Wolloscheck David, Krishnamoorthy Ganesh, Nguyen Jennifer, Zgurskaya Helen I
Department of Chemistry and Biochemistry, University of Oklahoma , 101 Stephenson Parkway, Norman, Oklahoma 73019, United States.
ACS Infect Dis. 2018 Feb 9;4(2):185-195. doi: 10.1021/acsinfecdis.7b00160. Epub 2017 Nov 10.
Pseudomonas aeruginosa is an important human pathogen, the physiology and virulence of which are under the control of quorum sensing signals. These signals often have dual roles, functioning as toxins to some cells and as oxidative-stress protectors for their producer cells. Hence, their internal and external concentrations should be tightly controlled. In this study, we analyzed the interplay between the multidrug efflux transporters MexEF-OprN and MexG/HI-OpmD in quorum sensing of P. aeruginosa. We found that the two transporters have overlapping substrate specificities but different efficiencies. When overproduced, both MexEF-OprN and MexG/HI-OpmD provide clinical levels of resistance to diverse fluoroquinolones and protect P. aeruginosa against toxic phenazines. However, this similarity is enabled by synergistic interactions with the outer membrane. In hyperporinated cells, MexG/HI-OpmD is saturated by much lower concentrations of fluoroquinolones but is more efficient than MexEF-OprN in efflux of phenazines. Unlike MexEF-OprN, mutational inactivation of MexG/HI-OpmD reduces the levels of pyocyanin and makes P. aeruginosa cells hypersusceptible to phenazines. Our results further show that MexG binds pyocyanin, physically associates with MexHI, and represses the activity of the transporter, revealing a negative regulatory role of this protein. We conclude that differences in kinetic properties of transporters are critical to maintain proper intra- and extracellular concentrations of phenazines and other signaling molecules and that MexG/HI-OpmD controls the steady state in the synthesis and secretion of phenazines.
铜绿假单胞菌是一种重要的人类病原体，其生理学和毒力受群体感应信号的控制。这些信号通常具有双重作用，对某些细胞起毒素作用，而对其产生细胞则起氧化应激保护剂的作用。因此，它们在细胞内和细胞外的浓度应受到严格控制。在本研究中，我们分析了多药外排转运蛋白MexEF - OprN和MexG/HI - OpmD在铜绿假单胞菌群体感应中的相互作用。我们发现这两种转运蛋白具有重叠的底物特异性，但效率不同。当过量表达时，MexEF - OprN和MexG/HI - OpmD都能提供对多种氟喹诺酮类药物的临床耐药水平，并保护铜绿假单胞菌免受有毒吩嗪的侵害。然而，这种相似性是通过与外膜的协同相互作用实现的。在高孔化细胞中，MexG/HI - OpmD被低得多的氟喹诺酮类药物浓度饱和，但在吩嗪外排方面比MexEF - OprN更有效。与MexEF - OprN不同，MexG/HI - OpmD的突变失活会降低绿脓菌素的水平，并使铜绿假单胞菌细胞对吩嗪高度敏感。我们的结果进一步表明，MexG结合绿脓菌素，与MexHI物理结合，并抑制转运蛋白的活性，揭示了该蛋白的负调控作用。我们得出结论，转运蛋白动力学特性的差异对于维持吩嗪和其他信号分子在细胞内和细胞外的适当浓度至关重要，并且MexG/HI - OpmD控制着吩嗪合成和分泌的稳态。
