Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 22: Cell Mechanics

BP 22.2: Talk

Thursday, February 28, 2008, 10:45–11:00, PC 203

Manipulation of stretch-activated calcium channels with the optical stretcher — •Markus Gyger and J. A. Käs — Universität Leipzig, Institut für Experimentelle Physik I, Linnéstr. 5, 04103 Leipzig

Cellular response to deforming forces can be measured with the optical stretcher. Cells are trapped by two anti-parallel laser beams. By increasing the laser power the momentum transfered to the cell surface causes visible deformations. This can be used to probe the global mechanical behaviour of single cells in suspension. For low stresses and small deformations most of the cells deform viscoelasticly. However, for higher stretching powers the cells start to counteract the deformations. Sometimes this active response to deformation results in a contraction of the cell relative to its initial, undeformed state. This raises interesting questions regarding the mechanisms by which cells register and respond to the applied forces. Under physiological conditions many must react to mechanical stimuli. As a prominent example, hair-cells in the Cochlea of vertebrate ears are known to open transmembrane calcium channels upon mechanical stresses. Calcium is one of the most important secondary messengers and is involved in most of the known mechano-activated cell responses. Since its normal concentration in the cell soma is very low and increases only by influx from outside the cell or release from intracellular calcium stores upon stimulus, the influx can be made visible by appropriate fluorescent dyes. The aim of this work is to investigate the dependence of calcium influx on the forces applied to the cell surface in order to gain insight into the mechanisms of active responses to stretching.