Functional Expression of Electron Transport Chain and FoF1-ATP Synthase in Optic Nerve Myelin Sheath.
Our previous studies reported evidence for aerobic ATP synthesis by myelin from both bovine brainstem and rat sciatic nerve. Considering that the optic nerve displays a high oxygen demand, here we evaluated the expression and activity of the five Respiratory Complexes in myelin purified from either bovine or murine optic nerves. Western blot analyses on isolated myelin confirmed the expression of ND4L (subunit of Complex I), COX IV (subunit of Complex IV) and β subunit of F1Fo-ATP synthase. Moreover, spectrophotometric and in-gel activity assays on isolated myelin, as well as histochemical activity assays on both bovine and murine transversal optic nerve sections showed that the respiratory Complexes are functional in myelin and are organized in a supercomplex. Expression of oxidative phosphorylation proteins was also evaluated on bovine optic nerve sections by confocal and transmission electron microscopy. Having excluded a mitochondrial contamination of isolated myelin and considering the results form in situ analyses, it is proposed that the oxidative phosphorylation machinery is truly resident in optic myelin sheath. Data may shed a new light on the unknown trophic role of myelin sheath. It may be energy supplier for the axon, explaining why in demyelinating diseases and neuropathies, myelin sheath loss is associated with axonal degeneration.
Biochemistry Laboratory, Department of Pharmacy (DIFAR), University of Genova, Viale Benedetto XV, 3, 16132, Genoa, Italy.
Martina
M
Bartolucci
Biochemistry Laboratory, Department of Pharmacy (DIFAR), University of Genova, Viale Benedetto XV, 3, 16132, Genoa, Italy. silvia.ravera@gmail.com.
Silvia
S
Ravera
Department of Earth, Environmental and Life Sciences, (DISTAV), University of Genova, C.so Europa 26, 16132, Genoa, Italy.
Greta
G
Garbarino
Department of Earth, Environmental and Life Sciences, (DISTAV), University of Genova, C.so Europa 26, 16132, Genoa, Italy.
Paola
P
Ramoino
Department of Earth, Environmental and Life Sciences, (DISTAV), University of Genova, C.so Europa 26, 16132, Genoa, Italy.
Sara
S
Ferrando
Biochemistry Laboratory, Department of Pharmacy (DIFAR), University of Genova, Viale Benedetto XV, 3, 16132, Genoa, Italy.
Daniela
D
Calzia
Department of Earth, Environmental and Life Sciences, (DISTAV), University of Genova, C.so Europa 26, 16132, Genoa, Italy.
Simona
S
Candiani
Biochemistry Laboratory, Department of Pharmacy (DIFAR), University of Genova, Viale Benedetto XV, 3, 16132, Genoa, Italy.
Alessandro
A
Morelli
Biochemistry Laboratory, Department of Pharmacy (DIFAR), University of Genova, Viale Benedetto XV, 3, 16132, Genoa, Italy.
Isabella
I
Panfoli
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D001369:Axons / Q000378:metabolism; D002417:Cattle; D045222:Electron Transport Chain Complex Proteins / Q000096:biosynthesis*; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009186:Myelin Sheath / Q000378:metabolism*; D009245:NADH Dehydrogenase / Q000096:biosynthesis; D009457:Neuroglia / Q000378:metabolism; D009900:Optic Nerve / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D006180:Proton-Translocating ATPases / Q000096:biosynthesis*
D045222:Electron Transport Chain Complex Proteins; C098483:NADH dehydrogenase subunit 4; D000255:Adenosine Triphosphate; D009245:NADH Dehydrogenase; D006180:Proton-Translocating ATPases
ATP synthesis; Glia metabolism; Myelin sheath; Optic nerve; Oxidative phosphorylation