B). The second chain of αMβ2 is the common integrin β2 subunit known as CD18, and integrin αMβ2 thus belongs to the β2 subfamily integrins.
Granulopoiesis is a part of haematopoiesis, that leads to the production of granulocytes. A granulocyte, also referred to as a polymorphonuclear leukocyte (PMN), is a type of white blood cell that has multi lobed nuclei, usually containing three lobes, and has a significant amount of cytoplasmic granules within the cell. Granulopoiesis takes place in the bone marrow. It leads to the production of three types of mature granulocytes: neutrophils, eosinophils and basophils.
An alveolar macrophage, pulmonary macrophage, is a type of macrophage, a professional phagocyte, found in the airways and at the level of the alveoli in the lungs, but separated from their walls.
Type I cytokine receptors are transmembrane receptors expressed on the surface of cells that recognize and respond to cytokines with four α-helical strands. These receptors are also known under the name hemopoietin receptors, and share a common amino acid motif (WSXWS) in the extracellular portion adjacent to the cell membrane. Members of the type I cytokine receptor family comprise different chains, some of which are involved in ligand/cytokine interaction and others that are involved in signal transduction.
The granulocyte colony-stimulating factor receptor (G-CSF-R) also known as CD114 is a protein that in humans is encoded by the CSF3R gene. G-CSF-R is a cell-surface receptor for the granulocyte colony-stimulating factor (G-CSF). The G-CSF receptors belong to a family of cytokine receptors known as the hematopoietin receptor family. The granulocyte colony-stimulating factor receptor is present on precursor cells in the bone marrow, and, in response to stimulation by G-CSF, initiates cell proliferation and differentiation into mature neutrophilic granulocytes and macrophages.
The interferon-α/β receptor (IFNAR) is a virtually ubiquitous membrane receptor which binds endogenous type I interferon (IFN) cytokines. Endogenous human type I IFNs include many subtypes, such as interferons-α, -β, -ε, -κ, -ω, and -ζ.
CD64 is a type of integral membrane glycoprotein known as an Fc receptor that binds monomeric IgG-type antibodies with high affinity. It is more commonly known as Fc-gamma receptor 1 (FcγRI). After binding IgG, CD64 interacts with an accessory chain known as the common γ chain, which possesses an ITAM motif that is necessary for triggering cellular activation.
Colony stimulating factor 1 receptor (CSF1R), also known as macrophage colony-stimulating factor receptor (M-CSFR), and CD115, is a cell-surface protein encoded by the human CSF1R gene. CSF1R is a receptor that can be activated by two ligands: colony stimulating factor 1 (CSF-1) and interleukin-34 (IL-34). CSF1R is highly expressed in myeloid cells, and CSF1R signaling is necessary for the survival, proliferation, and differentiation of many myeloid cell types in vivo and in vitro. CSF1R signaling is involved in many diseases and is targeted in therapies for cancer, neurodegeneration, and inflammatory bone diseases.
Interleukin 5 receptor, alpha (IL5RA) also known as CD125 is a subunit of the Interleukin-5 receptor. IL5RA also denotes its human gene.
Interleukin 3 receptor, alpha (IL3RA), also known as CD123, is a human gene.
The interleukin-5 receptor is a type I cytokine receptor. It is a heterodimer of the interleukin 5 receptor alpha subunit and CSF2RB.
The following outline is provided as an overview of and topical guide to immunology:
Otilimab is a fully human antibody which has been developed by the biotechnology company MorphoSys. It can also be referred to as HuCAL antibody, HuCAL standing for Human Combinatorial Antibody Library and being a technology used to generate monoclonal antibodies. Otilimab is directed against the granulocyte-macrophage colony stimulating factor (GM-CSF), a monomeric glycoprotein functioning as a cytokine promoting both proliferation and activation of macrophages and neutrophils.