A Bacterial Quorum Sensing Molecule Elicits a General Stress Response in Saccharomyces cerevisiae.

Bacteria assess their population density through a chemical communication mechanism termed quorum sensing, in order to coordinate group behavior. Most research on quorum sensing has focused primarily on its role as an intraspecies chemical signaling mechanism that enables the regulation of certain phenotypes through targeted gene expression. However, in recent years several seminal studies have revealed important phenomena in which quorum sensing molecules appear to serve additional roles as interspecies signals that may regulate microbial ecology. In this study, we asked whether the budding yeast Saccharomyces cerevisiae can sense chemical signals from prokaryotes. When exposed to a variety of quorum sensing molecules from different bacterial species and from Candida albicans we found that N-(3-oxododecanoyl)-L-homoserine lactone (C12) from the opportunistic human pathogen Pseudomonas aeruginosa induces a remarkable stress response in yeast. Microarray experiments confirmed and aided in interpreting these findings, showing a unique and specific expression pattern that differed significantly from the response to previously described stress factors. We further characterized this response and report preliminary findings on the molecular basis for the recognition of C12 by the yeast.

Immunoediting role for major vault protein in apoptotic signaling induced by bacterial N-acyl homoserine lactones.

The major vault protein (MVP) mediates diverse cellular responses, including cancer cell resistance to chemotherapy and protection against inflammatory responses to Pseudomonas aeruginosa Here, we report the use of photoactive probes to identify MVP as a target of the N-(3-oxo-dodecanoyl) homoserine lactone (C12), a quorum sensing signal of certain proteobacteria including P. aeruginosa. A treatment of normal and cancer cells with C12 or other N-acyl homoserine lactones (AHLs) results in rapid translocation of MVP into lipid raft (LR) membrane fractions. Like AHLs, inflammatory stimuli also induce LR-localization of MVP, but the C12 stimulation reprograms (functionalizes) bioactivity of the plasma membrane by recruiting death receptors, their apoptotic adaptors, and caspase-8 into LR. These functionalized membranes control AHL-induced signaling processes, in that MVP adjusts the protein kinase p38 pathway to attenuate programmed cell death. Since MVP is the structural core of large particles termed vaults, our findings suggest a mechanism in which MVP vaults act as sentinels that fine-tune inflammation-activated processes such as apoptotic signaling mediated by immunosurveillance cytokines including tumor necrosis factor-related apoptosis inducing ligand (TRAIL).

Species selective diazirine positioning in tag-free photoactive quorum sensing probes.

The synthesis and comparison of activities of 'tag-free' probes with diazirines at various positions are described. Remarkable differences in their effects on P. aeruginosa and on human bronchial epithelial cells were observed, supporting the efforts to isolate and identify receptors for N-acyl homoserine lactones.

Diazirine based photoaffinity labeling.

Diazirines are among the smallest photoreactive groups that form a reactive carbene upon light irradiation. This feature has been widely utilized in photoaffinity labeling to study ligand-receptor, ligand-enzyme and protein-protein interactions, and in the isolation and identification of unknown proteins. This review summarizes recent advances in the use of diazirines in photoaffinity labeling.

Synthesis and validation of a probe to identify quorum sensing receptors.

The synthesis and evaluation of a 'tag-free' probe to isolate and identify receptors for N-acyl homoserine lactones is described.