Biology subjects

Yan, K.

Publications and source records attributed to Yan, K..

4 recordsLinked to original sources

bioRxiv2020

The CEPR2-mediated phosphorylation of NRT1.2 mainly regulates ABA import in Arabidopsis

Abscisic acid (ABA) transport plays important role in systematic plant responses to environmental factors. Here, we showed that C-terminally encoded peptide receptor 2 (CEPR2) directly interacted with the ABA transporter NRT1.2. Using transgenic seedlings, we demonstrated that NRT1.2 positively regulated the ABA response, and that CEPR2 acted on NRT1.2 epistatically and negatively. Under normal conditions, CEPR2 phosphorylated NRT1.2 at least at serine 292 to promote the degradation of NRT1.2. However, ABA and serine 292 nonphospharylation strongly inhibited the degradation of NRT1.2, indicating that ABA-inhibited the phosphorylation of NRT1.2. Transport assays in yeast and Xenopus oocytes showed that nonphosphorylated NRT1.2 had high levels of ABA-import activity, but phosphorylated NRT1.2 did not import ABA. Analyses of complement nrt1.2 mutants by mimicking nonphospharylated and phospharylated NRT1.2 confirmed that nonphospharylated NRT1.2S292A had high stability and ABA import activity in planta. Further experiments indicated that NRT1.2 was degraded via the 26S proteasome and vacuolar degradation pathways. UBC32, UBC33, and UBC34 interacted with, and mediated the ubiquitination of NRT1.2. UBC32, UBC33, and UBC34 acted on NRT1.2 epistatically and negatively in planta. Thus, our results suggested the existence of novel plant mechanisms regulating NRT1.2 stability and ABA import activity in response to environmental conditions.

molecular biology↗

bioRxiv2019

A Holistic Analysis of the Intestinal Stem Cell Niche Network

Although many studies into the intestinal stem cell (ISC) niche have been carried out, they have focused on the role of a single cell type or molecular signal. However, no holistic comparisons of the predominant cell types and signals present within the intestinal mucosa have been conducted to date. We utilize bulk RNA sequencing to profile 20 different mucosal cell types covering four major cell categories: epithelial, stromal, endothelial and immune. We further examined the stromal signaling environment using scRNAseq to provide a more comprehensive view of the signaling microenvironment within the intestinal mucosa. We identified the primary signals for the major ISC regulatory pathways and their respective cellular sources. Our analysis suggests that a niche network exists, with no single cell type being responsible for ISC self-renewal, proliferation, or differentiation; rather, each cell type within the network carries out specific functions in a highly cooperative and coordinated manner.

cell biology↗

bioRxiv2019

Leukocyte-derived High-mobility group box 1 controls innate immune responses against Listeria monocytogenes.

High-mobility group box 1 (HMGB1) is a damage-associated molecular pattern with key proinflammatory functions following tissue injury. Moreover, HMGB1 neutralization was shown to alleviate LPS-induced shock, suggesting a role for the protein as a master therapeutic target for inflammatory and infectious diseases. Here, we report that HMGB1 neutralization impedes immune responses to Listeria monocytogenes, a wide-spread bacterium with pathogenic relevance for humans and rodents. Using genetic deletion strategies and neutralizing antibodies, we demonstrate that hepatocyte HMGB1, a major driver of post-necrotic inflammation in the liver, is dispensable for pathogen defense during moderately severe infection with listeria. In contrast, antibody-mediated HMGB1 neutralization and HMGB1 deficiency in myeloid cells effectuate rapid and uncontrolled bacterial dissemination in mice despite preserved basic leukocyte functionality and autophagy induction. During overwhelming infection, hepatocyte injury may contribute to increased HMGB1 serum levels and excessive inflammation in the liver, supporting context-dependent roles for HMGB1 from different cellular compartments during infection. We provide mechanistic evidence that HMGB1 from circulating immune cells contributes to the timely induction of hepatic immune regulatory gene networks, early inflammatory monocyte recruitment to the liver and promotion of neutrophil survival, which are mandatory for pathogen control. In summary, our data establish HMGB1 as a critical co-factor in the immunological clearance of listeria, and argue against HMGB1 neutralization as a universal therapeutic strategy for sepsis.\n\nAuthor summaryHigh-mobility group box 1 (HMGB1) is an abundantly expressed nucleoprotein with signaling properties following secretion or release into the extracellular space. Given its central immune-regulatory roles during tissue injury and LPS-induced septic shock, interventions aimed at HMGB1 signaling have been advocated as therapeutic options for various disease conditions. Here, we show that antibody-mediated HMGB1 neutralization interferes with immunological defense against Listeria monocytogenes, a gram-positive bacterium with high pathogenic relevance for rodents and humans, effectuating uncontrolled bacterial growth and inflammation. Using conditional knockout animals, we demonstrate that while leukocyte functionality is preserved in HMGB1-deficient myeloid cells, HMGB1 released in response to Listeria triggers hepatic inflammatory monocyte recruitment and activation of transcriptional immune networks required for the early control of bacterial dissemination. Hepatocyte HMGB1, a key driver of post-necrotic inflammation in the liver, is dispensable for the immune response during moderately severe infection, but likely contributes to excessive hepatitis when infection is uncontrolled and cellular injury is high. We demonstrate a critical and non-redundant role for HMGB1 in the immune-mediated clearance of listeriosis and argue against HMGB1 neutralization as a universal therapeutic option in the context of infection.

immunology↗

bioRxiv2019

3D imaging of colorectal cancer organoids identifies responses to Tankyrase inhibitors

Aberrant activation of the Wnt signalling pathway is required for tumour initiation and survival in the majority of colorectal cancers. The development of inhibitors of Wnt signalling has been the focus of multiple drug discovery programs targeting colorectal cancer and other malignancies associated with aberrant pathway activation. However, progression of new clinical entities targeting the Wnt pathway has been slow. One challenge lies with the limited predictive power of 2D cancer cell lines because they fail to fully recapitulate intratumoural phenotypic heterogeneity. In particular, the relationship between 2D cancer cell biology and cancer stem cell function is poorly understood. By contrast, 3D tumour organoids provide a platform in which complex cell-cell interactions can be studied. However, complex 3D models provide a challenging platform for the quantitative analysis of drug responses of therapies that have differential effects on tumour cell subpopulations. Here, we generated tumour organoids from colorectal cancer patients and tested their responses to inhibitors of Tankyrase (TNKSi) which are known to modulate Wnt signalling. Using compounds with 3 orders of magnitude difference in cellular mechanistic potency together with image-based assays, we demonstrate that morphometric analyses can capture subtle alterations in organoid responses to Wnt inhibitors that are consistent with activity against a cancer stem cell subpopulation. Overall our study highlights the value of phenotypic readouts as a quantitative method to asses drug-induced effects in a relevant preclinical model.

cancer biology↗