Activation of the MAPKs ERK1/2 by cell swelling in turbot hepatocytes.
BACKGROUND
Activation of MAPKs (mitogen-activated protein kinases), in particular ERK1/2 (extracellular-signal-regulated kinase 1/2), has been reported to take place in a large variety of cell types after hypo-osmotic cell swelling. Depending on cell type, ERK1/2 phosphorylation can then serve or not the RVD (regulatory volume decrease) process. The present study investigates ERK1/2 activation after aniso-osmotic stimulations in turbot hepatocytes and the potential link between phosphorylation of these proteins and RVD.


RESULTS
In turbot hepatocytes, Western-blot analysis shows that a hypo-osmotic shock from 320 to 240 mOsm kg(-1) induced a rapid increase in ERK1/2 phosphorylation, whereas a hyper-osmotic shock from 320 to 400 mOsm kg(-1) induced no significant change in the phosphorylation of these proteins. The hypo-osmotic-induced ERK1/2 phosphorylation was significantly prevented when hypo-osmotic shock was performed in the presence of the specific MEK (MAPK/ERK kinase) inhibitor PD98059 (100 microM). In these conditions, the RVD process was not altered, suggesting that ERK1/2 did not participate in this process in turbot hepatocytes. Moreover, the hypo-osmotic-induced activation of ERK1/2 was significantly prevented by breakdown of extracellular ATP by apyrase (10 units ml(-1)), by inhibition of purinergic P2 receptors by suramin (100 microM) or by calcium depletion using EGTA (1 mM) and thapsigargin (1 microM).


CONCLUSIONS
In turbot hepatocytes, hypo-osmotic swelling but not hyper-osmotic shrinkage induced the activation of ERK1/2. However, these proteins do not seem to be involved in the RVD process. Their hypo-osmotic-induced activation is partially due to cascades of signalling events triggered by the binding of released ATP on purinergic P2 receptors and requires the presence of calcium.
Fouchs
Audrey
A
Laboratoire ORPHY, Université Européenne de Bretagne, Université de Brest, Brest, France. Audrey.Fouchs@univ-brest.fr
Ollivier
Hélène
H
Haond
Christophe
C
Roy
Stella
S
Calvès
Patrick
P
Pichavant-Rafini
Karine
K
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology; D048429:Cell Size; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D005412:Flatfishes; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology*; D007038:Hypotonic Solutions / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009997:Osmotic Pressure; D010766:Phosphorylation; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology
D007038:Hypotonic Solutions; D018048:Receptors, Purinergic P2; D004533:Egtazic Acid; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium