Different constitutive heat shock protein 70 expression during proliferation and differentiation of rat C6 glioma cells.
Analysis of constitutive heat shock protein 70 (HSC70) concentration in unstressed proliferating and differentiated rat C6 glioma cells revealed a striking reduction in the amount of HSC70 in differentiated cells. Proliferating cells showed a significantly higher HSC70 concentration, particularly observable during S phase in synchronous cultures. The activity of the cAMP/PKA signaling pathway was enhanced in differentiated cells. cAMP-elevating treatments both inhibited growth and reduced HSC70 concentration. Inactivation of PKA by H-89 upregulated the reduced HSC70 expression in differentiated cells and stimulated proliferation. Treatment with an inhibitor of MAP kinase activation (PD98059) reduced the HSC70 concentration. We assume that cAMP does not directly inhibit HSC70 expression by transcriptional repression, but by its inhibitory effect on the MAP kinase pathway.
Helmbrecht
K
K
Institute of Cell Biology, Biochemistry and Biotechnology, University of Bremen, Germany.
Rensing
L
L
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002453:Cell Cycle; D002454:Cell Differentiation; D002455:Cell Division; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005910:Glioma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D004791:Enzyme Inhibitors; D018840:HSP70 Heat-Shock Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases