Biology subjects

Sheppard, L.

Publications and source records attributed to Sheppard, L..

3 recordsLinked to original sources

bioRxiv2021

The function of α-Catenin mechanosensing in tissue morphogenesis

-catenin couples the cadherin-catenin complex to the actin cytoskeleton. The mechanosensitive -catenin M region undergoes conformational changes upon application of force to recruit binding partners. Here, we took advantage to the tension landscape in the Drosophila embryo to define three different states of -catenin mechanosensing in support of cell adhesion. Low, medium, and high tension contacts showed -catenin M region-dependent low, medium, and high levels of Vinculin and Ajuba recruitment. In contrast, Afadin/Canoe acts in parallel to -catenin at bicellular low and medium tension junctions, but requires an interaction with -catenin for its tension-sensitive enrichment at high-tension tricellular junctions. Individual M region domains make complex contributions to cell adhesion through their impact on binding partner recruitment, and redundancies with the function of Afadin/Canoe. Our data argue that -catenin and its interaction partners are part of a cooperative and partially redundant, mechanoresponsive network that supports AJs remodelling during morphogenesis.

cell biology↗

bioRxiv2019

Transcriptomic profiling of PBDE-exposed HepaRG cells unveils critical lncRNA- PCG pairs involved in intermediary metabolism

Polybrominated diphenyl ethers (PBDEs) were formally used as flame-retardants and are chemically stable, lipophlic persistent organic pollutants which are known to bioaccumulate in humans. Although its toxicities are well characterized, little is known about the changes in transcriptional regulation caused by PBDE exposure. Long non-coding RNAs (lncRNAs) are increasingly recognized as key regulators of transcriptional and translational processes. It is hypothesized that lncRNAs can regulate nearby protein-coding genes (PCGs) and changes in the transcription of lncRNAs may act in cis to perturb gene expression of its neighboring PCGs. The goals of this study were to 1) characterize PCGs and lncRNAs that are differentially regulated from exposure to PBDEs; 2) identify PCG-lncRNA pairs through genome annotation and predictive binding tools; and 3) determine enriched canonical pathways caused by differentially expressed lncRNA-PCGs pairs. HepaRG cells, which are human-derived hepatic cells that accurately represent gene expression profiles of human liver tissue, were exposed to BDE-47 and BDE-99 at a dose of 25 M for 24 hours. Differentially expressed lncRNA-PCG pairs were identified through DESeq2 and HOMER; significant canonical pathways were determined through Ingenuity Pathway Analysis (IPA). LncTar was used to predict the binding of 19 lncRNA-PCG pairs with known roles in drug-processing pathways. Genome annotation revealed that the majority of the differentially expressed lncRNAs map to PCG introns. PBDEs regulated overlapping pathways with PXR and CAR such as protein ubiqutination pathway and PPAR-RXR activation but also regulate distinctive pathways involved in intermediary metabolism. BDE-47 uniquely regulated signaling by Rho Family GTPases and PBDE-99 uniquely regulates JAK/Stat signaling, bile acid biosynthesis, sirtuin signaling pathway, and autophagy. In conclusion, lncRNAs play essential roles in modifying important pathways involved in intermediary metabolism such as carbohydrate and lipid metabolism.

pharmacology and toxicology↗

bioRxiv2019

Role of α-Catenin and its mechanosensing properties in the regulation of Hippo/YAP-dependent tissue growth

-catenin is a key protein of adherens junctions (AJs) with mechanosensory properties. It also acts as a tumor suppressor that limits tissue growth. Here we analyzed the function of Drosophila -Catenin (-Cat) in growth regulation of the wing epithelium. We found that different -Cat levels led to a differential activation of Hippo/Yorkie or JNK signaling causing tissue overgrowth or degeneration, respectively. -Cat can modulate Yorkie-dependent tissue growth through recruitment of Ajuba, a negative regulator of Hippo signaling, to AJs but also through a mechanism that does not involve junctional recruitment of Ajuba. Further, both mechanosensory regions of -Cat, the M region and the actin-binding domain (ABD), contribute to growth regulation. Whereas M is dispensable for -Cat function in the wing, individual M domains (M1, M2, M3) have opposing effects on growth regulation. In particular, M1 limits Ajuba recruitment. Loss of M1 cause Ajuba hyper-recruitment to AJs promoting tissue-tension independent overgrowth. Although M1 binds Vinculin, Vinculin it is not responsible for this effect. Moreover, disruption of mechanosensing of the -Cat actin-binding domain affects tissue growth, with enhanced actin interactions stabilizing junctions and leading to tissue overgrowth. Together, our findings indicate that -Cat acts through multiple mechanisms to control tissue growth, including regulation of AJ stability, mechanosensitive Ajuba recruitment, and dynamic direct F-actin interactions.

cell biology↗