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Published on: January 23, 2012

Calmodulin-dependent protein kinases phosphorylate gp130 at the serine-based dileucine internalization motif

Robin M Gibson1, George S Laszlo, Neil M Nathanson

  • 1Department of Pharmacology, University of Washington, Box 357750, Seattle, WA 98195-7750, USA.

Biochimica Et Biophysica Acta
|July 23, 2005
PubMed

Insights

Leukemia inhibitory factor (LIF) receptor signaling involves gp130 phosphorylation at Ser782 by calmodulin-dependent protein kinase type II (CaMKII) and possibly CaMKIV, impacting cell surface expression and gene activity.

Area of Science:

  • Cell biology
  • Molecular signaling
  • Receptor biology

Background:

  • The leukemia inhibitory factor (LIF) receptor complex comprises LIFR and gp130.
  • LIF stimulation induces gp130 phosphorylation at Ser782, near an internalization motif.
  • Mutant receptors lacking Ser782 show increased cell surface expression and gene expression.

Purpose of the Study:

  • To identify the kinase responsible for phosphorylating gp130 at Ser782.
  • To elucidate the signaling pathway regulating gp130 Ser782 phosphorylation.

Main Methods:

  • In vitro kinase assays using gp130 fusion protein and cell extracts.
  • Inhibition studies with autocamtide-2-related inhibitory peptide (AIP) and MAPKK inhibitors (PD98059, U0126).
  • Immunoprecipitation assays using antibodies against CaMKII and CaMKIV.

Main Results:

  • Autocamtide-2-related inhibitory peptide (AIP), a calmodulin-dependent protein kinase type II (CaMKII) inhibitor, reduced Ser782 phosphorylation by 61%.
  • Purified CaMKII phosphorylated gp130 at Ser782 in vitro.
  • Antibodies against CaMKII and CaMKIV immunoprecipitated gp130 phosphorylating activity.
  • MAPKK inhibitors blocked Ser782 phosphorylation before LIF stimulation but not in cell extracts.

Conclusions:

  • Calmodulin-dependent protein kinase type II (CaMKII) and potentially CaMKIV phosphorylate gp130 at Ser782.
  • This phosphorylation occurs within a serine-based dileucine internalization motif.
  • The process is regulated by a mitogen-activated protein kinase (MAPK)-dependent pathway.

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