Identification of a novel carboxypeptidase encoded by Rv3627c that plays a potential role in mycobacteria morphology and cell division

Structural Insights into the Penicillin-Binding Protein 4 (DacB) from Mycobacterium tuberculosis

Mycobacterium tuberculosis, a major cause of mortality from a single infectious agent, possesses a remarkable mycobacterial cell envelope. Penicillin-Binding Proteins (PBPs) are a family of bacterial enzymes involved in the biosynthesis of peptidoglycan. PBP4 (DacB) from M. tuberculosis (MtbPBP4) has been known to function as a carboxypeptidase, and the role and significance of carboxypeptidases as targets for anti-tuberculosis drugs or antibiotics have been extensively investigated over the past decade. However, their precise involvement remains incompletely understood. In this study, we employed predictive modeling and analyzed the three-dimensional structure of MtbPBP4. Interestingly, MtbPBP4 displayed a distinct domain structure compared to its homologs. Docking studies with meropenem verified the presence of active site residues conserved in PBPs. These findings establish a structural foundation for comprehending the molecular function of MtbPBP4 and offer a platform for the exploration of novel antibiotics.

Transposon mutagenesis in Mycobacterium abscessus identifies an essential penicillin-binding protein involved in septal peptidoglycan synthesis and antibiotic sensitivity

Mycobacterium abscessus (Mab) is a rapidly growing non-tuberculous mycobacterium (NTM) that causes a wide range of infections. Treatment of Mab infections is difficult because the bacterium is intrinsically resistant to many classes of antibiotics. Developing new and effective treatments against Mab requires a better understanding of the unique vulnerabilities that can be targeted for future drug development. To achieve this, we identified essential genes in Mab by conducting transposon sequencing (TnSeq) on the reference Mab strain ATCC 19977. We generated ~51,000 unique transposon mutants and used this high-density library to identify 362 essential genes for in vitro growth. To investigate species-specific vulnerabilities in Mab, we further characterized MAB_3167c, a predicted penicillin-binding protein and hypothetical lipoprotein (PBP-lipo) that is essential in Mab and non-essential in Mycobacterium tuberculosis (Mtb). We found that PBP-lipo primarily localizes to the subpolar region and later to the septum as cells prepare to divide. Depletion of Mab PBP-lipo causes cells to elongate, develop ectopic branches, and form multiple septa. Knockdown of PBP-lipo along with PbpB, DacB1, and a carboxypeptidase, MAB_0519 lead to synergistic growth arrest. In contrast, these genetic interactions were absent in the Mtb model organism, Mycobacterium smegmatis, indicating that the PBP-lipo homologs in the two species exist in distinct genetic networks. Finally, repressing PBP-lipo sensitized the reference strain and 11 Mab clinical isolates to several classes of antibiotics, including the β-lactams, ampicillin, and amoxicillin by greater than 128-fold. Altogether, this study presents PBP-lipo as a key enzyme to study Mab-specific processes in cell wall synthesis and importantly positions PBP-lipo as an attractive drug target to treat Mab infections.

ADP/ATP translocase 1 protects against an α-synuclein-associated neuronal cell damage in Parkinson's disease model

BACKGROUND

ADP/ATP translocase 1 (ANT1) is involved in the exchange of cytosolic ADP and mitochondrial ATP, and its defection plays an important role in mitochondrial pathogenesis. To reveal an etiological implication of ANT1 for Parkinson's disease (PD), a neurodegenerative disorder, a mouse model treated with 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine and neuroblastoma cell model induced by 1-methyl-4-pehny1-pyridine were utilized in this study.

RESULTS

The tissue-specific abundance in ANT1 in mouse brains was accessed using the analysis of Western blot and immunohistochemistry. Down-regulated soluble ANT1 was found to be correlated with PD, and ANT1 was associated with PD pathogenesis via forming protein aggregates with α-synuclein. This finding was confirmed at cellular level using neuroblastoma cell models. ANT1 supplement in neuronal cells revealed the protective roles of ANT1 against cytotoxicity caused by MPP⁺. Protein interaction assay, coupled with the analysis of LC-MS/MS, silver-stained SDS-PAGE and Western blot against anti-ANT1 antibody respectively, illustrated the interaction of ANT1 with α-synuclein using the expressed α-synuclein as a bite. Additionally, a significant increasing ROSs was detected in the MPP⁺-treated cells.

CONCLUSIONS

This study indicated that ANT1 was a potentially causative factor of PD, and led to neuropathogenic injury via promoting the formation of protein aggregates with α-synuclein. This investigation potentially promotes an innovative understanding of ANT1 on the etiology of PD and provides valuable information on developing potential drug targets in PD treatment or reliable biomarkers in PD prognostication.