PagN: a multifunctional outer membrane protein in Salmonella virulence and host interaction.

Salmonella utilizes multiple virulence factors to adhere to, invade, and replicate within host cells, ensuring systemic dissemination. Among these, the outer membrane protein PagN functions as both an adhesin and invasin, playing a central role in early infection stages and in establishing persistent intracellular populations. PagN expression is controlled by the PhoP/PhoQ two-component system and is specifically induced under host-related environmental conditions such as acidic pH, low magnesium concentration, and the presence of antimicrobial peptides—conditions typically encountered within the Salmonella-containing vacuole. Structural and functional studies demonstrate that PagN binds to host cell heparan sulfate proteoglycans and β1 integrins, mediating receptor-dependent invasion through a zipper-like mechanism independent of type III secretion systems. Deletion of pagN results in attenuated virulence and reduced bacterial replication in vivo, while its conservation across serovars underscores its critical role in Salmonella pathogenesis. Importantly, PagN elicits strong humoral and cellular immune responses in experimental models, supporting its potential as a promising vaccine antigen and diagnostic biomarker for broad-spectrum Salmonella detection and control.