Tech UPTechnologyThe origin of consciousness could be in an ancient...

The origin of consciousness could be in an ancient virus

There is a lot about our genome, and how it was built, rebuilt, and modified over time that we don’t yet know. In recent years, however, it is clear that we have had on our journey. In this case, a protein to which we owe the communication between nerve cells and, with it, some of our more advanced cognitive abilities, could come from a past virus.

Once upon a time, there was a world in which stealthy virus-like creatures or virus-like ancestors managed to incorporate their genetic material into humans and become hidden passengers. If in 2015 a study from the University of Lund (Sweden) showed the effect of a virus from millions of years ago on our brain , now a team of scientists from the University of Utah (USA) shows a vital protein for the memory consolidation that behaves like a virus.

A protein that comes from an archaic virus

The protein, called Arc , has properties similar to those used by viruses to infect host cells, and it originated from a chance evolutionary event that occurred hundreds of millions of years ago.

The possibility that virus-like proteins could underlie a novel form of cell-to-cell communication in the brain could change our understanding of how memories are made , according to Jason Shepherd, leader of the work published in the journal Cell.

Shepherd observed that the Arc structures closely resembled the retrovirus, HIV. “At the time, we didn’t know much about the molecular function or evolutionary history of Arc,” says Shepherd, who has researched the protein for 15 years. “To be honest, I had almost lost interest in the protein. After looking at the capsids, we knew we had something interesting .”

Previous research had shown that mice lacking T he forgot Arc things they had learned about 24 hours earlier. Also, their brains lacked plasticity. There is a window of time early in life in which the brain is like a sponge, easily absorbing new knowledge and skills. Without Arc, this window never opens.


Scientists had never considered that the mechanisms responsible for acquiring knowledge could come from such particular origins. Now, the work of these scientists has raised this
intriguing possibility.

Seeing Arc’s unusual propensity to form virus-like structures, Shepherd again analyzed the protein sequence, discovering that the code regions were similar to those of viral capsids. An essential tool for viral infection, as the capsids carry the genetic information of the virus and transmit it from one cell to another in its victim.

Since Arc looks like a viral protein, they designed a series of experiments to test whether it also acted like one. For example, after viruses have invaded host cells, they emerge ready to infect again. It seems that Arc works in a similar way. The scientists gathered Arc that had been released from mouse neurons and determined that the proteins and their cargo could be absorbed by another set of neurons. Unlike viruses, activation of neurons mobilizes Arc, which triggers the release of capsids.

Arc’s similarity to retroviruses is also relevant, as they are excellent for infiltrating animals. Many viruses can incorporate their DNA into the host cell’s DNA. However, retroviruses are particularly good at integrating into the germ line, that is, a lineage of cells that pass DNA from generation to generation in a continuous line. Thus, once they infect a person, their DNA has the potential to spread through the sexual reproduction of the host.

 

“We entered this line of research knowing that Arc was special in many ways, but when we discovered that Arc could mediate RNA transport from cell to cell, we were speechless,” says Elissa. Pastuzyn, co-author of the study. “No other non-viral protein that we know of works in this way.”

 

Referencia: University of Utah. “The Neuronal Gene Arc Encodes a Repurposed Retrotransposon Gag Protein that Mediates Intercellular mRNA Transfer” online in Cell. 2018 DOI: DOI: 10.1016/j.cell.2017.12.024

 

Image credit: Elissa Pastuzyn / Chris Manfre

 

This image shows the neurons that took Arc and expressed the genetic material stored in it.

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