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Effects of insulin on protein phosphorylation and protein kinase C activity in human malignant gliomas

B C Yang1, R F Chen, C C Chio

  • 1Department of Microbiology and Immunology, Medical College, National Cheng Kung University, Tainan, Taiwan, Republic of China.

Proceedings of the National Science Council, Republic of China. Part B, Life Sciences
|April 16, 1998
PubMed

Insights

Insulin affects protein phosphorylation differently in glioma cells compared to normal glial cells, suggesting altered insulin signaling pathways in gliomas. This involves differential regulation of protein kinase C (PKC) isozymes, impacting cancer cell behavior.

Area of Science:

  • Oncology
  • Cell Biology
  • Biochemistry

Background:

  • Insulin signaling plays a crucial role in cellular processes, including cell growth and metabolism.
  • Aberrant insulin signaling is implicated in various cancers, including gliomas.
  • Understanding insulin's effects on protein phosphorylation in gliomas is vital for therapeutic development.

Purpose of the Study:

  • To investigate the differential effects of insulin on protein phosphorylation in human glioma cells versus normal glial cells.
  • To explore the role of protein kinase C (PKC) isozymes in insulin-mediated signaling in gliomas.

Main Methods:

  • In vitro assessment of protein phosphorylation activities in response to insulin.
  • Analysis of tyrosyl phosphoprotein expression before and after insulin treatment.
  • Measurement of casein kinase II and total protein kinase C (PKC) activities.
  • Detection and quantification of specific PKC isozymes (alpha, beta, delta, epsilon, gamma) in cell lysates and membranes.

Main Results:

  • Insulin suppressed in vitro protein phosphorylation in glioma cells but stimulated it in normal glial cells, meningiomas, and neurilemmomas.
  • Both glioma and normal glial cells exhibited similar tyrosyl phosphoprotein profiles after insulin treatment, despite differing pre-treatment profiles.
  • Insulin increased casein kinase II and total PKC activities in both cell types.
  • Specific PKC isozymes were differentially regulated by insulin in gliomas, with down-regulation of PKC-gamma and PKC-epsilon.

Conclusions:

  • Human gliomas exhibit an altered insulin signaling pathway compared to normal glial cells.
  • Differential regulation of PKC isozymes by insulin in gliomas may contribute to tumorigenesis.
  • Targeting insulin signaling pathways, particularly PKC isozymes, could be a potential therapeutic strategy for gliomas.

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