ALTERATIONS IN RAS-GENE EXPRESSION AND INTRACELLULAR-DISTRIBUTION OF PROTEIN-KINASE-C IN THE SPONGE GEODIA-CYDONIUM IN RESPONSE TO MARINE POLLUTION

The siliceous sponge Geodia cydonium Jameson was used to study the influence of pollution in marine environments on selected parameters of the intracellular signal transduction pathway. The parameters chosen were: intracellular distribution of protein kinase C (PK-C), ras-gene expression and DNA polymerase alpha (DNA Pol alpha) activity. Both PK-C and ras-gene product (ras-protein) have previously been established to be key molecules in the intracellular signalling pathway in sponges; increased level of ras-protein mediates events following sponge cell-cell contact. Three unpolluted and three polluted sites in the off-shore seawater around Rovinj (Yugoslavia) were selected for the study in 1989. The state of pollution of these sites has been well-defined in a series of previous studies (1976 to 1989). Transplantation of regenerating sponge cubes of G. cydonium to the polluted sites resulted in pronounced changes in the parameters chosen, compared to controls exposed to unpolluted environments. Expression of ras gene was increased by three- to five-fold after exposure of regenerating sponge tissue to the impacted sites. At the site with the highest pollutional load, ras mRNA level was about 50% of that at the reference sites. In parallel experiments it was established that, in response to pollution, a translocation of PK-C from the cytosolic to membrane fraction occurred. At the most impacted site, most of the enzyme activity was cytosolic. DNA Pol alpha-activity, as a measure of sponge cell proliferation, decreased in a pollutioncorrelated manner. Our results indicate that the intracellular signalling system within sponge cells is activated in response to moderate pollution but is depressed in heavily polluted environments. © 1990 Springer-Verlag.