Detection of Protein Targets of Protein Kinase A and C in Rat Brain Mitochondria

Phosphorylation of some membrane-bound proteins in mitochondria of rat liver and brain is regulated by Ca' and cAMP acting as secondary messengers. Among such membrane-bound proteins are main components of myelin 2 ',3 '-cyclone nucleotide-3 '-phosphodiesterase (CNP) of 46 kDa and two isoforms of the myelin basic protein (MBP) with molecular weights of 17 and 21.5 kDa that were previously identified and found in rat brain mitochondria, outside myelin. The level of phosphorylation of CNP and both isoforms of MBP increases when the mitochondrial permeability transition pore (mRTR) is opened. It is known that PKA and PKC directly bind to proteins-regulators of mPTP and are able to modulate the mPTP function. In the present study we show that the inhibitors of protein kinase A (PKA) (11-89) and protein kinase C (PKC) (staurosporin, Go 6976, and GF 109203 X) decrease the phosphorylation level of CNP and MBP in brain mitochondria when mPTP is opened. These findings indicate that CNP and the two isoforms of MBP studied are targets of the PKA and PKCE signaling.