Biology subjects

Jindra, M.

Publications and source records attributed to Jindra, M..

3 recordsLinked to original sources

bioRxiv2026

Capturing early events in aryl hydrocarbon receptor activation using two complementary protein-protein interaction assays

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that enables cellular adaptation to environmental, nutritional and metabolic cues. Upon ligand binding, AHR translocates to the nucleus, heterodimerizes with the AHR nuclear translocator (ARNT) and regulates gene expression. Current approaches to measure AHR activity rely on transcriptional readouts, which vary depending on cell type and ligand. Here, we introduce two complementary protein-protein interaction-based assays that detect AHR activation by monitoring AHR-ARNT complex formation. Split-luciferase (NanoBiT) and bimolecular fluorescence complementation (BiFC) detect AHR activation independently of transcriptional output, capturing agonist- and antagonist-dependent AHR modulation across multiple ligands and cellular contexts. NanoBiT enables rapid, real-time analysis of AHR dimerization, whereas BiFC supports imaging of AHR interactions at subcellular resolution. The assays capture further attributes of AHR signaling, including dissociation from chaperones or HIF-1-mediated competition for ARNT, and enable detection of AHR activation in biological samples. Hence, both assays provide versatile tools to study AHR signaling.

biochemistry↗

bioRxiv2024

Unique and Common Agonists Activate the Insect Juvenile Hormone Receptor and the Human AHR

AbstractTranscription factors of the bHLH-PAS family play vital roles in animal development, physiology, and disease. Two members of the family require binding of low-molecular weight ligands for their activity: the vertebrate aryl hydrocarbon receptor (AHR) and the insect juvenile hormone receptor (JHR). In the fly Drosophila melanogaster, the paralogous proteins GCE and MET constitute the ligand-binding component of JHR complexes. Whilst GCE/MET and AHR are phylogenetically heterologous, their mode of action is similar. JHR is targeted by several synthetic agonists that serve as insecticides disrupting the insect endocrine system. AHR is an important regulator of human endocrine homeostasis and it responds to environmental pollutants and endocrine disruptors. Whether AHR signaling is affected by compounds that can activate JHR has not been reported. To address this question, we screened a chemical library of 50,000 compounds to identify 93 novel JHR agonists in a reporter system based on Drosophila cells. Of these compounds, 26% modulated AHR signaling in an analogous reporter assay in a human cell line, indicating a significant overlap in the agonist repertoires of the two receptors. To explore the structural features of agonist-dependent activation of JHR and AHR, we compared the ligand-binding cavities and their interactions with selective and common ligands of AHR and GCE. Molecular dynamics modeling revealed ligand-specific as well as conserved side chains within the respective cavities. Significance of predicted interactions was supported through site-directed mutagenesis. The results have indicated that synthetic insect juvenile hormone agonists might interfere with AHR signaling in human cells.

biochemistry↗

bioRxiv2017

Atf3 links loss of epithelial polarity to defects in cell differentiation and cytoarchitecture

Interplay between apicobasal cell polarity modules and the cytoskeleton is critical for differentiation and integrity of epithelia. However, this coordination is poorly understood at the level of gene regulation by transcription factors. Here, we establish the Drosophila activating transcription factor 3 (atf3) as a cell polarity response gene acting downstream of the membrane-associated Scribble polarity complex. Loss of the tumor suppressors Scribble or Dlg1 induces atf3 expression via aPKC but independent of Jun-N-terminal kinase (JNK) signaling. Strikingly, removal of Atf3 from Dlg1 deficient cells restores polarized cytoarchitecture, levels and distribution of endosomal trafficking machinery, and differentiation. Conversely, excess Atf3 alters microtubule network, vesicular trafficking and the partition of polarity proteins along the apicobasal axis. Genomic and genetic approaches implicate Atf3 as a regulator of cytoskeleton organization and function, and identify Lamin C as one of its bona fide target genes. By affecting structural features and cell morphology, Atf3 functions in a manner distinct from other transcription factors operating downstream of disrupted cell polarity.\n\nAuthor summaryEpithelial cells form sheets and line both the outside and inside of our body. Their proper development and function require the asymmetric distribution of cellular components from the top to the bottom, known as apicobasal polarization. As loss of polarity hallmarks a majority of cancers in humans understanding how epithelia respond to a collapse of the apicobasal axis is of great interest. Here, we show that in the fruit fly Drosophila melanogaster, the breakdown of epithelial polarity engages Activating transcription factor 3 (Atf3), a protein that directly binds the DNA and regulates gene expression. We demonstrate that many of the pathological consequences of disturbed polarity require Atf3, as its loss in this context results in normalization of cellular architecture, vesicle trafficking and differentiation. Using unbiased genome-wide approaches we identify the genetic program controlled by Atf3 and experimentally verify select candidates. Given the evolutionary conservation of Atf3 between flies and man, we believe that our findings in the Drosophila model will contribute to a better understanding of diseases stemming from compromised epithelial polarity.

genetics↗