AI Article Synopsis
- Salmonella enterica uses two type III secretion systems (T3SS) for host cell interactions during infection, with the SPI2 system being crucial for its intracellular replication and survival in immune cells.
- Under acidic pH conditions, which mimic the phagosome environment, the T3SS shows increased protein secretion and higher levels of SsaC, a key protein for forming the secretin complex without an increase in gene expression.
- The study suggests that environmental factors not only influence gene expression of the SPI2 system but also enhance the assembly of a functional T3SS necessary for delivering effector proteins into the host cell.
Article Abstract
Salmonella enterica employs two type III secretion systems (T3SS) for interactions with host cells during pathogenesis. The T3SS encoded by Salmonella pathogenicity island 2 (SPI2) is required for the intracellular replication of Salmonella and the survival inside phagocytes. During growth in vitro, acidic pH is a signal that promotes secretion of proteins by this T3SS. We analyzed protein levels and subcellular localization of various T3SS subunits under in vitro conditions at acidic or neutral pH, inducing or ablating secretion, respectively. Growth at acidic pH resulted in higher levels of SsaC, a protein forming the outer membrane secretin, without increasing expression of the operon containing ssaC. Acidic pH also induced oligomerization of SsaC subunits, a prerequisite for a functional secretin pore. It has previously been described that environmental stimuli resembling the intraphagosomal habitat of Salmonella control the expression of SPI2 genes. Here we propose that such stimuli also modulate the assembly of a functional T3SS that is capable of translocation of effector proteins into the host cell.
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| http://dx.doi.org/10.1016/S0378-1097(03)00638-4 | DOI Listing |
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