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Osmosignalling in C6 glioma cells
Author(s) -
Sinning Ralf,
Schliess Freimut,
Kubitz Ralf,
Häussinger Dieter
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(96)01376-2
Subject(s) - mapk/erk pathway , kinase , osmotic concentration , wortmannin , forskolin , protein kinase c , pertussis toxin , cholera toxin , medicine , biology , endocrinology , chemistry , microbiology and biotechnology , signal transduction , phosphatidylinositol , stimulation , g protein
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 Ca 2+ concentration ([Ca 2+ ] i ). Absence of extracellular Ca 2+ largely abolished the [Ca 2+ ] i response to hypo‐osmolarity, whereas Erk activation following hypo‐osmotic stimulation remained unaffected, suggesting a Ca 2+ independence of the osmosignalling pathway to the MAP kinases. Both the Ca 2+ 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 Gö6850. 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.