Dynamics of single potassium channel proteins in the plasma membrane of migrating cells
Cell migration is an important cell physiological process, which is among others controlled by regulated ion channel activity. It was revealed that potassium channels, in particular calcium-activated potassium channels (KCa3.1), are required for optimal cell migration. In order to study the dynamics of individual channel proteins in the plasma membrane, single channel proteins were identified and tracked during cell migration. The identification was based on dual-colour labeling with quantum dots (QD) and it was proven that more than 90% of the observed QDs correspond to single potassium channel proteins. In migrating MDCK-F cells (Ncells = 10) single QD-labeled channels (NQD = 534) were visualised and tracked using time lapse total internal reflection fluorescence (TIRF) microscopy. Analysis of the trajectories of hKCa3.1 channels allowed the classification of their dynamics. KCa3.1 channel proteins moved subdiffusively in the plasma membrane with a mean diffusion coefficient Dα = 0.0673 ± 0.0005 μm2/sα and a mean subdiffusion exponent α = 0.824 ± 0.003. Ion channel proteins had a lower displacement at the lamellipodium and at the uropod than in the body of the cell which was due to a smaller subdiffusion coefficient α at these cell parts.