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p145, a protein with associated tyrosine kinase activity in a human gastric carcinoma cell line

S Giordano1, M F Di Renzo, R Ferracini

  • 1Department of Biomedical Sciences and Oncology, University of Torino Medical School, Turin, Italy.

Molecular and Cellular Biology
|August 1, 1988
PubMed

Insights

Researchers identified a novel protein, p145, in gastric cancer cells. This protein possesses tyrosine kinase activity and is activated by an unknown factor, suggesting a new target for cancer therapy.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Oncology

Background:

  • Gastric carcinoma cell lines harbor unique proteins.
  • Phosphotyrosine antibodies are crucial for identifying specific protein modifications.

Purpose of the Study:

  • To characterize a novel 145,000 molecular weight protein (p145) detected in gastric carcinoma.
  • To investigate the enzymatic activity and regulatory mechanisms of p145.

Main Methods:

  • Western blot (immunoblot) analysis using phosphotyrosine antibodies.
  • Metabolic labeling with 32Pi.
  • Immunoprecipitation and in vitro kinase assays.
  • Analysis of protein phosphorylation under varying pH conditions.

Main Results:

  • p145 was identified as a cysteine-rich transmembrane glycoprotein phosphorylated on tyrosine and serine.
  • p145 exhibited associated protein tyrosine kinase activity, independent of known growth factors.
  • Dephosphorylation occurred rapidly at low pH, indicating ligand-dependent regulation.

Conclusions:

  • p145 is a novel tyrosine kinase-associated protein in gastric cancer.
  • Its activity is regulated by an unidentified factor and is sensitive to pH-mediated ligand dissociation.
  • p145 represents a potential therapeutic target in gastric carcinoma.

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