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Séminaire - André Nadler“Photochemical tools for analyzing cellular signaling networks”

Abstract :

Andre Nadler travaille dans le groupe de Carsten Schultz à Heidelberg. Recherche centrée sur le développement d'outils photochimiques 

Dynamic changes of membrane composition and organization are crucial for key cellular processes. Cellular transport, migration and polarization all require membrane reorganization as well as initiation and maintenance of intracellular concentration gradients of molecular distinct lipid species. The role and importance of lipids has not been studied thoroughly in living cells, both due to technical limitations and the simple fact that cellular lipids constitute a molecular array of overwhelming complexity. Understanding why this complexity is required, how and when distinct lipid molecules interact with proteins and how these interactions are in turn modulated by lipid metabolism will be critical for elucidating how biological membranes function on a molecular level. Addressing these questions requires unique tools that allow monitoring the metabolism of signaling lipids in living cells, the detection and analysis of protein-lipid interactions and the correlation of such data with a given physiological outcome. These requirements are met by photochemical tools that are increasingly popular for studying cellular signaling processes. 

Figure 1. A) A caged lipid B) Schematic representation of changes in the cellular localization of a lipid binding protein upon lipid uncaging C) Fluorescence microscopy images of an actual live cell lipid uncaging experiment and schematic representation of a decay curve after a stepwise concentration increase.

A series of caged (photoactivatable) diacylglycerols were synthesized and applied to study the influence of concentration gradients and the importance of lipid side chain composition in cellular signaling processes. These compounds are currently being used to measure lipid metabolism in living cells in a quantitative fashion and conclude upon likely metabolites of signaling lipids. In additional approaches, novel photoaffinity (“snapshot”) probes have been developed which are designed to capture interactions between proteins and individual, molecular distinct lipid species as well as a caging group that allows liberating signaling lipids exclusively at the plasma membrane. A combination of these approaches will ultimately enable experiments which will basically amount to performing lipid biochemistry in living cells.