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CPP: Chemische Physik und Polymerphysik

CPP 26: Biological systems II

CPP 26.1: Vortrag

Dienstag, 8. März 2005, 15:15–15:30, TU C230

Tracking of individual G-protein coupled receptors on living cells — •Michael Prummer, Bruno Meyer, Raphael Franzini, Jean-Manuel Segura, and Horst Vogel — Laboratory of Physical Chemistry of Polymers and Membranes, Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland

The neurokinin-1 receptor (Nk1R), a typical representative of the G-protein coupled receptor (GPCR) superfamily, is essential for nociception and is a central drug target for anti-depressants. The agonist Substance P induces intracellular calcium signaling and subsequent desensitization of the receptor by internalization. Here we report on the imaging of individual Nk1Rs on the plasma membrane of living HEK293 cells. Single-molecule wide-field microscopy was utilized to record trajectories of Nk1Rs, which were labeled enzymatically in situ at an N-terminal targeting sequence with Cy5. Single particle tracking analysis of the trajectories revealed immobile and mobile receptors with an experimental position accuracy of 35 nm. The trajectories are analyzed in terms of the microscopic diffusion coefficient of each molecule, as well as the probability distribution P(msd,dt) of the occurrence of the mean-square displacement msd after a time-lag dt, averaged over many molecules. Current investigations are focused on how the mobility of Nk1R is influenced by the initiation of the cellular signaling cascade upon ligand binding and the modulation of the G-protein activity. The ultimate goal is to monitor the fate of individual Nk1Rs from their resting state through ligand binding until internalization occurs.