Both proteins and lipids contribute to the formation and the stability of membrane domains that should be called “membrane rafts” and are envisaged as small (10–200-nm), heterogeneous, highly dynamic, sterol- and sphingolipid-enriched domains that compartmentalize cellular processes ( 4). Recently a consensus emerged on the characteristics of these domains. This leads in particular to the formation of specialized phase domains, also called lipid rafts ( 2, 3). Evidence has been given that the various types of lipids forming this membrane are not uniformly distributed inside the bilayer but rather spatially organized ( 1). Over the last 10 years, a new aspect of the plasma membrane organization has arisen from biophysical and biochemical studies performed with animal cells. Thus it is particularly involved in environmental signal recognition and their transduction into intracellular responses, playing a crucial role in many essential functions such as cell nutrition (involving transport of solutes in and out of the cell) or response to environmental modifications (including defense against pathogens). The plasma membrane of eukaryotes delineates the interface between the cell and the environment. This suggests that the ways by which the dynamic association of proteins to microdomains could participate in the regulation of the signaling process may be conserved between plant and animals. Furthermore proteins identified as differentially associated to tobacco detergent-resistant membranes after cryptogein challenge are involved in signaling and vesicular trafficking as already observed in similar studies performed in animal cells upon biological stimuli. This analysis indicates that plant microdomains could, like their animal counterpart, play a role in the early signaling process underlying the setup of defense reaction. Four proteins related to cell trafficking (four dynamins) were less abundant in the detergent-resistant membrane fraction after cryptogein treatment, whereas one signaling protein (a 14-3-3 protein) was enriched. The results obtained indicate that, although the association to detergent-resistant membranes of most proteins remained unchanged upon cryptogein treatment, five proteins had their relative abundance modified. To analyze the data, we developed a software allowing an automatic quantification of the proteins identified. In the present study, we used 14N/ 15N metabolic labeling to compare, using a global quantitative proteomics approach, the content of tobacco detergent-resistant membranes extracted from cells treated or not with cryptogein, an elicitor of defense reaction. A characterization of their proteic content revealed their enrichment in proteins involved in signaling and response to biotic and abiotic stress and cell trafficking suggesting that these domains were likely to be involved in such physiological processes. In plants, as previously observed for animal microdomains, detergent-resistant fractions, enriched in sphingolipids and sterols, were isolated from plasma membrane. A large body of evidence from the past decade supports the existence, in membrane from animal and yeast cells, of functional microdomains playing important roles in protein sorting, signal transduction, or infection by pathogens.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |