Fibronectin is a high-molecular weight glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. Fibronectin binds to other extracellular matrix proteins such as collagen and heparan sulfate proteoglycans. Fibronectin exists as a protein dimer, consisting of two nearly identical monomers linked by a pair of disulfide bonds; the fibronectin protein is produced from a single gene, but alternative splicing of its pre-mRNA leads to the creation of several isoforms. Two types of fibronectin are present in vertebrates: soluble plasma fibronectin is a major protein component of blood plasma and is produced in the liver by hepatocytes. Insoluble cellular fibronectin is a major component of the extracellular matrix, it is secreted by various cells fibroblasts, as a soluble protein dimer and is assembled into an insoluble matrix in a complex cell-mediated process. Fibronectin plays a major role in cell adhesion, growth and differentiation, it is important for processes such as wound healing and embryonic development.
Altered fibronectin expression and organization has been associated with a number of pathologies, including cancer and fibrosis. Fibronectin exists as a protein dimer, consisting of two nearly identical polypeptide chains linked by a pair of C-terminal disulfide bonds; each fibronectin subunit has a molecular weight of 230–250 kDa and contains three types of modules: type I, II, III. All three modules are composed of two anti-parallel β-sheets resulting in a Beta-sandwich; the absence of disulfide bonds in type III modules allows them to unfold under applied force. Three regions of variable splicing occur along the length of the fibronectin protomer. One or both of the "extra" type III modules may be present in cellular fibronectin, but they are never present in plasma fibronectin. A "variable" V-region exists between III14–15; the V-region structure is different from the type I, II, III modules, its presence and length may vary. The V-region contains the binding site for α4β1 integrins, it is present in most cellular fibronectin, but only one of the two subunits in a plasma fibronectin dimer contains a V-region sequence.
The modules are arranged into several functional and protein-binding domains along the length of a fibronectin monomer. There are four fibronectin-binding domains, allowing fibronectin to associate with other fibronectin molecules. One of these fibronectin-binding domains, I1–5, is referred to as the "assembly domain", it is required for the initiation of fibronectin matrix assembly. Modules III9–10 correspond to the "cell-binding domain" of fibronectin; the RGD sequence is located in III10 and is the site of cell attachment via α5β1 and αVβ3 integrins on the cell surface. The "synergy site" is in III9 and has a role in modulating fibronectin's association with α5β1 integrins. Fibronectin contains domains for fibrin-binding, collagen-binding, fibulin-1-binding, heparin-binding and syndecan-binding. Fibronectin has numerous functions, it is involved in cell adhesion, growth and differentiation. Cellular fibronectin is assembled into the extracellular matrix, an insoluble network that separates and supports the organs and tissues of an organism.
Fibronectin plays a crucial role in wound healing. Along with fibrin, plasma fibronectin is deposited at the site of injury, forming a blood clot that stops bleeding and protects the underlying tissue; as repair of the injured tissue continues and macrophages begin to remodel the area, degrading the proteins that form the provisional blood clot matrix and replacing them with a matrix that more resembles the normal, surrounding tissue. Fibroblasts secrete proteases, including matrix metalloproteinases, that digest the plasma fibronectin, the fibroblasts secrete cellular fibronectin and assemble it into an insoluble matrix. Fragmentation of fibronectin by proteases has been suggested to promote wound contraction, a critical step in wound healing. Fragmenting fibronectin further exposes its V-region, which contains the site for α4β1 integrin binding; these fragments of fibronectin are believed to enhance the binding of α4β1 integrin-expressing cells, allowing them to adhere to and forcefully contract the surrounding matrix.
Fibronectin is necessary for embryogenesis, inactivating the gene for fibronectin results in early embryonic lethality. Fibronectin is important for migration during embryonic development. In mammalian development, the absence of fibronectin leads to defects in mesodermal, neural tube, vascular development; the absence of a normal fibronectin matrix in developing amphibians causes defects in mesodermal patterning and inhibits gastrulation. Fibronectin is found in normal human saliva, which helps prevent colonization of the oral cavity and pharynx by pathogenic bacteria. Cellular fibronectin is assembled into an insoluble fibrillar matrix in a complex cell-mediated process. Fibronectin matrix assembly begins when soluble, compact fibronectin dimers are secreted from cells fibroblasts; these soluble dimers bind to α5β1 integrin receptors on the cell surface and aid in clustering the integrins. The local concentration of integrin-bound fibronectin increases, allowing bound fibronectin molecules to more interact with one another.
Short fibronectin fibrils the
Labour Briefing is a monthly political magazine produced by members of the British Labour Party. The magazine began in 1980 as London Labour Briefing; the founders were the members of the Chartist Minority Tendency, a former Trotskyist part of the Chartist Collective. It was edited by Graham Bash, Chris Knight and Keith Veness and counted Ken Livingstone, Tony Benn and other prominent Labour councillors and MPs among its supporters. Throughout the early period, its masthead slogan was "Labour – take the power!" While the magazine's followers acted as a political faction, its internal politics were non-sectarian and open, ranging from democratic socialist backers of the former Labour MP Tony Benn to some of the Trotskyist groups. Jeremy Corbyn Leader of the Labour Party, became a regular contributor to London Labour Briefing in the 1980s, was described by The Times in 1981 as "Briefing's founder". In a 1982 article published by The Economist, Corbyn was named as "Briefing's general secretary figure", as he was in a profile on Corbyn compiled by parliamentary biographer Andrew Roth in 2004, which alleges that he joined the editorial board as General Secretary in 1979.
Michael Crick, in the 2016 edition of his book Militant, says that Corbyn was "a member of the editorial board" in the "mid 1980s", as does Lansley and Wolmar's The Rise and Fall of the Municipal Left in 1989. The Times said that Corbyn was still "closely linked" with the group in 1995. However, in 2017, Corbyn claimed these reports were inaccurate, telling Sky News presenter Sophy Ridge, "Andrew Roth has a wonderful reputation for having the most inaccurate parliamentary profiles known to anyone", that "I read the magazine. I wrote for the magazine. I was not a member of the editorial board. I didn't agree with it."The group campaigned for left-wing policies and greater democracy in the Labour Party, focused on issues relating to municipal affairs. The paper emphasised sexual and personal politics and anti-racism campaigns. London Labour Briefing was prominent in supporting Irish Republicanism and the UK Miners' Strike. In due course, London Labour Briefing spawned local papers around Britain, such as Devon Labour Briefing.
In July 1982, Corbyn argued against expulsions of Militant in Briefing. Following the Brighton hotel bombing by the Provisional Irish Republican Army, the editorial board of London Labour Briefing said the bombings showed that "the British only sit up and take notice when they are bombed into it". In December 1984, the magazine carried a reader's letter praising the "audacity" of the IRA attack and stating: "What do you call four dead Tories? A start." It mocked Norman Tebbit, the trade secretary, dug out of the rubble of the Grand Hotel and whose wife was left permanently paralysed, saying: "Try riding your bike now, Norman". The same issue carried a piece from the editorial board which "disassociated itself" from an article the previous month criticising the bombing, saying the criticism was a "serious political misjudgment". Throughout the 1990s, Briefing lost supporters and influence as New Labour's hold over the Labour Party increased. Liz Davies was vetoed by Labour's National Executive Committee as Labour's prospective parliamentary candidate for Leeds North East in 1995, in part for her association with Briefing.
Corbyn called the decision of the NEC "totally unacceptable" at the time. In 1995, Central Books, a left-wing publisher which used to distribute the magazine, said: "It used to be wacky and amusing. Now it's neo-Trotskyite rubbish."London Labour Briefing was renamed Labour Briefing and was known as Labour Left Briefing in 1995. In 2008, upon merging with Voice of the Unions, it reverted to Labour Briefing, it supports the Socialist Campaign Group of Members of Parliament, aims to promote and build the network of local Campaign Groups. Following a contested vote at the July 2012 AGM, some supporters of Labour Briefing decided to transfer control of the magazine to the Labour Representation Committee. Other Editorial Board members, including Labour Party NEC member Christine Shawcroft, opposed the move, continued to publish their own independent Labour Briefing magazine. There have been a number of notable members of the magazine's editorial board. Most contributors in the 1980s were prominent members of London's "outside left".
They included: Tony Banks Tony Benn Jeremy Corbyn, Labour MP for Islington North, now Leader of the Labour Party Bryn Davies, trade unionist and politician, Leader of the Inner London Education Authority in the early 1980s Andy Harris Tony Hart, Greater London Council member, husband of Judith Hart MP Chris Knight, anthropologist Ted Knight, former Lambeth council leader George Nicholson Jackie Walker, activist Official website
Hydnellum joeides is a species of tooth fungus in the family Bankeraceae. It was first described by Italian botanist Giovanni Passerini in 1872 as Hydnum joeides. Frédéric Bataille transferred it to the genus Sarcodon in 1924; the fungus makes fruit bodies with flattened to concave caps measuring 2.5–10 cm in diameter. They have a velvety surface texture that breaks up into reddish-brown scales; the crowded spines on the cap underside are up to 3 mm long, are decurrent on the stipe. Pale pink, they become brownish in age. Spores are tuberculate, measure 6.3–7.2 by 4–4.7 µm. The fungus is found in western and central Europe, where it is an ectomycorrhizal symbiont of European beech, English oak, sessile oak, it is on the red lists of several countries: Flandres and Norway. Because of the continued decline in sightings in Europe, it has been proposed for inclusion on the IUCN Red List of Threatened Species; the species has been reported from the United States, New Zealand, although mycologist Eef Arnolds regards these records as doubtful because of discrepancies in the reported sizes of the spores.
Hydnellum joeides in Index Fungorum