Figure 3. PKC and mitochondrial protein phosphorylation.

A schematic diagram of PKC and the involvement of protein phosphorylation in a variety of mitochondrial proteins and processes. The red asterisks indicate known phosphorylations to either subunits of the complex or enzymes within the cycles indicated. All of the major pathways of energy production within the mitochondria contain phosphoproteins: the TCA cycle (TCA), OxPhos complexes (I–V) and fatty acid beta oxidation (βox). Several major transporters and channels have also been seen as phosphoproteins including members of the mitochondrial permeability transition pore (MPTP) a known mediator of apoptosis. Other apoptosis related proteins (BAD and Bcl-2) are known to be associated with the mitochondria and appear as phosphorylated species (86). PKC is known to cause the phosphorylation of or interact with (either directly or indirectly) several proteins that are associated with the outer membrane of the mitochondria, including the MPTP proteins, mitoK_ATP channel (82), BAD and Bcl-2. Of importance is also the observation that PKC can mediate the import of some proteins into the mitochondria through differential phosphorylation of the cytosolic precursors of these mitochondrial proteins (85). Abbreviations and references for the phosphorylation: Boxes labeled I–V indicate the OxPhos complexes I (53, 57, 94–96), complex II (53), complex III (53), complex IV (86) and complex V (7, 86, 97); c, cytochorme c (98); GPCR, g protein coupled receptor; VDAC, voltage dependent anion channel (53, 86); ANT, adenine nucleotide transporter (86); HK2, hexokinase II; PDK, pyruvate dehydrogenase kinase; PDH, pyruvate dehydrogenase (53, 83); ROS, reactive oxygen species (53, 86); Tom, translocase of the outer membrane; Tim, translocase of the inner membrane; CPT1/2, carnitine palmytoltransferase 1/2 (86); βox, fatty acid beta oxidation (53, 86); TCA, Tricarboxylic acid cyle(53, 86).