Propagation of electrical activity coupled to actin dynamics in electrically active neuron-like cells*

Coupling between excitable systems is a well-known phenomenon. Recent work focused on the excitability of neural and cardiovascular systems has illuminated the dynamics behind electrical signal propagation in these tissues through the use of recording microelectrodes. Other studies have shown that dendritic spines are enriched with dynamic actin at the synapses of electrically-coupled neurons. Here we investigate both electrical activity propagation and actin dynamics in a simple, excitable system: in vitro cultures of human embryonic kidney (HEK-293) cells. This cell line (NK-HEKs) has been engineered to be electrically excitable through the expression of sodium (Na+) and potassium (K+) channels. We electrically stimulate the cells to induce changes in transmembrane potential monitored noninvasively through new, fast-acting- voltage sensitive dyes. We simultaneously image actin dynamics in the same cells using internal fluorophores with the goal of understanding how changes in actin dynamics may drive or be driven by changes in transmembrane potential. Our results suggest that actin fluctuates in response to stimulation in these electrically active cells.