Internalins are surface proteins found on ''

Listeria monocytogenes ''Listeria monocytogenes'' is the species of pathogenic bacteria that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. It can grow and reproduce inside the host' ...

''. They exist in two known forms, InlA and InlB. They are used by the bacteria to invade mammalian cells via

cadherin Cadherins (named for "calcium-dependent adhesion") are a type of cell adhesion molecule (CAM) that is important in the formation of adherens junctions to allow cells to adhere to each other . Cadherins are a class of type-1 transmembrane proteins, ...

s transmembrane proteins and Met receptors respectively. The exact role of these proteins and their invasiveness in vivo is not completely understood. In cultured cells, InlA is necessary to facilitate Listeria entry into human epithelial cells, while InlB is necessary for Listeria internalisation in several other cell types, including

hepatocyte A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in: * Protein synthesis * Protein storage * Transformation of carbohydrates * Synthesis of cholesterol, ...

fibroblast A fibroblast is a type of cell (biology), biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and plays a critical role in wound ...

s, and epithelioid cells. Internalins are mainly surface-exposed virulence factors present in a number of Gram-positive bacteria whose role ranges from recognition of cellular receptors to aid in pathogen entry to escape from autophagy.Structure of Internalin InlK from the Human Pathogen Listeria monocytogenes Listeria poses a particular threat to pregnant women because of its ability to cross the placental blood barrier through the combined binding of both InIA and InIB to host cells. Research has shown that only the combined binding of these two virulence factors allows the bacteria to cross that barrier. This is not the case in mice and guinea pigs whose cells only have affinity for InIB in mice and InIA in guinea pigs.Babinet, Charles, ''et al''. "Conjugated action of two species-specific invasion proteins for fetoplacental listeriosis." Nature 455.7216 (2008): 1114+. Academic OneFile. Web. 4 Dec. 2014. InlB blocks the action of cytotoxic T-cells and extents the infected cell lifespan.

References

Bacterial proteins Virulence factors {{Cell-biology-stub

See also

References