Evidence for protein kinase C stimulation in rat enterocytes pretreated with heat stable enterotoxin of Escherichia coli.
Rat intestinal epithelial cells were isolated and the activity of the calcium- and phospholipid-dependent protein kinase C (PKC) was investigated. The stimulation of activity by Escherichia coli heat stable enterotoxin (STa) was about 5-fold compared to control activity (16.91 +/- 1.69 vs 93.56 +/- 10.40 nmol/mg protein/min) and was dose dependent. Maximum enzyme activity was observed after incubation for 1 min with 6 ng of purified STa. The synergistic effects of calcium, phosphatidylserine and diolein on the enzyme activity were noted both in control and STa-treated cells. Staurosporine, a potent PKC inhibitor, significantly reduced the enzyme activity. Autoradiographic analysis of polyacrylamide gel electrophoresis revealed that pretreatment of the cells with STa also resulted in the phosphorylation of specific membrane proteins each with a molecular mass of 37 kDa, 100 kDa and 140 kDa. However, STa had no direct role on the enzyme activity. Our results, therefore, provide evidence for the involvement of PKC in STa-induced signal transduction in rat enterocytes.
Chaudhuri
A G
AG
National Institute of Cholera and Enteric Diseases, Beliaghata, Calcutta, India.
Sen
P C
PC
Ganguly
U
U
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D004768:Enterotoxins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology*; D007583:Jejunum / Q000166:cytology / Q000201:enzymology; D007976:Leupeptins / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D010718:Phosphatidylserines / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D051381:Rats; D015398:Signal Transduction; D019311:Staurosporine
D000470:Alkaloids; D001427:Bacterial Toxins; D002147:Calmodulin; D004075:Diglycerides; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D007976:Leupeptins; D008565:Membrane Proteins; D010718:Phosphatidylserines; C027538:heat-labile enterotoxin, E coli; D000242:Cyclic AMP; D011493:Protein Kinase C; D006152:Cyclic GMP; D019311:Staurosporine; D008274:Magnesium; C032854:leupeptin; D002118:Calcium; C013965:diolein