Biological complexity: cells exchange information (Introduction)

by David Turell , Friday, May 04, 2018, 20:38 (2176 days ago) @ David Turell
edited by David Turell, Friday, May 04, 2018, 20:51

They use vesicle packages to transmit information in the form of molecules:

https://www.quantamagazine.org/cells-talk-in-a-language-that-looks-like-viruses-20180502

"scientists discovered that cells could package their molecular information in what are known as extracellular vesicles. Like notes passed by children in class, the information packaged in an extracellular vesicle is folded and delivered to the recipient.

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"As scientists uncovered the secrets about how the vesicles are made, how they package their information and how they’re released, it became clear that there are powerful similarities between vesicles and viruses.

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"Extracellular vesicles and viruses, Margolis argues, are part of a continuum of membranous particles produced by cells. Between these two extremes are lipid-lined sacs filled with a variety of genetic material and proteins — some from hosts, some from viruses — that cells can use to send messages to one another.

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"Sending information in extracellular vesicles must have first appeared billions of years ago because even bacteria do it. “This idea of using a membrane-bound sac of information to transport between cells has been around a long time,”

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"One of the most striking pieces of evidence supporting Margolis and Gallo’s hypothesis is the recent discovery, widely reported in January, that a mammalian protein called Arc, which is implicated in learning and memory, is actually a repurposed retroviral protein. More important, Arc appears to be secreted from the synapses of neurons in extracellular vesicles. “These vesicles may be acting like a viral envelope,”

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"The field took off in 2006–2007 when a Swedish team and a joint American-European group independently discovered that exosomes and extracellular vesicles could carry several types of RNA. These included the messenger RNAs (mRNAs) that are intermediaries in the translation of DNA into proteins, as well as the small molecules called microRNAs that affect gene expression.

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“'Cell-cell communication is one of the most ancient mechanisms that makes us who we are,” Margolis said. “Since vesicles resemble viruses, the question of course is whether the first extracellular vesicles were primitive viruses and the viruses learned from extracellular vesicles or vice versa.”

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"What researchers have come to realize is that sometime millions of years ago, part of a retrovirus genome inserted itself into its host’s DNA, and that sequence was then passed on to countless generations of offspring. Around 8 percent of the human genome is ultimately derived from viruses. Although some of this DNA is, in fact, “junk,” scientists are learning that much of it plays a role in our biology.

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“'Although these viruses aren’t good for individuals, they provide the raw materials for new genes,” Shepherd says. “They’re a potential gold mine.”

In the case of Arc, the Gag-derived viral gene gave mammals a ready-made delivery device that could be packaged in an extracellular vesicle. A retrovirus packages RNA and moves it out of the cell, Feschotte said. “Arc has preserved many of these same functions.”

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"Because extracellular vesicles and exosomes can pass information between cells, scientists have begun to implicate them in everything from cancer to viral infections to basic neural functioning. To Lynne Maquat, an expert on retrotransposons at the University of Rochester, this process shows how parts of the genome we used to think of as junk actually have important functions.

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"Although it’s now clear that extracellular vesicles are far from simple cellular debris, and the viral genes littering our DNA aren’t exactly junk, researchers have only just begun to crack the mystery of what they can do."

Comment: Life runs on transmitting information. We are learning how. Too complex for chance development. Only design can do this.