kt-5720 and 4-aminocrotonic-acid

In our previous study, anti-apoptotic effects of GABA(C)-receptor stimulation was suppressed by inhibitors of cAMP-dependent protein kinase (PKA), implying GABA(C) receptor-mediated PKA activation. The present study showed that GABA(C)-receptor stimulation with its agonist, cis-4-aminocrotonic acid (CACA), protected cultured hippocampal neurons from amyloid beta 25 - 35 (Abeta25 - 35) peptide-enhanced glutamate neurotoxicity. This protective effect of CACA was blocked by PKA inhibitors, KT 5720 and H-89, as well as a specific GABA(C)-receptor antagonist, (1,2,5,6-tetrahydropyridine-4-yl) methylphosphinic acid (TPMPA). To test the possibility of GABA(C) receptor-mediated PKA activation, association of GABA(C) receptor with A-kinase anchoring proteins (AKAPs) and effect of an AKAP antisense oligonucleotide on the PKA activation were examined in primary cultured rat hippocampal neurons. Stimulation of the cells with CACA-activated PKA was assessed by the phosphorylated PKA substrate (135 kDa) level. Specific antibodies raised against GABA(C)-receptor rho subunits precipitated each rho subunit, AKAP220, and PKA regulatory and catalytic subunits from rat brain lysates, suggesting that rho is associated with the AKAP220/PKA complex. Furthermore, antisense oligonucleotide of AKAP220 suppressed such GABA(C) stimulation-induced PKA activation, suggesting that GABA(C)-receptor stimulation activates PKA via AKAP220.

Topics: A Kinase Anchor Proteins; Amyloid beta-Peptides; Animals; Apoptosis; Carbazoles; Cells, Cultured; Crotonates; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Enzyme Activation; GABA Agonists; GABA Antagonists; Hippocampus; Isoquinolines; Neurons; Neuroprotective Agents; Oligonucleotides, Antisense; Peptide Fragments; Phosphinic Acids; Phosphorylation; Protein Kinase Inhibitors; Protein Subunits; Pyridines; Pyrroles; Rats; Rats, Wistar; Receptors, GABA; Receptors, GABA-A; Signal Transduction; Sulfonamides