Mechanism of A-kinase-anchoring protein 79 (AKAP79) and protein kinase C interaction

The A-kinase-anchoring protein AKAP79 co-ordinates the location of cAMP-dep endent protein kinase, phosphatase 2B (PP2B/calcineurin) and protein kinase C (PKC) at postsynaptic sites in neurons. In this report we focus on the m echanism of interaction between AKAP79 and PKC. We show that neither lipid activators nor kinase activation are required for association with AKAP79, The anchoring protein binds and inhibits the conserved catalytic core of PK C beta II. AKAP79 also associates with conventional, novel and atypical iso forms of PKC in vitro and in vivo and immunofluorescence staining of rat hi ppocampal neurons demonstrates that the murine anchoring-protein homologue AKAP150 is co-distributed with PKC alpha/beta, PKCe or PKCt. Binding of the AKAP79(31-52) peptide, which inhibits kinase activity, exposes the pseudos ubstrate domain of PKC beta II, allowing endoproteinase Arg-C proteolysis i n the absence of kinase activators. Reciprocal experiments have identified two arginine residues at positions 39 and 40 that are essential for AKAP79( 31-52) peptide inhibition of PKC beta II. Likewise, the same mutations in t he full-length anchoring protein reduced inhibition of PKC beta II, Thus AK AP79 associates with multiple PKC isoforms through a mechanism involving pr otein-protein interactions at the catalytic core where binding of the ancho ring protein; inhibits kinase activity through displacement of the pseudosu bstrate.