Lipids of Brain Mitochondria

Abstract

Mitochondrial inner membrane is a dynamic structure that changes shape rapidly in response to variations of osmotic or metabolic conditions. The intrinsic curvature of its constituent monolayers contributes to flexibility, allowing the conversion from flat structures to inverted hexagonal phases. The anchorage of cytochrome c to the inner mitochondrial membrane is mainly due to the interaction with the peculiar mitochondrial lipid cardiolipin. Any cellular event perturbing the stationary state of the lipid may influence the stability of the anchored protein, thus initiating its release outside mitochondria and caspase activation. We describe biochemical and functional characterization of brain mitochondria, focusing mainly on lipid classes and fatty acid composition. The role of cardiolipin fatty acid composition on its interaction with cytochrome c is discussed. In addition, since mitochondria are not able to synthesize all the lipids they contain, with the exception of cardiolipin, processes of lipid translocation from the site of synthesis to the acceptor membranes are described. Emphasis has been given to cholesterol synthesis in brain and to the mitochondrial importation of this lipid in neuronal cells. Finally, some aspects of physiopathology of mitochondrial lipids in aging, ischemia, and neurodegeneration are reviewed.