STa-induced translocation of protein kinase C from cytosol to membrane in rat enterocytes

Escherichia coli heat stable enterotoxin (STa) binds to isolated rat intest inal epithelial cells and triggers a cascade reaction including increase of intracellular calcium levels ([Ca2+](i)) and membrane bound protein kinase C (PKC) activity. In response to STa, the cytosolic PKC activity falls fro m 110 to 35 nmol with increase of membrane bound PKC activity from 15 to 78 nmol. Furthermore, the increase of PKC activity induced by STa treatment w as always preceded by an increase in [Ca2+](i). Cytosolic [Ca2+](i) was sig nificantly higher (161 nM) in STa treated cells as compared to untreated ce lls (51.3 nM). In addition, immunoblot performed an extracts of STa treated rat enterocytes with a monoclonal antibody against PKC a showed a prominen t band of PKC cc. Translocation of PKC a could be blocked by dantrolene, a drug which inhibits the mobilisation of [Ca2+](i) from the intracellular st ore. Our results, therefore, provide evidence for the role of [Ca2+](i) in STa treated cells for the translocation of PKC a from cytosol to membrane. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Microbiological Societies.