exoA

The exoA gene encodes a protein that is a key component of the type III secretion system in Pseudomonas aeruginosa. This protein, often referred to as ExoS, is a bifunctional toxin that can exhibit both GTPase-activating protein (GAP) and ADP-ribosyltransferase (ADPRT) activities. These activities contribute to the virulence of P. aeruginosa by interfering with host cell signaling pathways, particularly those involving Rho family GTPases like Rho, Rac, and Cdc42.

ExoS plays a significant role in modulating the actin cytoskeleton of host cells, leading to cellular disruption and facilitating bacterial invasion and survival within the host. Its GAP activity promotes the inactivation of Rho GTPases, which can lead to altered cell morphology, detachment from the extracellular matrix, and impaired immune cell function. The ADPRT activity of ExoS can modify other host proteins, further contributing to cellular dysfunction.

The expression and secretion of ExoS are tightly regulated by the type III secretion system, allowing P. aeruginosa to deliver this effector protein directly into the cytoplasm of host cells during infection. The presence and activity of exoA are thus critical for the pathogenesis of P. aeruginosa in various infections, including pneumonia, cystic fibrosis lung infections, and wound infections. Understanding the function of exoA and its encoded protein ExoS provides insights into bacterial virulence mechanisms and potential targets for therapeutic intervention.