INLA

InlA, also known as internalin A, is a surface-anchored protein of the bacterium Listeria monocytogenes. It belongs to the internalin family and is encoded by the inlA gene within the Listeria pathogenicity island-1 (LIPI-1). The protein is anchored to the bacterial cell wall via an LPXTG motif and sortase A, exposing a large extracellular region rich in leucine-rich repeats that mediate interaction with host cells.

InlA mediates invasion of non-phagocytic epithelial cells by binding to the host cell receptor E-cadherin. This interaction promotes receptor-mediated endocytosis and bacterial uptake, enabling traversal of the intestinal barrier and dissemination to deep tissues. The InlA–E-cadherin interaction is species-specific; human E-cadherin is a preferred receptor, whereas murine E-cadherin binds poorly, a limitation overcome in mouse models via humanized E-cadherin alleles.

Expression of InlA is regulated by the transcriptional activator PrfA and is typically higher in intracellular environments. InlA is part of LIPI-1, which also encodes other virulence factors such as InlB and listeriolysin O. InlA variants with premature stop codons or downregulated expression are associated with attenuated virulence and can be found in some food isolates.

InlA is a focus of studies on Listeria pathogenesis and host–pathogen interactions, with relevance to infection control, vaccine design, and understanding tissue tropism.