Biology subjects

LIU, L.

Publications and source records attributed to LIU, L..

6 recordsLinked to original sources

bioRxiv2026

A murine model of Shigella sonnei intestinal colonization

Shigella sonnei is a leading cause of bacterial dysentery and a high priority WHO pathogen because of the spread of multidrug resistant strains. Understanding microbiome-Shigella-host interactions during colonization of the gastrointestinal tract, and the development of vaccines have been hampered by the lack of small animal models of shigellosis. Here, we developed a murine model of intestinal colonization with S. sonnei. Pre-treatment of mice with antibiotics disturbed the intestinal microbiome and rendered mice susceptible to high level, gastrointestinal colonization with S. sonnei for over one week. Infection with S. sonnei CS14 harbouring a stable virulence plasmid induced an initial inflammatory response in wild type mice, with weight loss and elevated levels of fecal lipocalin 2; the S. sonnei Type III Secretion System was responsible for this inflammatory response. Expression of O-antigen and Group IV capsule by S. sonnei promoted sustained intestinal colonization, with infected mice developing mucosal and systemic antibody responses predominantly directed at these glycans. Finally, infection with S. sonnei induced a degree of protection against subsequent re-challenge. Overall, this murine model successfully mimics aspects of S. sonnei colonization and should be helpful in understanding how S. sonnei successfully survives within the gastrointestinal tract and competes with the microbiota as well as the evaluation of vaccine candidates.

microbiology↗

bioRxiv2025

β-cell-specific Non-invasive Ultrasound Stimulation to Enhance Insulin Release and Glucose Control in Mice

AbstractsDiabetes poses a significant global health burden, with complications such as cardiovascular disease, stroke, and kidney failure. While insulin therapy is central to type 2 diabetes (T2D) management, its limitations--including rapid degradation and the need for frequent injections--highlight the demand for non-invasive alternatives. Here, we present an ultrasound (US)-mediated approach to enhance insulin release by selectively stimulating pancreatic {beta}-cells via targeted microbubbles (MBs). In vitro experiments using RINm5F {beta}-cells demonstrated that US-MB stimulation induces significant calcium influx and subsequent insulin release. In addition, this method effectively decreased blood glucose levels in mice by promoting insulin release. Mechanistic studies revealed that mechanosensitive ion channels play a pivotal role, as their inhibition (via GdCl3) abolished the ultrasonic effect. Importantly, the approach exhibited high biosafety, with no detectable cell death or tissue damage. Our findings establish ultrasound-stimulated {beta}-cell targeting as a promising non-invasive strategy for diabetes treatment, offering a potential alternative to conventional insulin therapy.

bioengineering↗

bioRxiv2023

A Cryptic Basic Groove formed by Ubiquitin and Histone H3 Mediates the Selective Recognition of H2AK119Ub Nucleosomes by Synovial Sarcoma X Breakpoint 1 Protein

The cancer-specific fusion oncoprotein SS18-SSX1 disturbs chromatin accessibility by hijacking the BAF complex from the promoters and enhancers to the polycomb-repressed chromatin regions. This process relies on the selective recognition of H2AK119Ub nucleosomes by SSX1. However, the mechanism by which SSX1 selective recognition of H2AK119Ub nucleosomes in the absence of ubiquitin (Ub)-binding capacity remains unknown. Here we report the cryo-EM structure of SSX1 bound to H2AK119Ub nucleosomes at 3.1 [A] resolution. Combined in vitro biochemical and cellular assays revealed that the Ub recognition by SSX1 is unique and depends on a cryptic basic groove formed by H3 and the Ub motif on the H2AK119 site. Moreover, this unorthodox binding mode of SSX1 induces DNA unwrapping at the entry/exit sites. Together, our results describe a unique mode of site-specific ubiquitinated nucleosome recognition that underlies the specific hijacking of the BAF complex to polycomb regions by SS18-SSX1 in synovial sarcoma.

molecular biology↗

bioRxiv2023

Structural Visualization of HECT-E3 Ufd4 accepting and transferring Ubiquitin to Form K29/K48-branched Polyubiquitination on N-degron

The K29/K48-linked ubiquitination generated by the cooperative catalysis of E3 ligase Ufd4 and Ubr1 is an enhanced protein degradation signal, in which Ufd4 is responsible for introducing K29-linked ubiquitination to K48-linked ubiquitin chains to augment polyubiquitination. How HECT-E3 ligase Ufd4 mediates the ubiquitination event remains unclear. Here, we biochemically determine that Ufd4 preferentially catalyses K29-linked ubiquitination on K48-linked ubiquitin chains to generate K29/K48-branched ubiquitin chains and capture structural snapshots of Ub transfer cascades for Ufd4-mediated ubiquitination. The N-terminal ARM region and HECT domain C-lobe of Ufd4 are identified and characterized as key structural elements that together recruit K48-linked diUb and orient Lys29 of its proximal Ub to the active cysteine of Ufd4 for K29-linked branched ubiquitination. These structures not only provide mechanistic insights into the architecture of the Ufd4 complex but also provide structural visualization of branched ubiquitin chain formation by a HECT-type E3 ligase.

biochemistry↗

bioRxiv2020

Dissecting the microenvironment around biosynthetic scaffolds in murine skin wound healing

Structural properties of biomaterials play critical roles in guiding cell behaviors and influence the immune response against them. We fabricated electrospun membranes with three types of surface topography (Random, Aligned, and Latticed). The aligned membranes showed immunomodulatory ability, and led to faster wound healing, reduced fibrotic response and enhanced regeneration of cutaneous appendages when used in skin wound repair. Based on that, we performed single-cell RNA sequencing analysis on cells from wounded mouse skin in the presence or absence of the Aligned scaffold. Keratinocytes, fibroblasts, and immune cells including neutrophils, monocytes, macrophages, dendritic cells, and T cells showed diverse cellular heterogeneity. More hair follicle progenitor cells, inner root sheath cells (anagen-related) and fibroblast subsets were found in the Aligned group, which corresponded to the improved regeneration of hair follicles and faster wound closure in the presence of scaffold. Immune responses towards the biomaterial differed from that of control group. In aligned samples, infiltrated macrophages and neutrophils were reduced, whereas more effector T cells were recruited. The time course of immune response was possibly advanced towards an adaptive immunity-dominant stage by the scaffold. The microenvironment around scaffold involved intricate interplay of immune cells and cutaneous cells, and wound healing was the comprehensive results of numerous influencing factors working together.

immunology↗

bioRxiv2020

Accurate CNV identification from only a few cells with low GC bias in a single-molecule sequencing platform

A technical problem of characterizing copy number variation of several cells with next-generation sequencing is the whole genome amplification induced bias. The result of CNVs and mosaicism detection is affected by the GC bias. Here, we report a rapid non-WGA sample preparation strategy for a single-molecule sequencing platform GenoCare1600. This approach, combined with a single-molecule sequencing platform that avoids the use of WGA and bridge PCR processes, can provide higher reliability with its lower GC bias. By combining our optimized Tn5-based transposon insertion approach with GenoCare, we successfully detected CNVs as small as 1.29M and mosaicism as small as 20%, which is consistent with next-generation sequencing (NGS) data. Moreover, our GenoCare-TTI protocol showed less GC bias and less Mad of Diff. These results suggest that the optimized TTI approach, together with the GenoCare1600 sequencing platform, is a promising option for CNV characterization from maybe one single cell.

genetics↗