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AKB: Biologische Physik

AKB 22: Sensory Biophysics and Signal Transduction

AKB 22.3: Vortrag

Donnerstag, 30. März 2006, 15:15–15:30, ZEU 255

Polarized dynamics of individual G-protein coupled receptors in Dictyostelium chemotaxis. — •Thomas Schmidt¹, Sandra de Keijzer¹, Freek van Hemert¹, Herman Spaink², and Ewa Snaar-Jagalska² — ¹Physics of Life Processes, Leiden University — ²Cell Biology, Leiden Univesity

Single molecule microscopy was used to unravel the role of the G-protein coupled cAMP receptor, cAR1, in establishing polarity during chemotaxis of living Dictyostelium discoideum cells. We analyzed the mobility of individual cAR1-eYFP under different physiological conditions. In all cells an immobile and a mobile receptor fraction was found. The latter increased from 38% to 54% at the anterior of chemotaxing cells. The mobile fraction was characterized by a diffusion constant D = 0.19 um2/s. The anterior/posterior mobility shift was neither caused by a difference in membrane viscosity nor by a conformational change of the receptor due to phosphorylation. Comparison with studies on Ga2-protein deficient cell lines allowed us to conclude that the mobility shift of the receptors at the leading edge resembles the uncoupling/activation of the Ga2-protein. Our data further suggest that the mobility shift is directly related to the primary amplification steps in chemotaxic signalling and leads to a straightforward molecular explanation of the parameters in current models.