Abstract
Some bacterial proteins involved in cell division and oxidative phosphorylation are tightly bound to cardiolipin. Cardiolipin is a non-bilayer anionic phospholipid found in bacterial inner membrane. It forms lipid microdomains located at the cell poles and division plane. Mechanisms by which microdomains are affected by membrane-acting antibiotics and the impact of these alterations on membrane properties and protein functions remain unclear. In this study, we demonstrated cardiolipin relocation and clustering as a result of exposure to a cardiolipin-acting amphiphilic aminoglycoside antibiotic, the 3′,6-dinonyl neamine. Changes in the biophysical properties of the bacterial membrane of P. aeruginosa, including decreased fluidity and increased permeability, were observed. Cardiolipin-interacting proteins and functions regulated by cardiolipin were impacted by the amphiphilic aminoglycoside as we demonstrated an inhibition of respiratory chain and changes in bacterial shape. The latter effect was characterized by the loss of bacterial rod shape through a decrease in length and increase in curvature. It resulted from the effect on MreB, a cardiolipin dependent cytoskeleton protein as well as a direct effect of 3′,6-dinonyl neamine on cardiolipin. These results shed light on how targeting cardiolipin microdomains may be of great interest for developing new antibacterial therapies.
Highlights
In previous studies, we showed that one of the most promising amphiphilic aminoglycoside derivatives synthesized by Decout’s team[13,14,15], the 3′,6-dinonyl neamine had bactericidal effect on a wide range of wild type Gram-negative and Gram-positive bacteria as well as resistant strains
We report how a promising amphipihilic aminoglycoside derivative, the 3′,6-dinonyl neamine, by targeting cardiolipin-bacterial microdomains mainly located at the cell poles, leads to microdomains disassembly into cardiolipin clusters and relocation of cardiolipin domains as confirmed by using membrane model systems mimicking inner membrane of P. aeruginosa
When cardiolipin was exogeneously added, more complex processes than it seems at first sight could appear, including (i) potential effect on cardiolipin synthases, (ii) potential displacement of dinonyl neamine (diNn) from its primarily binding to LPS16, (iii) ration of cardiolipin located within the outer and the inner membranes, in relation with lipid transfer and with the activity of proteins involved in cardiolipin transfer from the inner membrane to the outer membrane like PbgA in Gram-negative bacteria[48] and lastly, (iv) equilibrium between the interaction of cardiolipin with the diNn and with proteins depending upon cardiolipin and involved in bacterial shape and division
Summary
Micheline El Khoury[1], Jitendriya Swain[1], Guillaume Sautrey[1,4], Louis Zimmermann[2], Patrick Van Der Smissen[3], Jean-Luc Décout2 & Marie-Paule Mingeot-Leclercq[1]. At 5 μM (around 0.75 MIC) (Fig. 7c), diNn induced severe morphological defects characterized by membrane blebbing (regions with high membrane curvature), loss of rod morphology, increase in overall membrane curvature, and depressions on the surface The appearance of these highly curved microscopic regions could be the consequence of cardiolipin redistribution, fluidity changes and enhancement in lipid phase separation. Based on the decrease of fluidity induced by diNn and by the fact MreB, an actin homolog protein associated with lipids that are in fluid, liquid-disordered state[49], we questioned the potential role of this cardiolipin-interacting protein in the effect afforded by diNn. MreB is a curvature dependent protein[50] that interacts with bacterial membranes via its N-terminal amphipathic helix[51, 52] MreB localization determines the basic rod shape, whereas MreB dynamics promotes robust rod-like morphogenesis and prevents these local defects from being amplified[53, 54]. When cardiolipin was exogeneously added, more complex processes than it seems at first sight could appear, including (i) potential effect on cardiolipin synthases, (ii) potential displacement of diNn from its primarily binding to LPS16, (iii) ration of cardiolipin located within the outer and the inner membranes, in relation with lipid transfer and with the activity of proteins involved in cardiolipin transfer from the inner membrane to the outer membrane like PbgA in Gram-negative bacteria[48] and lastly, (iv) equilibrium between the interaction of cardiolipin with the diNn and with proteins depending upon cardiolipin and involved in bacterial shape and division
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