title: FKBP-12 is not an inhibitor of protein kinase C.
abstract: It was recently noted that the amino acid sequence of FK506 binding protein (FKBP-12) is nearly identical to that of an endogenous inhibitor of protein kinase C, PKCI-2. To follow up on this observation, we have tested the hypothesis that FKBP-12 is an inhibitor of PKC. The kinase activity of rat brain protein kinase C (PKC) was not inhibited by the presence of up to 700 micrograms recombinant human FKBP-12 per ml, in either the presence or absence of FK506. FKBP-12 also did not affect PMA-induced phosphorylation of an endogenous PKC substrate, an 80 kDa protein, in permeabilized cells. To test whether FKBP-12 could account for endogenous PKC inhibitory activity in cells, Jurkat cell lysate was chromatographed on an anion exchange column. A peak of PKC inhibitory activity was eluted at approximately 200 mM NaCl. As shown by both Western blots and FK506 binding activity, FKBP-12 was eluted only in the flow-through and wash fractions. These results demonstrate that FKBP-12 is clearly distinct from endogenous PKC inhibitory activity.
authors.affiliation: Department of Cell Biology, Upjohn Company, Kalamazoo, MI 49001.
authors.forename: V A
authors.initials: VA
authors.lastname: Ruff
authors.forename: J E
authors.initials: JE
authors.lastname: McGee
authors.forename: A W
authors.initials: AW
authors.lastname: Yem
authors.forename: M R
authors.initials: MR
authors.lastname: Deibel
authors.forename: K L
authors.initials: KL
authors.lastname: Leach
mesh_terms: D015153:Blotting, Western; D002352:Carrier Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D002845:Chromatography; D006801:Humans; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000494:pharmacology; D016559:Tacrolimus / Q000378:metabolism*; D022021:Tacrolimus Binding Proteins; D014407:Tumor Cells, Cultured
chemical_list: D002352:Carrier Proteins; D011994:Recombinant Proteins; D011493:Protein Kinase C; D022021:Tacrolimus Binding Proteins; D016559:Tacrolimus