Two antagonistic response regulators control Pseudomonas aeruginosa polarization during mechanotaxis

Abstract

The opportunistic pathogen Pseudomonas aeruginosa adapts to solid surfaces to enhance virulence and infect its host. Type IV pili (T4P), long and thin filaments that power surface‐specific twitching motility, allow single cells to sense surfaces and control their direction of movement. T4P distribution is polarized to the sensing pole by the chemotaxis‐like Chp system via a local positive feedback loop. However, how the initial spatially resolved mechanical signal is translated into T4P polarity is incompletely understood. Here, we demonstrate that the two Chp response regulators PilG and PilH enable dynamic cell polarization by antagonistically regulating T4P extension. By precisely quantifying the localization of fluorescent protein fusions, we show that phosphorylation of PilG by the histidine kinase ChpA controls PilG polarization. Although PilH is not strictly required for twitching reversals, it becomes activated upon phosphorylation and breaks the local positive feedback mechanism established by PilG, allowing forward‐twitching cells to reverse. Chp thus uses a main output response regulator, PilG, to resolve mechanical signals in space and employs a second regulator, PilH, to break and respond when the signal changes. By identifying the molecular functions of two response regulators that dynamically control cell polarization, our work provides a rationale for the diversity of architectures often found in non‐canonical chemotaxis systems.

Spatial control of sensory adaptation modulates mechanosensing inPseudomonas aeruginosa

“…We have previously reported that pilHLOF and pilHGOF mimic the inactive (non-phosphorylated) and active (phosphorylated) state of PilH, respectively, as assessed by twitching motility, cAMP production, and localization assays 34 . We observed that pilHLOF phenocopied DpilH with increased ChpB asymmetric polar localization, while ChpB-mNG localization was comparable to WT in ensure that upon twitching reversals, PilJ at the new leading pole is methylated and "poised" to efficiently promote Pil-Chp signaling once mechanosensing occurs (Figure 7).…”

“…Nevan Krogan has a financially compensated consulting agreement with Maze Therapeutics. He is the President and is on the Board of Directors of Rezo The mechanical signals, sensed by PilJ, initiate a positive feedback loop that continuously activates the Pil-Chp system at the leading pole 33,34 . The lagging pole has fewer or no TFP and thus less activation of the Pil-Chp system.…”

“…Either spontaneously or upon mechanical perturbations, such as cell-cell collisions, the Pil-Chp system also inverts TFP polarity to induce reversals in twitching motility direction 33,34 . The twitching motility reversals are coordinated by the spatial organization of PilG and PilH, two antagonistic CheY-like response regulators that are downstream components of the Pil-Chp system 34 . Local Pil-Chp activation at the leading pole recruits and activates PilG through phosphorylation, which drives the positive feedback loop that sustains forward movement.…”

Evidence for the Type IV Pili Retraction Motor PilT as a Component of the Surface Sensing System inPseudomonas aeruginosa

“…Recent work by Yarrington, Limoli and colleagues shows that the PilJ likely detects phenyl soluble modulins via its periplasmic domain as a ligand to trigger signaling, a finding that strongly suggests that PilJ can function like a classic MCP (25). Others have recently uncovered the function of PilG and PilH in twitching motility and surface adaptation (26,27). In contrast, how surface engagement by T4P triggers cAMP signaling in a PilJ-dependent manner is still an open question.…”

Systematic mapping of chemoreceptor specificities forPseudomonas aeruginosa

“…Other three receptors McpB/Aer2, WspA, and PilJ are involved in an F7-type pathway of unknown function, an alternative cellular function pathway that mediates c-di-GMP synthesis, and type IV pili chemosensory pathway that is associated with twitching motility, respectively. The latter two pathways were found to perform mechano-and surface sensing rather than chemosensing (29)(30)(31). Of the 18 chemoreceptors with a periplasmic LBD that belong to the F6 pathway (28), ten have been functionality annotated (Table 1).…”