Protein kinase C-dependent phosphorylation of profilin is specifically stimulated by phosphatidylinositol bisphosphate (PIP2).
Calf spleen profilin is shown to be an in vitro substrate of purified human placental protein kinase C (PKC), with an apparent Km of 4 microM. Phosphatidylinositol bisphosphate (PIP2) was an effective activator of the profilin phosphorylation by PKC and caused a maximum 13-fold increase of Vmax with a half maximal effect at 40 micrograms/ml. The action of PIP2 was not mimicked by phosphatidylserine, phosphatidic acid or phosphatidylinositol, whereas phosphatidylinositol monophosphate was slightly stimulatory. By contrast, protein kinase C-dependent phosphorylation of histone type III-S, myelin basic protein or lipocortin-I was not affected by PIP. It is suggested that PIP2 modifies the nature of the profilin-PKC interactions.
Hansson
A
A
Dept. of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
Skoglund
G
G
Lassing
I
I
Lindberg
U
U
Ingelman-Sundberg
M
M
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D003285:Contractile Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007700:Kinetics; D008840:Microfilament Proteins / Q000302:isolation & purification / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000494:pharmacology*; D010766:Phosphorylation; D010920:Placenta / Q000201:enzymology; D051304:Profilins; D011493:Protein Kinase C / Q000378:metabolism*; D013154:Spleen / Q000378:metabolism
D000596:Amino Acids; D003285:Contractile Proteins; D008840:Microfilament Proteins; C495738:PFN1 protein, human; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D051304:Profilins; D011493:Protein Kinase C