RESUMEN
Elevated temperature induces a rapid heat shock transcription factor (HSFs)-mediated expression of heat shock (hsp) genes. The effect of cold exposure on hsp gene expression has hardly been investigated, although ectothermic animals experience both cold and heat stress. We have previously shown in zebrafish that the expression of hsf1a and a unique isoform hsf1b vary in a tissue-specific manner upon heat stress. In the current study, using a zebrafish (Danio rerio) embryonic cell line (ZF4), we have compared the effects of heat shock (28-->37 degrees C) vs. cold shock (28-->20 degrees C) on the expression of ahsf1a, zhsf1b and hsp70. Concomitantly, the suitability of the ZF4 cells as a model system was verified. The expression pattern of HSP70 proteins following heat or cold exposure is distinct, and the total HSP70 level is upregulated or stable, respectively. Moreover, heat exposure specifically increases the ratio of zhsf1a/b expression (10-fold), whereas cold exposure decreases it to one half. These data suggest that the zhsf1a/zhsf1b ratio is regulated in a temperature-dependent manner, and the ratio may be indicative of the stressor-specific HSP70 expression. Furthermore, the response in ZF4 cells upon heat shock resembles the response observed in zebrafish liver and thus, supports the use of this cell line in stress response studies.
Asunto(s)
Frío , Regulación de la Expresión Génica , Proteínas HSP70 de Choque Térmico/genética , Respuesta al Choque Térmico/genética , Calor , Pez Cebra/genética , Animales , Línea Celular , Factores de Transcripción del Choque Térmico , Isoformas de Proteínas/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Tiempo , Factores de Transcripción/genética , Proteínas de Pez Cebra/genéticaRESUMEN
Heat shock transcription factors (HSFs) regulate expression of heat shock proteins (Hsps). We have previously shown that in zebrafish a unique isoform, zHSF1b, disappears concomitant with heat shock-induced Hsp70 expression. To characterize the role of zHSF1a and zHSF1b isoforms in the regulation of the stress response in vivo, we have carried out cadmium (10-100 microM) and copper (10-30 microM) exposures in order to specify whether the disappearance of HSF1b is specific for heat stress. After 4-h metal exposures we analyzed the expression of hsp70, zHSF1a, zHSF1b and metallothionein (MT) by reverse transcriptase polymerase chain reaction in zebrafish liver, gonads and gills. Although cadmium is a known inducer of Hsps, it did not affect hsp70 expression significantly in the studied tissues. Induction of hsp70 was observed upon copper exposure in liver and gonads, but not in gills. Neither metal affected the zHSF1a/b ratio. Both cadmium and copper exposure caused upregulation of MT, regulator of metal homeostasis and detoxification, confirming that the tissues were subjected to metal loads. Thus, hsp70 appears to be more weakly induced upon metal exposure than in response to heat shock and HSF1 isoforms may participate in stressor-specific regulation of hsp70.