A Mouse Homologue of the Drosophila Tumor Suppressor l(2)tid Gene Defines a Novel Ras GTPase-activating Protein (RasGAP)-binding Protein

• Published in: The Journal of biological chemistry 2001-04, Vol.276 (16), p.13087-13095
• Main Authors: Trentin, G A, Yin, X, Tahir, S, Lhotak, S, Farhang-Fallah, J, Li, Y, Rozakis-Adcock, M
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Alternative Splicing; Amino Acid Sequence; Animals; Breast Neoplasms; Cell Line, Transformed; chaperone proteins; Chlorocebus aethiops; COS Cells; DnaJ protein; Drosophila - genetics; Drosophila Proteins; Female; GAP protein; Genes, src; Genes, Tumor Suppressor; GTPase-activating protein; Heat-Shock Proteins - genetics; HSP40 Heat-Shock Proteins; Humans; iltid gene; Mice; Mitochondria - metabolism; Mitochondrial Proteins; Molecular Sequence Data; mTid-1 protein; p120 protein; Protein Isoforms - chemistry; Protein Isoforms - genetics; Protein Isoforms - metabolism; ras GTPase-Activating Proteins - chemistry; ras GTPase-Activating Proteins - genetics; ras GTPase-Activating Proteins - metabolism; Recombinant Proteins - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; Transfection; Tumor Cells, Cultured; v-src gene
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M009267200

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.