Noradrenaline and alpha-adrenergic signaling induce the hsp70 gene promoter in mollusc immune cells

Expression of heat shock proteins (hsp) is a homeostatic mechanism induced in both prokaryotic and eukaryotic cells in response to metabolic and envir onmental insults. A growing body of evidence suggests that in mammals, the hsp response is integrated with physiological responses through neuroendocr ine signaling. In the present study, we have examined the effect of noradre naline (NA) on the hsp70 response in mollusc immune cells. Oyster and abalo ne hemocytes transfected with a gene construct containing a gastropod hsp70 gene promoter linked to the luciferase reporter-gene were exposed to physi ological concentrations of NA, or to various alpha- and beta -adrenoceptor agonists and antagonists. Results show that NA and alpha -adrenergic stimul ations induced the expression of luciferase in transfected mollusc immunocy tes. Furthermore, exposure of hemocytes to NA or to the alpha -adrenoceptor agonist phenylephrine (PE) resulted in the expression of the inducible iso form of the hsp70 protein. Pertussis toxin (PTX), the phospholipase C (PLC) inhibitor U73122, the protein kinase C (PKC) inhibitor calphostin C, the C a2+-dependent PKC inhibitor Go 6976 and the phosphatidylinositol 3-kinase ( PI 3-kinase) inhibitor LY294002 blocked the PE-mediated induction of the hs p70 gene promoter. These results suggest that alpha -adrenergic signaling i nduces the transcriptionnal upregulation of hsp70 in mollusc hemocytes thro ugh a PTX-sensitive G-protein, PLC, Ca2+-dependent PKC and PI 3-kinase. Thu s, a functional link exists between neuroendocrine signaling and the hsp70 response in mollusc immune cells.