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Insulin induces tyrosine dephosphorylation of a 92 kDA protein in suspended monocytes

G Zoppini1, P Galante, M Zardini

  • 1Divisione di Endocrinologia e Malattie del Metabolismo, Università di Verona, Italy.

Journal of Endocrinological Investigation
|May 19, 1998
PubMed

Insights

Insulin triggers dephosphorylation of a 92 kDa protein in suspended monocytes, suggesting activation of a tyrosine phosphatase. This occurs without phosphorylating Insulin Receptor Substrate-1 (IRS-1), revealing a unique insulin signaling pathway in these immune cells.

Area of Science:

  • Immunology
  • Cellular Biology
  • Endocrinology

Background:

  • Monocytes possess insulin receptors, but their insulin response is not well understood.
  • Cell adhesion can alter cellular responses to hormones like insulin.
  • Investigating insulin's effects on monocytes is crucial for understanding immune cell function and metabolic regulation.

Purpose of the Study:

  • To characterize insulin-induced tyrosine phosphorylation patterns in monocytes.
  • To investigate how insulin affects protein phosphorylation in suspended monocytes.
  • To determine if insulin signaling in monocytes involves Insulin Receptor Substrate-1 (IRS-1).

Main Methods:

  • Monocytes were isolated using sequential gradient centrifugation.
  • Tyrosine phosphoproteins were analyzed via immunoblotting using antiphosphotyrosine antibodies.
  • Insulin's effect on protein phosphorylation was assessed in a dose- and time-dependent manner.

Main Results:

  • Insulin induced a dose- and time-dependent dephosphorylation of a ~92 kDa protein in suspended monocytes.
  • Insulin did not stimulate tyrosine phosphorylation of Insulin Receptor Substrate-1 (IRS-1).
  • The findings suggest insulin activates a tyrosine phosphatase in monocytes.

Conclusions:

  • In suspended monocytes, insulin appears to activate a tyrosine phosphatase.
  • This phosphatase dephosphorylates a specific protein (~92 kDa).
  • Insulin signaling in monocytes differs from pathways involving IRS-1 phosphorylation.

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