The mechanistic basis of the membrane-permeabilizing activities of the virulence-associated protein A (VapA) from...

Area of Science:

• Microbiology
• Biophysics
• Cell Biology

Background:

• Pathogenic Rhodococcus equi utilizes virulence-associated protein A (VapA) to survive within host macrophages.
• VapA disrupts phagosome and lysosome function, including membrane integrity and acidification, crucial for bacterial proliferation.

Purpose of the Study:

• To elucidate the biophysical mechanisms by which VapA interacts with and perturbs model cell membranes.
• To understand the role of VapA-mediated membrane permeabilization in Rhodococcus equi pathogenesis.

Main Methods:

• Utilized biophysical techniques including biosensors and atomic force microscopy (AFM) to study VapA-membrane interactions.
• Investigated VapA's effects on lipid monolayers and bilayers under varying pH and lateral pressure conditions.

Main Results:

• VapA integrates into membranes in a pH-dependent manner, decreasing membrane fluidity and increasing surface heterogeneity.
• VapA induces the formation of novel microstructured membrane domains, with significant structural changes observed at acidic pH.
• VapA-mediated membrane permeabilization is distinct from classical pore-forming mechanisms and is influenced by lipid composition, pH, and protein concentration.

Conclusions:

• VapA's interaction with membranes is a multi-step process involving binding, domain formation, and pH-specific structural changes.
• These VapA-induced membrane alterations are critical for Rhodococcus equi's survival and multiplication within the phagolysosomal environment.
• The unique mechanism of VapA action offers insights into host-pathogen interactions and potential therapeutic targets.