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How listeria breaches the placenta

Date:
January 26, 2015
Source:
The Rockefeller University Press
Summary:
A gut bacterium called Listeria, which is often found in soft cheese, is known to present a risk to pregnant women. Researchers now show how Listeria uses distinct tactics to breach the intestine and the placenta, using a protein called PI3-kinase.
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In this image of tissue from the intestinal wall of healthy mice, PI3-K is detectable (green) along with the presence of internalin A receptors (red).
Credit: Gessain et al., 2015

A gut bacterium called Listeria (Listeria monocytogenes), which is often found in soft cheese, is known to present a risk to pregnant women. Listeria uses distinct tactics to breach the intestine and the placenta, using a protein called phosphoinositide-3 kinase (PI3-K), according to a study published in The Journal of Experimental Medicine.

Listeria has two proteins that help it cross mucosal tissue barriers. Both proteins, called internalins A and B, attach to tissue receptors and are needed for Listeria to invade the placenta, but protein A alone can propel Listeria across the intestine. What underlies these differences has remained unknown.

Tissue invasion by Listeria also requires the enzyme PI3-K. This enzyme is turned on by both of the Listeria's internalin proteins, but only the B protein has a built-in activation mechanism. Lecuit and colleagues at the Pasteur Institute in France have been able to visualize the activation of PI3-K, finding that this enzyme is very important for Listeria invasiveness via internalins. They uncover that PI3-K is perpetually turned on in intestinal cells, using only internalin A and rendering internalin B dispensable. The placenta, by contrast, has little to no inherent PI3-K activity, which is why passage of the bug through the placenta requires both A and B internalins.

These findings open up exciting new opportunities to examine whether other microbes -- in addition to those posing a pregnancy risk -- are capable of crossing host barriers using PI3-K activation, and whether this mechanism of bug invasion also occurs in other mucosal tissues and organs.


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Materials provided by The Rockefeller University Press. Note: Content may be edited for style and length.


Journal Reference:

  1. G. Gessain, Y.-H. Tsai, L. Travier, M. Bonazzi, S. Grayo, P. Cossart, C. Charlier, O. Disson, M. Lecuit. PI3-kinase activation is critical for host barrier permissiveness to Listeria monocytogenes. Journal of Experimental Medicine, 2015; DOI: 10.1084/jem.20141406

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The Rockefeller University Press. "How listeria breaches the placenta." ScienceDaily. ScienceDaily, 26 January 2015. <www.sciencedaily.com/releases/2015/01/150126095331.htm>.
The Rockefeller University Press. (2015, January 26). How listeria breaches the placenta. ScienceDaily. Retrieved May 23, 2017 from www.sciencedaily.com/releases/2015/01/150126095331.htm
The Rockefeller University Press. "How listeria breaches the placenta." ScienceDaily. www.sciencedaily.com/releases/2015/01/150126095331.htm (accessed May 23, 2017).

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