Epigallocatechin-3-Gallate Allosterically Activates Protein Kinase C-α and Improves the Cognition of Estrogen Deficiency Mice.

Protein kinase C (PKC) isozymes play essential roles in biological processes, and activation of PKC is proposed to alleviate the symptoms of a variety of diseases. It would be of great significance to find effective pharmacological modulators of PKC isozymes that can be translated for clinical use. Here, using in vitro activity assay, we demonstrated that green tea extract (-)-epigallocatechin-3-gallate (EGCG) dose-dependently activated PKCα with a half effective concentration (EC50) of 0.49 μM. We also performed surface plasmon resonance analysis and found that EGCG binds PKCα with an equilibrium dissociation constant (KD) value of 4.11 × 10-6 mol/L. Further computational flexible docking analysis revealed that EGCG interacted with the catalytic C3-C4 domain of PKCα (PDB: 4RA4) through establishing polar hydrogen bonds with V420, T401, E387, and K368 of PKCα, and the benzene ring group of EGCG hydrophobically interacted with the hydrophobic pocket formed by L345, M470, I479, and V353 of PKCα. Interestingly, the PKCα-selective blocker Ro-32-0432 could compete with EGCG for the same substrate-binding pocket of PKCα. Moreover, we found that EGCG dose-dependently improved the spatial memory, object recognition ability, and hippocampal long-term potentiation of ovariectomized mice, which was offset by Ro-32-0432. Collectively, our findings reveal a novel PKCα agonist and open the way to a new perspective on PKCα pharmacology and the treatment of PKCα-related diseases, including cognitive impairment.