Pseudomonas aeruginosa ExsA Regulates a Metalloprotease, ImpA, That Inhibits Phagocytosis of Macrophages

Abstract

Pseudomonas aeruginosa is an opportunistic pathogenic bacterium whose type III secretion system (T3SS) plays a critical role in acute infections. Translocation of the T3SS effectors into host cells induces cytotoxicity. In addition, the T3SS promotes the intracellular growth of P. aeruginosa during host infections. The T3SS regulon genes are regulated by an AraC-type regulator, ExsA. In this study, we found that an extracellular metalloprotease encoded by impA (PA0572) is under the regulation of ExsA. An ExsA consensus binding sequence was identified upstream of the impA gene, and direct binding of the site by ExsA was demonstrated via an electrophoretic mobility shift assay. We further demonstrate that secreted ImpA cleaves the macrophage surface protein CD44, which inhibits the phagocytosis of the bacterial cells by macrophages. Combined, our results reveal a novel ExsA-regulated virulence factor that cooperatively inhibits the functions of macrophages with the T3SS.

Ezrin and CD44 participate in the internalization process of Coxiella burnetii into non‐phagocytic cells

“…We observe that knockdown of CD44 reduces the levels of internalization of C. burnetii without affecting bacterial adhesion to HeLa cells that could depend mainly on the α v β 3 integrins. Our results are consistent with a recent work which demonstrated that CD44 knockdown in macrophages produces lower levels of internalization of S. aureus without affecting its adhesion to the cell (Li et al., 2018) or inhibits phagocytosis of P. aeruginosa (Tian et al., 2019).…”

Structural evidence for a proline-specific glycopeptide recognition domain in an O-glycopeptidase

“…PA0572 from Pseudomonas aeruginosa was identified as a protease by its ability to cleave glycoproteins involved in leukocyte homing, thus compromising immune function and leading to the enzyme being called IMPa (immunomodulating protease of Pseudomonas aeruginosa) (Bardoel et al, 2012). Through its ability to cleave CD44, IMPa also inhibits phagocytosis (Tian et al, 2019). This secreted effector, therefore, is a potentially important factor in the hostpathogen interaction.…”

The Psychrotrophic Pseudomonas lundensis, a Non- aeruginosa Pseudomonad, Has a Type III Secretion System of the Ysc Family, Which Is Transcriptionally Active at 37°C

“…Preliminary analysis of scanning the genome for the conserved ExsA-binding motif ( 41 ) identified four putative type III effectors (DNA polymerase IV, TonB-dependent receptor, heme-binding protein, and response regulator transcription factor) (data not shown). However, it is important to note that ExsA has also been reported to regulate the expression of non-T3SS genes, including the metalloprotease impA and other secretory proteins in P. aeruginosa ( 42 ). Thus, it remains to be determined biochemically if there are additional T3SS effector proteins in P. lundensis , but there are some potential targets.…”