Role of calcium activated kinases and phosphatases in heat shock factor-1 activation.
HSF-1 is regulated at multiple molecular levels through intra- and intermolecular protein-protein interactions as well as by post-translational modification through phosphorylation. We have found that elevating intracellular calcium ion levels by exposure to the ionophore A23187 or thapsigargin inhibits the conversion of HSF-1 from a latent cytoplasmic form to its nuclear/DNA binding form. To examine a role for calcium/calmodulin regulated enzymes in this process, we examined the ability of specific inhibitors to abrogate the effects of calcium elevation. While the inhibitor of calmodulin dependent kinase II, KCN62 enhanced activation of HSF-1 during heat shock, it failed to block the inhibitory effects of calcium increase. By contrast, the immunosuppresant drugs cyclosporin A and FK506 abolished the effects of calcium elevation on HSF-1 activation. As the biological effects of the drugs are effected through inhibition of the calcium/calmodulin regulated phosphatase calcineurin, this suggests a role for calcineurin in antagonizing HSF-1 activity. The experiments suggest the existence of phosphorylated residue(s) in HSF-1 important in one or more of the processes that lead to activation (trimerization, nuclear localization, DNA binding) and which becomes dephosphorylated due to the activation of a calcium/calmodulin/calcineurin complex.
Soncin
F
F
Division of Radiation Oncology, Department of Adult Oncology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA 02115, USA.
Asea
A
A
Zhang
X
X
Stevenson
M A
MA
Calderwood
S K
SK
D000001:Calcimycin / Q000494:pharmacology; D019703:Calcineurin / Q000378:metabolism; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D016572:Cyclosporine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000076249:Heat Shock Transcription Factors; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors; D014407:Tumor Cells, Cultured; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D065095:Calcineurin Inhibitors; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D000076249:Heat Shock Transcription Factors; D007166:Immunosuppressive Agents; D047428:Protein Kinase Inhibitors; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D000001:Calcimycin; D019284:Thapsigargin; D016572:Cyclosporine; D008156:Luciferases; D011494:Protein Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D001616:beta-Galactosidase; D002118:Calcium; D016559:Tacrolimus