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Defective protein phosphorylation and Ca2+ mobilization in a low secreting variant of the rat basophilic leukemia

B R Bingham1, P N Monk, B A Helm

  • 1Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, United Kingdom.

The Journal of Biological Chemistry
|July 29, 1994
PubMed

Insights

Low secreting leukemia cells reveal defects in Fc epsilon R1 complex phosphorylation and signaling pathways. This impacts mediator release and provides insights into early events in signal transduction.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Signaling

Background:

  • Rat basophilic leukemia cell lines are valuable tools for studying stimulus/secretion coupling.
  • The high-affinity immunoglobulin E receptor (Fc epsilon R1) complex is central to this process.
  • Understanding differences between high and low secreting variants can elucidate signaling pathways.

Purpose of the Study:

  • To investigate the molecular basis of reduced mediator secretion in a low-secreting rat basophilic leukemia cell variant.
  • To identify differences in Fc epsilon R1 complex phosphorylation and early signaling events between high and low secreting variants.

Main Methods:

  • Comparative analysis of high and low secreting rat basophilic leukemia cell variants.
  • Investigation of protein phosphorylation (threonine and tyrosine) of Fc epsilon R1 subunits.
  • Analysis of early signaling events, including protein phosphorylation, inositol phosphate production, and calcium mobilization.

Main Results:

  • The low secreting variant exhibits defects in threonine and tyrosine phosphorylation of Fc epsilon R1 subunits.
  • Tyrosine phosphorylation of a 72-kDa protein precedes gamma-chain phosphorylation, indicating early protein-tyrosine kinase and protein kinase C activation.
  • Reduced inositol phosphate production and lack of intracellular calcium mobilization in the low secretor suggest a defect upstream of phospholipase C activation.

Conclusions:

  • Defects in Fc epsilon R1 phosphorylation are associated with reduced mediator secretion.
  • Early signal transduction involves sequential phosphorylation events and activation of specific kinases.
  • A defect upstream of phospholipase C activation contributes to the impaired signaling in the low secreting variant.

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