Using Total Internal Reflection Fluorescence Microscopy to Observe Ion Channel Trafficking and Assembly

Ion channels are integral membrane proteins that allow the flow of ions across membranes down their electrochemical gradients and are a major determinant of cellular excitability. They play an important role in a variety of biological processes as diverse as insulin release from beta cells in the pancreas through to cardiac and smooth muscle contraction. We have used total internal reflection fluorescence (TIRF) microscopy to watch ion channels being transported in vesicles along microtubules within the cytoplasm of the cell. Furthermore, we can directly observe the fusion of these vesicles with the plasma membrane and the release and radial dispersion of single ion channels into the membrane. Finally, automated single-particle tracking of these objects allowed us to determine their diffusional behavior.