Comparison of the effect of heat shock factor inhibitor, KNK437, on heat shock- and chemical stress-induced hsp30 gene expression in Xenopus laevis A6 cells

In this study, we compared the effect of KNK437 (N-formyl-3, 4-methylenedioxy-benzylidene-γ-butyrolactam), a benzylidene lactam compound, on heat shock and chemical stressor-induced hsp30 gene expression in Xenopus laevis A6 kidney epithelial cells. Previously, KNK437 was shown to inhibit HSE-HSF1 binding activity and heat-induced hsp gene expression. In the present study, Northern and Western blot analysis revealed that pretreatment of A6 cells with KNK437 inhibited hsp30 mRNA and HSP30 and HSP70 protein accumulation induced by chemical stressors including sodium arsenite, cadmium chloride and herbimycin A. In A6 cells subjected to sodium arsenite, cadmium chloride, herbimycin A or a 33 °C heat shock treatment, immunocytochemistry and confocal microscopy revealed that HSP30 accumulated primarily in the cytoplasm. However, incubation of A6 cells at 35 °C resulted in enhanced HSP30 accumulation in the nucleus. Pre-treatment with 100 μM KNK437 completely inhibited HSP30 accumulation in A6 cells heat shocked at 33 or 35 °C as well as cells treated with 10 μM sodium arsenite, 100 μM cadmium chloride or 1 μg/mL herbimycin A. These results show that KNK437 is effective at inhibiting both heat shock- and chemical stress-induced hsp gene expression in amphibian cells.