| dc.description.abstracteng | Lipids are essential components of cellular membranes, which constitute not only the physical platforms that harbor the membrane proteins, but also the biochemical interfaces where the exchange of biomolecules, the communication between cells / organelles and the perception of exterior signals occur. Despite their structural importance, the functions and the mechanisms by which lipids orchestrate the compositional remodeling of cellular membranes in response to environmental stimuli are still poorly understood.
The work presented here provides comprehensive and detailed information about distinct membrane composition as resolved by profound lipid analyses. For this, the acquisition of functional but minor membrane lipids, such as phosphoinositides, complex glycosphingolipids and phosphorylated sphingolipids, was incorporated into the pre-existing analytical lipidomics platform. The underlying liquid chromatographic separation coupled with mass spectrometric detection allows the selective and sensitive determination of individual lipid molecular species in complex biological samples.
This enhanced method was then applied to investigate how the plasma membrane from Arabidopsis remodels its lipid composition under cold stress or in response to the loss of specific lipid species. The results indicated that the cold-induced lipid alterations within the plant plasma membrane resemble those of mutant plants with an impaired biosynthesis of α-hydroxylated sphingolipids. In addition, the lipidomics platform revealed a species-specific transversal distribution of certain lipids in purified and differently oriented plasma membrane vesicles. Individual lipid species, even from the same lipid class, are distributed differently within the two leaflets of the Arabidopsis plasma membrane, suggesting they may exert distinct functions within the particular membrane leaflet. In addition, the application of lipidomics together with proteomics and online database mining enabled the construction of the lipid metabolic pathways in the plant mitochondria. Possible lipid exchange and biosynthesis was unveiled with the assistance of membrane contact site-localizing proteins, indicating that several phospholipid classes as well as free sterols can be synthesized in plant mitochondria. Overall, these studies contribute to the understanding of the lipid organization of distinct subcellular membranes. | de |