The mechanism of heat shock activation of ERK mitogen-activated protein kinases in the interleukin 3-dependent ProB cell line BaF3.
We have investigated heat shock stimulation of MAPK cascades in an interleukin 3-dependent cell line, BaF3. Following exposure to 42 degrees C, the stress-activated JNK MAPKs were phosphorylated and activated, but p38 MAPKs remained unaffected. Surprisingly, heat shock also activated ERK MAPKs in a potent (>60-fold), delayed (>30 min), and sustained (>/=120 min) manner. These characteristics suggested a novel mechanism of ERK MAPK activation and became the focus of this study. A MEK-specific inhibitor, PD98059, inhibited heat shock ERK MAPK activation by >75%. Surprisingly, a role for Ras in the heat shock response was eliminated by the failure of a dominant-negative Ras(Asn-17) mutant to inhibit ERK MAPK activation and the failure to observe increases in Ras.GTP. Heat shock also failed to stimulate activation of A-, B-, and c-Raf. Instead, a serine/threonine phosphatase inhibitor, okadaic acid, activated ERK MAPK in a similar manner to heat shock. Furthermore, pretreatment with suramin, generally recognized as a broad range inhibitor of growth factor receptors, inhibited both okadaic acid-stimulated and heat shock-stimulated ERK MAPK activity by >40%. Inhibiting ERK MAPK activation during heat shock with PD98059 enhanced losses in cell viability. These results demonstrate Ras- and Raf-independent ERK MAPK activation maintains cell viability following heat shock.
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Department of Biochemistry, University of Western Australia, Nedlands 6907, Australia.
Bogoyevitch
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D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology*; D002460:Cell Line; D002470:Cell Survival; D004789:Enzyme Activation; D005419:Flavonoids / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000201:enzymology*; D006358:Hot Temperature; D007377:Interleukin-3 / Q000494:pharmacology*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism
D005419:Flavonoids; D007377:Interleukin-3; D014443:Tyrosine; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one