Design, synthesis and evaluation of bacterial sialic acid uptake inhibitors
(2022)- Abstract
- Antibiotic resistance is a major threat for our society and finding novel antibacterial therapies is of great
importance. In this thesis, we investigate bacterial sialic acid uptake inhibitors as a novel antibacterial approach.
Bacteria do not biosynthesise sialic acid and therefore harvest it from the host. Sialic acid plays a crucial role for
pathogenic bacteria, since it is used as a source of carbon and in a immuno-evasive mechanism called “molecular
mimicry”. Disrupting genes involved in bacterial sialic acid catabolism and transport has been proven to alter the
bacterial growth and infectivity in vivo. We identified the SiaT transporter, from the sodium solute transporter
(SSS) family, from Proteus mirabilis... (More) - Antibiotic resistance is a major threat for our society and finding novel antibacterial therapies is of great
importance. In this thesis, we investigate bacterial sialic acid uptake inhibitors as a novel antibacterial approach.
Bacteria do not biosynthesise sialic acid and therefore harvest it from the host. Sialic acid plays a crucial role for
pathogenic bacteria, since it is used as a source of carbon and in a immuno-evasive mechanism called “molecular
mimicry”. Disrupting genes involved in bacterial sialic acid catabolism and transport has been proven to alter the
bacterial growth and infectivity in vivo. We identified the SiaT transporter, from the sodium solute transporter
(SSS) family, from Proteus mirabilis (PmSiaT) and Staphylococcus aureus (SaSiaT), as starting targets for our
investigations. Firstly, a library of sialic acid derivatives with single modifications at O4, N5 and C9 was designed,
synthesised and tested on the two targets with a thermal shift assay called nano differential scanning fluorimetry
(nanoDSF). Subsequentially, the most promising hits were investigated with isothermal titration calorimetry (ITC),
and proteoliposome and bacterial growth assays. Our best compound, with a 3,5-dibromobenzyl substituent at O4,
showed mid-nanomolar affinity, a 185-fold increase for PmSiaT compared to the natural substrate. The best
compounds block sialic acid uptake with a competitive mode of action and delay bacterial growth in the case of S.
aureus.
With these initial promising results, we focussed on targeting multiple bacterial sialic acid transporter families, in
particular the substrate binding proteins (SBP) from the ATP-binding cassette (ABC) and tripartite ATPindipendent
periplasmic (TRAP) transporter families. NanoDSF and ITC were again employed as methods to
evaluate the previously developed compound library and establish structure activity relationships for the new
targets. We identified C9 and, potentially, O4 as promising sites of derivatisation for broad spectrum bacterial
sialic acid uptake inhibitors.
To follow on the promising leads obtained from the 4-O-benzyl series, we designed a new library of derivatives
bearing 4-N-piperidine and piperazine as spacers between C4 and the aromatic moiety. Clear trends were
observed when adding either electron-withdrawing or donating groups, with the former significantly enhancing
affinity.
Lastly, we developed a new methodology to functionalise C4 of sialic acid, starting from methyl (5-acetamido-
4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-D-galacto-2-nonulopyranosid)onate. The procedure allows for the
introduction of nitrogen, sulfur and carbon nucleophiles in a single step, with retention of the configuration, without
the requirement for special conditions. With this procedure, the scope of C4 functionalisations is greatly expanded
to sustain future sialic acid centered drug discovery and chemical biology investigations.
The results of this thesis represent the first examples of bacterial sialic acid uptake inhibition. Our efforts enabled
the identification of promising leads and methodologies to be used in the future to develop this class of
compounds as novel antibacterial drugs. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/5467f961-7659-41d6-b2aa-195216af415f
- author
- Bozzola, Tiago LU
- supervisor
- opponent
-
- Professor Field, Robert, Department of Chemistry and Manchester Institute of Biotechnology, University of Manchester
- organization
- publishing date
- 2022
- type
- Thesis
- publication status
- published
- subject
- keywords
- Sialic Acid, antibacterial agents, Medicinal Chemistry, Synthesis, uptake inhibitors
- pages
- 127 pages
- publisher
- MediaTryck Lund
- defense location
- Lecture Hall A, Kemicentrum, Lund. Join via zoom: https://lu-se.zoom.us/j/61118772468
- defense date
- 2022-06-09 09:00:00
- ISBN
- 978-91-7422-886-1
- 978-91-7422-887-8
- language
- English
- LU publication?
- yes
- id
- 5467f961-7659-41d6-b2aa-195216af415f
- date added to LUP
- 2022-05-10 12:01:50
- date last changed
- 2022-05-11 13:25:04
@phdthesis{5467f961-7659-41d6-b2aa-195216af415f,
abstract = {{Antibiotic resistance is a major threat for our society and finding novel antibacterial therapies is of great<br/>importance. In this thesis, we investigate bacterial sialic acid uptake inhibitors as a novel antibacterial approach.<br/>Bacteria do not biosynthesise sialic acid and therefore harvest it from the host. Sialic acid plays a crucial role for<br/>pathogenic bacteria, since it is used as a source of carbon and in a immuno-evasive mechanism called “molecular<br/>mimicry”. Disrupting genes involved in bacterial sialic acid catabolism and transport has been proven to alter the<br/>bacterial growth and infectivity in vivo. We identified the SiaT transporter, from the sodium solute transporter<br/>(SSS) family, from Proteus mirabilis (PmSiaT) and Staphylococcus aureus (SaSiaT), as starting targets for our<br/>investigations. Firstly, a library of sialic acid derivatives with single modifications at O4, N5 and C9 was designed,<br/>synthesised and tested on the two targets with a thermal shift assay called nano differential scanning fluorimetry<br/>(nanoDSF). Subsequentially, the most promising hits were investigated with isothermal titration calorimetry (ITC),<br/>and proteoliposome and bacterial growth assays. Our best compound, with a 3,5-dibromobenzyl substituent at O4,<br/>showed mid-nanomolar affinity, a 185-fold increase for PmSiaT compared to the natural substrate. The best<br/>compounds block sialic acid uptake with a competitive mode of action and delay bacterial growth in the case of S.<br/>aureus.<br/>With these initial promising results, we focussed on targeting multiple bacterial sialic acid transporter families, in<br/>particular the substrate binding proteins (SBP) from the ATP-binding cassette (ABC) and tripartite ATPindipendent<br/>periplasmic (TRAP) transporter families. NanoDSF and ITC were again employed as methods to<br/>evaluate the previously developed compound library and establish structure activity relationships for the new<br/>targets. We identified C9 and, potentially, O4 as promising sites of derivatisation for broad spectrum bacterial<br/>sialic acid uptake inhibitors.<br/>To follow on the promising leads obtained from the 4-O-benzyl series, we designed a new library of derivatives<br/>bearing 4-N-piperidine and piperazine as spacers between C4 and the aromatic moiety. Clear trends were<br/>observed when adding either electron-withdrawing or donating groups, with the former significantly enhancing<br/>affinity.<br/>Lastly, we developed a new methodology to functionalise C4 of sialic acid, starting from methyl (5-acetamido-<br/>4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-D-galacto-2-nonulopyranosid)onate. The procedure allows for the<br/>introduction of nitrogen, sulfur and carbon nucleophiles in a single step, with retention of the configuration, without<br/>the requirement for special conditions. With this procedure, the scope of C4 functionalisations is greatly expanded<br/>to sustain future sialic acid centered drug discovery and chemical biology investigations.<br/>The results of this thesis represent the first examples of bacterial sialic acid uptake inhibition. Our efforts enabled<br/>the identification of promising leads and methodologies to be used in the future to develop this class of<br/>compounds as novel antibacterial drugs.}},
author = {{Bozzola, Tiago}},
isbn = {{978-91-7422-886-1}},
keywords = {{Sialic Acid; antibacterial agents; Medicinal Chemistry; Synthesis; uptake inhibitors}},
language = {{eng}},
publisher = {{MediaTryck Lund}},
school = {{Lund University}},
title = {{Design, synthesis and evaluation of bacterial sialic acid uptake inhibitors}},
url = {{https://lup.lub.lu.se/search/files/117889706/Thesis_Bozzola.pdf}},
year = {{2022}},
}