The outer membrane protein OprQ and adherence of Pseudomonas aeruginosa to human fibronectin

Outer membrane proteins of the Gram-negative organism Pseudomonas aeruginosa play a significant role in membrane permeability, antibiotic resistance, nutrient uptake, and virulence in the infection site. In this study, we show that the P. aeruginosa outer membrane protein OprQ, a member of the OprD superfamily, is involved in the binding of human fibronectin (Fn). Some members of the OprD subfamily have been reported to be important in the uptake of nutrients from the environment. Comparison of wild-type and mutant strains of P. aeruginosa revealed that inactivation of the oprQ gene does not reduce the growth rate. Although it does not appear to be involved in nutrient uptake, an increased doubling time was reproducibly observed with the loss of OprQ in P. aeruginosa. Utilizing an oprQ-xy/E transcriptional fusion, we determined that the PA2760 gene, encoding OprQ, was upregulated under conditions of decreased iron and magnesium. This upregulation appears to occur in early exponential phase. Insertional inactivation of PA2760 in the P. aeruginosa wild-type background did not produce a significant increase in resistance to any antibiotic tested, a phenotype that is typical of OprD family members. Interestingly, the in trans expression of OprQ in the Delta oprQ PAO1 mutant resulted in increased sensitivity to certain antibiotics. These findings suggest that OprQ is under dual regulation with other P. aeruginosa genes. Intact P. aeruginosa cells are capable of binding human Fn. We found that loss of OprQ resulted in a reduction of binding to plasmatic Fn in vitro. Finally, we present a discussion of the possible role of the P. aeruginosa outer membrane protein OprQ in adhesion to epithelial cells, thereby increasing colonization and subsequently enhancing lung destruction by P. aeruginosa.