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A new antibiotic with potent activity targets MscL.

Iscla I, Wray R, Blount P, Larkins-Ford J, Conery AL, Ausubel FM, Ramu S, Kavanagh A, Huang JX, Blaskovich MA, Cooper MA, Obregon-Henao A, Orme I, Tjandra ES, Stroeher UH, Brown MH, Macardle C, van Holst N, Ling Tong C, Slattery AD, Gibson CT, Raston CL, Boulos RA - J. Antibiot. (2015)

Bottom Line: As predicted from in silico modeling, we show that the mechanism of action of compound 10 is at least partly dependent on interactions with MscL.Moreover we show that compound 10 cured a methicillin-resistant S. aureus infection in the model nematode Caenorhabditis elegans.Our work shows that compound 10, and other drugs that target MscL, are potentially important therapeutics against antibiotic-resistant bacterial infections.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, UT Southwestern Med Ctr, Dallas, TX, USA.

ABSTRACT
The growing problem of antibiotic-resistant bacteria is a major threat to human health. Paradoxically, new antibiotic discovery is declining, with most of the recently approved antibiotics corresponding to new uses for old antibiotics or structurally similar derivatives of known antibiotics. We used an in silico approach to design a new class of nontoxic antimicrobials for the bacteria-specific mechanosensitive ion channel of large conductance, MscL. One antimicrobial of this class, compound 10, is effective against methicillin-resistant Staphylococcus aureus with no cytotoxicity in human cell lines at the therapeutic concentrations. As predicted from in silico modeling, we show that the mechanism of action of compound 10 is at least partly dependent on interactions with MscL. Moreover we show that compound 10 cured a methicillin-resistant S. aureus infection in the model nematode Caenorhabditis elegans. Our work shows that compound 10, and other drugs that target MscL, are potentially important therapeutics against antibiotic-resistant bacterial infections.

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Microscopic analysis of S. aureus ATCC 29213 treated with 10 at different concentrations. (a) SEM images and size measurements of S. aureus with an inset showing the mean±95% confidence (n=12). Scale bar 1 μm and magnification ~ × 85 000. (b) The change in the ‘a' parameter (representing bacteria curvature) is shown with representative 3D AFM images beneath (3 μm × 3 μm × 700 nm). The top 25 nm of an AFM scan was used as a basis for a parabolic equation fit y=ax2+bx+c to show the change in curvature after treatment with the drug. The inset shows the mean±95% confidence (n=10 for 1 × MBC and n=20 for other concentrations). A full color version of this figure is available at The Journal of Antibiotics journal online.
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fig3: Microscopic analysis of S. aureus ATCC 29213 treated with 10 at different concentrations. (a) SEM images and size measurements of S. aureus with an inset showing the mean±95% confidence (n=12). Scale bar 1 μm and magnification ~ × 85 000. (b) The change in the ‘a' parameter (representing bacteria curvature) is shown with representative 3D AFM images beneath (3 μm × 3 μm × 700 nm). The top 25 nm of an AFM scan was used as a basis for a parabolic equation fit y=ax2+bx+c to show the change in curvature after treatment with the drug. The inset shows the mean±95% confidence (n=10 for 1 × MBC and n=20 for other concentrations). A full color version of this figure is available at The Journal of Antibiotics journal online.

Mentions: On the basis of the observations from the patch-clamp experiments and the titration experiments above, we hypothesized that the opening of the MscL channel caused by 10 might result in changes in the size and shape of bacterial cells. Low-magnification scanning electron microscopy (SEM) of S. aureus ATCC 6538 showed a decrease in bacterial density and biofilm formation, concurrent with an increase in the concentration of 10 (Supplementary Figure S3). Bacterial size measurements revealed that bacteria treated with 0.5 μg ml−1 were significantly wider than the control (Figure 3a). At concentrations of 10 >0.5 μg ml−1, there was a gradual but significant reduction in the size of the bacteria. Moreover, untreated S. aureus showed a round and firm geometry with distinct surface features, which become distorted with increasing drug concentrations. Atomic force microscopy (AFM) also revealed a statistically significant change in morphology of the uppermost 25 nm region of S. aureus (see Figure 3b for illustration). This region was observed to be of narrow parabolic geometry in the control sample, which then flattened as the drug concentration increased (Figure 3b). The AFM and SEM results support each other, as the latter width measurement is inversely proportional to the measurement of the parabolic curvature parameter ‘a'. These morphological changes are consistent with the spontaneous activation of MscL in the presence of 10 leading to solute loss and osmolytes and consequently a reduction in the size of S. aureus.


A new antibiotic with potent activity targets MscL.

Iscla I, Wray R, Blount P, Larkins-Ford J, Conery AL, Ausubel FM, Ramu S, Kavanagh A, Huang JX, Blaskovich MA, Cooper MA, Obregon-Henao A, Orme I, Tjandra ES, Stroeher UH, Brown MH, Macardle C, van Holst N, Ling Tong C, Slattery AD, Gibson CT, Raston CL, Boulos RA - J. Antibiot. (2015)

Microscopic analysis of S. aureus ATCC 29213 treated with 10 at different concentrations. (a) SEM images and size measurements of S. aureus with an inset showing the mean±95% confidence (n=12). Scale bar 1 μm and magnification ~ × 85 000. (b) The change in the ‘a' parameter (representing bacteria curvature) is shown with representative 3D AFM images beneath (3 μm × 3 μm × 700 nm). The top 25 nm of an AFM scan was used as a basis for a parabolic equation fit y=ax2+bx+c to show the change in curvature after treatment with the drug. The inset shows the mean±95% confidence (n=10 for 1 × MBC and n=20 for other concentrations). A full color version of this figure is available at The Journal of Antibiotics journal online.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4430313&req=5

fig3: Microscopic analysis of S. aureus ATCC 29213 treated with 10 at different concentrations. (a) SEM images and size measurements of S. aureus with an inset showing the mean±95% confidence (n=12). Scale bar 1 μm and magnification ~ × 85 000. (b) The change in the ‘a' parameter (representing bacteria curvature) is shown with representative 3D AFM images beneath (3 μm × 3 μm × 700 nm). The top 25 nm of an AFM scan was used as a basis for a parabolic equation fit y=ax2+bx+c to show the change in curvature after treatment with the drug. The inset shows the mean±95% confidence (n=10 for 1 × MBC and n=20 for other concentrations). A full color version of this figure is available at The Journal of Antibiotics journal online.
Mentions: On the basis of the observations from the patch-clamp experiments and the titration experiments above, we hypothesized that the opening of the MscL channel caused by 10 might result in changes in the size and shape of bacterial cells. Low-magnification scanning electron microscopy (SEM) of S. aureus ATCC 6538 showed a decrease in bacterial density and biofilm formation, concurrent with an increase in the concentration of 10 (Supplementary Figure S3). Bacterial size measurements revealed that bacteria treated with 0.5 μg ml−1 were significantly wider than the control (Figure 3a). At concentrations of 10 >0.5 μg ml−1, there was a gradual but significant reduction in the size of the bacteria. Moreover, untreated S. aureus showed a round and firm geometry with distinct surface features, which become distorted with increasing drug concentrations. Atomic force microscopy (AFM) also revealed a statistically significant change in morphology of the uppermost 25 nm region of S. aureus (see Figure 3b for illustration). This region was observed to be of narrow parabolic geometry in the control sample, which then flattened as the drug concentration increased (Figure 3b). The AFM and SEM results support each other, as the latter width measurement is inversely proportional to the measurement of the parabolic curvature parameter ‘a'. These morphological changes are consistent with the spontaneous activation of MscL in the presence of 10 leading to solute loss and osmolytes and consequently a reduction in the size of S. aureus.

Bottom Line: As predicted from in silico modeling, we show that the mechanism of action of compound 10 is at least partly dependent on interactions with MscL.Moreover we show that compound 10 cured a methicillin-resistant S. aureus infection in the model nematode Caenorhabditis elegans.Our work shows that compound 10, and other drugs that target MscL, are potentially important therapeutics against antibiotic-resistant bacterial infections.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, UT Southwestern Med Ctr, Dallas, TX, USA.

ABSTRACT
The growing problem of antibiotic-resistant bacteria is a major threat to human health. Paradoxically, new antibiotic discovery is declining, with most of the recently approved antibiotics corresponding to new uses for old antibiotics or structurally similar derivatives of known antibiotics. We used an in silico approach to design a new class of nontoxic antimicrobials for the bacteria-specific mechanosensitive ion channel of large conductance, MscL. One antimicrobial of this class, compound 10, is effective against methicillin-resistant Staphylococcus aureus with no cytotoxicity in human cell lines at the therapeutic concentrations. As predicted from in silico modeling, we show that the mechanism of action of compound 10 is at least partly dependent on interactions with MscL. Moreover we show that compound 10 cured a methicillin-resistant S. aureus infection in the model nematode Caenorhabditis elegans. Our work shows that compound 10, and other drugs that target MscL, are potentially important therapeutics against antibiotic-resistant bacterial infections.

Show MeSH
Related in: MedlinePlus