Induction of gene expression of the chaperones 14-3-3 and HSP70 by PCB 118 (2,3′,4,4′,5-pentachloro-biphenyl) in the marine sponge Geodia cydonium:: novel biomarkers for polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are ubiquitous industrial compounds found in almost every component of the terrestrial and marine ecosystem. Most of the PCB congeners bind to the aryl hydrocarbon receptor and in turn cause expression of stress response genes. Here we report for the first time that PCB 118 acts in the marine sponge Geodia cydonium as an inducer of 2 chaperones, the 14-3-3 protein(s) (a protein targeting molecule) and the heat shock protein HSP70 (a chaperone, primarily involved in folding of proteins). While the cDNA encoding the latter protein has been cloned previously, the 14-3-3 cDNA from sponges is reported in this study. The full-length cDNA clone of G. cydonium, GC14-3-3, has a size of 912 nucleotides (nt) and contains a 744 nt long potential open reading frame; the relative molecular weight (M-r) of the deduced aa sequence is 28 378 Da. The sponge polypeptide is closely related to the deduced polypeptides of the 14-3-3 sequences belonging to isoforms eta and gamma. Using the cDNAs, coding for the 14-3-3 and the HSP70 proteins as well as antibodies raised against these 2 proteins, it was demonstrated that neither chaperone can be detected in the absence of PCB. However, after incubation of sponge tissue with PCB 118 the transcripts of the 2 chaperones are detectable after 12 h, while the corresponding proteins appear after 1 d. Subsequently, the levels of the transcripts and of the proteins increase steadily. From these data we conclude that the 2 chaperones, 14-3-3 and HSP70, are useful biomarkers in sponges. Due to the broad cross-reactivity of their antibodies throughout the Metazoa, these chaperones may be useful biomarkers for monitoring environmental contaminants, as shown here for PCB 118, in all organisms.