Natures wonders: how giardia attack human guts (Introduction)

by David Turell @, Tuesday, January 30, 2018, 01:09 (683 days ago) @ David Turell

By imitating our own proteins to get food from injured cells:

"If you've ever sipped some untreated tap water while you were abroad on vacation, you may have returned home with an unexpected souvenir: diarrhea.
In most cases, there's a good chance you can blame a resilient, waterborne parasite called Giardia, which is responsible for one of the most common gastrointestinal illnesses in the world. Giardiasis infects an estimated 2 percent of people in high-income countries and 33 percent of people in developing countries.


"The first family of proteins that jumped out to the researchers are called proteases, proteins that help the human body digest other proteins, Tyler told Live Science.
"However, if you put them onto a cell, they'll eat through the cell lining and cause damage," Tyler said. "So, we knew those were probably part of the story."

"The second family of proteins was more surprising. "There was a large group that looked very much like human proteins we call tenascins," Tyler said. "We believe that these are structural and functional mimics that've evolved independently in the parasite to do the same things that our proteins do."

"In the human body, tenascins work as part of your cellular remodeling crew. "Tenascins are part of our extracellular matrix, which is present between cells to glue them together and make tissues," Tyler said.

"'Most of the proteins in the extracellular matrix are there to bind the cells together, but when you need to move cells around and remodel tissue, then you need proteins that can unstick them," he said. "That's what tenascins do: unstick cells."

"Combined with proteases, these tenascin-look-alike proteins could pack a powerful one-two punch in the host's intestinal cells. "With the protease, these parasites are pulling the cells of the intestine apart in order to get nutrients from the host," Tyler said, "and with the tenascins, they're stopping the cells from coming back together. So, they've essentially made these human proteins to keep the flow of nutrients open."


"'The majority of damage [from Giardia infection] probably comes from accompanying bacteria that can get into that environment and start to proliferate on the foodstuffs that are released between the cellular junctions," Tyler said. "Because people have different bacteria in their guts than one another, some [people] may have more bacteria that causes an inflammatory reaction, or they may have immune systems that react in a more inflammatory way. That probably is the difference between those people who experience severe symptoms and those people who don't.'"

Comment: How Giardia learned to create these mimicking proteins while in the human gut is unknown. It must have taken a period of time to adapt to production of these active proteins, before being able to eat in the gut. Perhaps they just passed through while learning. Giardia are carried by grazing animals in the wild, who while defecating in the waterways pass it on to anyone who takes a drink. It is obvious they learned how to do it.

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