HMN 2025: How Biophysicists uncover new electrical transmission in cells

Many biological processes are regulated by electricity—from nerve impulses to heartbeats to the movement of molecules in and out of cells.

A study by Scripps Research scientists reveals a previously unknown potential regulator of this bioelectricity: droplet-like structures called condensates. Condensates are better known for their role in compartmentalizing the cell, but this study shows they can also act as tiny biological batteries that charge the cell membrane from within.

The team showed that when electrically charged condensates collide with cell membranes, they change the cell membrane’s voltage—which influences the amount of electrical charge flowing across the membrane—at the point of contact.

The discovery, published in the journal Small, highlights a new fundamental feature about how our cells work, and could one day help scientists treat certain diseases.

How condensates function in cells

“This represents an entirely new paradigm in bioelectricity that has substantial implications for electrical regulation in biology and health,” says Ashok Deniz, senior author of the new paper and professor at Scripps Research.

Condensates are organelles—structures within cells that carry out specific functions—but unlike more well-known organelles such as the nucleus and mitochondria, they are not enclosed within membranes. Instead, condensates are held together by a combination of molecular and electrical forces. They also occur outside of cells, such as at neuronal synapses.

Condensates are involved in many essential biological processes, including compartmentalizing cells, protein assembly and signaling both within and between cells. Previous studies have also shown that condensates carry electrical charges on their surfaces, but little is known about how their electrical properties relate to cellular functions.

Investigating condensates’ electrical effects

“You can think of condensates as electrically charged droplets in the cell, kind of like a tiny battery,” says first author Anthony Gurunian, a Ph.D. candidate who is jointly advised by Deniz and Scripps Research associate professor and co-author Keren Lasker.

“Since condensates can often be charged, we wanted to test whether they can induce voltage changes across the cell membrane.”

If condensates can alter the electrical properties of cell membranes, it could have big implications, because many cellular processes are controlled by changes in the cell membrane voltage. For example, ion channels—proteins that rapidly transport molecules across the cell membrane—are activated by changes in cell membrane voltage.

In the nervous system, this rapid, one-directional transport of electrically charged molecules is what drives the propagation of electrical signals between nerves.

Experimental approach and findings

To test whether condensates can alter cell membrane voltage, the researchers used cell models called Giant Unilamellar Vesicles (GUVs). To allow them to visualize changes in voltage, they stained GUV membranes with a dye that changes color in response to changes in electrical charge. Then, they put GUVs in the same vessel as lab-made condensates and photographed their interactions under the microscope.

They showed that when the condensates and GUVs collided, it caused a local change in the GUV membranes’ electrical charge at their point of contact.

“That’s one of the interesting things and novel things about this, because cell membrane voltage has traditionally been considered in terms of a larger scale property,” says Deniz. “Local changes in membrane potential could have important biological implications, for example, for the function of ion channels and other membrane proteins that are regulated by voltage.”

By varying the chemical makeup of the condensates, the researchers showed that the more electrical charge a condensate carried, the bigger its impact on cell membrane voltage. They also found that the shape of the condensates appeared to be correlated with variations in the voltage change.

“In some instances, the voltages induced are quite substantial in magnitude—on the same scale as voltage changes in nerve impulses,” says Gurunian.

Future directions and implications

More tests are needed to understand the precise mechanisms by which condensates cause these electrical changes, the researchers say, and to investigate the phenomenon’s impact on cellular function.

“Now that we know that condensates can locally induce these voltages, the next step is to test whether this novel physics is functionally important for cells and organisms,” says Deniz.

“If we see functional consequences, it will not only tell us something new about cell biology, but it might also help scientists engineer therapeutics in the future.”

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