Mitochondrial localization of CNP2 is regulated by phosphorylation of the N-terminal targeting signal by PKC: implications of a mitochondrial function for CNP2 in glial and non-glial cells.
Both 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNP) isoforms are abundantly expressed in myelinating cells. CNP2 differs from CNP1 by a 20 amino acid N-terminal extension and is also expressed at much lower levels in non-myelinating tissues. The functional role of CNP2, apart from CNP1, and the significance for CNP2 expression in non-myelinating tissues are unknown. Here, we demonstrate that CNP2 is translocated to mitochondria by virtue of a mitochondrial targeting signal at the N-terminus. PKC-mediated phosphorylation of the targeting signal inhibits CNP2 translocation to mitochondria, thus retaining it in the cytoplasm. CNP2 is imported into mitochondria and the targeting signal cleaved, yielding a mature, truncated form similar in size to CNP1. CNP2 is entirely processed in adult liver and embryonic brain, indicating that it is localized specifically to mitochondria in non-myelinating cells. Our results point to a broader biological role for CNP2 in mitochondria that is likely to be different from its specific role in the cytoplasm, along with CNP1, during myelination.
Lee
John
J
Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3G 1Y6. johnlee@gene.com
O'Neill
Ryan C
RC
Park
Min Woo
MW
Gravel
Michel
M
Braun
Peter E
PE
D063309:2',3'-Cyclic Nucleotide 3'-Phosphodiesterase; D000818:Animals; D001921:Brain / Q000196:embryology / Q000201:enzymology* / Q000648:ultrastructure; D019069:Cell Respiration / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D022781:Hepatocytes / Q000201:enzymology / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D008099:Liver / Q000201:enzymology / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000201:enzymology* / Q000648:ultrastructure; D009457:Neuroglia / Q000201:enzymology* / Q000648:ultrastructure; D009474:Neurons / Q000201:enzymology* / Q000648:ultrastructure; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D013347:Subcellular Fractions; D014162:Transfection
D049452:Green Fluorescent Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010727:Phosphoric Diester Hydrolases; D063309:2',3'-Cyclic Nucleotide 3'-Phosphodiesterase; C571337:CNP protein, human; C571339:Cnp protein, rat