Newswise — 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.
Gessain, G., et al. 2015. J. Exp. Med. doi:10.1084/jem.20141406
About The Journal of Experimental MedicineThe Journal of Experimental Medicine (JEM) is published by The Rockefeller University Press. All editorial decisions on manuscripts submitted are made by active scientists in conjunction with our in-house scientific editors. JEM content is posted to PubMed Central, where it is available to the public for free six months after publication. Authors retain copyright of their published works and third parties may reuse the content for non-commercial purposes under a creative commons license. For more information, please visit www.jem.org .
MEDIA CONTACTRegister for reporter access to contact details
Journal of Experimental Medicine, Vol. 212, No. 2