Inhibitory effect of annexin V on protein kinase C activity in mesangial cell lysates.
Annexin V belongs to a large family of calcium-binding and phospholipid-binding proteins and may act as an endogenous regulator of the protein kinase C (PKC) activity. This study examines the effect of annexin V on the in vitro PKC activity in cultured mesangial cells using histone H1, the peptide [Ser25]PKC-(19-31), or endogenous proteins as substrates. The SDS/PAGE pattern of 32P-labeled mesangial proteins showed that the calcium-independent PKC [(n+a)PKC] phosphorylated several proteins from 70 kDa to 40 kDa and 22 kDa to 15 kDa. Three additional proteins from 34 kDa to 29 kDa, including annexin I and its proteolytic forms, were detected after activation of calcium-dependent PKC (cPKC). Increasing concentrations of annexin V did not alter the phosphorylation of (n+a)PKC substrates. By contrast, specific phosphorylation of proteins and annexin I by cPKC, was reduced in a dose-dependent manner. Addition of high concentration of calcium and phosphatidylserine did not reverse the inhibitory effect of annexin V. Annexin V also inhibited the phosphorylation of histone H1 or peptide [Ser25]PKC-(19-31) by cPKC. Moreover, removal of annexin V from cytosols increased the annexin I phosphorylation by these isoforms. From these results, we propose that annexin V may regulate the signal-transduction pathway involving the activation of cPKC, as they act in vitro as an inhibitor of these kinases.
Rothhut
B
B
U 332 INSERM, ICGM, Paris, France.
Dubois
T
T
Feliers
D
D
Russo-Marie
F
F
Oudinet
J P
JP
D017304:Annexin A5 / Q000187:drug effects / Q000378:metabolism / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D002474:Cell-Free System; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005920:Glomerular Mesangium / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D007527:Isoenzymes; D010718:Phosphatidylserines / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*
D017304:Annexin A5; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010718:Phosphatidylserines; D011493:Protein Kinase C; D002118:Calcium