Heat shock effects on second messenger systems of Neurospora crassa.
Exposure of growing hyphae of Neurospora crassa to heat shock (44 degrees C) or ethanol (2.6 M) for 1 h induced a significant increase in the cAMP level, which reached a maximum approximately 2 min after the beginning of treatment and then decreased to control values despite continued heat or ethanol exposure. A 10-s heat shock or a 5-s ethanol shock also resulted in a transient cAMP increase 2 min after the pulse. Heat shock or ethanol treatment led to an increase in the amount of catalytic subunits of the cAMP-dependent protein kinase A in the nucleus almost synchronously with the increase of cAMP in the cytoplasm. The concentration of cGMP decreased a few seconds after the beginning of heat shock (44 degrees C) or ethanol treatment (2.6 M) to approximately 50% of the control level. Exposure to heat shock (44 degrees C, 1 h) led to an increase in the amount of inositol phosphates 0.5-2 min after the onset of heat shock. Thereafter, inositol phosphate levels dropped to control values despite continued heat exposure. Incubation of growing hyphae with cAMP or 8-Br-cAMP led to a two- to threefold increase of inositol phosphates 10-300 s after the beginning of incubation. Heat treatment furthermore caused a rapid release of calcium from vacuoles as determined by Fura-2 measurement of the calcium content released from isolated vacuoles. These heat-shock-dependent second messenger changes may play a role in the heat-shock-induced phase shifts of the circadian clock and heat-shock-induced conidiation.
Institut für Zellbiologie, Biochemie und Biotechnologie, Universität Bremen, P.O. Box 330 440, D-28334 Bremen, Germany.
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Kallies
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Gebauer
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Rensing
D002118:Calcium / Q000378:metabolism; D002384:Catalysis; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000201:enzymology; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004789:Enzyme Activation; D000431:Ethanol / Q000494:pharmacology; D016257:Fura-2; D018869:Heat-Shock Response; D007295:Inositol Phosphates / Q000378:metabolism; D009492:Neurospora crassa / Q000378:metabolism*; D015290:Second Messenger Systems; D014617:Vacuoles / Q000378:metabolism
D007295:Inositol Phosphates; D000431:Ethanol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP; D002118:Calcium; D016257:Fura-2