Phosphatidylinositol 4,5-bisphosphate competitively inhibits phorbol ester binding to protein kinase C

Journal Article · Tue Jun 13 00:00:00 EDT 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00438a007· OSTI ID:5443476

Chauhan, A; Cauhan, V P.S.; Deshmukh, D S; Brokerhoff, H ^[1]

---

1. New York State Office of Mental Retardation and Developmental Disabilities, Staten Island (USA)

Calcium phospholipid dependent protein kinase C (PKC) is activated by diacylglycerol (DG) and by phorbol esters and is recognized to be the phorbol ester receptor of cells; DG displaces phorbol ester competitively from PKC. A phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP{sub 2}), can also activate PKC in the presence of phosphatidylserine (PS) and Ca{sup 2+} with a K{sub PIP{sub 2}} of 0.04 mol %. Preliminary experiments have suggested a common binding site for PIP{sub 2} and DG on PKC. Here, the authors investigate the effect of PIP{sub 2} on phorbol ester binding to PKC in a mixed micellar assay. In the presence of 20 mol % PS, PIP{sub 2} inhibited specific binding of ({sup 3}H)phorbol 12,13-dibutyrate (PDBu) in a dose-dependent fashion up to 85% at 1 mol %. Inhibition of binding was more pronounced with PIP{sub 2} than with DG. Scatchard analysis indicated that the decrease in binding of PDBu in the presence of PIP{sub 2} is the result of an altered affinity for the phorbol ester rather than of a change in maximal binding. The plot of apparent dissociation constants (K{sub d{prime}}) against PIP{sub 2} concentration was linear over a range of 0.01-1 mol % with a K{sub i} of 0.043 mol % and confirmed the competitive nature of inhibition between PDBu and PIP{sub 2}. Competition between PIP{sub 2} and phorbol ester could be determined in a liposomal assay system also. These results indicate that PIP{sub 2}, DG, and phorbol ester all compete for the same activator-receiving region on the regulatory moiety of protein kinase C, and they lend support to the suggestion that PIP{sub 2} is a primary activator of the enzyme.

• OSTI ID: 5443476
• Journal Information: Biochemistry; (USA), Vol. 28:12; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ENZYME INDUCTION
INHIBITION
PHORBOL ESTERS
BIOLOGICAL EFFECTS
PHOSPHOTRANSFERASES
BIOCHEMICAL REACTION KINETICS
INOSITOLS
PHOSPHONIC ACID ESTERS
TRITIUM COMPOUNDS
CARBOHYDRATES
CARCINOGENS
ENZYMES
ESTERS
GENE REGULATION
HYDROGEN COMPOUNDS
KINETICS
MONOSACCHARIDES
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHORUS-GROUP TRANSFERASES
REACTION KINETICS
SACCHARIDES
TRANSFERASES
550201* - Biochemistry- Tracer Techniques