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.
Trentin
G A
GA
Faculty of Health Sciences and Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, L8N 3Z5, Canada.
Yin
X
X
Tahir
S
S
Lhotak
S
S
Farhang-Fallah
J
J
Li
Y
Y
Rozakis-Adcock
M
M
D016475:3T3 Cells; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001943:Breast Neoplasms; D019556:COS Cells; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins; D005260:Female; D016147:Genes, Tumor Suppressor; D016391:Genes, src; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014407:Tumor Cells, Cultured; D020703:ras GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
C093721:CG5504 protein, Drosophila; C120664:DNAJA3 protein, human; C485636:Dnaja3 protein, mouse; D029721:Drosophila Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D020703:ras GTPase-Activating Proteins