1X0H , 2RR8 , 3FAY , 3I6X
43-524: MDIA may refer to: mDia , or mammalian diaphanous, a Rho effector protein involved in cytoskeletal polymerisation (see DIAPH1 ) Men's Division of Intercollegiate Associates, now called the Men's Collegiate Lacrosse Association Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title MDIA . If an internal link led you here, you may wish to change
86-481: A yeast two-hybrid system. Further it was shown that p140mDia1 binds to the GTP-bound form of RhoA only by precipitation from Swiss 3T3 cell lysates. Watanabe et al. could also show the interaction of p140mDia1 with profilin and the colocalization of RhoA, p140mDia and profilin in membrane ruffles of motile cells. A subsequent study in 1997 by Bione et al. established a link between human DIA and oogenesis, with
129-506: A cell ahead; the later is mediated via cell adhesions . Stress fibers are bundles of about 20 actin filaments linked via non-muscle myosin II. In vitro studies showed that mDia1 assembled stress fibers downstream of Rho . Live-cell imaging analysis revealed that mDia1 indeed assembles stress fibers, which are connected at one of their ends to focal adhesions , where actin polymerization occurs. Stress fiber assembly at focal adhesions by mDia1
172-499: A cell to its neighbors by clasping on to the extracellular portion of the neighbor’s cadherins. Actin binds a-catenin which binds beta-catenin which in turn binds E-cadherin . E-cadherin juts into the extracellular space to grasp the extracellular domains of neighboring E-cadherins. IQGAP1 localizes to cell-cell contacts and binds actin, b-catenin, and E-cadherin, weakening these junctions and thus decreasing cell-cell adhesion. IQGAP weakens cell adhesion by displacing a-catenin from
215-504: A defect in the gene leading to premature ovarian failure . IQGAP1 8826 29875 ENSG00000140575 ENSMUSG00000030536 P46940 Q9JKF1 NM_003870 NM_016721 NP_003861 NP_057930 Ras GTPase-activating-like protein IQGAP1 (IQGAP1) also known as p195 is a ubiquitously expressed protein that in humans is encoded by the IQGAP1 gene . IQGAP1
258-447: A link between logically related but molecularly distinct cellular functions. In the above example, actin cytoskeleton rearrangement is required for proliferation ( cytokinesis during mitosis ). IQGAP1 helps cells both listen to and act on signals, playing an integral role in connecting the dots between signals for proliferation and the actual cellular response. The Ras → Raf → MEK → ERK MAPK signaling pathway plays an integral part in
301-515: A modulatory protein intersecting all of these pathways, IQGAP1 can couple many of them, and is also responsible for their proper propagation. Since cancer is a disease characterized by the perturbation of many of these cellular processes, IQGAP1 is a logical oncogene candidate and therapeutic target. Expression analysis has implicated IQGAP1 in colorectal , squamous cell , breast , gastric , liver , lung , and ovarian cancers, and in some of these cancers, higher IQGAP1 expression levels indicate
344-484: A molecular weight of 139,343 daltons. The mDia1 polypeptide chain can be divided into four protein domains: Three supplementary domains were discovered: The active region of the C terminus consists of formin homology 1 and 2 (FH1 and FH2) and the Dia autoregulatory domain (DAD). The FH1 domain is predicted to be rope-like and it contains binding sites for profilin -actin complexes. The adjacent FH2 domain forms together with
387-406: A poor prognosis. In order for a cancer to metastasize , cells must gain migratory abilities and invade other tissues. Through Rac1/CDC42, IQGAP1 regulates cellular adhesion and actin dynamics. In normal cells IQGAP1 localizes to areas of high actin turnover. This characteristic is echoed in invasive tissues, where IQGAP1 localizes to the leading edge of migrating cells. Over-expression of IQGAP1
430-416: A protein scaffold that integrates signals regulating cell adhesion , actin cytoskeleton, the cell cycle , and other cellular functions. IQGAP is particularly interesting as a therapeutic target since it acts as a node for so many signaling pathways implicated in cancer progression. Analysis of IQGAP1 expression in human tissues has indicated that the scaffold is more or less ubiquitously expressed. It
473-590: A unique ability to potentially couple diverse cellular functions. For example IQGAP1 is associated with actin dynamics through direct binding of actin and indirect regulation via Cdc42/Rac1, but also modulates the MAPK pathway which is associated with cell cycle control. Thus IQGAP1 may couple MAPK signaling (decisions about cell fate ) to the cytoskeleton or cellular adhesion (potentially acting out those decisions)—an important implication for cancer. To simplify, due to its diverse range of binding partners, IQGAP1 may act as
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#1732787338074516-506: Is a scaffold protein involved in regulating various cellular processes ranging from organization of the actin cytoskeleton , transcription, and cellular adhesion to regulating the cell cycle . IQGAP1 was discovered in 1994. Its name stems from the fact that its RasGAP-related domain (GRD) has sequence homology to the Sar1 GTPase. It was hypothesized that IQGAP1 would act as a GTPase activating protein (GAP) protein, promoting
559-410: Is a 190 kDa protein with 5 domains. A protein domain is a subsection of a protein that shows up multiple times in biology and can exist independently of the surrounding protein. It is very similar to subsections of other proteins, and could be cut out of the current protein, exist and function by itself, or be pasted in to a new protein strand and still function properly. Since this area of the protein
602-524: Is a major building block of every eukaryotic cell’s cytoskeleton. Actin dynamics play a major role in cell motility (filaments are built at the leading edge of a moving cell and deconstructed at the receding edge). IQGAP1 binds actin and influences actin dynamics by localizing to the leading edge and recruiting actin polymerization machinery. IQGAP1 binds and is a target of the Rho GTPases CDC42 and RAC1 which are well known regulators of
645-534: Is a member of the protein family called the formins and is a Rho effector. It is the mouse version of the diaphanous homolog 1 of Drosophila. mDia1 localizes to cells' mitotic spindle and midbody, plays a role in stress fiber and filopodia formation, phagocytosis, activation of serum response factor, formation of adherens junctions, and it can act as a transcription factor. mDia1 accelerates actin nucleation and elongation by interacting with barbed ends (fast-growing ends) of actin filaments . The gene encoding mDia1
688-501: Is a protein-protein interaction domain that associates with proline-rich regions of other proteins. The WW domain is followed by 4 IQ motifs which form an IQ domain. This domain binds calmodulin , a protein known as a calcium sensor that can bind and regulate many target proteins. A GRD (rasGAP-related domain) follows the IQ domain. This domain is highly similar to the functional subunit of Ras GTPase-activating proteins (GAPs) and
731-564: Is associated with most actin monomers in cells. Interactions between profilin-actin with the FH1 domain can accelerate the elongation at the FH2-capped barbed ends. The formin homology protein mDia1 is a Rho GTPase effector protein, which appears to be universally present in eukaryotic cells and participates in: Stress fibers are acto-myosin structures, which are important for establishment of cellular tension and thus traction to move
774-506: Is conserved in amino acid sequence and structure, it can be characterized by function or binding partner. IQGAP1 has 5 well-known domains separated by other amino acids. Starting at the N-terminus (or front of the protein), IQGAP1 contains a calponin homology domain (CHD), which mediates actin-binding and binds calponin . The WW, or poly-proline protein-protein domain , so named because of two functionally conserved tryptophans, W,
817-466: Is located on Chromosome 18 of Mus musculus and named Diap1 . mDia1 is highly homologous to Drosophila diaphanous, regulating the cytokinetic ring during cytokinesis. Homologues in other species are known as well, like the human DIAP1, budding yeast Bni1 or fission yeast Cdc12p. The gene has been knocked-out in mice. The product of the Diap1 ( Diaph1 ) gene consists of 1255 amino acids resulting in
860-437: Is necessary for neuronal process outgrowth on the cell adhesion molecule PTPmu ( PTPRM ). Expression of the protein is upregulated by gene amplification in two gastric cancer cell lines and its over-expression and distinct membrane localisation is also observed in a range of tumours. IQGAP1 is a node intersected by many signaling pathways. As such it has many binding partners, many of which have essential roles in control of
903-429: Is not fully understood yet. However, the affinity of formins for actin are much higher than for microtubules. By catalyzing actin polymerization and stabilizing microtubules , mDia1 plays also an important role for cell migration. mDia1 was discovered as p140mDia1 by Watanabe et al. in 1997 as a downstream effector of Rho . A mouse embryo cDNA library was screened to identify a RhoA-GTP-binding protein using
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#1732787338074946-512: Is to integrate and mediate signaling from diverse pathways and insulate key pathway members from crosstalk . Scaffolds organize signaling pathways —help regulate how various extracellular signals can be transduced by the same canonical pathway members into various cellular outputs. Generally, scaffolds regulate output, localization, and selectivity of pathways. As a scaffold involved in different signaling pathways (actin cytoskeleton , cellular adhesion , cell cycle , transcription), IQGAP1 has
989-535: Is usually found in the nucleus , plasma membrane , and cytoplasm . In other words it is found throughout the cell as well as throughout tissue types. Expression analysis has also indicated that IQGAP1 is overexpressed in many cancers, and in more aggressive colorectal and ovarian cancers, IQGAP1 is localized at the invasive front of the neoplasm, indicating a role in mobilization of the cells. Importantly, approximately 10% of genes that show increased expression in metastatic cells are IQGAP1 binding partners. IQGAP1
1032-479: Is usually sequestered in a complex and excluded from the nucleus, but upon WNT activation this complex is broken and beta-catenin translocates to the nucleus where it activates transcriptional programs. IQGAP1 binds b-catenin and increases nuclear localization and expression of beta-catenin’s transcriptional targets. IQGAP1 is associated with cytoskeletal dynamics, transcription, cell adhesion , cell cycle , and morphology , all of which are disrupted in cancer . As
1075-458: The FH2 domain of a second mDia1 molecule a head-to-tail doughnut shaped dimer that encircles the barbed end of an actin filament. Thus the FH2 domain has the ability to dimerize. The N terminus consists of a Rho GTPase -binding domain (GBD), which is joint to the formin homology 3 (FH3). DAD can mediate autoinhibition through interactions with the Dia inhibitory domain (DID), which is a subdomain of
1118-702: The GDB/FH3 domain (see section Regulation). Autoinhibition is achieved through binding of the C-terminal DAD to the N-terminal DID. This interaction inhibits the ability of FH2 to nucleate actin assembly. Rho-GTP binds to the GDB domain and disrupts the DAD-DID-interaction thus promoting actin assembly. But this requires high concentrations of Rho-GTP, which may be not physiological. Hence,
1161-424: The actin cytoskeleton. Despite its name, IQGAP1 does not have GAP function, and instead stabilizes active Cdc42. This increase in a local pool of active Cdc42 stimulates actin filament formation and thus filopodia formation. IQGAP1 can crosslink actin, and in many organisms, IQGAP1 is involved in cytokinesis . Cadherins are a family of adhesion proteins that localize to the cell surface where they anchor
1204-588: The brain, IQGAP3 appears to play an important role in neuronal morphogenesis. This gene encodes a member of the IQGAP family. The protein contains four IQ domains , one calponin homology domain , one Ras-GAP domain and one WW domain . It interacts with components of the cytoskeleton such as the formin Dia1 ( mDia1 ), with cell adhesion molecules ( CAMs ), and with several signaling molecules to regulate cell morphology and motility . For example, IQGAP1 expression
1247-442: The cell cycle and actin cytoskeleton. IQGAP1 has been shown to interact with: Protein binding does not by itself construct an interesting story. Far more important is the outcome of the binding event. Does binding change the target protein’s localization? Does it activate the target, or in some way change the target (or effector molecule’s) conformation? As a scaffolding protein , IQGAP1 binds and regulates many targets—its role
1290-477: The complex. Active RAC1 binds IQGAP1 to crosslink actin filaments and prevents IQGAP1 from interacting with beta-catenin , stabilizing cell-cell contacts . When IQGAP1 does not bind Rac1, however, it binds beta-catenin, displacing a-catenin from the cadherin-catenin cellular adhesion complex. IQGAP1 also affects transcription through the Wnt signaling pathway by its interaction with beta-catenin . Beta-catenin
1333-493: The domains are not always highly conserved. IQGAP1 is the most well studied member of the IQGAP family of scaffold proteins. The two other members of the family include IQGAP2 and IQGAP3 which have far more restricted expression patterns in comparison with IQGAP1. IQGAP2 is found in the liver, stomach, and platelets and is 62% identical to IQGAP1, but appears to have a drastically divergent function in terms of pathology. In
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1376-486: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=MDIA&oldid=983810548 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages MDia mDia1 (also known as Dia1 , Drf1 for Diaphanous-related formin-1 , Diaph1 , KIAA4062 , p140mDia , mKIAA4062 , or D18Wsu154e )
1419-481: The mice, and MCF-7 cells with stable knockdown of IQGAP1 only formed tumors 20% of the time. The mechanism for how IQGAP1 may modulate tumorigenesis/invasion through its various binding partners is of great interest. IQGAP1 null mice appear significantly normal, with the only life history abnormality being an increase in gastric hyperplasia . Thus, IQGAP1 may be an effective therapeutic target, if its knockdown has little effect in homeostatic tissue but its expression
1462-508: The plus end of an actin filament despite ongoing polymerization. One formin of a dimer dissociates from the barbed end to take the next step while the second formin of the dimer remains bound. Thus the formin dimer processively adds actin monomers to the barbed end and are constantly present at the barbed end of an actin filament (processive capping). The FH1 domain recruits actin monomers through profilin binding, but it does not promote nucleation. Studies demonstrated that FH2 domains protect
1505-575: The processes of cell proliferation , differentiation , and apoptosis . This pathway is conserved across all eukaryotes . Various extracellular signals induce the ERK MAPK pathway including EGF , IGF-1 , PDGF , and NGF . The various scaffolds of this pathway, including IQGAP1, are responsible for modulating the cellular response to the activity of this pathway. For instance, in a given cell line, activation by one extracellular signal may induce differentiation but not proliferation, while activation of
1548-409: The rapidly elongating barbed ends of filaments from the vast molar excesses of actin capping proteins. The precise mechanisms of actin filament nucleation remains an area of active investigation. The rate of FH2 movement while elongation on an actin filament matches the rate of actin subunit addition, which can exceed 100 subunits per second. Profilin as a ubiquitous actin-binding protein
1591-417: The release of mDia1 from autoinhibition seems to require nonspecific membrane-associated factors that cooperate with Rho-GTP. Several binding proteins can regulate mDia1 localization and activity: Furthermore the scaffold protein ( IQGAP1 ) seems to impact on mDia1. IQGAP1 regulates the localization of mDia1 to the leading edge to cells. The only tested short C-terminal fragment of IQGAP1 (aa 1503 to 1657)
1634-450: The same ERK MAPK pathway by a different extracellular signal will induce proliferation but not differentiation. IQGAP1 seems to be responsible for the specific output of the pathway upon activation by EGF. IQGAP1 plays a significant role in the propagation of this MAPK signaling pathway. IQGAP directly binds b-RAF , MEK1/2 and ERK1/2, and is in fact necessary for the phosphorylation (activation) of ERK upon stimulation by EGF. Actin
1677-412: The switch of ras GTPases from the active GTP to GDP-bound forms. However, despite the homology of IQGAP’s GAP domain to sar1 and the fact that IQGAP1 binds Rho GTPases Rac1 and Cdc42, IQGAP does not actually have GAP function. Instead, it binds the active (GTP-bound) forms of RAC1 and CDC42 with higher affinity than GDP-bound forms, and stabilizes the active form in vivo. IQGAP1 is now recognized as
1720-711: Was associated with increased migration and invasion in a human breast epithelial cancer cell line ( MCF-7 cells). IQGAP1 may also be involved in the deregulation of proliferation and differentiation through its modulation of the ERK MAPK pathway . IQGAP1 may be necessary for tumorigenesis . IQGAP1 knockdown in MCF-7 cancer cells reduced the malignant phenotype (serum-dependent proliferation and anchorage independent growth). 100% of mice injected with MCF-7 cells overexpressing IQGAP1 developed tumors and these tumors were highly invasive. Control MCF-7 cells formed tumors in 60% of
1763-407: Was later shown to promote their growth and stabilization, suggesting mDia1 exerts effects on the interactions of cells with their environment. Formins regulate endocytosis . mDia 1 localizes to endosomes and regulates phagocytic cup formation in macrophages . mDia1 (and mDia2) seems to stabilize microtubules by decreasing the tubulin subunit exchange at their plus ends. The exact mechanism
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1806-693: Was not activating the mDia1 actin polymerization activity in vitro . However expression of this fragment in macrophages reduced phagocytosis. Thus it remains open if IQGAP1 influences the activity of mDia1 directly like it does for NWASP. In contrast to the Arp 2/3 complex , formins nucleate the formation of unbranched actin filaments. FH2 domains lack structural similarity to actin but can bind actin monomers with very weak affinity. The FH2 dimer nucleates filament assembly by interacting directly with and stabilizing actin polymerization intermediates (dimers and trimers). A formin dimer remains constantly bound to
1849-462: Was thus thought to have GAP function. IQGAP1 does bind Rho GTPases CDC42 and RAC1 , however, IQGAP1 is unusual in that it actually has no GAP function, and instead stabilizes the GTP-bound proteins in their active state. Finally, IQGAP1 has a RasGAP_c carboxy terminal sequence important for binding Beta-catenin and E-cadherin . Homologues of IQGAP1 are known in species as divergent as yeast, worms, and humans (as well as other mammals), though
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