Characterization of epidermal growth factor receptors in astrocytic glial and neuronal cells in primary culture

Endocrinology. 1989 Jan;124(1):240-7. doi: 10.1210/endo-124-1-240.

Abstract

Studies characterized the structure and function of epidermal growth factor (EGF) receptors in astrocytic glial cells and neuronal cells in primary culture from neonatal rat brain. [125I]EGF binding to membranes prepared from glial and neuronal cultures was specific and dependent on protein concentration; however, glial preparations bound 5-fold more [125I]EGF per mg protein. Unlabeled EGF competed for binding to both glial and neuronal membranes with an IC50 of 5 nM, whereas insulin, insulin-like growth factor I, and nerve growth factor failed to compete. Scatchard plot analysis of binding data for glial cells yielded a curvilinear plot with dissociation constants of 7.12 nM for high affinity and 6.2 microM for low affinity sites. The higher level of binding in glial compared to neuronal membranes reflected a greater number of binding sites rather than differences in receptor affinity. In glial membranes, [125I]EGF covalently cross-linked to one major protein with a mol wt of 170,000, and EGF stimulated the phosphorylation of a 170,000 protein which was half-maximal at 20 nM. In contrast, neither covalent cross-linking nor receptor autophosphorylation could be detected in neuronal membranes. Culture of glial cells in the presence of EGF stimulated [35S]methionine incorporation into both cellular and secreted proteins, whereas no effect of EGF was observed in neuronal cultures. The addition of EGF to glial cultures produced a dose-dependent stimulation of [3H]thymidine incorporation as well as the multiplication of cells over a 6-day period. These observations show that functional EGF receptors in the neonatal brain are predominantly localized in glial cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Newborn
  • Astrocytes / metabolism*
  • Binding, Competitive
  • Brain / cytology
  • Cell Division
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Cross-Linking Reagents
  • Epidermal Growth Factor / metabolism
  • Epidermal Growth Factor / pharmacology
  • ErbB Receptors / metabolism*
  • Molecular Weight
  • Nerve Tissue Proteins / biosynthesis
  • Neurons / metabolism*
  • Phosphorylation
  • Rats

Substances

  • Cross-Linking Reagents
  • Nerve Tissue Proteins
  • Epidermal Growth Factor
  • ErbB Receptors