Multiple independent kinase cascades are targeted by hyperosmotic stress but only one activates stress kinase p38.
In this report, we analyse the effects of osmotic shock on signal transduction in CHO cells. We demonstrate that at least three different kinase cascades are switched on upon osmotic shock, namely PKA, AMPK, and MLTK. Whereas PKA from cells treated with forskolin activated stress kinase p38, PKA from cells treated with sorbitol did not activate p38, although the enzyme is activated in both cases as analysed in vitro using a specific peptide target. Further, osmolar shock activated AMPK but treatment of the cells with the AMPK activator 5-amino-4-imidazolecarboxamide (AICAr) did not result in p38 activation, strongly suggesting that AMPK is not involved in stress kinase activation. Transfection of CHO cells with dominant negative recombinants of MLTKalpha resulted in inhibition of sorbitol-mediated p38 activation, indicating that the mixed-lineage kinase is involved in the activation of p38 by sorbitol. Finally, in CHO cells overexpressing wild-type MLTKalpha, no activation of AMPK of PKA could be demonstrated, indicating that the activated kinase cascades are not involved in a cross-talk process.
Mao
Xiaohong
X
Deutsches Krebsforschungszentrum, Im Neuenheimer Feld-242, 69120 Heidelberg, Germany.
Bravo
Ignacio G
IG
Cheng
Hao
H
Alonso
Angel
A
D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000187:drug effects / Q000378:metabolism; D009997:Osmotic Pressure / Q000187:drug effects; D010770:Phosphotransferases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012265:Ribonucleotides / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013012:Sorbitol / Q000494:pharmacology; D013312:Stress, Physiological / Q000201:enzymology*; D014162:Transfection; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*; D020764:cdc42 GTP-Binding Protein / Q000187:drug effects / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein / Q000187:drug effects / Q000378:metabolism
D009097:Multienzyme Complexes; D011993:Recombinant Fusion Proteins; D012265:Ribonucleotides; D005576:Colforsin; D000620:Aminoimidazole Carboxamide; D013012:Sorbitol; D010770:Phosphotransferases; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C428384:MLK-like mitogen-activated protein triple kinase; D055372:AMP-Activated Protein Kinases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; C031143:AICA ribonucleotide