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AKB: Biologische Physik

AKB 30: Poster Session I

AKB 30.39: Poster

Montag, 27. März 2006, 15:30–18:00, P1

Investigation of the first steps of TNF-mediated apoptosis by FCS and FCCS in live cells — •Felix Neugart¹, Carsten Tietz¹, Magarita Gerken¹, Andrea Zappe¹, Anja Krippner-Heidenreich², Peter Scheurich², and Jörg Wrachtrup¹ — ¹3. Physikalisches Institut, Universit"at Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart — ²Institut f"ur Zellbiologie und Immunoligie, Universit"at Stuttgart, Allmandring 31, 70569 Stuttgart

Due to its high sensitivity fluorescence correlation spectroscopy is suited to investigate processes in live cells where the endogenous concentration of the participating molecules are low, e.g., in many signaling cascades. Here, FCS is used to unravel dynamics of the membrane receptors TNFR1 and TNFR2 which play important roles in apoptotic signaling pathways. Although structurally similar in their transmembrane domains both receptors behave markedly different in the cell membrane. Upon binding of the ligand TNF the diffusion constant of TNFR2 is reduced from 3.3 × 10⁻⁹ to 0.8 × 10⁻⁹ cm²/s. Experiments on receptors without its binding domain in the cytoplasm show that interaction of the receptor signaling complex with immobile parts of the cellular interior is not responsible for the reduction in diffusion rate. Rather it appears that the TNFR2 receptor attaches to slowly diffusing membrane microdomains after stimulation. Using a new set-up for cross-talk free FCCS with the fluorophore pair CFP and YFP it was shown that there is no pre-association behavior of TNFR2 before stimulation.