Biology subjects

Pal, A. K.

Publications and source records attributed to Pal, A. K..

5 recordsLinked to original sources

bioRxiv2025

A cross-week analysis of urinary extracellular vesicles after respiratory tract exposure intervention identifies systemic signaling changes -- a pilot study of isocyanate-exposed workers

Extracellular vesicles (EVs) from various biofluids have demonstrated potential as prognostic and diagnostic biomarkers in several diseases. However, their utility in early stages of disease development has not been extensively investigated. Additionally, given their role in intercellular communication, decoding the landscape of underlying cell-to-cell signaling in a clinical or subclinical condition based on EV-specific analyses has so far remained challenging. Here, we demonstrate the utility of urinary EVs for cross-week biomonitoring and for capturing the perturbation of underlying organismal signaling in a small well-characterized group of workers with inhalational exposure to methylene diphenyl diisocyanate (MDI) in fabric coating factory. Workers wore organic vapor cartridge respirators during the week to eliminate respiratory exposures. Spot urine was collected before and after the respirator intervention - pre-RESP and post-RESP, respectively. Following extensive characterization of EVs isolated from the urine samples, the relative enrichment of EV-specific RNAs and proteins and their associated biological processes were determined between pre-RESP and post-RESP samples. Distinct EV-specific RNA and protein signatures between the two groups strongly correlated with established biological and immune-related processes involved in asthma and lung inflammation. Using single cell transcriptomics data from the human cell atlas, EV-mRNAs highly enriched in pre-RESP, but not post-RESP, samples revealed global immune dysregulation and enrichment of associated cell types, such as monocytes, macrophages, and neutrophils. The findings indicate that urinary EVs and their contents can be utilized for biomonitoring of lung health and can reveal the effects of exposure on the underlying organismal signaling. One Sentence Summary: Urinary extracellular vesicles and their cargo hold great potential to monitor lung health and changes in systemic signaling in inhalational exposures.

pharmacology and toxicology↗

bioRxiv2023

Second messenger c-di-AMP regulates multiple antibiotic sensitivity pathways in Mycobacterium smegmatis by discrete mechanisms

One of the debilitating causes of high mortality in the case of tuberculosis and other bacterial infections is the resistance development against standard drugs. There are limited studies so far to describe how a bacterial second messenger molecule can directly participate in distinctive antibiotic tolerance characteristics of a cell in a mechanism-dependent manner. Here we show that intracellular cyclic di-AMP (c-di-AMP) concentration can modulate drug sensitivity of Mycobacterium smegmatis by directly interacting with either a protein effector or with the 5-UTR regions in mRNA of the genes and thus causing transcriptional downregulation of important genes in the pathways. We studied four antibiotics with different mechanisms of action: rifampicin, ciprofloxacin, erythromycin, and tobramycin and subsequently found that the level of drug sensitivity of the bacteria is directly proportional to the c-di-AMP concentration inside the cell. Further, we unraveled the underlying molecular mechanisms to delineate the specific genes and pathways regulated by c-di-AMP and hence result in differential drug sensitivity in M. smegmatis. Thus, our findings of c-di-AMP messenger controlling drug resistance phenotypes of mycobacteria against four different classes of antibiotics is a unique observation that will contribute to scientific advancement in the field. One Sentence SummaryHere we describe how second messenger c-di-AMP modulates the antibiotic sensitivity and resistance profile of M. smegmatis by diverse mechanisms.

microbiology↗

bioRxiv2022

Sub-operon promoter arrangement of disA facilitates c-di-AMP homeostasis and selective stress responses in M. smegmatis

Bacterial second messenger signaling often plays an important role in cellular physiology. In this study, we have attempted to understand how c-di-AMP synthesis and degradation are transcriptionally regulated in M. smegmatis. We have discovered that, although c-di-AMP synthesis gene disA exists in a multi-gene operon; a sub-operon promoter arrangement plays a key role under various stress conditions, keeping its dual function property intact. Further, we learned that c-di-AMP plays a role in the autoregulation of the disA promoter to limit intracellular c-di-AMP concentration. We also identified an alternate start codon within the disA gene which can lead to the synthesis of truncated DisA protein at times using an independent stress-inducible promoter. All in all, this study was helpful to understand how c-di-AMP synthesis is regulated under normal and stress conditions linked to its physiological relevance in M. smegmatis.

microbiology↗

bioRxiv2022

Understanding the role of c-di-AMP signaling in determining antibiotic tolerance in Mycobacterium smegmatis: generation of resistant mutants and regrowth of persisters

In this study, we probe the role of secondary messenger c-di-AMP in drug tolerance, which includes both persister and resistant mutant characterization of Mycobacterium smegmatis. Specifically, with the use of c-di-AMP null and overproducing mutants, we showed how c-di-AMP plays a significant role in resistance mutagenesis against antibiotics with different mechanisms of action. We elucidated the specific molecular mechanism linking the elevated intracellular c-di-AMP level and high mutant generation and highlighted the significance of non-homology-based DNA repair. Further investigation enabled us to identify the unique mutational landscape of target and non-target mutation categories linked to intracellular c-di-AMP levels. Overall fitness cost of unique target mutations was estimated in different strain backgrounds, and then we showed the critical role of c-di-AMP in driving epistatic interactions between resistance genes, resulting in the evolution of multi-drug tolerance. Finally, we identified the role of c-di-AMP in persister cells regrowth and mutant enrichment upon cessation of antibiotic treatment.

microbiology↗

bioRxiv2022

Elucidating the role of c-di-AMP in Mycobacterium smegmatis: phenotypic characterization and functional analysis

Cyclic-di-AMP (c-di-AMP) is a newly discovered secondary messenger molecule that plays a critical role in monitoring several important cellular processes, especially in several Gram-positive bacteria signal transduction pathways. In this study, we seek to unravel the physiological significance of the molecule c-di-AMP in Mycobacterium smegmatis under different conditions, using strains with altered c-di-AMP levels: c-di-AMP null mutant ({Delta}disA) and a c-di-AMP over-expression mutant ({Delta}pde). Our thorough analysis of the mutants revealed that the intracellular concentration of c-di-AMP could determine many basic phenotypes such as colony architecture, cell shape, cell size, membrane permeability etc. Additionally, it was shown to play a significant role in multiple stress adaptation pathways in the case of different DNA and membrane stresses. Our study also revealed how the biofilm phenotype of M. smegmatis cells are dependent on intracellular c-di-AMP concentration. Next, we checked how c-di-AMP contributes to antibiotic tolerance characteristics of M. smegmatis, which was followed by a detailed transcriptome profile analysis to reveal key genes and pathways regulated by c-di-AMP in mycobacteria.

microbiology↗