ORCID

0009000232839751

Keywords

Mycobacterium abscessus, beta-lactam, resistance, BlaRI, clofazimine, respiration

Abstract

The increasing incidence of Mycobacterium abscessus (Mab) infections is a global concern as the treatment failure rate is more than 50%. Mab is an opportunistic pathogen, thriving in harsh conditions in the environment and in hosts. To respond to these conditions, Mab employs many signal transduction mechanisms. This work characterizes two non-redundant systems using a novel mechanism in Mab: BlaRI-type protease-mediated two-component systems. In the Staphylococcus aureus prototype, BlaR binds β-lactams with a C-terminal extracellular sensing domain, activating BlaR through acylation and autoproteolysis. Activated BlaR then cleaves DNA-bound dimerized BlaI, disrupting repression by BlaI and enabling transcription of blaZ, a β-lactamase. Before this work, the only characterized mycobacterial BlaRI ortholog was in Mycobacterium tuberculosis. Based on sequence homology, three possible BlaRI homologs were identified in Mab, and two of these systems are characterized in this work. After comparing structural models to BlaRSa and BlaIMtb, MAB_2414c-2415c (BlaIR1Mab) and MAB_4287-4288 (BlaIR2Mab) were established as BlaRI systems in Mab. While BlaRI systems typically regulate β-lactam resistance, neither BlaIR1Mab nor BlaIR2Mab mediate a response to β-lactams, consistent with their lack of an extracellular sensing domain. Instead, both BlaIR1Mab and BlaIR2Mab appear to control regulons comprised of genes related to respiration and redox homeostasis and respond to the respiration inhibitor clofazimine (CFZ) by de-repressing their respective regulons. Despite sharing this cue, BlaIR1Mab and BlaIR2Mab have distinct regulons with some potential overlap and do not appear capable of binding the motif of the other system. The regulation of respiration and energy metabolism but not antibiotic resistance by BlaRI systems is unique to Mab, and the role of the unprecedented third system remains to be investigated. Elucidation of the full regulons and roles of the three Mab BlaIR systems and mechanisms of signal transduction will undoubtedly reveal novel aspects of Mab-host interactions.

Completion Date

2024

Semester

Fall

Committee Chair

Rohde, Kyle

Degree

Doctor of Philosophy (Ph.D.)

College

College of Medicine

Department

Burnett School of Biomedical Sciences

Degree Program

Biomedical Sciences

Format

PDF

Identifier

DP0028972

Language

English

Release Date

12-15-2024

Access Status

Dissertation

Accessibility Status

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