Methicillin-resistant Staphylococcus aureus (MRSA) is a problematic human bacterial pathogen, which is broadly resistant to ?-lactam antibiotics. This resistance is inducible and is conferred by a set of genes that encode an antibiotic sensor/signal transducer protein, a gene repressor and two resistance determinants (a class A ?-lactamases and a unique penicillin-binding protein (PBP) designated as PBP2a). Covalent binding of the ?-lactam antibiotic to the surface domain of the sensor/signal transducer protein initiates the induction of resistance, which entails biochemical events on the cytoplasmic side involving proteolysis of the gene repressor and transcription of the genes for the antibiotic-resistance determinants. We address the sequence of events that take place in the cytoplasm in this grant application. We propose in Specific Aim 1 to study two responses that MRSA experiences after the recognition of the antibiotic on the surface. One is a fragmentation of the BlaR1 (the sensor/transducer protein) in its cytoplasmic protease domain, which is believed to activate it (i.e., bring it out of latency). Another is phosphorylation of a protein that we refer to as BlaR2. We propose to document that proteolysis of the cytoplasmic domain initiates the onset of induction. Phosphorylation of BlaR2 also ensues antibiotic recognition on the surface and is essential for the antibiotic response. We propose to identify and characterize BlaR2 and determine the site of its phosphorylation in elucidating a functional link between activation of BlaR1 and phosphorylation of BlaR2.
In Specific Aim 2, we would like to build on our preliminary findings on inhibitors of BlaR2 phosphorylation in identification of molecules that could serve as potentiators of ?-lactam antibiotics. This class of compounds prevents BlaR2 phosphorylation, which we have documented to result in sensitization of the organism to ?-lactam antibiotics. Such a class of molecules has the potential of bring back ?-lactam antibiotics from obsolescence in treatment of MRSA infections. MRSA has been with humanity for over 50 years. These studies will shed definitive light on the complex machinery that MRSA strains have evolved for resistance to ?-lactam antibiotics.

Public Health Relevance

Methicillin-resistant Staphylococcus aureus (MRSA), a difficult human pathogen, emerged for the first time in 1961, but soon became a global problem. MRSA exhibit broad resistance to essentially the entire class of ?-lactam antibiotics, which were the agents of choice in treatment of S. aureus infections previously. We investigate in this grant application the complex machinery that results in ?- antibiotic resistance in MRSA. We also seek agents that have the ability to reverse the ?-lactam- resistance trait, bringing back from obsolescence ?-lactam antibiotics for treatment of MRSA infections.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
2R01AI104987-06
Application #
9382418
Study Section
Drug Discovery and Mechanisms of Antimicrobial Resistance Study Section (DDR)
Program Officer
Huntley, Clayton C
Project Start
2013-01-01
Project End
2022-12-31
Budget Start
2018-01-01
Budget End
2018-12-31
Support Year
6
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Notre Dame
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
824910376
City
Notre Dame
State
IN
Country
United States
Zip Code
46556
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Fisher, Jed F; Mobashery, Shahriar (2016) Endless Resistance. Endless Antibiotics? Medchemcomm 7:37-49
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Acebrón, Iván; Chang, Mayland; Mobashery, Shahriar et al. (2015) The Allosteric Site for the Nascent Cell Wall in Penicillin-Binding Protein 2a: An Achilles' Heel of Methicillin-Resistant Staphylococcus aureus. Curr Med Chem 22:1678-86
Boudreau, Marc A; Fishovitz, Jennifer; Llarrull, Leticia I et al. (2015) Phosphorylation of BlaR1 in Manifestation of Antibiotic Resistance in Methicillin-Resistant Staphylococcus aureus and Its Abrogation by Small Molecules. ACS Infect Dis 1:454-9
Staude, Michael W; Frederick, Thomas E; Natarajan, Sivanandam V et al. (2015) Investigation of signal transduction routes within the sensor/transducer protein BlaR1 of Staphylococcus aureus. Biochemistry 54:1600-10
Fishovitz, Jennifer; Taghizadeh, Negin; Fisher, Jed F et al. (2015) The Tipper-Strominger Hypothesis and Triggering of Allostery in Penicillin-Binding Protein 2a of Methicillin-Resistant Staphylococcus aureus (MRSA). J Am Chem Soc 137:6500-5
Blázquez, Blas; Llarrull, Leticia I; Luque-Ortega, Juan R et al. (2014) Regulation of the expression of the ?-lactam antibiotic-resistance determinants in methicillin-resistant Staphylococcus aureus (MRSA). Biochemistry 53:1548-50

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