Osmosignalling in C6 Glioma Cells

FEBS Lett. 1997 Jan 3;400(2):163-7. doi: 10.1016/s0014-5793(96)01376-2.

Abstract

The influence of aniso-osmolarity on the activity of the MAP kinases Erk-1 and Erk-2 was studied in C6 glioma cells. Hypo-osmotic treatment (205 mosmol/l) led to an increased activity of Erk-1 and Erk-2 within 3 min, which became maximal at 10 min and returned to basal level within 120 min. In contrast, Erk activity was reduced under hyper-osmotic conditions (405 mosmol/l), compared to the normo-osmotic control (305 mosmol/l). Erk activation was accompanied by a mobility shift of Raf-1. Hypo-osmotic exposure increased the cytosolic Ca2+ concentration ([Ca2+]i). Absence of extracellular Ca2+ largely abolished the [Ca2+]i response to hypo-osmolarity, whereas Erk activation following hypo-osmotic stimulation remained unaffected, suggesting a Ca2+ independence of the osmosignalling pathway to the MAP kinases. Both the Ca2+ response as well as the Erk activation following hypo-osmotic exposure were maintained in the presence of the phospholipase C inhibitor U73122. Application of 8-CPT cAMP, forskolin/isobutylmethylxanthine or isoproterenol blocked Erk activation following hypo-osmotic treatment of the cells, suggesting a role of the Ras/Raf pathway upstream from Erk-1 and Erk-2. Protein kinase C (PKC) is unlikely to play a role in the hypo-osmolarity- induced signalling towards MAP kinases, as revealed by inhibition of PKC with Go6850. Inhibition of pertussis- or cholera toxin-sensitive G-proteins as well as inhibition of tyrosine kinases with genistein and of PI3 kinase by wortmannin had no effect on the Erk response to hypo-osmolarity. It is concluded that osmosignalling in C6 glioma cells differs upstream of the MAP kinases from that observed in primary rat astrocytes, H4IIE rat hepatoma cells and isolated rat hepatocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cyclic AMP / metabolism*
  • Glioma / pathology
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases*
  • Osmolar Concentration
  • Protein-Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-raf
  • Rats
  • Signal Transduction / physiology*
  • Tumor Cells, Cultured

Substances

  • Proto-Oncogene Proteins
  • Cyclic AMP
  • Protein-Tyrosine Kinases
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • Calcium