Regulated proteolysis controls mucoid conversion in Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Alginate overproduction in Pseudomonas aeruginosa causes mucoid conversion, a negative prognostic indicator in cystic fibrosis.
• The ECF sigma factor AlgU and its anti-sigma factor MucA are key regulators of alginate biosynthesis.

Purpose of the Study:

• Identify novel positive regulators of alginate biosynthesis in Pseudomonas aeruginosa.
• Elucidate the regulatory mechanism involving AlgU, MucA, and newly identified factors.

Main Methods:

• Global mariner transposon screening to identify new regulators.
• Analysis of gene expression and protein levels.
• Site-directed mutagenesis to investigate critical amino acid residues.

Main Results:

• Identified three positive regulators: PA4033 (MucE), PA3649 (MucP), and AlgW.
• MucE overexpression, driven by transposon insertion, caused mucoid conversion.
• MucE accumulation increased AlgU activity and decreased MucA levels.
• Specific C-terminal amino acids (WVF) of MucE and proteases AlgW and MucP are essential for mucoid conversion.
• AlgW's PDZ domain is crucial for signal transduction, similar to E. coli DegS.

Conclusions:

• MucE, MucP, and AlgW are positive regulators of Pseudomonas aeruginosa alginate production.
• The AlgU regulatory pathway shares similarities with E. coli sigma(E) but involves distinct signaling components.
• Understanding these regulators offers potential therapeutic targets for cystic fibrosis treatment.