Protein Kinase C δ (δPKC)-Annexin V Interaction

Protein kinase C (PKC) plays a critical role in diseases such as cancer, stroke, and cardiac ischemia, and participates in a variety of signal transduction pathways such as apoptosis, cell proliferation, and tumor suppression. Though much is known about PKC downstream signaling events, the mechanisms of regulation of PKC activation and subsequent translocation have not been elucidated. Protein-protein interactions regulate and determine the specificity of many cellular signaling events. Such a specific protein-protein interaction is described here between δPKC and annexin V. We demonstrate, at physiologically relevant conditions, that a transient interaction between annexin V and δPKC occurs in cells after δPKC stimulation, but before δPKC translocates to the particulate fraction. Evidence of δPKC-annexin V binding is provided also by FRET and by in vitro binding studies. Dissociation of the δPKC-annexin V complex requires ATP and microtubule integrity. Furthermore, depletion of endogenous annexin V, but not annexin IV, with siRNA inhibits δPKC translocation following PKC stimulation. A rationally designed eight amino acid peptide, corresponding to the interaction site for δPKC on annexin V, inhibits δPKC translocation and δPKC-mediated function as evidenced by its protective effect in a model of myocardial infarction. Our data indicate that translocation of δPKC is not simply a diffusion-driven process, but is instead a multi-step event regulated by protein-protein interactions. We show that following cell activation, δPKC-annexin V binding is a transient and an essential step in the function of δPKC, thus identifying a new role for annexin V in PKC signaling and a new step in PKC activation.