词条 | MARCO |
释义 |
Cell expressionCertain subtypes of macrophages are likely to express MARCO, but the receptor is also present on circulating monocytes, dendritic cells, and B cells.[6][11] MARCO is typically present on the macrophages in the marginal zone of the spleen and the medullary lymph nodes, but it is also found in the liver.[9] Dendritic cells increase expression of MARCO when exposed to certain pathogens, which leads to an increase in phagocytosis by the dendritic cell.[5] When ligand binds to MARCO on dendritic cells, the cytoskeleton of the cell is altered, allowing for the formation of the long arms that also increase the phagocytic ability of dendritic cells.[5][12] Macrophages that constitutively express MARCO are within the spleen marginal zone and medullary lymph nodes.[5] Certain interactions between the macrophage and bacteria up-regulate its expression, as well as stimulating the expression of MARCO on tissue macrophages.[5][6] FunctionPhagocytosisThe primary function of scavenger receptors is to phagocytose pathogens, but they are also able to participate in cell–cell recognition and are important in initiating inflammatory responses.[7][6] MARCO, being a PRR, is able to bind to a wide variety of bacteria, making it an important receptor for immunity against bacteria.[8] Both soluble LPS and entire bacteria are able to bind to MARCO.[13] MARCO is also able to bind to both acetylated LDL (AcLDL) and oxidized LDL (OxLDL), as well as to B cells in the marginal zone of the spleen and apoptotic cells.[5][6] Since MARCO is able to recognize and phagocytose pathogens and apoptotic cells, expression of MARCO increases the phagocytic ability of the cell. MARCO operates independently of opsonization.[8] InflammationMARCO does not directly cause an inflammatory response, but it helps other receptors interact with PAMPs, so they may initiate inflammation.[7][8] One way MARCO does this is by tethering a pathogen to other proteins on the cell that do cause an inflammatory response.[8] These proteins could be other PRRs such as TLR2.[8] These receptors may then lead to the activation of NF-κB which allows for the production and release of pro-inflammatory cytokines.[8] Through phagocytosis, MARCO also brings pathogens into the cell so that there are more pathogens available to intracellular compartments containing receptors such as TLR3, NOD2, and NALP3 that are capable of initiating an inflammatory response.[7] StructureMARCO is a transmembrane protein that has five domains.[6] The first domain is within the cell, called the cytoplasmic domain.[6] Moving into the cell membrane is the transmembrane domain, which is followed by the spacer domain located outside of the cell, then the collagenous domain, and finally the SRCR domain.[6] The SRCR domain is necessary for MARCO to bind to ligands.[6] Other members of the class A scavenger receptors tend to have alpha helical coiled coil domains, but MARCO does not.[5] The C-terminal SRCR domain of MARCO plays a key role in the ability of the receptor to bind and take up ligand, enhance downstream inflammatory responses, and adhere to surfaces.[8] The SRCR domain is where the ligand binds to MARCO.[8] There are two highly conserved arginine amino acids, called the RxR motif, that are crucial for the binding of the ligand.[8] Associated diseasesThe activity of MARCO on microglia, the macrophages of the brain, is associated with Alzheimer's disease.[7][10] One primary characteristic of Alzheimer's disease is the presence of numerous senile plaques in the brain that contain amyloid beta peptides (Aβ).[10] Initially, the microglia clear the Aβ which binds to receptors such as MARCO.[10] As the disease progresses, however, their ability to clear Aβ decreases, resulting in Aβ accumulation.[10] This accumulation of Aβ occurs early on in Alzheimer's disease, harming the brain as Aβ is neurotoxic.[10] MARCO also interacts with formyl peptide receptor (FPR2) to form a complex that causes the microglia to release pro-inflammatory cytokines which leads to inflammation that results in damage to neurons.[10] {{clear}}References1. ^{{cite journal | vauthors = Elomaa O, Sankala M, Pikkarainen T, Bergmann U, Tuuttila A, Raatikainen-Ahokas A, Sariola H, Tryggvason K | title = Structure of the human macrophage MARCO receptor and characterization of its bacteria-binding region | journal = The Journal of Biological Chemistry | volume = 273 | issue = 8 | pages = 4530–8 | date = February 1998 | pmid = 9468508 | doi = 10.1074/jbc.273.8.4530 }} 2. ^{{cite journal | vauthors = Elomaa O, Kangas M, Sahlberg C, Tuukkanen J, Sormunen R, Liakka A, Thesleff I, Kraal G, Tryggvason K | title = Cloning of a novel bacteria-binding receptor structurally related to scavenger receptors and expressed in a subset of macrophages | journal = Cell | volume = 80 | issue = 4 | pages = 603–9 | date = February 1995 | pmid = 7867067 | pmc = | doi = 10.1016/0092-8674(95)90514-6 }} 3. ^{{cite journal | vauthors = Kangas M, Brännström A, Elomaa O, Matsuda Y, Eddy R, Shows TB, Tryggvason K | title = Structure and chromosomal localization of the human and murine genes for the macrophage MARCO receptor | journal = Genomics | volume = 58 | issue = 1 | pages = 82–9 | date = May 1999 | pmid = 10331948 | pmc = | doi = 10.1006/geno.1999.5811 }} 4. ^{{cite web | title = Entrez Gene: MARCO macrophage receptor with collagenous structure| url = https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=8685| accessdate = }} 5. ^1 2 3 4 5 6 7 {{cite journal | vauthors = Plüddemann A, Neyen C, Gordon S | title = Macrophage scavenger receptors and host-derived ligands | journal = Methods | volume = 43 | issue = 3 | pages = 207–17 | date = November 2007 | pmid = 17920517 | doi = 10.1016/j.ymeth.2007.06.004 | url = http://linkinghub.elsevier.com/retrieve/pii/S1046202307001296 }} 6. ^1 2 3 4 5 6 7 8 9 10 {{cite journal | vauthors = Bowdish DM, Gordon S | title = Conserved domains of the class A scavenger receptors: evolution and function | journal = Immunological Reviews | volume = 227 | issue = 1 | pages = 19–31 | date = January 2009 | pmid = 19120472 | doi = 10.1111/j.1600-065x.2008.00728.x }} 7. ^1 2 3 4 5 {{cite journal | vauthors = Mukhopadhyay S, Varin A, Chen Y, Liu B, Tryggvason K, Gordon S | title = SR-A/MARCO-mediated ligand delivery enhances intracellular TLR and NLR function, but ligand scavenging from cell surface limits TLR4 response to pathogens | journal = Blood | volume = 117 | issue = 4 | pages = 1319–28 | date = January 2011 | pmid = 21098741 | doi = 10.1182/blood-2010-03-276733 | url = http://www.bloodjournal.org/content/117/4/1319 }} 8. ^1 2 3 4 5 6 7 8 9 10 11 {{cite journal | vauthors = Novakowski KE, Huynh A, Han S, Dorrington MG, Yin C, Tu Z, Pelka P, Whyte P, Guarné A, Sakamoto K, Bowdish DM | title = A naturally occurring transcript variant of MARCO reveals the SRCR domain is critical for function | journal = Immunology and Cell Biology | volume = 94 | issue = 7 | pages = 646–55 | date = August 2016 | pmid = 26888252 | doi = 10.1038/icb.2016.20 | pmc = 4980223 }} 9. ^1 {{cite journal | vauthors = Sun H, Song J, Weng C, Xu J, Huang M, Huang Q, Sun R, Xiao W, Sun C | title = Association of decreased expression of the macrophage scavenger receptor MARCO with tumor progression and poor prognosis in human hepatocellular carcinoma | journal = Journal of Gastroenterology and Hepatology | volume = 32 | issue = 5 | pages = 1107–1114 | date = May 2017 | pmid = 27806438 | doi = 10.1111/jgh.13633 }} 10. ^1 2 3 4 5 6 {{cite journal | vauthors = Yu Y, Ye RD | title = Microglial Aβ receptors in Alzheimer's disease | journal = Cellular and Molecular Neurobiology | volume = 35 | issue = 1 | pages = 71–83 | date = January 2015 | pmid = 25149075 | doi = 10.1007/s10571-014-0101-6 }} 11. ^{{cite journal | vauthors = Getts DR, Terry RL, Getts MT, Deffrasnes C, Müller M, van Vreden C, Ashhurst TM, Chami B, McCarthy D, Wu H, Ma J, Martin A, Shae LD, Witting P, Kansas GS, Kühn J, Hafezi W, Campbell IL, Reilly D, Say J, Brown L, White MY, Cordwell SJ, Chadban SJ, Thorp EB, Bao S, Miller SD, King NJ | title = Therapeutic inflammatory monocyte modulation using immune-modifying microparticles | journal = Science Translational Medicine | volume = 6 | issue = 219 | pages = 219ra7 | date = January 2014 | pmid = 24431111 | doi = 10.1126/scitranslmed.3007563 | url = http://stm.sciencemag.org/content/6/219/219ra7 | pmc = 3973033 }} 12. ^{{cite journal | vauthors = Kissick HT, Dunn LK, Ghosh S, Nechama M, Kobzik L, Arredouani MS | title = The scavenger receptor MARCO modulates TLR-induced responses in dendritic cells | journal = PLOS One | volume = 9 | issue = 8 | pages = e104148 | date = 2014-08-04 | pmid = 25089703 | pmc = 4121322 | doi = 10.1371/journal.pone.0104148 }} 13. ^{{cite journal | vauthors = Athanasou NA | title = The pathobiology and pathology of aseptic implant failure | journal = Bone & Joint Research | volume = 5 | issue = 5 | pages = 162–8 | date = May 2016 | pmid = 27146314 | pmc = 4921050 | doi = 10.1302/2046-3758.55.bjr-2016-0086 | url = http://bjr.boneandjoint.org.uk/content/5/5/162 }} Further reading{{refbegin|32em}}
1 : Scavenger receptors |
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