Single-molecule imaging of L-type CA²⁺ channels in live cells

L-type Ca²⁺ channels are an important means by which a cell regulates the Ca²⁺ influx into the cytosol on electrical stimulation. Their structure and dynamics in the plasma membrane, including their molecular mobility and aggregation, is of key interest for the in-depth understanding of their function. Construction of a fluorescent variant by fusion of the yellow-fluorescent protein to the ion channel and expression in a human cell line allowed us to address its dynamic embedding in the membrane at the level of individual channels in vivo. We report on the observation of individual fluorescence-labeled human cardiac L-type Ca²⁺ channels using wide-field fluorescence microscopy in living cells. Our fluorescence and electrophysiological data indicate that L-type Ca²⁺ channels tend to form larger aggregates which are mobile in the plasma membrane.