A Fluorescent Protein Voltage Sensor in the Endoplasmic Reticulum

Abstract

In eukaryotic cells, the endoplasmic reticulum (ER) is the largest continuous membrane-enclosed network which surrounds a single lumen. Using a newly designed genetically encoded voltage indicator (GEVI), we applied the patch clamp technique to HEK293 cells and found that there is a direct electrical interaction between plasma membrane and ER membrane. We have optically monitored the voltage changes in both of these membranes simultaneously. The optical signal of the GEVI in the plasma membrane is consistent from trial to trial. However, the ER signal decreases in size with repeated trials. This dynamic behavior of the internal signal suggests that voltage may stress the ER causing it to remodel and change its resistance. Our findings further suggest that the ER may transfer electrical signals from the plasma membrane to the nuclear envelope.