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Tyrosine phosphorylation of NOS3 in a breast cancer cell line and Src-transformed cells

Yasushi Takenouchi1, Myat Lin Oo, Takeshi Senga

  • 1Division of Cancer Biology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya 466-8550, Japan.

Oncology Reports
|April 8, 2004
PubMed

Insights

Active Src kinases phosphorylate endothelial nitric oxide synthase (NOS3) in human breast cancer cells. This phosphorylation is dependent on Src activity and its membrane-bound form, suggesting a role in cancer progression.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Oncology

Background:

  • Endothelial nitric oxide synthase (NOS3) plays a role in various cellular processes.
  • Src kinases are known to regulate cellular signaling pathways, including those implicated in cancer.

Purpose of the Study:

  • To investigate the role of active Src in the tyrosine phosphorylation of NOS3.
  • To determine the specific forms of Src that mediate NOS3 phosphorylation.

Main Methods:

  • Utilized human breast cancer cell line (BT474).
  • Employed Src kinase inhibitors (PP1) and various Src mutants (v-Src, c-Src, Y527F, G2A, K295M).
  • Analyzed NOS3 phosphorylation levels via Western blotting and kinase activity assays.

Main Results:

  • Confirmed activation of c-Src and NOS3 tyrosine phosphorylation in BT474 cells.
  • Demonstrated dose-dependent suppression of NOS3 phosphorylation by PP1, indicating Src kinase involvement.
  • Observed significant NOS3 phosphorylation with v-Src and Y527Fc-Src, but not with c-Src, G2Av-Src, or K295Mv-Src.
  • Showed temperature-dependent NOS3 phosphorylation with a temperature-sensitive v-Src mutant.

Conclusions:

  • Active, membrane-bound Src kinases induce constitutive tyrosine phosphorylation of NOS3.
  • Specific Src forms and kinase activity are critical for NOS3 phosphorylation.
  • Findings suggest a potential mechanism linking Src activity to NOS3 regulation in breast cancer.

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