Abstract
Gem is a Ras-related protein whose expression is induced in several cell types upon activation by extracellular stimuli. With the aim of isolating the cellular partners of Gem that mediate its biological activity we performed a yeast two-hybrid screen and identified a novel protein of 970 amino acids, Gmip, that interacts with Gem through its N-terminal half, and presents a cysteine-rich domain followed by a Rho GTPase-activating protein (RhoGAP) domain in its C-terminal half. The RhoGAP domain of Gmip stimulates in vitro the GTPase activity of RhoA, but is inactive towards other Rho family proteins such as Rac1 and Cdc42; it is also specific for RhoA in vivo. The same is true for the full-length protein, which is furthermore able to down-regulate RhoA-dependent stress fibres in Ref-52 rat fibroblasts. These findings suggest that the signalling pathways controlled by two proteins of the Ras superfamily, RhoA and Gem, are linked via the action of the RhoGAP protein Gmip (Gem-interacting protein).
MeSH terms
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Actins / metabolism
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Amino Acid Sequence
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Animals
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Blotting, Northern
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Cell Line
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Cloning, Molecular
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Cytoskeleton / metabolism
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DNA, Complementary / metabolism
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Fibroblasts / metabolism
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GTPase-Activating Proteins / metabolism*
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GTPase-Activating Proteins / physiology*
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Gene Library
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Guanosine Triphosphate / metabolism
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Humans
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Immediate-Early Proteins / chemistry*
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Immediate-Early Proteins / metabolism*
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Immediate-Early Proteins / physiology*
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Microscopy, Fluorescence
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Molecular Sequence Data
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Monomeric GTP-Binding Proteins / chemistry*
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Monomeric GTP-Binding Proteins / metabolism*
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Monomeric GTP-Binding Proteins / physiology*
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Precipitin Tests
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Protein Binding
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Protein Serine-Threonine Kinases / metabolism
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Protein Structure, Tertiary
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Proto-Oncogene Proteins c-akt
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Rats
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Recombinant Proteins / chemistry
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Sequence Homology, Amino Acid
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Time Factors
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Tissue Distribution
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Two-Hybrid System Techniques
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cdc42 GTP-Binding Protein / metabolism
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rho GTP-Binding Proteins / chemistry*
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rho GTP-Binding Proteins / metabolism
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rhoA GTP-Binding Protein / chemistry
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rhoA GTP-Binding Protein / metabolism
Substances
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Actins
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DNA, Complementary
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GMIP protein, human
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GTPase-Activating Proteins
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Immediate-Early Proteins
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Recombinant Proteins
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Guanosine Triphosphate
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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GEM protein, human
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Monomeric GTP-Binding Proteins
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cdc42 GTP-Binding Protein
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rho GTP-Binding Proteins
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rhoA GTP-Binding Protein