Characterisation of peptide interactions that regulate PKCε activation

Targeting the interaction between PKC isoforms and their anchoring proteins can specifically regulate kinase activity. epsilon V1-2 and pseudo epsilon RACK peptides, derived from the PKC epsilon C2 domain, modulate its association with receptor for activated C-kinase 2 (RACK2) and thus its function. Details of these interactions remain obscure, and we therefore investigated binding of these peptides using biophysical techniques. Surface plasmon resonance (SPR) indicated that the inhibitory epsilon V1-2 peptide bound to RACK2, and inhibited PKC epsilon binding as expected. In contrast, SPR and NMR demonstrated that the activating pseudo epsilon RACK peptide and related sequences did not bind to PKC epsilon, indicating that their mechanisms of action do not involve binding to the kinase as previously proposed. Our results clarify which interactions could be targeted in developing new therapeutics that inhibit PKC epsilon-RACK2 interaction.