A tail-specific protease is required for Legionella pneumophila intracellular multiplication

Abstract

Legionella pneumophila (Lp) is a Gram-negative bacterium found in natural and man-made water systems where it replicates within amoebas and ciliates. In humans, once inside the lungs, Lp replicates in alveolar macrophages and causes Legionnaires disease, a severe pneumonia. The Icm/Dot type IVb secretion system (T4SS) is a major virulence factor required for intracellular multiplication. The Icm/Dot system allows the secretion of effectors into the cytoplasm of the host cell. These effectors modify host cell vesicular trafficking and prevent maturation of the phagosome. The innate immune response is crucial in restricting Lp’s proliferation. TNF-α is one of the major cytokines involved in this process as it renders macrophages more resistant to Lp infection and induces apoptosis of Lp-infected macrophages. Tail-specific proteases (Tsp) are involved in tolerating thermal stress and in virulence. We have previously characterized the Tsp encoded by Lp, showing that it is important for surviving thermal stress and for infection of amoeba when a temperature change occurs during infection. Here, we demonstrate that Tsp is required for intracellular multiplication in macrophages. Absence of tsp is associated with higher production of TNF-α by macrophages in response to Lp infection. This effect is independent of the Icm/Dot secretion system.

Antibacterial Ingredients and Modes of the Methanol-Phase Extract from the Fruit of Amomum villosum Lour.

“…For instance, the RNA chaperone ProQ ( Vp_B2_28_2494 ) and tail-specific protease ( Vp_B2_28_2495 ) were repressed (0.353-fold and 0.42-fold). The former mediates sRNA-directed gene regulation in Gram-negative bacteria, while the latter is involved in tolerance to heat stress and virulence [ 43 , 44 ]. In addition, the DEG encoding a phage shock protein (Psp) G was greatly down-regulated (0.098-fold).…”