The Experts below are selected from a list of 268566 Experts worldwide ranked by ideXlab platform
Haizhong Feng - One of the best experts on this subject based on the ideXlab platform.
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protein kinase a dependent phosphorylation of Dock180 at serine residue 1250 is important for glioma growth and invasion stimulated by platelet derived growth factor receptor α
Neuro-oncology, 2015Co-Authors: Haizhong Feng, Jann N Sarkaria, Yuhua Yin, Weiwei Zhang, Yanli Hou, Lei Zhang, Baoshu Xie, Wei-qiang Gao, Jeffery J RaizerAbstract:Background Dedicator of cytokinesis 1 (Dock1 or Dock180), a bipartite guanine nucleotide exchange factor for Rac1, plays critical roles in receptor tyrosine kinase–stimulated cancer growth and invasion. Dock180 activity is required in cell migration cancer tumorigenesis promoted by platelet derived growth factor receptor (PDGFR) and epidermal growth factor receptor.
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Protein kinase A–dependent phosphorylation of Dock180 at serine residue 1250 is important for glioma growth and invasion stimulated by platelet derived-growth factor receptor α
Neuro-oncology, 2014Co-Authors: Haizhong Feng, Yuhua Yin, Weiwei Zhang, Yanli Hou, Lei Zhang, Baoshu Xie, Wei-qiang Gao, Jann N SarkariaAbstract:Background Dedicator of cytokinesis 1 (Dock1 or Dock180), a bipartite guanine nucleotide exchange factor for Rac1, plays critical roles in receptor tyrosine kinase–stimulated cancer growth and invasion. Dock180 activity is required in cell migration cancer tumorigenesis promoted by platelet derived growth factor receptor (PDGFR) and epidermal growth factor receptor.
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egfrviii stimulates glioma growth and invasion through pka dependent serine phosphorylation of Dock180
Oncogene, 2014Co-Authors: Haizhong Feng, Kristiina Vuori, Jann N Sarkaria, Frank B Furnari, Webster K Cavenee, Shi Yuan ChengAbstract:Glioblastomas (GBMs), the most common and malignant brain tumors, are highly resistant to current therapies. The failure of targeted therapies against aberrantly activated oncogenic signaling, such as that of the EGFR-PI3K/Akt pathway, underscores the urgent need to understand alternative downstream pathways and to identify new molecular targets for the development of more effective treatments for gliomas. Here, we report that EGFRvIII (ΔEGFR/de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in clinical GBM tumors, promotes glioma growth and invasion through protein kinase A (PKA)-dependent phosphorylation of Dock180, a bipartite guanine nucleotide exchange factor (GEF) for Rac1. We demonstrate that EGFRvIII induces serine phosphorylation of Dock180, stimulates Rac1 activation and glioma cell migration. Treatments of glioma cells using the PKA inhibitors H-89 and KT5720, overexpression of a PKA inhibitor (PKI), and in vitro PKA kinase assays show that EGFRvIII induction of serine phosphorylation of Dock180 is PKA-dependent. Significantly, PKA induces phosphorylation of Dock180 at amino acid residue S1250 that resides within its Rac1-activating DHR-2 domain. Expression of the Dock180(S1250L) mutant, but not wild type Dock180(WT), protein in EGFRvIII-expressing glioma cells inhibited receptor-stimulated cell proliferation, survival, migration in vitro and glioma tumor growth and invasion in vivo. Together, our findings describe a novel mechanism by which EGFRvIII drives glioma tumorigenesis and invasion through PKA-dependent phosphorylation of Dock180, thereby suggesting that targeting EGFRvIII-PKA-Dock180-Rac1 signaling axis could provide a novel pathway to develop potential therapeutic strategies for malignant gliomas.
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EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180.
Oncogene, 2013Co-Authors: Haizhong Feng, Kristiina Vuori, Jann N Sarkaria, Frank B Furnari, Webster K Cavenee, Shi Yuan ChengAbstract:EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180
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phosphorylation of dedicator of cytokinesis 1 Dock180 at tyrosine residue y722 by src family kinases mediates egfrviii driven glioblastoma tumorigenesis
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Haizhong Feng, Careen K Tang, Terrance Grant Johns, Susan Keezer, Michael J. Jarzynka, Kristiina Vuori, Ronald L Hamilton, Yanxin Li, Bo Hu, Ryo NishikawaAbstract:Glioblastoma, the most common primary malignant cancer of the brain, is characterized by rapid tumor growth and infiltration of tumor cells throughout the brain. These traits cause glioblastomas to be highly resistant to current therapies with a resultant poor prognosis. Although aberrant oncogenic signaling driven by signature genetic alterations, such as EGF receptor (EGFR) gene amplification and mutation, plays a major role in glioblastoma pathogenesis, the responsible downstream mechanisms remain less clear. Here, we report that EGFRvIII (also known as ΔEGFR and de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in human glioblastoma, promotes tumorigenesis through Src family kinase (SFK)-dependent phosphorylation of Dock180, a guanine nucleotide exchange factor for Rac1. EGFRvIII induces phosphorylation of Dock180 at tyrosine residue 722 (Dock180Y722) and stimulates Rac1-signaling, glioblastoma cell survival and migration. Consistent with this being causal, siRNA knockdown of Dock180 or expression of a Dock180Y722F mutant inhibits each of these EGFRvIII-stimulated activities. The SFKs, Src, Fyn, and Lyn, induce phosphorylation of Dock180Y722 and inhibition of these SFKs by pharmacological inhibitors or shRNA depletion markedly attenuates EGFRvIII-induced phosphorylation of Dock180Y722, Rac1 activity, and glioblastoma cell migration. Finally, phosphorylated Dock180Y722 is coexpressed with EGFRvIII and phosphorylated SrcY418 in clinical specimens, and such coexpression correlates with an extremely poor survival in glioblastoma patients. These results suggest that targeting the SFK-p-Dock180Y722-Rac1 signaling pathway may offer a novel therapeutic strategy for glioblastomas with EGFRvIII overexpression.
Kodi S Ravichandran - One of the best experts on this subject based on the ideXlab platform.
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ELMO1 signaling in apoptotic germ cell clearance and spermatogenesis
Annals of the New York Academy of Sciences, 2010Co-Authors: Michael R. Elliott, Kodi S RavichandranAbstract:Apoptosis and the subsequent removal of dying cells are crucial processes for tissue development and maintenance. Although we are beginning to understand the signaling pathways that control the phagocytic clearance of apoptotic cells, the physiological relevance of these pathways is lacking. During spermatogenesis, over half of the developing germ cells eventually die by apoptosis, yet the signaling pathways that regulate the phagocytic clearance of these dying cells or the impact of this clearance on development and maintenance of the germ cell population is not well understood. The ELMO1/Dock180 proteins form an evolutionarily conserved signaling module that functions as a bipartite guanine nucleotide exchange factor for the small GTPase Rac. The subsequent Rac-dependent cytoskeletal changes play an important role in the physical engulfment of apoptotic cells. Recent findings demonstrate an in vivo role for ELMO1-dependent clearance in the testes, with implications for spermatogenesis. Here we will discuss the role of apoptotic cell clearance during spermatogenesis, with a particular emphasis on ELMO1/Dock180 signaling.
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ELMO1 and Dock180, a Bipartite Rac1 Guanine Nucleotide Exchange Factor, Promote Human Glioma Cell Invasion
Cancer research, 2007Co-Authors: Michael J. Jarzynka, Ryo Nishikawa, Kodi S Ravichandran, Lisa B. Haney, Kwok Min Hui, Ifat Bar-joseph, Takanori Hirose, Shi Yuan ChengAbstract:A distinct feature of malignant gliomas is the intrinsic ability of single tumor cells to disperse throughout the brain, contributing to the failure of existing therapies to alter the progression and recurrence of these deadly brain tumors. Regrettably, the mechanisms underlying the inherent invasiveness of glioma cells are poorly understood. Here, we report for the first time that engulfment and cell motility 1 (ELMO1) and dedicator of cytokinesis 1 (Dock180), a bipartite Rac1 guanine nucleotide exchange factor (GEF), are evidently linked to the invasive phenotype of glioma cells. Immunohistochemical analysis of primary human glioma specimens showed high expression levels of ELMO1 and Dock180 in actively invading tumor cells in the invasive areas, but not in the central regions of these tumors. Elevated expression of ELMO1 and Dock180 was also found in various human glioma cell lines compared with normal human astrocytes. Inhibition of endogenous ELMO1 and Dock180 expression significantly impeded glioma cell invasion in vitro and in brain tissue slices with a concomitant reduction in Rac1 activation. Conversely, exogenous expression of ELMO1 and Dock180 in glioma cells with low level endogenous expression increased their migratory and invasive capacity in vitro and in brain tissue. These data suggest that the bipartite GEF, ELMO1 and Dock180, play an important role in promoting cancer cell invasion and could be potential therapeutic targets for the treatment of diffuse malignant gliomas.
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identification of two signaling submodules within the crkii elmo Dock180 pathway regulating engulfment of apoptotic cells
Cell Death & Differentiation, 2007Co-Authors: Anniecarole Tosellotrampont, Enrico Brugnera, Lisa B. Haney, Jason M. Kinchen, Michael O. Hengartner, Kodi S RavichandranAbstract:Removal of apoptotic cells is a dynamic process coordinated by ligands on apoptotic cells, and receptors and other signaling proteins on the phagocyte. One of the fundamental challenges is to understand how different phagocyte proteins form specific and functional complexes to orchestrate the recognition/removal of apoptotic cells. One evolutionarily conserved pathway involves the proteins cell death abnormal (CED)-2/chicken tumor virus no. 10 (CT10) regulator of kinase (Crk)II, CED-5/180 kDa protein downstream of chicken tumor virus no. 10 (Crk) (Dock180), CED-12/engulfment and migration (ELMO) and MIG-2/RhoG, leading to activation of the small GTPase CED-10/Rac and cytoskeletal remodeling to promote corpse uptake. Although the role of ELMO : Dock180 in regulating Rac activation has been well defined, the function of CED-2/CrkII in this complex is less well understood. Here, using functional studies in cell lines, we observe that a direct interaction between CrkII and Dock180 is not required for efficient removal of apoptotic cells. Similarly, mutants of CED-5 lacking the CED-2 interaction motifs could rescue engulfment and migration defects in CED-5 deficient worms. Mutants of CrkII and Dock180 that could not biochemically interact could colocalize in membrane ruffles. Finally, we identify MIG-2/RhoG (which functions upstream of Dock180 : ELMO) as a possible point of crosstalk between these two signaling modules. Taken together, these data suggest that Dock180/ELMO and CrkII act as two evolutionarily conserved signaling submodules that coordinately regulate engulfment.
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Identification of two signaling submodules within the CrkII/ELMO/Dock180 pathway regulating engulfment of apoptotic cells
Cell death and differentiation, 2007Co-Authors: Annie-carole Tosello-trampont, Enrico Brugnera, Lisa B. Haney, Jason M. Kinchen, Michael O. Hengartner, Kodi S RavichandranAbstract:Removal of apoptotic cells is a dynamic process coordinated by ligands on apoptotic cells, and receptors and other signaling proteins on the phagocyte. One of the fundamental challenges is to understand how different phagocyte proteins form specific and functional complexes to orchestrate the recognition/removal of apoptotic cells. One evolutionarily conserved pathway involves the proteins cell death abnormal (CED)-2/chicken tumor virus no. 10 (CT10) regulator of kinase (Crk)II, CED-5/180 kDa protein downstream of chicken tumor virus no. 10 (Crk) (Dock180), CED-12/engulfment and migration (ELMO) and MIG-2/RhoG, leading to activation of the small GTPase CED-10/Rac and cytoskeletal remodeling to promote corpse uptake. Although the role of ELMO : Dock180 in regulating Rac activation has been well defined, the function of CED-2/CrkII in this complex is less well understood. Here, using functional studies in cell lines, we observe that a direct interaction between CrkII and Dock180 is not required for efficient removal of apoptotic cells. Similarly, mutants of CED-5 lacking the CED-2 interaction motifs could rescue engulfment and migration defects in CED-5 deficient worms. Mutants of CrkII and Dock180 that could not biochemically interact could colocalize in membrane ruffles. Finally, we identify MIG-2/RhoG (which functions upstream of Dock180 : ELMO) as a possible point of crosstalk between these two signaling modules. Taken together, these data suggest that Dock180/ELMO and CrkII act as two evolutionarily conserved signaling submodules that coordinately regulate engulfment.
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Dock180–ELMO Cooperation in Rac Activation
Methods in enzymology, 2006Co-Authors: Kodi S RavichandranAbstract:Dock180 superfamily of proteins has been recently identified as novel, unconventional guanine nucleotide exchange factors (GEF) for Rho‐family GTPases. Unlike most other GEFs for Rho‐family GTPases, Dock180 family members do not contain the characteristic Dbl homology (DH) domain. Instead, they use a conserved “Docker” or “CZH2” domain to mediate the nucleotide exchange on Rho‐family GTPases. The Dock180 family members are evolutionarily conserved from worms to mammals. They play critical roles in a number of biological processes essential for the normal development of entire organisms, as well as for the physiological responses of these organisms, including removal of apoptotic cells and directed cell migration in C. elegans; myoblast fusion, and dorsal closure in Drosophila; lymphocyte migration, T‐cell activation, tumor metastasis, HIV infection, and development of neuronal degenerative diseases in mammals. All these biological activities of the Dock180 family members have been linked to their ability to activate their specific GTPase substrate. At least four members of the Dock180 family bind to another evolutionarily conserved protein ELMO to optimally activate the Rac GTPase. The best characterized is the Rac activation by the Dock180–ELMO complex. ELMO modulates the Rac activation by Dock180 by means of at least three distinct mechanisms: helping Dock180 stabilize Rac in its nucleotide‐free transition state; relieving a self‐inhibition of Dock180; and targeting Dock180 to the plasma membrane to gain access to Rac. Thus, Dock180 and ELMO function together as a bipartite GEF to optimally activate Rac on upstream stimulation to mediate the engulfment of apoptotic cells and cell migration.
Raymond B. Birge - One of the best experts on this subject based on the ideXlab platform.
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c terminal sh3 domain of crkii regulates the assembly and function of the Dock180 elmo rac gef
Journal of Cellular Physiology, 2005Co-Authors: Shin Akakura, Kodimangalam S. Ravichandran, Bishnupriya Kar, Sukhwinder Singh, Leong Cho, Nitu Tibrewal, Charles Reichman, Reiko Sanokawaakakura, Raymond B. BirgeAbstract:Genetic studies in Caenorhabditis elegans identified an evolutionarily conserved CED-2 (CrkII), CED-5 (Dock180), CED-12 (ELMO), CED-10 (Rac1) module important for cell migration and phagocytosis of apoptotic cells. Previous studies have shown that Dock180 and ELMO comprise an unconventional bipartite Dbl homology domain-independent Rac guanine nucleotide exchange factor (Rac-GEF); but it is still unclear how CrkII functions in Rac-GEF activity. In this study, we have characterized a unique function of CrkII in phagocytosis and Rac activation mediated by the C-terminal SH3 domain, a region of CrkII that has no clear cellular or biochemical function. We found that mutations that disrupt the C-terminal SH3 domain of CrkII (CrkII-SH3-C) abrogate engulfment of apoptotic cells and impair cell spreading on extracellular matrix. Surprisingly, despite the effects on engulfment, W276K CrkII strongly potentiated Rac-GTP loading when ectopically expressed in HEK 293T cells. Contrary to the effects of the true dominant negative SH2 domain mutants (R38K CrkII) and SH3-N domain mutants (W170K CrkII) that prevent macromolecular assembly of signaling proteins, W276K CrkII increases association between Dock180 and CrkII as well as constitutive tethering of the Crk/Dock180/ELMO protein complex that interacted with RhoG. Our results indicate that while N-terminal SH3 of CrkII promotes assembly between CrkII and Dock180, the C-terminal SH3 of CrkII regulates the stability and turnover of the Dock180/ELMO complex. Studies with W276K CrkII may offer a unique opportunity to study the structure and function of the Dock180/ELMO Rac-GEF.
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C-terminal SH3 domain of CrkII regulates the assembly and function of the Dock180/ELMO Rac-GEF.
Journal of cellular physiology, 2005Co-Authors: Shin Akakura, Kodimangalam S. Ravichandran, Bishnupriya Kar, Sukhwinder Singh, Leong Cho, Nitu Tibrewal, Reiko Sanokawa-akakura, Charles Reichman, Raymond B. BirgeAbstract:Genetic studies in Caenorhabditis elegans identified an evolutionarily conserved CED-2 (CrkII), CED-5 (Dock180), CED-12 (ELMO), CED-10 (Rac1) module important for cell migration and phagocytosis of apoptotic cells. Previous studies have shown that Dock180 and ELMO comprise an unconventional bipartite Dbl homology domain-independent Rac guanine nucleotide exchange factor (Rac-GEF); but it is still unclear how CrkII functions in Rac-GEF activity. In this study, we have characterized a unique function of CrkII in phagocytosis and Rac activation mediated by the C-terminal SH3 domain, a region of CrkII that has no clear cellular or biochemical function. We found that mutations that disrupt the C-terminal SH3 domain of CrkII (CrkII-SH3-C) abrogate engulfment of apoptotic cells and impair cell spreading on extracellular matrix. Surprisingly, despite the effects on engulfment, W276K CrkII strongly potentiated Rac-GTP loading when ectopically expressed in HEK 293T cells. Contrary to the effects of the true dominant negative SH2 domain mutants (R38K CrkII) and SH3-N domain mutants (W170K CrkII) that prevent macromolecular assembly of signaling proteins, W276K CrkII increases association between Dock180 and CrkII as well as constitutive tethering of the Crk/Dock180/ELMO protein complex that interacted with RhoG. Our results indicate that while N-terminal SH3 of CrkII promotes assembly between CrkII and Dock180, the C-terminal SH3 of CrkII regulates the stability and turnover of the Dock180/ELMO complex. Studies with W276K CrkII may offer a unique opportunity to study the structure and function of the Dock180/ELMO Rac-GEF.
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The opsonin MFG-E8 is a ligand for the alphavbeta5 integrin and triggers Dock180-dependent Rac1 activation for the phagocytosis of apoptotic cells.
Experimental Cell Research, 2004Co-Authors: Shin Akakura, Sukhwinder Singh, Matthew Spataro, Reiko Akakura, Jong-il Kim, Matthew L Albert, Raymond B. BirgeAbstract:Opsonization of apoptotic cells facilitates recognition by phagocytes for the rapid clearance of potentially inflammatory cellular material. The secreted glycoprotein Milk Fat Globule Factor-E8 (MFG-E8) is a member of this family of bridging molecules and is believed to bind phosphatidylserine (PS) on the dying cell, linking it to integrin receptors on the phagocyte. Here we report the characterization of a functional signaling module involving MFG-E8, alphavbeta5 integrin, and Dock180 for the activation of Rac1. We show that MFG-E8 and Dock180 are both expressed in phagocytic-competent primary immature dendritic cells (DCs) and DC2.4 cells, and are potently down-regulated upon DC maturation, consistent with their role in phagocytosis and antigen capture. Coexpression of MFG-E8 with alphavbeta5 integrin potentiated integrin-mediated Rac1 activation, which was abrogated by mutagenesis in the RGD motif in MFG-E8. Moreover, expression of antisense Dock180 abrogated MFG-E8-alphavbeta5-mediated Rac activation and impaired the phagocytosis of apoptotic cells. These data demonstrate a biochemical link between an opsonin of apoptotic cells, the alphavbeta5 integrin, and the Crk-Dock180-Rac1 pathway, and importantly, show that MFG-E8 and Dock180 are expressed according to the functional status of the phagocyte.
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The opsonin MFG-E8 is a ligand for the αvβ5 integrin and triggers Dock180-dependent Rac1 activation for the phagocytosis of apoptotic cells
Experimental cell research, 2004Co-Authors: Shin Akakura, Sukhwinder Singh, Matthew Spataro, Reiko Akakura, Jong-il Kim, Matthew L Albert, Raymond B. BirgeAbstract:Abstract Opsonization of apoptotic cells facilitates recognition by phagocytes for the rapid clearance of potentially inflammatory cellular material. The secreted glycoprotein Milk Fat Globule Factor-E8 (MFG-E8) is a member of this family of bridging molecules and is believed to bind phosphatidylserine (PS) on the dying cell, linking it to integrin receptors on the phagocyte. Here we report the characterization of a functional signaling module involving MFG-E8, αvβ5 integrin, and Dock180 for the activation of Rac1. We show that MFG-E8 and Dock180 are both expressed in phagocytic-competent primary immature dendritic cells (DCs) and DC2.4 cells, and are potently down-regulated upon DC maturation, consistent with their role in phagocytosis and antigen capture. Coexpression of MFG-E8 with αvβ5 integrin potentiated integrin-mediated Rac1 activation, which was abrogated by mutagenesis in the RGD motif in MFG-E8. Moreover, expression of antisense Dock180 abrogated MFG-E8–αvβ5-mediated Rac activation and impaired the phagocytosis of apoptotic cells. These data demonstrate a biochemical link between an opsonin of apoptotic cells, the αvβ5 integrin, and the Crk–Dock180–Rac1 pathway, and importantly, show that MFG-E8 and Dock180 are expressed according to the functional status of the phagocyte.
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αvβ5 integrin recruits the crkii Dock180 rac1 complex for phagocytosis of apoptotic cells
Nature Cell Biology, 2000Co-Authors: Matthew L Albert, Raymond B. BirgeAbstract:α v β 5 integrin recruits the CrkII–Dock180–Rac1 complex for phagocytosis of apoptotic cells
Kristiina Vuori - One of the best experts on this subject based on the ideXlab platform.
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egfrviii stimulates glioma growth and invasion through pka dependent serine phosphorylation of Dock180
Oncogene, 2014Co-Authors: Haizhong Feng, Kristiina Vuori, Jann N Sarkaria, Frank B Furnari, Webster K Cavenee, Shi Yuan ChengAbstract:Glioblastomas (GBMs), the most common and malignant brain tumors, are highly resistant to current therapies. The failure of targeted therapies against aberrantly activated oncogenic signaling, such as that of the EGFR-PI3K/Akt pathway, underscores the urgent need to understand alternative downstream pathways and to identify new molecular targets for the development of more effective treatments for gliomas. Here, we report that EGFRvIII (ΔEGFR/de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in clinical GBM tumors, promotes glioma growth and invasion through protein kinase A (PKA)-dependent phosphorylation of Dock180, a bipartite guanine nucleotide exchange factor (GEF) for Rac1. We demonstrate that EGFRvIII induces serine phosphorylation of Dock180, stimulates Rac1 activation and glioma cell migration. Treatments of glioma cells using the PKA inhibitors H-89 and KT5720, overexpression of a PKA inhibitor (PKI), and in vitro PKA kinase assays show that EGFRvIII induction of serine phosphorylation of Dock180 is PKA-dependent. Significantly, PKA induces phosphorylation of Dock180 at amino acid residue S1250 that resides within its Rac1-activating DHR-2 domain. Expression of the Dock180(S1250L) mutant, but not wild type Dock180(WT), protein in EGFRvIII-expressing glioma cells inhibited receptor-stimulated cell proliferation, survival, migration in vitro and glioma tumor growth and invasion in vivo. Together, our findings describe a novel mechanism by which EGFRvIII drives glioma tumorigenesis and invasion through PKA-dependent phosphorylation of Dock180, thereby suggesting that targeting EGFRvIII-PKA-Dock180-Rac1 signaling axis could provide a novel pathway to develop potential therapeutic strategies for malignant gliomas.
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EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180.
Oncogene, 2013Co-Authors: Haizhong Feng, Kristiina Vuori, Jann N Sarkaria, Frank B Furnari, Webster K Cavenee, Shi Yuan ChengAbstract:EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180
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phosphorylation of dedicator of cytokinesis 1 Dock180 at tyrosine residue y722 by src family kinases mediates egfrviii driven glioblastoma tumorigenesis
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Haizhong Feng, Careen K Tang, Terrance Grant Johns, Susan Keezer, Michael J. Jarzynka, Kristiina Vuori, Ronald L Hamilton, Yanxin Li, Bo Hu, Ryo NishikawaAbstract:Glioblastoma, the most common primary malignant cancer of the brain, is characterized by rapid tumor growth and infiltration of tumor cells throughout the brain. These traits cause glioblastomas to be highly resistant to current therapies with a resultant poor prognosis. Although aberrant oncogenic signaling driven by signature genetic alterations, such as EGF receptor (EGFR) gene amplification and mutation, plays a major role in glioblastoma pathogenesis, the responsible downstream mechanisms remain less clear. Here, we report that EGFRvIII (also known as ΔEGFR and de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in human glioblastoma, promotes tumorigenesis through Src family kinase (SFK)-dependent phosphorylation of Dock180, a guanine nucleotide exchange factor for Rac1. EGFRvIII induces phosphorylation of Dock180 at tyrosine residue 722 (Dock180Y722) and stimulates Rac1-signaling, glioblastoma cell survival and migration. Consistent with this being causal, siRNA knockdown of Dock180 or expression of a Dock180Y722F mutant inhibits each of these EGFRvIII-stimulated activities. The SFKs, Src, Fyn, and Lyn, induce phosphorylation of Dock180Y722 and inhibition of these SFKs by pharmacological inhibitors or shRNA depletion markedly attenuates EGFRvIII-induced phosphorylation of Dock180Y722, Rac1 activity, and glioblastoma cell migration. Finally, phosphorylated Dock180Y722 is coexpressed with EGFRvIII and phosphorylated SrcY418 in clinical specimens, and such coexpression correlates with an extremely poor survival in glioblastoma patients. These results suggest that targeting the SFK-p-Dock180Y722-Rac1 signaling pathway may offer a novel therapeutic strategy for glioblastomas with EGFRvIII overexpression.
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In Vitro Guanine Nucleotide Exchange Activity of DHR‐2/DOCKER/CZH2 Domains
Methods in enzymology, 2006Co-Authors: Jeanfrancois Cote, Kristiina VuoriAbstract:Abstract Rho family GTPases regulate a large variety of biological processes, including the reorganization of the actin cytoskeleton. Like other members of the Ras superfamily of small GTP‐binding proteins, Rho GTPases cycle between a GDP‐bound (inactive) and a GTP‐bound (active) state, and, when active, the GTPases relay extracellular signals to a large number of downstream effectors. Guanine nucleotide exchange factors (GEFs) promote the exchange of GDP for GTP on Rho GTPases, thereby activating them. Most Rho‐GEFs mediate their effects through their signature domain known as the Dbl Homology‐Pleckstrin Homology (DH‐PH) module. Recently, we and others identified a family of evolutionarily conserved, Dock180‐related proteins that also display GEF activity toward Rho GTPases. The Dock180‐family of proteins lacks the canonical DH‐PH module. Instead, they rely on a novel domain, termed DHR‐2, DOCKER, or CZH2, to exchange GDP for GTP on Rho targets. In this chapter, the experimental approach that we used to uncover the exchange activity of the DHR‐2 domain of Dock180‐related proteins will be described.
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a novel and evolutionarily conserved ptdins 3 4 5 p3 binding domain is necessary for Dock180 signalling
Nature Cell Biology, 2005Co-Authors: Jeanfrancois Cote, Andrea Motoyama, Jason A Bush, Kristiina VuoriAbstract:A novel and evolutionarily conserved PtdIns(3,4,5)P 3 -binding domain is necessary for Dock180 signalling
Amalia Slomiany - One of the best experts on this subject based on the ideXlab platform.
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Porphyromonas gingivalis-Induced GEF Dock180 Activation by Src/PKCδ-Dependent Phosphorylation Mediates PLCγ2 Amplification in Salivary Gland Acinar Cells: Modulatory Effect of Ghrelin
Journal of Biosciences and Medicines, 2015Co-Authors: Bronislaw L. Slomiany, Amalia SlomianyAbstract:Phospholipase Cγ2 (PLCγ2) plays a pivotal role in mediation of inflammatory reaction to bacterial lipopolysaccharide (LPS) as well as serves as a key target in modulatory influence of the hormone ghrelin. Here we explore the involvement of Rac1 and its activator, guanine nucleotide exchange factor (GEF), Dock180, in mediation of PLCγ2 activation in salivary gland acinar cells in response to P. gingivalis LPS and ghrelin. We show that stimulation of the acinar cells with the LPS leads to up-regulation in Dock and PLCγ2 activation, and is reflected in the membrane translocation of Rac1 and PLCγ2, while the effect of ghrelin is manifested by the suppression in Rac1 translocation. Further, we reveal that stimulation with the LPS leads to Dock180 phosphorylation on Tyr and Ser, while the modulatory influence of ghrelin, manifested by a drop in membrane Rac1-GTP, is asso-ciated with a distinct decrease in Dock180 phosphorylation on Ser. Moreover, we demonstrate that phosphorylation on Tyr remains under the control of Src kinase and is accompanied by Dock180 membrane translocation, while protein kinase Cδ(PKCδ) is involved in the LPS-induced phosphorylation of the membrane-recruited Dock180 on Ser. Thus, our findings underscore the role of Src/PKCδ-mediated GEF Dock180 phosphorylation on Tyr/Ser in modulation of salivary gland acinar cell PLCγ2 activation in response to P. gingivalis as well as ghrelin.
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porphyromonas gingivalis induced gef Dock180 activation by src pkcδ dependent phosphorylation mediates plcγ2 amplification in salivary gland acinar cells modulatory effect of ghrelin
Journal of Biosciences and Medicines, 2015Co-Authors: Bronislaw L. Slomiany, Amalia SlomianyAbstract:Phospholipase Cγ2 (PLCγ2) plays a pivotal role in mediation of inflammatory reaction to bacterial lipopolysaccharide (LPS) as well as serves as a key target in modulatory influence of the hormone ghrelin. Here we explore the involvement of Rac1 and its activator, guanine nucleotide exchange factor (GEF), Dock180, in mediation of PLCγ2 activation in salivary gland acinar cells in response to P. gingivalis LPS and ghrelin. We show that stimulation of the acinar cells with the LPS leads to up-regulation in Dock and PLCγ2 activation, and is reflected in the membrane translocation of Rac1 and PLCγ2, while the effect of ghrelin is manifested by the suppression in Rac1 translocation. Further, we reveal that stimulation with the LPS leads to Dock180 phosphorylation on Tyr and Ser, while the modulatory influence of ghrelin, manifested by a drop in membrane Rac1-GTP, is asso-ciated with a distinct decrease in Dock180 phosphorylation on Ser. Moreover, we demonstrate that phosphorylation on Tyr remains under the control of Src kinase and is accompanied by Dock180 membrane translocation, while protein kinase Cδ(PKCδ) is involved in the LPS-induced phosphorylation of the membrane-recruited Dock180 on Ser. Thus, our findings underscore the role of Src/PKCδ-mediated GEF Dock180 phosphorylation on Tyr/Ser in modulation of salivary gland acinar cell PLCγ2 activation in response to P. gingivalis as well as ghrelin.
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Regulatory role of guanine nucleotide exchange factor (GEF) Dock180 phosphorylation on Tyr/Ser in mediation of gastric mucosal Rac1 activation in response to Helicobacter pylori and ghrelin
Inflammopharmacology, 2015Co-Authors: Bronislaw L. Slomiany, Amalia SlomianyAbstract:A small GTPase, Rac1, is recognized as an important modulator of the inflammatory responses to bacterial lipopolysaccharide (LPS) by affecting the processes of phospholipase C activation. The activation of Rac1 involves the exchange of GDP for GTP and is catalyzed by the guanine nucleotide exchange factors (GEFs). Here, we report on the gastric mucosal GEF, Dock180, activation in response to H. pylori PS, and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to up-regulation in Dock180 phosphorylation on Tyr and Ser that is accompanied by a massive rise in Rac1-GTP level, while the effect of ghrelin, manifested by a drop in Dock180 phosphorylation on Ser, is associated with a decrease in Rac1-GTP formation. Furthermore, we demonstrate that phosphorylation on Tyr remains under the control of the Src family protein tyrosine kinases (SFK-PTKs), and is accompanied by Dock180 membrane translocation, while phosphorylation of the membrane-localized Dock180 on Ser represents the stimulatory contribution of protein kinase Cδ (PKCδ) to Dock180 activation. Moreover, we reveal that the interaction between Dock180 and PKCδ is dependent on Dock180 Tyr phosphorylation as well as the activity of PKCδ. Thus, our findings point to the involvement of PKCδ in the LPS-induced up-regulation of Dock180 activation, and suggest the modulatory mechanism of ghrelin influence on the gastric mucosal inflammatory responses to H. pylori.
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regulatory role of guanine nucleotide exchange factor gef Dock180 phosphorylation on tyr ser in mediation of gastric mucosal rac1 activation in response to helicobacter pylori and ghrelin
Inflammopharmacology, 2015Co-Authors: Bronislaw L. Slomiany, Amalia SlomianyAbstract:A small GTPase, Rac1, is recognized as an important modulator of the inflammatory responses to bacterial lipopolysaccharide (LPS) by affecting the processes of phospholipase C activation. The activation of Rac1 involves the exchange of GDP for GTP and is catalyzed by the guanine nucleotide exchange factors (GEFs). Here, we report on the gastric mucosal GEF, Dock180, activation in response to H. pylori PS, and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to up-regulation in Dock180 phosphorylation on Tyr and Ser that is accompanied by a massive rise in Rac1-GTP level, while the effect of ghrelin, manifested by a drop in Dock180 phosphorylation on Ser, is associated with a decrease in Rac1-GTP formation. Furthermore, we demonstrate that phosphorylation on Tyr remains under the control of the Src family protein tyrosine kinases (SFK-PTKs), and is accompanied by Dock180 membrane translocation, while phosphorylation of the membrane-localized Dock180 on Ser represents the stimulatory contribution of protein kinase Cδ (PKCδ) to Dock180 activation. Moreover, we reveal that the interaction between Dock180 and PKCδ is dependent on Dock180 Tyr phosphorylation as well as the activity of PKCδ. Thus, our findings point to the involvement of PKCδ in the LPS-induced up-regulation of Dock180 activation, and suggest the modulatory mechanism of ghrelin influence on the gastric mucosal inflammatory responses to H. pylori.