A mouse homologue of the Drosophila tumor suppressor l(2)tid gene defines a novel Ras GTPase-activating protein (RasGAP)-binding protein.
p120 GTPase-activating protein (GAP) down-regulates Ras by stimulating GTP hydrolysis of active Ras. In addition to its association with Ras, GAP has been shown to bind to several tyrosine-phosphorylated proteins in cells stimulated by growth factors or expressing transforming tyrosine kinase variants. Here we report the cloning and characterization of ... a novel GAP-binding protein, mTid-1, a DnaJ chaperone protein that represents the murine homolog of the Drosophila tumor suppressor l(2)tid gene. Three alternatively spliced variants of mTid-1 were isolated, two of which correspond to the recently identified hTid-1(L) and hTid-1(S) forms of the human TID1 gene that exhibit opposing effects on apoptosis. We demonstrate that both cytoplasmic precursor and mitochondrial mature forms of mTid-1 associate with GAP in vivo. Interestingly, although mTid-1 is found tyrosine-phosphorylated in v-src-transformed fibroblast cells, GAP selectively binds to the unphosphorylated form of mTid-1. In immunofluorescence experiments, GAP and Tid-1 were shown to colocalize at perinuclear mitochondrial membranes in response to epidermal growth factor stimulation. These findings raise the possibility that Tid chaperone proteins may play a role in governing the conformation, activity, and/or subcellular distribution of GAP, thereby influencing its biochemical and biological activity within cells.
Mesh Terms:
3T3 Cells, Alternative Splicing, Amino Acid Sequence, Animals, Breast Neoplasms, COS Cells, Cell Line, Transformed, Cercopithecus aethiops, Drosophila, Drosophila Proteins, Female, Genes, Tumor Suppressor, Genes, src, HSP40 Heat-Shock Proteins, Heat-Shock Proteins, Humans, Mice, Mitochondria, Molecular Sequence Data, Protein Isoforms, Recombinant Proteins, Sequence Alignment, Sequence Homology, Amino Acid, Transfection, Tumor Cells, Cultured, ras GTPase-Activating Proteins
3T3 Cells, Alternative Splicing, Amino Acid Sequence, Animals, Breast Neoplasms, COS Cells, Cell Line, Transformed, Cercopithecus aethiops, Drosophila, Drosophila Proteins, Female, Genes, Tumor Suppressor, Genes, src, HSP40 Heat-Shock Proteins, Heat-Shock Proteins, Humans, Mice, Mitochondria, Molecular Sequence Data, Protein Isoforms, Recombinant Proteins, Sequence Alignment, Sequence Homology, Amino Acid, Transfection, Tumor Cells, Cultured, ras GTPase-Activating Proteins
J. Biol. Chem.
Date: Apr. 20, 2001
PubMed ID: 11116152
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