Protein that enables transport of cargo between cells

Scientists reveal the secret to the structural integrity of tiny particles that transport cargo from one cell to another through blood vessels and body fluids: Special proteins that maintain their cell membranes as they deliver changing electrical impulses in different biological environments whole.

These particles, known as extracellular vesicles, are considered attractive carrier models for new drug therapies. But until now, researchers haven’t fully understood how they work.

In a new study, a team led by Ohio State University Medical researchers determined that these vesicles contain ion channels—proteins that open corridors that allow electrical charges to pass through the protective outer membrane that keeps the contents in and Necessary steps for conditions to be internally stable.

Animal experiments have also shown that ion channels can affect cargo, meaning that proteins are important not only to the structure of extracellular vesicles (EVs), but also to their function. The researchers compared the effects of RNA molecules delivered by EVs with and without membrane proteins on mice with heart disease. Only molecules carried by EVs with ion channels can repair heart damage.

Harpreet Singh, professor of physiology and cell biology, and Mahmood Khan, professor of emergency medicine at The Ohio State University College of Medicine, co-led the study.

“We didn’t just find ion channels in these vesicles. We documented functional ion channels for the first time ever,” Singer said. “From forming a simple basic hypothesis that these vesicles should have ion channels, to showing that these vesicles will contain different substances that can protect or harm your cells – in this case, the heart – We’ve told the whole story.

The paper was published on January 2 in nature communications.

Extracellular vesicles carry proteins and other molecules from donor cells to recipient cells to alter physiological and biological responses. In addition to facilitating cell communication and maintaining cellular homeostasis, these particles have been implicated in immune responses, viral infectivity, cardiovascular disease, cancer, and neurological disorders.

Based on his expertise in ion channel research, Singer predicted that EVs would have to have ion channels to safely transport molecules from inside the cell to the extracellular environment and back to another type of cell. Otherwise, as the ions ebb and flow in positive and negative charges in different environments, their membranes may rupture—caused by osmotic pressure or shock-induced water flow.

“We know from our experience and all the great work that’s been done over the past hundred years that ion channels are very, very important for maintaining any structure that has a membrane,” Singer said.

Take the electrolyte potassium, for example. It is the most abundant positively charged ion within cells, but its concentration is 30 times lower in the extracellular environment.

“Suddenly, the extracellular vesicle goes from a high potassium concentration to a low potassium concentration. What happens if the ion balance is not maintained? You get an osmotic shock,” he said.

In this work, the researchers isolated mouse EVs provided by Khan, who is also director of basic and translational research in the Department of Emergency Medicine and whose lab focuses on repairing damaged heart muscle through stem cell therapy.

Because these particles are so small, the scientists created a technique called near-field electrophysiology to record electrical currents in EV membranes. This method determines the presence of calcium-activated large conductance potassium channels (BKCa).

Subsequently, they isolated EVs from normal mice and knockout mice lacking the gene encoding the BK potassium channel, and found that the cargo in the EVs of the knockout mice was greatly different in number and size, suggesting that the BKCa channel is functional sexual effect.

Some small RNA fragments found in normal mouse vesicles that regulate gene activation help protect the heart from oxidative stress, Khan said. EVs from mice lacking the BK channel gene contain a distinct set of segments called microRNAs.

This discovery led to animal experiments in Khan’s lab, in which EVs from normal mice and mice lacking the BK gene were injected into mice with heart disease.

“Electric vehicles from wild animals can protect the heart,” Singh said. “EVs from knockout mice failed to properly protect the heart and, in fact, made it worse. Bad microRNAs were enriched in vesicles without channels.

“Is it because the packaging is different, the cargo is different, or is it because vesicles without channels cannot survive? This is an open question and we are working hard to solve it.

Another major unanswered question is the identification of proteins called transporters that maintain ion balance when vesicles transition from the extracellular environment back into the cell with high potassium concentrations.

In addition to increasing basic knowledge about extracellular vesicles, this work has the potential to advance the development of their therapeutic uses, Singer said.

“People talk about loading these vesicles with charged molecules—whether they’re drugs, RNA proteins, or something else. If you load them with charged molecules and you don’t manage ion homeostasis, you’re going to have some kind of consequence,” he said. “That’s our focus, if you’re bioengineering electric vehicles, you have to have the right combination of ion channels and transporters.”

This work was supported by the Ohio State University President’s Predoctoral Fellowship, Department of Physiology and Cell Biology, and Graduate School Alumni Grants; American Heart Association; National Heart, Lung, and Blood Institute; National Institute of Arthritis and Musculoskeletal and Skin Diseases ; and the National Center for Advancing Translational Sciences.

Other co-authors include Shridhar Sanghvi, Divya Sridharan, Parker Evans, Julie Dougherty, Kalina Szteyn, Denis Gabrilovich, Mayukha Dyta, Jessica Weist and Lianbo Yu of Ohio State University; Sandrine Pierre, Marshall University; Shubha Gururaja Rao, Ohio Northern University; Dan Halm, Wright State University; and Tingting Chen, Panagiotis Athanasopoulos and Amalia Dolga, University of Groningen.