Biology subjects

Lehner, A.

Publications and source records attributed to Lehner, A..

3 recordsLinked to original sources

bioRxiv2025

Dual role of the receptor kinase FERONIA in regulating tissue mechanics and growth

During morphogenesis, growing organisms adapt to internal and external mechanical stress. In plants, the receptor kinase FERONIA is involved in a broad range of responses to perturbations of the cell wall, but it is unclear which cues are sensed and how this sensing controls growth. Here, we addressed these questions in Marchantia vegetative propagules. We combined culture in microfluidic chips to quantify growth and mechanical properties of propagules, perturbations with osmotic treatments, characterisation of cell wall polysaccharides, and a mathematical model of cell wall expansion that incorporates sensing. We found that FERONIA independently regulates tissue mechanical properties and growth rates. We propose that the regulation of growth by the FERONIA pathway relies on both a positive feedback from elastic deformation of the wall and a negative feedback from wall expansion. Altogether, we expect our quantitative framework to be broadly relevant to the investigation of how mechanical cues guide development.

plant biology↗

bioRxiv2021

E3 ubiquitin ligase RNF213 employs a non-canonical zinc finger active site and is allosterically regulated by ATP

RNF213 is a giant E3 ubiquitin ligase and a major susceptibility factor of Moyamoya disease, a cerebrovascular disorder that can result in stroke or death. In the cell, RNF213 is involved in lipid droplet formation, lipotoxicity, hypoxia, and NF-{kappa}B signaling, but its exact function in these processes is unclear. Structural characterization has revealed the presence of a dynein- like ATPase module and an unprecedented but poorly understood E3 module. Here, we demonstrate that RNF213 E3 activity is dependent on ATP binding, rather than ATP hydrolysis, and is particularly responsive to the ATP/ADP/AMP ratio. Biochemical and activity-based probe analyses identify a non-canonical zinc finger domain as the E3 active site, which utilizes the strictly conserved Cys4462, not involved in zinc coordination, as the reactive nucleophile. The cryo-EM structure of the trapped RNF213:E2[~]Ub intermediate reveals RNF213 C-terminal domain as the E2 docking site, which positions the ubiquitin-loaded E2 proximal to the catalytic zinc finger, facilitating nucleophilic attack of Cys4462 on the E2[~]Ub thioester. Our findings show that RNF213 represents an undescribed type of a transthiolation E3 enzyme and is regulated by adenine nucleotide concentration via its ATPase core, possibly allowing it to react to changing metabolic conditions in the cell.

biochemistry↗

bioRxiv2020

Analysis of the oxidative stress regulon identifies soxS as a genetic target for resistance reversal in multi-drug resistant Klebsiella pneumoniae

In bacteria, the defense system deployd to counter oxidative stress is orchestrated by three transcriptional factors - SoxS, SoxR, and OxyR. Although the regulon that these factors control is known in many bacteria, similar data is not available for Klebsiella pneumoniae. To address this data gap, oxidative stress was artificially induced in K. pneumoniae MGH 78578 using paraquat and the corresponding oxidative stress regulon recorded using RNA-seq. The soxS gene was significantly induced during oxidative stress and a knock-out mutant was constructed, to explore its functionality. The wild-type and mutant were grown in the presence of paraquat and subjected to RNA-seq to elucidate the soxS regulon in K. pneumoniae MGH78578. Genes that are commonly regulated both in the oxidative stress regulon and soxS regulon were identified and denoted as the oxidative SoxS regulon - these included a stringent group of genes specifically regulated by SoxS. Efflux pump encoding genes such as acrAB-tolC, acrE, and global regulators such as marRAB were identified as part of this regulon. Consequently, the isogenic soxS mutant was found to exhibit a reduction in the minimum bactericidal concentration against tetracycline compared to that of the wild type. Impaired efflux activity, allowing tetracycline to be accumulated in the cytoplasm to bactericidal levels, was further evaluated using a tetraphenylphosphonium (TPP+) accumulation assay. The soxS mutant was also susceptible to tetracycline in vivo, in a zebrafish embryo model. We conclude that the soxS gene could be considered as a genetic target against which an inhibitor could be developed in the future and used in combinatorial therapy with tetracycline to combat infections associated with multi-drug resistant K. pneumoniae.

microbiology↗