Scientists have observed a crucial protein for long-term memory acting like a HIV virus

A virus-like protein is believed to be at the root of how our brains store long-term memories – and it may stem back to an ancient infection that occurred hundreds of millions of years ago.

Researchers at the University of Utah Health have been studying a protein called activity-regulated cytoskeleton-associated protein, or Arc. Arc has long been believed to play a critical role in how long-term memories are created and stored in the brain, but little is known about its specific molecular function or evolutionary history.

In a study published in the journal Cell, the researchers show how they captured an image of the protein assembled into large structures with virus-like capsid shells. These structures look remarkably like those of the retrovirus HIV, and this led the scientists to investigate whether Arc is in fact an evolutionary remnant of a very old virus.

In their experiments, they found that several copies of Arc self-assembled into virus-like capsid shells and tucked their own genetic material (mRNA) inside. When the team added these capsids into mouse neurons, grown in a dish, the Arc proteins transferred their genetic cargo into the cells. Much like a virus, the Arc that had been released by mouse brain cells could then subsequently be taken up by another set of neurons, ‘infecting’ cells.

“We went into this line of research knowing that Arc was special in many ways, but when we discovered that Arc was able to mediate cell-to-cell transport of RNA, we were floored,” says the study’s lead author, postdoctoral fellow Elissa Pastuzyn. “No other non-viral protein that we know of acts in this way.”

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