TBID,CL AND CYT C · Mitochondrial membrane reorganisation induced by tBid during apoptosis: cardiolipin and cytochrome c redistribution analysed by single molecule spectroscopy and microscopy
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2006-12-01 → 2008-11-30
- EU contribution
- €149,722
- Participants
- 1
- Scheme
- EIF
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Results in brief
Final Activity Report Summary - tBid,CL and cyt c (Mitochondrial membrane reorganisation (...): cardiolipin and cytochrome c redistribution analysed by single molecule spectroscopy and microscopy)
As a Marie Curie fellow, my work focused on the quantitative study of dynamic processes in membranes via molecular imaging. This included the lateral organisation of membranes, i.e. the formation of lipid domains and rafts, and the study of apoptotic signalling processes, i.e. the pore formation by Bax fragments and the interactions between Bcl-2 proteins. With the aim of quantitative biology, during this period I acquired deep insight in single molecule techniques, such as atomic force microscopy and fluorescence correlation spectroscopy, combined with advanced imaging techniques like confocal microscopy, spinning disc, fluorescence recovery after photobleaching (FRAP), fluorescence resonance energy transfer (FRET) and live cell imaging. The Bcl-2 proteins are key regulators of apoptosis, which is a form of programmed cell death. They control the release of the apoptotic factors from the mitochondria that initiate apoptosis. Two important questions about the mechanism of the Bcl-2 proteins involve the interaction network between pro- and anti-apoptotic family members as well as the role of their translocation to the mitochondrial outer membrane during apoptosis. By quantifying the interactions of Bid and tBid with Bcl-xLdeltaCt in solution and membranes using fluorescence correlation spectroscopy, we found that: 1. only the active form tBid bound to Bcl-xLdelatCt, and 2. the membrane strongly promoted binding between them. Particularly, a BH3 peptide from Bid disrupted the tBid and Bcl-xL complex in solution, but not in lipid bilayers. These data indicated that tBid and Bcl-xL interactions in solution and lipid membranes were not equivalent and supported a model in which Bcl-xL inhibition of tBid happened predominantly at the membrane. Our findings implied an active role of the membrane in modulating the interactions between Bcl-2 proteins that was so far underestimated.
Data: CORDIS, © European Union
Project objective
One of the main control points of programmed cell death affects the release of cytochrome c and other proapoptotic factors from the mitochondria. The detailed mechanism by which cytochrome c is completely and rapidly liberated to the cytosol is not yet well understood, but it appears to involve two steps: i) redistribution of the cytochrome c stored in the mitochondrial cristae and ii) selective permeabilization of the outer mitochondrial membrane. tBid, a proapoptotic protein of the Bcl-2 family, has been recently related to the lipidic reorganization that takes place at the mitochondria during apoptosis. Addition of tBid to mitochondria induces quick morphological changes, which interconnect cristae and make cytochromec available at the outer mitochondria l membrane.This activity seems to depend on interactions with the mitochondrial lipid cardiolipin, which, being an anchor to cytochrome c at the inner mitochondrial membrane, redistributes during apoptosis, and mediates the selective targeting of tBid to the outer mitochondrial membrane. Recently, it has been observed by epifluorescence microscopy that tBid induces the appearance of novel cardiolipin micro-domains in monolayers. Single molecule optical techniques have been applied to study raft-associated proteins and lipid mobility in vivo and in vitro.Fluorescence correlation spectroscopy uses the temporal dimension and constitutes a powerful tool to study lipid and protein dynamics in domain-forming membranes. It is the objective of this project to characterize the formation of cardiolipin enriched domains induced by the presence of tBid in connection with the process of mitochondrial cytochrome c redistribution that occurs during apoptosis, by means of fluorescence correlation spectroscopy and microscopy in membrane model systems and mitochondria.
Original text from CORDIS.
Participants
- TECHNISCHE UNIVERSITAET DRESDEN · DRESDENCoordinatorGermany
Links
Data: CORDIS, © European Union