Proteína quinase activada por mitóxeno: Diferenzas entre revisións

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Miguelferig (conversa | contribucións)
Miguelferig (conversa | contribucións)
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[[Ficheiro:MAPK-pathway-yeast.png|miniatura|Diagrama global da vía MAPK en lévedos. Os compoñentes non canónicos dos cinco módulos coñecidos (vías do apareamento, filamentación, hiperosmose, integridade da parede celular, esporulación) están coloreados en azul.]]
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MAPK pathways of fungi are also well studied. In yeast, the Fus3 MAPK is responsible for cell cycle arrest and [[Mating of yeast|mating]] in response to pheromone stimulation. The pheromone alpha-factor is sensed by a [[G protein-coupled receptor|seven transmembrane receptor]]. The recruitment and activation of Fus3 pathway components are strictly dependent on [[heterotrimeric G-protein]] activation. The mating MAPK pathway consist of three tiers (Ste11-Ste7-Fus3), but the MAP2 and MAP3 kinases are shared with another pathway, the Kss1 or filamentous growth pathway. While Fus3 and Kss1 are closely related ERK-type kinases, yeast cells can still activate them separately, with the help of a scaffold protein Ste5 that is selectively recruited by the G-proteins of the mating pathway. The trick is that Ste5 can associate with and "unlock" Fus3 for Ste7 as a substrate in a tertiary complex, while it does not do the same for Kss1, leaving the filamentous growth pathway to be activated only in the absence of Ste5 recruitment.<ref name="pmid19303851">{{cite journal | vauthors = Good M, Tang G, Singleton J, Reményi A, Lim WA | title = The Ste5 scaffold directs mating signaling by catalytically unlocking the Fus3 MAP kinase for activation | journal = Cell | volume = 136 | issue = 6 | pages = 1085–97 | date = Mar 2009 | pmid = 19303851 | pmc = 2777755 | doi = 10.1016/j.cell.2009.01.049 }}</ref>
 
As vías MAPK dos fungos foron ben estudadas. En [[lévedo]]s, a MAPK Fus3 é responsable da parad do ciclo celular e apareamento en resposta á estimulación por [[feromona]]s. A feromona factor-alfa é percibida por un [[receptor acoplado á proteína G|receptor sete transmembrana]]. O recrutamento e activación dos compoñentes da vía Fus3 depende estrititamente da activación da [[proteína G heterotrimérica]]. A vía MAPK do apareamento consta de tres pasos (Ste11-Ste7-Fus3), pero as MAP2 e MAP3 quinases que interveñen están compartidas con outra vía, a Kss1 ou vía do crecemento filamentoso. Aínda que Fus3 e Kss1 son quinases de tipo ERK estreitamente relacionadas, as células de lévedos poden activalas separadamente, coa axuda dunha proteína armazón Ste5 que é recrutada selectivamente polas proteíns G da vía do apareamento. O truco é que Ste5 pode asociarse con e "abrir" Fus3 para Ste7 como substrato nun complexo terciario, mentres que non fai o mesmo para Kss1, deixandoque a vía docrecemento filamentoso sexa activada só en ausencia de recrutamento de Ste5.<ref name="pmid19303851">{{cite journal | vauthors = Good M, Tang G, Singleton J, Reményi A, Lim WA | title = The Ste5 scaffold directs mating signaling by catalytically unlocking the Fus3 MAP kinase for activation | journal = Cell | volume = 136 | issue = 6 | pages = 1085–97 | date = Mar 2009 | pmid = 19303851 | pmc = 2777755 | doi = 10.1016/j.cell.2009.01.049 }}</ref>
Fungi also have a pathway reminiscent of mammalian JNK/p38 signaling. This is the Hog1 pathway: activated by high osmolarity (in ''[[Saccharomyces cerevisiae|S. cerevisiae]]'') or a number of other abiotic stresses (in ''[[Schizosaccharomyces pombe|S. pombe]]''). The MAP2 kinase of this pathway is called Pbs2 (related to mammalian MKK3/4/6/7), the dedicated MAP3 kinases involved in activation are Ssk2 and SSk22. The system in ''S. cerevisiae'' is activated by a sophisticated osmosensing module consisting of the Sho1 and Sln1 proteins, but it is yet unclear how other stimuli can elicit activation of Hog1. Yeast also displays a number of other MAPK pathways without close homologs in animals, such as the cell wall integrity pathway (Mpk1/Slt2) or the [[sporulation]] pathway (Smk1).<ref name="pmid9841672">{{cite journal | vauthors = Gustin MC, Albertyn J, Alexander M, Davenport K | title = MAP kinase pathways in the yeast Saccharomyces cerevisiae | journal = Microbiology and Molecular Biology Reviews | volume = 62 | issue = 4 | pages = 1264–300 | date = Dec 1998 | pmid = 9841672 | pmc = 98946 | doi = }}</ref>
 
FungiOs alsofungos havetamén ateñen pathwayunha reminiscentvía ofque mammalianlembra a sinalización JNK/p38 signalingdos mamíferos. ThisTrátase isda the Hog1 pathway: activatedactivada bypola highalta osmolarityosmolaridade (inen ''[[Saccharomyces cerevisiae|S. cerevisiae]]'') or aou numberpor ofvarios otheroutros abioticestreses stressesabióticos (inen ''[[Schizosaccharomyces pombe|S. pombe]]''). TheA MAP2 kinase of thisquinase pathwaydesta isvía calleddenomínase Pbs2 (relatedrelacionda to mammaliancoas MKK3/4/6/7 de mamíferos), the dedicatede as MAP3 quinase kinases involvedimplicadas inna activationactivación areson Ssk2 ande SSk22. TheO systemsistema inen ''S. cerevisiae'' isé activatedactivado bypor aun sophisticatedsofisticado osmosensingmódulo modulede consistingosmopercepción ofconsistente thenas proteínas Sho1 ande Sln1 proteins, butpero itaínda isnon yetestá unclearclaro howcomo otherfan stimulioutros canestímulos elicitpara activationcausar ofa activación de Hog1. YeastOs alsolévedos displaystamén apresentan numberoutras of othervías MAPK pathwaysque non withoutteñen closeclaros homologshomólogos inen animalsanimais, suchcomo asa thevía cellda wallintegridade integrityda pathwayparede celular (Mpk1/Slt2) orou thea vía da [[sporulationesporulación]] pathway (Smk1).<ref name="pmid9841672">{{cite journal | vauthors = Gustin MC, Albertyn J, Alexander M, Davenport K | title = MAP kinase pathways in the yeast Saccharomyces cerevisiae | journal = Microbiology and Molecular Biology Reviews | volume = 62 | issue = 4 | pages = 1264–300 | date = Dec 1998 | pmid = 9841672 | pmc = 98946 | doi = }}</ref>
 
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