Heat shock and oxidative stress-induced exposure of hydrophobic protein domains as common signal in the induction of hsp68.
The hypothesis of a common signal for heat shock (HS) and oxidative stress (OS) was analyzed in C6 cells with regard to the induction of heat shock proteins (Hsps). The synthesis rate and level of the strictly inducible Hsp68 was significantly higher after HS (44 degrees C) compared with OS (2 mm H2O2). This difference corresponded to higher and lower activation of the heat shock factor (HSF) by HS and OS, respectively. OS, on the other hand, showed stronger cytotoxicity compared with HS as indicated by drastic lipid peroxidation and inhibition of protein synthesis as well as of mitochondrial and endocytotic activity. Lactic dehydrogenase also revealed stronger inhibition of enzyme activity by OS than by HS as shown in cells and in vitro experiments. Conformational analysis of lactic dehydrogenase by the fluorophore 1-anilinonaphtalene-8-sulfonic acid, however, showed stronger exposure of hydrophobic domains after HS than after OS which correlates positively with the Hsp68 response. Treatment of cells with deoxyspergualin, which exhibits high affinity to Hsps, the putative inhibitors of HSF, strongly increased only OS-induced hsp68 expression. In conclusion, the results suggest that exposure of hydrophobic domains of cytosolic proteins represents the common first signal in the multistep activation pathway of HSF.
Gosslau
A
A
Institute of Cell Biology, Biochemistry and Biotechnology, University of Bremen, D-28334 Bremen, Germany and the School of Technology and Science, Stavanger University College, P. O. Box 2557 Ullandhaug, N-4091 Stavanger, Norway.
Ruoff
P
P
Mohsenzadeh
S
S
Hobohm
U
U
Rensing
L
L
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D000076249:Heat Shock Transcription Factors; D018869:Heat-Shock Response; D018384:Oxidative Stress; D011489:Protein Denaturation; D051381:Rats; D015398:Signal Transduction; D014157:Transcription Factors; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; C490786:HSPA1A protein, human; D000076249:Heat Shock Transcription Factors; C097210:Hspa1a protein, rat; D014157:Transcription Factors