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Assessment of Resistance to Tyrosine Kinase Inhibitors by an Interrogation of Signal Transduction Pathways by Antibody Arrays
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Assessment of Resistance to Tyrosine Kinase Inhibitors by an Interrogation of Signal Transduction Pathways by Antibody Arrays

Published on: September 19, 2018

Phorbol ester inhibition of hormonal induction of tyrosine aminotransferase

J W Koontz, S Goodman

    Biochemical and Biophysical Research Communications
    |September 16, 1985
    PubMed

    Insights

    Phorbol esters inhibit the liver enzyme tyrosine aminotransferase induction by insulin, glucocorticoids, and cAMP. This suggests a common pathway for these inducers, contrary to previous beliefs.

    Area of Science:

    • Biochemistry
    • Molecular Biology
    • Enzymology

    Background:

    • Tyrosine aminotransferase is a liver-specific enzyme.
    • Glucocorticoids, cAMP analogs, and insulin induce tyrosine aminotransferase via separate pathways.
    • Phorbol esters are known to inhibit insulin's induction of this enzyme by affecting the insulin receptor.

    Purpose of the Study:

    • To investigate the effect of TPA (12-O-tetradecanoylphorbol-13-acetate) on tyrosine aminotransferase induction.
    • To determine if TPA affects induction by agents other than insulin.

    Main Methods:

    • Enzyme assays to measure tyrosine aminotransferase activity.
    • Treatment of liver cells with TPA, insulin, glucocorticoids, and cAMP analogs.

    Main Results:

    • TPA inhibited insulin-stimulated tyrosine aminotransferase induction.
    • TPA also inhibited tyrosine aminotransferase induction by glucocorticoids.
    • TPA inhibited tyrosine aminotransferase induction by cAMP analogs.

    Conclusions:

    • TPA inhibits tyrosine aminotransferase induction by multiple agents.
    • These findings suggest a potential convergence or common regulatory mechanism for these induction pathways.
    • This challenges the established model of separate pathways for insulin, glucocorticoid, and cAMP induction.

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