Endothelin-1 causes a prolonged protein kinase C activation and acts as a co-mitogen in vascular smooth muscle cells.
Endothelin-1 (ET-1) is known to act via G-protein coupled receptors. It has therefore been suggested that any mitogenic activity it may possess, is due to activation of phospholipase C and protein kinase C (PKC). We have therefore examined both the ability of ET-1 to act as a mitogen and its ability to activate PKC. We found that ET-1 significantly increased thymidine incorporation and enhanced platelet-derived growth factor-induced DNA synthesis, as well as causing a prolonged translocation of PKC to the cell membrane. ET-1 significantly increased PKC dependent phosphorylation of two specific substrates. The phosphorylation of MBP4-14 (from myelin basic protein) was partially dependent on extracellular Ca2+, implicating activation of PKC-alpha, whereas phosphorylation of the so called epsilon-peptide was Ca(2+)-independent and prolonged. This could be due either to the delta or zeta isoform of PKC, known to be present in these cells. However, ET-1 induced little proliferation of PKC activity in a transformed smooth muscle cell line, DDT1 MF-2, which lacks expression of the PKC-alpha isoform, but expresses the zeta-isoform. Thus, it would appear the ET-1-induced mitogenicity in smooth muscle cells may be related to the sustained, Ca(2+)-independent activation of PKC-delta.
Assender
J W
JW
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Irenius
E
E
Fredholm
B B
BB
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D006224:Cricetinae; D019332:Endothelin-1 / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008934:Mitogens / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta
D019332:Endothelin-1; D007527:Isoenzymes; D008934:Mitogens; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D019204:GTP-Binding Proteins; D002118:Calcium