Distinct mechanisms of Taxol-induced serine phosphorylation of the 66-kDa Shc isoform in A549 and RAW 264.7 cells

Chia Ping Huang Yang, Susan Band Horwitz

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


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-α) in mouse macrophages. The time course of Taxol-induced TNF-α expression coincides with that of Taxol-induced p66shc phosphorylation, and U0126 inhibits significantly Taxol-induced TNF-α 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-α 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.

Original languageEnglish (US)
Pages (from-to)76-83
Number of pages8
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Issue number1-3
StatePublished - Jun 12 2002
Externally publishedYes


  • Macrophage
  • Microtubule-interacting agent
  • Taxol
  • p66shc phosphorylation

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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