Abstract
The gene mutated in the human genetic disorder ataxia-telangiectasia (A-T) has been described recently (Savitsky et al., 1995a) and the complete coding sequence of this gene, ATM, has been reported (Savitsky et al., 1995b). The derived amino acid sequence demonstrates significant homologies to several proteins containing a phosphatidylinositol 3-kinase (PI3-kinase) domain, including the yeast TOR proteins and the human protein FRAP. Since the TOR and FRAP proteins are targets for the immunosuppressive drug rapamycin, we have investigated the effects of this compound on A-T cells. We report here that 3 A-T cell lines are more resistant than control cells to rapamycin's growth inhibiting effects but were more sensitive to the PI3-kinase inhibitor wortmannin. As expected rapamycin (1 nM) inhibited the rate of exit of control cells from G1 phase but failed to perturb the progression of A-T cells. This difference in cell cycle progress after rapamycin treatment is reflected in ribosomal S6 protein kinase (p70S6k) by both a downward mobility shift on SDS-PAGE and inhibition of activity. Furthermore, the G1 phase cyclin-dependent kinase, cyclin E-cdk2, was rapidly inhibited in control cells post-treatment, whereas in A-T cells it took considerably longer to observe inhibition. There was no evidence that a GST-FKBP12 fusion protein specifically precipitated the ATM protein in the presence of rapamycin in either cell type. These results demonstrate that the ATM protein is not a direct target for rapamycin but its functional loss renders cells more resistant to this compound.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Androstadienes / pharmacology
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Antibiotics, Antineoplastic / pharmacology
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Antifungal Agents / pharmacology
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Ataxia Telangiectasia / drug therapy*
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Ataxia Telangiectasia / pathology
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Ataxia Telangiectasia Mutated Proteins
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Binding Sites
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Carrier Proteins / genetics
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Carrier Proteins / pharmacology
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Cell Cycle / drug effects
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Cell Cycle / genetics
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Cell Cycle Proteins
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Cells, Cultured
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / pharmacology
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Dose-Response Relationship, Drug
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Drug Resistance / genetics*
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Enzyme Inhibitors / pharmacology
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Heat-Shock Proteins / genetics
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Heat-Shock Proteins / pharmacology
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Humans
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Immunosuppressive Agents / pharmacology
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Molecular Sequence Data
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Mutation
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Nocodazole / pharmacology
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Phosphatidylinositol 3-Kinases
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Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors
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Polyenes / pharmacology*
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Protein Serine-Threonine Kinases / drug effects
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Protein Serine-Threonine Kinases / metabolism
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Proteins / drug effects*
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Proteins / metabolism
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Ribosomal Protein S6 Kinases
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Sirolimus
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Tacrolimus Binding Proteins
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Tumor Cells, Cultured
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Tumor Suppressor Proteins
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Wortmannin
Substances
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Androstadienes
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Antibiotics, Antineoplastic
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Antifungal Agents
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Carrier Proteins
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Cell Cycle Proteins
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DNA-Binding Proteins
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Enzyme Inhibitors
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Heat-Shock Proteins
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Immunosuppressive Agents
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Polyenes
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Proteins
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Recombinant Fusion Proteins
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Tumor Suppressor Proteins
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Phosphotransferases (Alcohol Group Acceptor)
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ATM protein, human
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Ataxia Telangiectasia Mutated Proteins
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Protein Serine-Threonine Kinases
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Ribosomal Protein S6 Kinases
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Tacrolimus Binding Proteins
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Nocodazole
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Sirolimus
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Wortmannin