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Marcelo G Kazanietz - One of the best experts on this subject based on the ideXlab platform.
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β3-Chimaerin, a novel member of the chimaerin Rac-GAP family
Molecular Biology Reports, 2014Co-Authors: Lautaro Zubeldia-brenner, Hongbin Wang, Marcelo G Kazanietz, Alvaro Gutierrez-uzquiza, Laura Barrio-real, Federico Coluccio LeskowAbstract:Chimaerins are a family of diacylglycerol- and phorbol ester-regulated GTPase activating proteins (GAPs) for the small G-protein Rac. Extensive evidence indicates that these proteins play important roles in development, axon guidance, metabolism, cell motility, and T cell activation. Four isoforms have been reported to-date, which are products of CHN1 (α1- and α2-chimaerins) and CHN2 (β1- and β2-chimaerins) genes. Although these gene products are assumed to be generated by alternative splicing, bioinformatics analysis of the CHN2 gene revealed that β1- and β2-chimaerins are the products of alternative transcription start sites (TSSs) in different promoter regions. Furthermore, we found an additional TSS in CHN2 gene that leads to a novel product, which we named β3-chimaerin. Expression profile analysis revealed predominantly low levels for the β3-chimaerin transcript, with higher expression levels in epididymis, plasma blood leucocytes, spleen, thymus, as well as various areas of the brain. In addition to the prototypical SH2, C1, and Rac-GAP domains, β3-chimaerin has a unique N-terminal domain. Studies in cells established that β3-chimaerin has Rac-GAP activity and is responsive to phorbol esters. The enhanced responsiveness of β3-chimaerin for phorbol ester-induced translocation relative to β2-chimaerin suggests differential ligand accessibility to the C1 domain.
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the zebrafish homologue of mammalian Chimerin rac gaps is implicated in epiboly progression during development
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Federico Coluccio Leskow, Beth A Holloway, Hongbin Wang, Mary C Mullins, Marcelo G KazanietzAbstract:In this paper, we report an in vivo model for the Chimerins, a family of Rac GTPase-activating proteins (Rac-GAPs) that are uniquely regulated by the lipid second messenger diacylglycerol and have been implicated in the control of actin dynamics, migration, and proliferation. We cloned the zebrafish homologue of mammalian α2-Chimerin (chn1) and determined that it possesses Rac-GAP activity and a C1 domain with phorbol ester/diacylglycerol-binding capability. chn1 morpholino knockdown embryos exhibit severe abnormalities, including the development of round somites, lack of yolk extension, and a kinked posterior notochord. These zebrafish morphants show Rac hyperactivation and progress faster through epiboly, leading to tailbud-stage embryos that have a narrow axis and an enlarged tailbud with expanded bmp4 and shh expression. Phenotypic rescue was achieved by mRNA microinjection of chn1 or an active Chimerin Rac-GAP domain into the yolk syncytial layer but not by a chn1 mutant deficient in Rac-GAP activity, suggesting that the lack of chn1 Rac-GAP activity in the yolk syncytial layer was causative of the misbalance in morphogenetic movements. Our results reveal a crucial role for chn1 in early development and implicate Rac as a key regulator of morphogenetic movements during zebrafish epiboly.
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rac gap dependent inhibition of breast cancer cell proliferation by β2 Chimerin
Journal of Biological Chemistry, 2005Co-Authors: Chengfeng Yang, Federico Coluccio Leskow, Valerie M Weaver, Marcelo G KazanietzAbstract:Abstract β2-Chimerin is a member of the “non-protein kinase C” intracellular receptors for the second messenger diacylglycerol and the phorbol esters that is yet poorly characterized, particularly in the context of signaling pathways involved in proliferation and cancer progression. β2-Chimerin possesses a C-terminal Rac-GAP (GTPase-activating protein) domain that accelerates the hydrolysis of GTP from the Rac GTPase, leading to its inactivation. We found that β2-Chimerin messenger levels are significantly down-regulated in human breast cancer cell lines as well as in breast tumors. Adenoviral delivery of β2-Chimerin into MCF-7 breast cancer cells leads to inhibition of proliferation and G1 cell cycle arrest. Mechanistic studies show that the effect involves the reduction in Rac-GTP levels, cyclin D1 expression, and retinoblastoma dephosphorylation. Studies using the mutated forms of β2-Chimerin revealed that these effects were entirely dependent on its C-terminal GAP domain and Rac-GAP activity. Moreover, MCF-7 cells stably expressing active Rac (V12Rac1) but not RhoA (V14RhoA) were insensitive to β2-Chimerin-induced inhibition of proliferation and cell cycle progression. The modulation of G1/S progression by β2-Chimerin not only implies an essential role for Rac in breast cancer cell proliferation but also raises the intriguing possibility that diacylglycerol-regulated non-protein kinase C pathways can negatively impact proliferation mechanisms controlled by Rho GTPases.
Federico Coluccio Leskow - One of the best experts on this subject based on the ideXlab platform.
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β3-Chimaerin, a novel member of the chimaerin Rac-GAP family
Molecular Biology Reports, 2014Co-Authors: Lautaro Zubeldia-brenner, Hongbin Wang, Marcelo G Kazanietz, Alvaro Gutierrez-uzquiza, Laura Barrio-real, Federico Coluccio LeskowAbstract:Chimaerins are a family of diacylglycerol- and phorbol ester-regulated GTPase activating proteins (GAPs) for the small G-protein Rac. Extensive evidence indicates that these proteins play important roles in development, axon guidance, metabolism, cell motility, and T cell activation. Four isoforms have been reported to-date, which are products of CHN1 (α1- and α2-chimaerins) and CHN2 (β1- and β2-chimaerins) genes. Although these gene products are assumed to be generated by alternative splicing, bioinformatics analysis of the CHN2 gene revealed that β1- and β2-chimaerins are the products of alternative transcription start sites (TSSs) in different promoter regions. Furthermore, we found an additional TSS in CHN2 gene that leads to a novel product, which we named β3-chimaerin. Expression profile analysis revealed predominantly low levels for the β3-chimaerin transcript, with higher expression levels in epididymis, plasma blood leucocytes, spleen, thymus, as well as various areas of the brain. In addition to the prototypical SH2, C1, and Rac-GAP domains, β3-chimaerin has a unique N-terminal domain. Studies in cells established that β3-chimaerin has Rac-GAP activity and is responsive to phorbol esters. The enhanced responsiveness of β3-chimaerin for phorbol ester-induced translocation relative to β2-chimaerin suggests differential ligand accessibility to the C1 domain.
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the zebrafish homologue of mammalian Chimerin rac gaps is implicated in epiboly progression during development
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Federico Coluccio Leskow, Beth A Holloway, Hongbin Wang, Mary C Mullins, Marcelo G KazanietzAbstract:In this paper, we report an in vivo model for the Chimerins, a family of Rac GTPase-activating proteins (Rac-GAPs) that are uniquely regulated by the lipid second messenger diacylglycerol and have been implicated in the control of actin dynamics, migration, and proliferation. We cloned the zebrafish homologue of mammalian α2-Chimerin (chn1) and determined that it possesses Rac-GAP activity and a C1 domain with phorbol ester/diacylglycerol-binding capability. chn1 morpholino knockdown embryos exhibit severe abnormalities, including the development of round somites, lack of yolk extension, and a kinked posterior notochord. These zebrafish morphants show Rac hyperactivation and progress faster through epiboly, leading to tailbud-stage embryos that have a narrow axis and an enlarged tailbud with expanded bmp4 and shh expression. Phenotypic rescue was achieved by mRNA microinjection of chn1 or an active Chimerin Rac-GAP domain into the yolk syncytial layer but not by a chn1 mutant deficient in Rac-GAP activity, suggesting that the lack of chn1 Rac-GAP activity in the yolk syncytial layer was causative of the misbalance in morphogenetic movements. Our results reveal a crucial role for chn1 in early development and implicate Rac as a key regulator of morphogenetic movements during zebrafish epiboly.
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rac gap dependent inhibition of breast cancer cell proliferation by β2 Chimerin
Journal of Biological Chemistry, 2005Co-Authors: Chengfeng Yang, Federico Coluccio Leskow, Valerie M Weaver, Marcelo G KazanietzAbstract:Abstract β2-Chimerin is a member of the “non-protein kinase C” intracellular receptors for the second messenger diacylglycerol and the phorbol esters that is yet poorly characterized, particularly in the context of signaling pathways involved in proliferation and cancer progression. β2-Chimerin possesses a C-terminal Rac-GAP (GTPase-activating protein) domain that accelerates the hydrolysis of GTP from the Rac GTPase, leading to its inactivation. We found that β2-Chimerin messenger levels are significantly down-regulated in human breast cancer cell lines as well as in breast tumors. Adenoviral delivery of β2-Chimerin into MCF-7 breast cancer cells leads to inhibition of proliferation and G1 cell cycle arrest. Mechanistic studies show that the effect involves the reduction in Rac-GTP levels, cyclin D1 expression, and retinoblastoma dephosphorylation. Studies using the mutated forms of β2-Chimerin revealed that these effects were entirely dependent on its C-terminal GAP domain and Rac-GAP activity. Moreover, MCF-7 cells stably expressing active Rac (V12Rac1) but not RhoA (V14RhoA) were insensitive to β2-Chimerin-induced inhibition of proliferation and cell cycle progression. The modulation of G1/S progression by β2-Chimerin not only implies an essential role for Rac in breast cancer cell proliferation but also raises the intriguing possibility that diacylglycerol-regulated non-protein kinase C pathways can negatively impact proliferation mechanisms controlled by Rho GTPases.
Christine Hall - One of the best experts on this subject based on the ideXlab platform.
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GTPase-activating protein activity of n(alpha 1)-Chimaerin and effect of lipids.
Methods in Enzymology, 2004Co-Authors: Sohail Ahmed, Robert Kozma, Christine HallAbstract:Publisher Summary This chapter describes the GTPase-activating protein (GAP) activity of n (α 1 )-Chimerin and the effect of lipids. n (α 1 )-Chimerin cDNA encodes a 38-kDa GAP for Rac1 and Cdc42Hs, which possesses a protein kinase C (PKC)-like cysteine-rich regulatory domain. The cysteine-rich domain of n -Chimerin coordinates 2 mol of Zn 2+ per mole protein and binds phorbol esters. Zn 2+ is required for n -Chimerin and PKC to bind phorbol esters. n -Chimerin is a novel functional target for phorbol esters and phospholipids. Other proteins with a sequence identity to the cysteine-rich regulatory domain of n -Chimerin are the oncogene products, Raf and Vav, diacylglycerol kinase, and the Caenorhabditis elegans unc-13 gene product. Similarly, a number of proteins have sequence a identity to the C-terminal GAP domain of n -Chimerin, including Cdc42Hs–GAP, breakpoint cluster region gene product (Bcr), active Bcr-related gene product (Abr), and the Ras–GAP binding protein p190. The Chimerin family of proteins consists of a cysteine-rich domain coupled to a GAP domain with variable N -terminal sequences.
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alpha 2 Chimerin an sh2 containing gtpase activating protein for the ras related protein p21rac derived by alternate splicing of the human n Chimerin gene is selectively expressed in brain regions and testes
Molecular and Cellular Biology, 1993Co-Authors: Christine Hall, G J Michael, P Smith, Jingming Dong, Edward Manser, N K Spurr, T A JonesAbstract:Abstract n-Chimerin (alpha 1-Chimerin) is a brain GTPase-activating protein (GAP) for the ras-related p21rac. We now report the occurrence of another form of Chimerin, termed alpha 2-Chimerin. This is the product of an alternately spliced transcript of the human n-Chimerin gene encoding an N-terminal SH2 (src homology 2) domain in addition to the phorbol ester receptor and GAP domains. alpha 1- and alpha 2-Chimerin mRNAs were expressed differently. In the rat brain, only alpha 1-Chimerin mRNA was expressed in cerebellar Purkinje cells, although both alpha 1- and alpha 2-Chimerin mRNAs occurred in neurons in the cerebral cortex, hippocampus, and thalamus. Only alpha 2-Chimerin RNA was expressed in rat testes, in early pachytene spermatocytes. A 45-kDa SH2-containing Chimerin corresponding to the alpha 2 form was purified from rat brain. As with Escherichia coli 45-kDa recombinant alpha 2-Chimerin, purified brain alpha 2-Chimerin exhibited racGAP activity which was stimulated by phosphatidylserine. The recombinant SH2 domain bound several 32P-labelled phosphoproteins of PC12 cells, whose phosphorylation increased in response to trophic factors, including nerve growth factor. To examine the relationships of alpha 1- and alpha 2-Chimerin transcripts, human genomic DNA clones were characterized. In alpha 2-Chimerin mRNA, a 3' splice acceptor site within exon 1 of alpha 1-Chimerin mRNA was used, replacing its 5' untranslated region and N-terminal coding sequence. The single human n-Chimerin gene was mapped to chromosome 2q31-q32.1, colocalizing with the CRE-BP1 transcription factor gene (2q32). It contained several splice junctions conserved with the sequence-related protein kinase C and bcr genes. alpha 2-Chimerin is only the second SH2-containing GAP and the first example of an SH2 domain generated by alternate splicing.
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novel human brain cdna encoding a 34 000 mr protein n chimaerin related to both the regulatory domain of protein kinase c and bcr the product of the breakpoint cluster region gene
Journal of Molecular Biology, 1990Co-Authors: Christine Hall, Sohail Ahmed, Robert Kozma, Clinton Monfries, Paul E Smith, Vasanthi Vanniasingham, Thomas LeungAbstract:A novel human brain complementary DNA sequence encodes n-chimaerin, a 34,000 Mr protein. A single cysteine-rich sequence CX2CX13CX2CX7CX7C in the N-terminal half of n-chimaerin shares almost 50% identity with corresponding sequences in the C1 regulatory domain of protein kinase C. The C-terminal half of n-chimaerin has 42% identity with the C-terminal region (amino acid residues 1050 to 1225) of BCR, the product of the breakpoint cluster region gene involved in Philadelphia (Ph′) chromosome translocation. n-Chimaerin mRNA (2.2 × 103 base-pairs) is specifically expressed in the brain, with the highest amounts being in the hippocampus and cerebral cortex. The mRNA has a neuronal distribution and is expressed in neuroblastoma cells, but not in C6 glioma or primary astrocyte cultures. The similarity of two separate regions of n-chimaerin to domains of protein kinase C and BCR has intriguing implications with respect to its evolutionary origins, its function in the brain and potential phorbol-ester-binding properties.
T A Jones - One of the best experts on this subject based on the ideXlab platform.
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alpha 2 Chimerin an sh2 containing gtpase activating protein for the ras related protein p21rac derived by alternate splicing of the human n Chimerin gene is selectively expressed in brain regions and testes
Molecular and Cellular Biology, 1993Co-Authors: Christine Hall, G J Michael, P Smith, Jingming Dong, Edward Manser, N K Spurr, T A JonesAbstract:Abstract n-Chimerin (alpha 1-Chimerin) is a brain GTPase-activating protein (GAP) for the ras-related p21rac. We now report the occurrence of another form of Chimerin, termed alpha 2-Chimerin. This is the product of an alternately spliced transcript of the human n-Chimerin gene encoding an N-terminal SH2 (src homology 2) domain in addition to the phorbol ester receptor and GAP domains. alpha 1- and alpha 2-Chimerin mRNAs were expressed differently. In the rat brain, only alpha 1-Chimerin mRNA was expressed in cerebellar Purkinje cells, although both alpha 1- and alpha 2-Chimerin mRNAs occurred in neurons in the cerebral cortex, hippocampus, and thalamus. Only alpha 2-Chimerin RNA was expressed in rat testes, in early pachytene spermatocytes. A 45-kDa SH2-containing Chimerin corresponding to the alpha 2 form was purified from rat brain. As with Escherichia coli 45-kDa recombinant alpha 2-Chimerin, purified brain alpha 2-Chimerin exhibited racGAP activity which was stimulated by phosphatidylserine. The recombinant SH2 domain bound several 32P-labelled phosphoproteins of PC12 cells, whose phosphorylation increased in response to trophic factors, including nerve growth factor. To examine the relationships of alpha 1- and alpha 2-Chimerin transcripts, human genomic DNA clones were characterized. In alpha 2-Chimerin mRNA, a 3' splice acceptor site within exon 1 of alpha 1-Chimerin mRNA was used, replacing its 5' untranslated region and N-terminal coding sequence. The single human n-Chimerin gene was mapped to chromosome 2q31-q32.1, colocalizing with the CRE-BP1 transcription factor gene (2q32). It contained several splice junctions conserved with the sequence-related protein kinase C and bcr genes. alpha 2-Chimerin is only the second SH2-containing GAP and the first example of an SH2 domain generated by alternate splicing.
Hongbin Wang - One of the best experts on this subject based on the ideXlab platform.
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β3-Chimaerin, a novel member of the chimaerin Rac-GAP family
Molecular Biology Reports, 2014Co-Authors: Lautaro Zubeldia-brenner, Hongbin Wang, Marcelo G Kazanietz, Alvaro Gutierrez-uzquiza, Laura Barrio-real, Federico Coluccio LeskowAbstract:Chimaerins are a family of diacylglycerol- and phorbol ester-regulated GTPase activating proteins (GAPs) for the small G-protein Rac. Extensive evidence indicates that these proteins play important roles in development, axon guidance, metabolism, cell motility, and T cell activation. Four isoforms have been reported to-date, which are products of CHN1 (α1- and α2-chimaerins) and CHN2 (β1- and β2-chimaerins) genes. Although these gene products are assumed to be generated by alternative splicing, bioinformatics analysis of the CHN2 gene revealed that β1- and β2-chimaerins are the products of alternative transcription start sites (TSSs) in different promoter regions. Furthermore, we found an additional TSS in CHN2 gene that leads to a novel product, which we named β3-chimaerin. Expression profile analysis revealed predominantly low levels for the β3-chimaerin transcript, with higher expression levels in epididymis, plasma blood leucocytes, spleen, thymus, as well as various areas of the brain. In addition to the prototypical SH2, C1, and Rac-GAP domains, β3-chimaerin has a unique N-terminal domain. Studies in cells established that β3-chimaerin has Rac-GAP activity and is responsive to phorbol esters. The enhanced responsiveness of β3-chimaerin for phorbol ester-induced translocation relative to β2-chimaerin suggests differential ligand accessibility to the C1 domain.
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the zebrafish homologue of mammalian Chimerin rac gaps is implicated in epiboly progression during development
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Federico Coluccio Leskow, Beth A Holloway, Hongbin Wang, Mary C Mullins, Marcelo G KazanietzAbstract:In this paper, we report an in vivo model for the Chimerins, a family of Rac GTPase-activating proteins (Rac-GAPs) that are uniquely regulated by the lipid second messenger diacylglycerol and have been implicated in the control of actin dynamics, migration, and proliferation. We cloned the zebrafish homologue of mammalian α2-Chimerin (chn1) and determined that it possesses Rac-GAP activity and a C1 domain with phorbol ester/diacylglycerol-binding capability. chn1 morpholino knockdown embryos exhibit severe abnormalities, including the development of round somites, lack of yolk extension, and a kinked posterior notochord. These zebrafish morphants show Rac hyperactivation and progress faster through epiboly, leading to tailbud-stage embryos that have a narrow axis and an enlarged tailbud with expanded bmp4 and shh expression. Phenotypic rescue was achieved by mRNA microinjection of chn1 or an active Chimerin Rac-GAP domain into the yolk syncytial layer but not by a chn1 mutant deficient in Rac-GAP activity, suggesting that the lack of chn1 Rac-GAP activity in the yolk syncytial layer was causative of the misbalance in morphogenetic movements. Our results reveal a crucial role for chn1 in early development and implicate Rac as a key regulator of morphogenetic movements during zebrafish epiboly.