Mothers against decapentaplegic homolog 2, also known as SMAD family member 2 or SMAD2, is a protein that in humans is encoded by the SMAD2 gene. [5] [6] MAD homolog 2 belongs to the SMAD, a family of proteins similar to the gene products of the Drosophila gene 'mothers against decapentaplegic' (Mad) and the C. elegans gene Sma. SMAD proteins are signal transducers and transcriptional modulators that mediate multiple signaling pathways.
SMAD2 mediates the signal of the transforming growth factor (TGF)-beta, and thus regulates multiple cellular processes, such as cell proliferation, apoptosis, and differentiation. This protein is recruited to the TGF-beta receptors through its interaction with the SMAD anchor for receptor activation (SARA) protein. In response to TGF-beta signal, this protein is phosphorylated by the TGF-beta receptors. The phosphorylation induces the dissociation of this protein with SARA and the association with the family member SMAD4. The association with SMAD4 is important for the translocation of this protein into the cell nucleus, where it binds to target promoters and forms a transcription repressor complex with other cofactors. This protein can also be phosphorylated by activin type 1 receptor kinase, and mediates the signal from the activin. Alternatively spliced transcript variants encoding the same protein have been observed. [7]
Like other SMADs, SMAD2 plays a role in the transmission of extracellular signals from ligands of the Transforming Growth Factor beta (TGFβ) superfamily of growth factors into the cell nucleus. Binding of a subgroup of TGFβ superfamily ligands to extracellular receptors triggers phosphorylation of SMAD2 at a Serine-Serine-Methionine-Serine (SSMS) motif at its extreme C-terminus. Phosphorylated SMAD2 is then able to form a complex with SMAD4. These complexes accumulate in the cell nucleus, where they are directly participating in the regulation of gene expression.
The SMAD proteins are homologs of both the drosophila protein, mothers against decapentaplegic (MAD), and the C. elegans protein SMA. The name is a combination of the two. During Drosophila research, it was found that a mutation in the gene MAD in the mother repressed the gene decapentaplegic in the embryo. The phrase "Mothers against" was added, since mothers often form organizations opposing various issues, e.g., Mothers Against Drunk Driving, or (MADD). The nomenclature for this protein is based on a tradition of such unusual naming within the gene research community. [8]
Mothers against decapentaplegic homolog 2 has been shown to interact with:
In cellular biology, paracrine signaling is a form of cell signaling, a type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse over a relatively short distance, as opposed to cell signaling by endocrine factors, hormones which travel considerably longer distances via the circulatory system; juxtacrine interactions; and autocrine signaling. Cells that produce paracrine factors secrete them into the immediate extracellular environment. Factors then travel to nearby cells in which the gradient of factor received determines the outcome. However, the exact distance that paracrine factors can travel is not certain.
Mothers against decapentaplegic homolog 3 also known as SMAD family member 3 or SMAD3 is a protein that in humans is encoded by the SMAD3 gene.
SMAD4, also called SMAD family member 4, Mothers against decapentaplegic homolog 4, or DPC4 is a highly conserved protein present in all metazoans. It belongs to the SMAD family of transcription factor proteins, which act as mediators of TGF-β signal transduction. The TGFβ family of cytokines regulates critical processes during the lifecycle of metazoans, with important roles during embryo development, tissue homeostasis, regeneration, and immune regulation.
SMAD family member 6, also known as SMAD6, is a protein that in humans is encoded by the SMAD6 gene.
Mothers against decapentaplegic homolog 7 or SMAD7 is a protein that in humans is encoded by the SMAD7 gene.
R-SMADs are receptor-regulated SMADs. SMADs are transcription factors that transduce extracellular TGF-β superfamily ligand signaling from cell membrane bound TGF-β receptors into the nucleus where they activate transcription TGF-β target genes. R-SMADS are directly phosphorylated on their c-terminus by type 1 TGF-β receptors through their intracellular kinase domain, leading to R-SMAD activation.
Smads comprise a family of structurally similar proteins that are the main signal transducers for receptors of the transforming growth factor beta (TGF-B) superfamily, which are critically important for regulating cell development and growth. The abbreviation refers to the homologies to the Caenorhabditis elegans SMA and MAD family of genes in Drosophila.
The transforming growth factor beta (TGFβ) signaling pathway is involved in many cellular processes in both the adult organism and the developing embryo including cell growth, cell differentiation, cell migration, apoptosis, cellular homeostasis and other cellular functions. The TGFβ signaling pathways are conserved. In spite of the wide range of cellular processes that the TGFβ signaling pathway regulates, the process is relatively simple. TGFβ superfamily ligands bind to a type II receptor, which recruits and phosphorylates a type I receptor. The type I receptor then phosphorylates receptor-regulated SMADs (R-SMADs) which can now bind the coSMAD SMAD4. R-SMAD/coSMAD complexes accumulate in the nucleus where they act as transcription factors and participate in the regulation of target gene expression.
Zinc finger FYVE domain-containing protein 9 or SARA is a protein that in humans is encoded by the ZFYVE9 gene. SARA contains a double zinc finger.
Activin receptor type-1B is a protein that in humans is encoded by the ACVR1B gene.
Transforming growth factor beta receptor I is a membrane-bound TGF beta receptor protein of the TGF-beta receptor family for the TGF beta superfamily of signaling ligands. TGFBR1 is its human gene.
The SKI protein is a nuclear proto-oncogene that is associated with tumors at high cellular concentrations. SKI has been shown to interfere with normal cellular functioning by both directly impeding expression of certain genes inside the nucleus of the cell as well as disrupting signaling proteins that activate genes.
The upstream signaling pathway is triggered by the binding of a signaling molecule, a ligand, to a receiving molecule, a receptor. Receptors and ligands exist in many different forms, and only recognize/bond to particular molecules. Upstream extracellular signaling transduce a variety of intracellular cascades.
E3 SUMO-protein ligase PIAS4 is one of several protein inhibitor of activated STAT (PIAS) proteins. It is also known as protein inhibitor of activated STAT protein gamma, and is an enzyme that in humans is encoded by the PIAS4 gene.
Ski-like protein is a protein that in humans is encoded by the SKIL gene.
Serine-threonine kinase receptor-associated protein is an enzyme that in humans is encoded by the STRAP gene.
E3 ubiquitin-protein ligase SMURF2 is an enzyme that in humans is encoded by the SMURF2 gene which is located at chromosome 17q23.3-q24.1.
Forkhead box protein H1 is a protein that in humans is encoded by the FOXH1 gene.
The Nodal signaling pathway is a signal transduction pathway important in regional and cellular differentiation during embryonic development.
In Xenopus laevis, the specification of the three germ layers occurs at the blastula stage. Great efforts have been made to determine the factors that specify the endoderm and mesoderm. On the other hand, only a few examples of genes that are required for ectoderm specification have been described in the last decade. The first molecule identified to be required for the specification of ectoderm was the ubiquitin ligase Ectodermin ; later, it was found that the deubiquitinating enzyme, FAM/USP9x, is able to overcome the effects of ubiquitination made by Ectodermin in Smad4. Two transcription factors have been proposed to control gene expression of ectodermal specific genes: POU91/Oct3/4 and FoxIe1/Xema. A new factor specific for the ectoderm, XFDL156, has shown to be essential for suppression of mesoderm differentiation from pluripotent cells.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.