Distinct mechanisms of taxol-induced serine phosphorylation of the 66-kDa Shc isoform in A549 and RAW 264.7 cells.
Nanomolar concentrations of Taxol, and other antimitotic agents that interact with microtubules, mediate serine phosphorylation of the 66-kDa Shc isoform (p66shc) in A549 human lung carcinoma cells, 9-18 h after drug treatment. This event coincides with the release of PARP cleavage fragments that are early indicators of apoptosis. Taxol-induced serine phosphorylation of p66shc results from a MEK-independent signaling pathway that is activated in A549 cells that have a prolonged or abnormal mitotic phase of the cell cycle [Cancer Res. 60 (2000) 5171]. In contrast, in murine macrophage RAW 264.7 cells, micromolar concentrations of Taxol but not other microtubule-interacting agents induced serine phosphorylation of p66shc that correlated with the phosphorylation of Raf-1 and extracellular signal-regulated kinase (ERK1/2), within 15-30 min after Taxol treatment. This event also was induced by lipopolysaccharide (LPS). The MEK-inhibitor, U0126, that specifically inhibits the activation of ERK also blocked the phosphorylation of p66shc and Raf-1, suggesting that these processes were MEK-dependent, quite different from that which was observed in A549 cells. Taxol also induced phosphorylation of p38 and JNK MAP kinases within 8-15 min after drug treatment. It is known that Taxol, but not other microtubule-interacting agents, induces the production of cytokines, such as tumor necrosis factor alpha (TNF-alpha) in mouse macrophages. The time course of Taxol-induced TNF-alpha expression coincides with that of Taxol-induced p66shc phosphorylation, and U0126 inhibits significantly Taxol-induced TNF-alpha expression in RAW 264.7 cells. Our data indicate that the Taxol-induced serine phosphorylation of p66shc in RAW 264.7 cells is microtubule-independent and may be related to increased TNF-alpha expression after Taxol and LPS treatment. It is concluded that the mechanisms involved in Taxol-induced p66shc phosphorylation are distinct in A549 and RAW 264.7 cells.
Yang
Chia-Ping Huang
CP
Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Horwitz
Susan Band
SB
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012694:Serine / Q000737:chemistry; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013912:Threonine / Q000737:chemistry; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000972:Antineoplastic Agents, Phytogenic; D002070:Butadienes; D004791:Enzyme Inhibitors; D007093:Imidazoles; D009570:Nitriles; D011506:Proteins; D011725:Pyridines; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014409:Tumor Necrosis Factor-alpha; C113580:U 0126; D013912:Threonine; D012694:Serine; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580; D017239:Paclitaxel