The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Greg J Bashaw - One of the best experts on this subject based on the ideXlab platform.
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The Adam family metalloprotease Kuzbanian regulates the cleavage of the Roundabout Receptor to control axon repulsion at the midline
Development (Cambridge England), 2010Co-Authors: Hope A. Coleman, Rebecca K Chance, Juan-pablo Labrador, Greg J BashawAbstract:Slits and their Roundabout (Robo) Receptors mediate repulsive axon guidance at the Drosophila ventral midline and in the vertebrate spinal cord. Slit is cleaved to produce fragments with distinct signaling properties. In a screen for genes involved in Slit-Robo repulsion, we have identified the Adam family metalloprotease Kuzbanian (Kuz). Kuz does not regulate midline repulsion through cleavage of Slit, nor is Slit cleavage essential for repulsion. Instead, Kuz acts in neurons to regulate repulsion and Kuz can cleave the Robo extracellular domain in Drosophila cells. Genetic rescue experiments using an uncleavable form of Robo show that this Receptor does not maintain normal repellent activity. Finally, Kuz activity is required for Robo to recruit its downstream signaling partner, Son of sevenless (Sos). These observations support the model that Kuz-directed cleavage is important for Robo Receptor activation.
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son of sevenless directly links the robo Receptor to rac activation to control axon repulsion at the midline
Neuron, 2006Co-Authors: Long Yang, Greg J BashawAbstract:Son of sevenless (Sos) is a dual specificity guanine nucleotide exchange factor (GEF) that regulates both Ras and Rho family GTPases and thus is uniquely poised to integrate signals that affect both gene expression and cytoskeletal reorganization. Here, using genetics, biochemistry, and cell biology, we demonstrate that Sos is recruited to the plasma membrane, where it forms a ternary complex with the Roundabout Receptor and the SH3-SH2 adaptor protein Dreadlocks (Dock) to regulate Rac-dependent cytoskeletal rearrangement in response to the Slit ligand. Intriguingly, the Ras and Rac-GEF activities of Sos can be uncoupled during Robo-mediated axon repulsion; Sos axon guidance function depends on its Rac-GEF activity, but not its Ras-GEF activity. These results provide in vivo evidence that the Ras and RhoGEF domains of Sos are separable signaling modules and support a model in which Robo recruits Sos to the membrane via Dock to activate Rac during midline repulsion.
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cross gtpase activating protein crossgap vilse links the Roundabout Receptor to rac to regulate midline repulsion
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Juan-pablo Labrador, Corey S Goodman, Jason Mcewen, Eric C Lai, Greg J BashawAbstract:The regulators of the Rho-family GTPases, GTPase-activating proteins (GAPs) and guanine exchange factors (GEFs), play important roles in axon guidance. By means of a functional genomic study of the Rho-family GEFs and GAPs in Drosophila, we have identified a Rho-family GAP, CrossGAP (CrGAP), which is involved in Roundabout (Robo) Receptor-mediated repulsive axon guidance. CrGAP physically associates with the Robo Receptor. Too much or too little CrGAP activity leads to defects in Robo-mediated repulsion at the midline choice point. The CrGAP gain-of-function phenotype mimics the loss-of-function phenotypes of both Robo and Rac. Dosage-sensitive genetic interactions among CrGAP, Robo, and Rac support a model in which CrGAP transduces signals downstream of Robo Receptor to regulate Rac-dependent cytoskeletal changes.
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Slit stimulation recruits Dock and Pak to the Roundabout Receptor and increases Rac activity to regulate axon repulsion at the CNS midline.
Neuron, 2003Co-Authors: Xueping Fan, Juan-pablo Labrador, Huey Hing, Greg J BashawAbstract:Drosophila Roundabout (Robo) is the founding member of a conserved family of repulsive axon guidance Receptors that respond to secreted Slit proteins. Here we present evidence that the SH3-SH2 adaptor protein Dreadlocks (Dock), the p21-activated serine-threonine kinase (Pak), and the Rac1/Rac2/Mtl small GTPases can function during Robo repulsion. Loss-of-function and genetic interaction experiments suggest that limiting the function of Dock, Pak, or Rac partially disrupts Robo repulsion. In addition, Dock can directly bind to Robo's cytoplasmic domain, and the association of Dock and Robo is enhanced by stimulation with Slit. Furthermore, Slit stimulation can recruit a complex of Dock and Pak to the Robo Receptor and trigger an increase in Rac1 activity. These results provide a direct physical link between the Robo Receptor and an important cytoskeletal regulatory protein complex and suggest that Rac can function in both attractive and repulsive axon guidance.
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repulsive axon guidance abelson and enabled play opposing roles downstream of the Roundabout Receptor
Cell, 2000Co-Authors: Greg J Bashaw, Thomas Kidd, Dave Murray, Tony Pawson, Corey S GoodmanAbstract:Drosophila Roundabout (Robo) is the founding member of a conserved family of repulsive axon guidance Receptors that respond to secreted Slit proteins. Little is known about the signaling mechanisms which function downstream of Robo to mediate repulsion. Here, we present genetic and biochemical evidence that the Abelson (Abl) tyrosine kinase and its substrate Enabled (Ena) play direct and opposing roles in Robo signal transduction. Genetic interactions support a model in which Abl functions to antagonize Robo signaling, while Ena is required in part for Robo's repulsive output. Both Abl and Ena can directly bind to Robo's cytoplasmic domain. A mutant form of Robo that interferes with Ena binding is partially impaired in Robo function, while a mutation in a conserved cytoplasmic tyrosine that can be phosphorylated by Abl generates a hyperactive Robo Receptor.
Lukasz Huminiecki - One of the best experts on this subject based on the ideXlab platform.
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Magic Roundabout is an endothelial-specific ohnolog of ROBO1 which neo-functionalized to an essential new role in angiogenesis.
PloS one, 2019Co-Authors: Lukasz HuminieckiAbstract:Background Magic Roundabout (ROBO4) is an unusual endothelial-specific paralog of the family of neuronally-expressed axon guidance Receptors called Roundabouts. Endothelial cells (ECs), whose uninterrupted sheet delimits the lumen of all vertebrate blood vessels and which are absent from invertebrate species, are a vertebrate-specific evolutionary novelty. Results Herein, the evolutionary mechanism of the duplication, retention and divergence of ROBO4 was investigated for the first time. Phylogenetic analyses carried out suggested that ROBO4 is a fast-evolving paralog of ROBO1 formed at the base of vertebrates. The ancestral expression pattern was neuronal. ROBO4 dramatically shifted its expression and became exceptionally specific to ECs. The data-mining of FANTOM5 and ENCODE reveals that ROBO4’s endothelial expression arises from a single transcription start site (TSS), conserved in mouse, controlled by a proximal promoter with a complex architecture suggestive of regulatory neo-functionalization. (An analysis of promoter probabilities suggested the architecture was not due to a chance arrangement of TFBSes). Further evidence for the neo-functionalization of ROBO4 comes from the analysis of its protein interactions, the rates of protein evolution, and of positively selected sites. Conclusions The neo-functionalization model explains why ROBO4 protein acquired new context-specific biological functions in the control of angiogenesis. This endothelial-specific Roundabout Receptor is an illustrative example of the emergence of an essential vertebrate molecular novelty and an endothelial-specific signaling sub-network through 2R-WGD. The emergence of novel cell types, such as ECs, might be a neglected evolutionary force contributing to the high rate of retention of duplicates post-2R-WGD. Crucially, expression neo-functionalization to evolutionarily novel sites of expression conceptually extends the classical model of neo-functionalization.
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Magic Roundabout is a new member of the Roundabout Receptor family that is endothelial specific and expressed at sites of active angiogenesis.
Genomics, 2002Co-Authors: Lukasz Huminiecki, Michael Gorn, Steven Suchting, Richard Poulsom, Roy BicknellAbstract:We have used bioinformatic data mining to identify a novel, endothelial-specific gene encoding a protein with homology to the axon guidance protein Roundabout (ROBO1). The new gene has been called magic Roundabout (ROBO4; GenBank acc. no. AF361473) and is smaller than other members of the Roundabout gene family. Thus, in the extracellular region, magic Roundabout has only two of the five immunoglobulin and two of the three fibronectin domains present in other Roundabout genes. Expression of magic Roundabout in vitro was detected in only endothelial cells and was greater in cells exposed to hypoxia. In situ hybridization and immunohistochemistry validated the bioinformatic prediction that magic Roundabout expression would be endothelial specific in vivo. Magic Roundabout expression in the adult was restricted exclusively to sites of active angiogenesis, notably tumor vessels. The identification of magic Roundabout shows that the Roundabout gene family extends beyond neuronal tissue and that Roundabout/slit interactions are likely to have a role in angiogenesis.
Roy Bicknell - One of the best experts on this subject based on the ideXlab platform.
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Functionally defining the endothelial transcriptome, from Robo4 to ECSCR.
Biochemical Society Transactions, 2009Co-Authors: Ana Raquel Verissimo, John Herbert, Victoria L. Heath, John A. Legg, Helen Sheldon, Maud Andre, Rajeeb K. Swain, Roy BicknellAbstract:We have applied search algorithms to expression databases to identify genes whose expression is restricted to the endothelial cell. Such genes frequently play a critical role in endothelial biology and angiogenesis. Two such genes are the Roundabout Receptor Robo4 and the ECSCR (endothelial-cell-specific chemotaxis regulator). Endothelial cells express both Robo1 and Robo4, which we have knocked down using siRNA (small interfering RNA) and then studied the effect in a variety of in vitro assays. Both Robo4 and Robo1 knockdown inhibited in vitro tube formation on Matrigel. Transfection of Robo4 into endothelial cells increased the number of filopodial extensions from the cell, but failed to do so in Robo1-knockdown cells. Separate immunoprecipitation studies showed that Robo1 and Robo4 heterodimerize. We conclude from this and other work that a heteroduplex of Robo1 and Robo4 signals through WASP (Wiskott-Aldrich syndrome protein) and other actin nucleation-promoting factors to increase the number of filopodia and cell migration. Knockdown of the transmembrane ECSCR protein in endothelial cells also reduced chemotaxis and impaired tube formation on Matrigel. Yeast two-hybrid analysis and immunoprecipitation studies showed that, in contrast with the Roundabouts, ECSCR binds to the actin-modulatory filamin A. We conclude that all three of these genes are critical for effective endothelial cell migration and, in turn, angiogenesis.
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Magic Roundabout is a new member of the Roundabout Receptor family that is endothelial specific and expressed at sites of active angiogenesis.
Genomics, 2002Co-Authors: Lukasz Huminiecki, Michael Gorn, Steven Suchting, Richard Poulsom, Roy BicknellAbstract:We have used bioinformatic data mining to identify a novel, endothelial-specific gene encoding a protein with homology to the axon guidance protein Roundabout (ROBO1). The new gene has been called magic Roundabout (ROBO4; GenBank acc. no. AF361473) and is smaller than other members of the Roundabout gene family. Thus, in the extracellular region, magic Roundabout has only two of the five immunoglobulin and two of the three fibronectin domains present in other Roundabout genes. Expression of magic Roundabout in vitro was detected in only endothelial cells and was greater in cells exposed to hypoxia. In situ hybridization and immunohistochemistry validated the bioinformatic prediction that magic Roundabout expression would be endothelial specific in vivo. Magic Roundabout expression in the adult was restricted exclusively to sites of active angiogenesis, notably tumor vessels. The identification of magic Roundabout shows that the Roundabout gene family extends beyond neuronal tissue and that Roundabout/slit interactions are likely to have a role in angiogenesis.
Juan-pablo Labrador - One of the best experts on this subject based on the ideXlab platform.
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The Adam family metalloprotease Kuzbanian regulates the cleavage of the Roundabout Receptor to control axon repulsion at the midline
Development (Cambridge England), 2010Co-Authors: Hope A. Coleman, Rebecca K Chance, Juan-pablo Labrador, Greg J BashawAbstract:Slits and their Roundabout (Robo) Receptors mediate repulsive axon guidance at the Drosophila ventral midline and in the vertebrate spinal cord. Slit is cleaved to produce fragments with distinct signaling properties. In a screen for genes involved in Slit-Robo repulsion, we have identified the Adam family metalloprotease Kuzbanian (Kuz). Kuz does not regulate midline repulsion through cleavage of Slit, nor is Slit cleavage essential for repulsion. Instead, Kuz acts in neurons to regulate repulsion and Kuz can cleave the Robo extracellular domain in Drosophila cells. Genetic rescue experiments using an uncleavable form of Robo show that this Receptor does not maintain normal repellent activity. Finally, Kuz activity is required for Robo to recruit its downstream signaling partner, Son of sevenless (Sos). These observations support the model that Kuz-directed cleavage is important for Robo Receptor activation.
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cross gtpase activating protein crossgap vilse links the Roundabout Receptor to rac to regulate midline repulsion
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Juan-pablo Labrador, Corey S Goodman, Jason Mcewen, Eric C Lai, Greg J BashawAbstract:The regulators of the Rho-family GTPases, GTPase-activating proteins (GAPs) and guanine exchange factors (GEFs), play important roles in axon guidance. By means of a functional genomic study of the Rho-family GEFs and GAPs in Drosophila, we have identified a Rho-family GAP, CrossGAP (CrGAP), which is involved in Roundabout (Robo) Receptor-mediated repulsive axon guidance. CrGAP physically associates with the Robo Receptor. Too much or too little CrGAP activity leads to defects in Robo-mediated repulsion at the midline choice point. The CrGAP gain-of-function phenotype mimics the loss-of-function phenotypes of both Robo and Rac. Dosage-sensitive genetic interactions among CrGAP, Robo, and Rac support a model in which CrGAP transduces signals downstream of Robo Receptor to regulate Rac-dependent cytoskeletal changes.
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Slit stimulation recruits Dock and Pak to the Roundabout Receptor and increases Rac activity to regulate axon repulsion at the CNS midline.
Neuron, 2003Co-Authors: Xueping Fan, Juan-pablo Labrador, Huey Hing, Greg J BashawAbstract:Drosophila Roundabout (Robo) is the founding member of a conserved family of repulsive axon guidance Receptors that respond to secreted Slit proteins. Here we present evidence that the SH3-SH2 adaptor protein Dreadlocks (Dock), the p21-activated serine-threonine kinase (Pak), and the Rac1/Rac2/Mtl small GTPases can function during Robo repulsion. Loss-of-function and genetic interaction experiments suggest that limiting the function of Dock, Pak, or Rac partially disrupts Robo repulsion. In addition, Dock can directly bind to Robo's cytoplasmic domain, and the association of Dock and Robo is enhanced by stimulation with Slit. Furthermore, Slit stimulation can recruit a complex of Dock and Pak to the Robo Receptor and trigger an increase in Rac1 activity. These results provide a direct physical link between the Robo Receptor and an important cytoskeletal regulatory protein complex and suggest that Rac can function in both attractive and repulsive axon guidance.
Subhash C. Chauhan - One of the best experts on this subject based on the ideXlab platform.
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Slit/Robo pathway: a promising therapeutic target for cancer
Drug discovery today, 2014Co-Authors: Rishi K. Gara, Sonam Kumari, Aditya Ganju, Murali M. Yallapu, Meena Jaggi, Subhash C. ChauhanAbstract:Axon guidance molecules, slit glycoprotein (Slit) and Roundabout Receptor (Robo), have implications in the regulation of physiological processes. Recent studies indicate that Slit and Robo also have important roles in tumorigenesis, cancer progression and metastasis. The Slit/Robo pathway can be considered a master regulator for multiple oncogenic signaling pathways. Herein, we provide a comprehensive review on the role of these molecules and their associated signaling pathways in cancer progression and metastasis. Overall, the current available data suggest that the Slit/Robo pathway could be a promising target for development of anticancer drugs.
