Differential effect of plant lipids on membrane organization: hot features and specificities of phytosphingolipids and phytosterols [Lipids]

January 9th, 2015 by Grosjean, K., Mongrand, S., Beney, L., Simon-Plas, F., Gerbeau-Pissot, P.

The high diversity of the plant lipid mixture raises the question of their respective involvement in the definition of membrane organization. This is particularly the case for plant plasma membrane, which is enriched in specific lipids such as free- and conjugated- forms of phytosterols, and typical phytosphingolipids, such as glycosylinositolphosphoceramides (GIPC). This question was here addressed extensively by characterizing the order level of membrane from vesicles prepared using various plant lipid mixtures and labeled with the environment-sensitive probe di-4-ANEPPDHQ. Fluorescence spectroscopy experiments showed that among major phytosterols, campesterol exhibits a stronger ability than sitosterol and stigmasterol to order model membranes. Multispectral confocal microscopy allowing spatial analysis of membrane organization, demonstrated accordingly the strong ability of campesterol to promote ordered domain formation, and to organize their spatial distribution at the membrane surface. Conjugated-sterol forms, alone and in synergy with free sterols, exhibit a striking ability to order membrane. Plant sphingolipids, particularly GIPC, enhanced the sterol-induced ordering effect, emphasizing the formation and increasing the size of sterol-dependent ordered domains. Altogether, our results support a differential involvement of free- and conjugated- phytosterols in the formation of ordered domains and suggest that the diversity of plant lipids, allowing various local combinations of lipid species, could be a major contributor to membrane organization in particular through the formation of sphingolipid-sterol interacting domains.