Isozyme‐specific interaction of protein kinase C δ with mitochondria dissected using live cell fluorescence imaging

Abstract

Protein kinase C δ (PKCδ) signaling to mitochondria has been implicated in both mitochondrial apoptosis and metabolism. Using FRET‐based imaging, we observe that phorbol ester induces PKCδ to translocate to the outer membrane of mitochondria by an isozyme‐specific mechanism, resulting in increased mitochondrial respiration. A structure‐function study of the molecular mechanisms driving PKCδ's unique interactions with mitochondria reveals that the C1A and C1B domains and residues near the turn motif of PKCδ are required for its acute translocation to mitochondria and that the C2 domain, a critical charged residue in the activation loop, kinase activity, and mitochondrial transmembrane potential enable it to be retained there. PKCδ localized to the mitochondrial outer membrane has robust activity, as revealed by a FRET reporter of PKCδ‐specific activity (δCKAR). Perturbation of the kinase activity of PKCδ, by means of various kinase‐dead mutants, pharmacological inhibition, or a gate‐keeper mutant of PKCδ, demonstrates that its activity plays a role in both its translocation to and retention at mitochondria. These data support a model in which determinants unique to PKCδ drive a highly specific interaction with mitochondria. This work was supported by NIH GM43154 (ACN), UCSD Pharmacology Training Grant NIGMS T32 GM007752 (AXW), and UCSD GK‐ 12 STEM fellowship in education NSF 0742551 (AXW).