Sep 222011
Dog Shark

Image by tollers via Flickr

Scientists have known for some time that dogfish sharks, like the one pictured up top, naturally produce a broad-spectrum antibiotic called squalamine in their livers. Now, new research into the cellular function of squalamine reveals how it also confers a broad-spectrum antiviralbenefit for the shark — one we humans could benefit from, as well.

Many sharks demonstrate a natural immunity to numerous forms of viral infection, even in the absence of a rapidly adapting immune system like ours. This observation got University of Pennsylvania geneticist Michael Zasloff thinking: what if researchers could identify the molecule (or molecules) responsible for conferring this antiviral characteristic?

“I was interested in sharks because of their seemingly primitive but effective immune system.” Explains Zasloff. “No-one could explain why the shark was so hardy.”

The research team figured that a good place to start looking would be the protein squalamine. Since its discovery in the livers of dogfish sharks 1993, squalamine has received quite a bit of attention for its antibacterial and antitumorigenic properties.

Some of the most recent research surrounding squalamine has revealed that it is also capable of displacing proteins commonly found anchored in cell membranes. (A cell’s membrane is the barrier separating its insides from the outside environment, including other cells.) Zasloff hypothesized that squalamine’s ability to displace membrane-anchored proteins could grant it antiviral properties, as well.

Zasloff and his colleagues explain their reasoning in the latest issue of Proceedings of the National Academy of Sciences:

Many viruses enter cells through engagement of [membrane-anchored proteins]…Displacement of key proteins anchored through electrostatic forces (of host or viral origin) from the cytoplasmic face of the plasma membrane might interfere with [viral] entry, protein synthesis, virion assembly, virion budding , or other steps in the viral replication cycle.

In other words, the researchers hypothesized that squalamine could interfere with a virus’s ability to not only enter and infect healthy cells, but to replicate and propagate, as well.

And the researchers’ results suggest that squalamine does exactly that. In tissue cultures and animal models, squalamine was shown to control — and, in some cases, cure — infections by hepatitis B, hepatitus D, yellow fever, dengue virus, Eastern equine encephalitus virus, and murine cytomegalovirus.

Read more . . .

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