Project description:Alzheimer's disease (AD) is associated with the formation of extracellular amyloid-β (Aβ) plaque, perturbing the mechanical properties of brain tissue. Microglia sense and integrate biochemical and mechanical cues in their local microenvironment, intimately linked with AD progress. However, little is known about how microglial mechanosensing pathways are implicated in AD pathogenesis. Gene Ontology (GO) analysis of the significantly down-regulated genes in Piezo1 conditional knockout microglia revealed a significant functional reduction in synapse organization, cell-substrate adhesion, and cytoskeleton system-based events (morphogenesis, migration, and endocytosis) in 5×FAD mice.
Project description:To investigate the influence of Aβ40WT and Aβ42WT fibrils on astrocyte and microglia, we isolated astrocyte and microglia from P2 SD rats and treated glia cells with Aβ40WT and Aβ42WT fibrils for 24 hours. We then performed gene expression profiling analysis using data obtained from RNA-seq of astrocyte and microglia treated with Aβ fibrils.
Project description:Muscle satellite cells (MuSCs), skeletal muscle-resident stem cells, are crucial for regeneration of myofibers. Mechanical cues are thought to be important for activation and proliferation of muscle satellite cells, but the molecular entity that senses biophysical forces in MuSCs remains to be elucidated. In this study, we identified PIEZO1, a mechanosensitive ion channel that is activated by membrane tension, as a critical determinant for myofiber regeneration. We investigated gene profiles of Piezo1-deficient MuSCs to understand the role of PIEZO1 during myogenesis. Our results suggest that PIEZO1 governs the cytoskeletal reorganization to regulate cellular events in MuSCs (i.e., activation, cell-division, and proliferation) during skeletal muscle regeneration.
Project description:The aggregation of amyloid beta (Aβ) peptide is associated with Alzheimer’s disease (AD) pathogenesis. Cell membrane composition, especially monosialotetrahexosylganglioside (GM1), is known to promote the formation of Aβ fibrils, yet little is known about the roles of GM1 in the early steps of Aβ oligomer formation. Here, by using GM1-contained liposomes as a mimic of neuronal cell membrane, we demonstrate that GM1 is a critical trigger of Aβ oligomerization and aggregation. We find that GM1 not only promotes the formation of Aβ fibrils, but also facilitates the maintenance of Aβ oligomers on liposome membranes. We structurally characterize the Aβ oligomers formed on the membrane and find that GM1 captures Aβ by binding to its arginine-5 residue. To interrogate the mechanism of Aβ oligomer toxicity, we design a new liposome-based Ca2+-encapsulation assay and provide new evidence for the Aβ ion channel hypothesis. Finally, we conduct cell viability assay to determine the toxicity of Aβ oligomers formed on membranes. Overall, by uncovering the roles of GM1 in mediating early Aβ oligomer formation and maintenance, our work provides a novel direction for pharmaceutical research for AD.
Project description:Despite the importance of Aβ aggregation in Alzheimer’s disease etiology, our understanding of the sequence determinants of aggregation is sparse and largely derived from in vitro studies. For example, in vitro proline and alanine scanning mutagenesis of Aβ40 proposed core regions important for aggregation. However, we lack even this limited mutagenesis data for the more disease-relevant Aβ42. Thus, to better understand the molecular determinants of Aβ42 aggregation in a cell-based system, we combined a yeast DHFR aggregation assay with deep mutational scanning. We measured the effect of 791 of the 798 possible single amino acid substitutions on the aggregation propensity of Aβ42. We found that ~75% of substitutions, largely to hydrophobic residues, maintained or increased aggregation. We identified 11 positions at which substitutions, particularly to hydrophilic and charged amino acids, disrupted Aβ aggregation. These critical positions were similar but not identical to critical positions identified in previous Aβ mutagenesis studies. Finally, we analyzed our large-scale mutagenesis data in the context of different Aβ aggregate structural models, finding that the mutagenesis data agreed best with models derived from fibrils seeded using brain-derived Aβ aggregates.
Project description:In gastric cancer (GC), PIEZO1 was suggested to promote cell migration by interacting with Trefoil factor family 1 (TFF1) and serve as a therapeutic target against invasion and metastasis. In addition, PIEZO1 demonstrates abundant expression in most GC cell lines and primary samples and highly-expressed PIEZO1 is associated with poor disease-specific survival. As Yoda1 is known to be an agonist of PIEZO1, we try to explore the PIEZO1 function in GC by Yoda1 treatment.
Project description:Piezo1 is a mechanosensitive ion channel that has gained recognition for its role in regulating diverse physiological processes. However, the influence of Piezo1 in inflammatory disease, including infection and tumor-immunity, is not well-studied. We postulated that Piezo1 links physical forces to immune regulation in myeloid cells. We discovered signal transduction via Piezo1 in myeloid cells and established this channel as the primary sensor of mechanical stress in these cells. Global inhibition of Piezo1 was protective against both cancer and septic shock and resulted in a diminution in suppressive myeloid cells. Moreover, deletion of Piezo1 in myeloid cells protected against cancer and increased survival in poly-microbial sepsis. Mechanistically, we show that mechanical stimulation promotes Piezo1-dependent myeloid cell expansion by suppressing Rb. We further show Piezo1-mediated silencing of Rb is regulated via upregulation of HDAC2. Collectively, our work uncovers Piezo1 as a targetable immune checkpoint that drives immune-suppressive myelopoiesis in cancer and infectious disease.
Project description:In gastric cancer (GC), PIEZO1 was suggested to promote cell migration by interacting with Trefoil factor family 1 (TFF1) and serve as a therapeutic target against invasion and metastasis. In addition, PIEZO1 demonstrates abundant expression in most GC cell lines and primary samples and highly-expressed PIEZO1 is associated with poor disease-specific survival. Thus, we try to explore the PIEZO1 function in GC by knocking down assay.
Project description:The mechanisms by which physical forces regulate cells to determine complexities of vascular structure and function are enigmatic. Here we show the role the ion channel subunit Piezo1 (FAM38A). Disruption of mouse Piezo1 gene disturbed vascular development and was embryonic lethal within days of the heart beating to cause blood flow. Importance of Piezo channels as sensors of blood flow was indicated by Piezo1 dependence of shear stress-evoked ionic current and calcium influx in endothelial cells and the ability of exogenous Piezo1 to confer shear stress sensitivity on cells that otherwise lacked. Downstream of this calcium influx was proteoase activity and spatial organization of endothelial cells to the polarity of the applied force. Without Piezo1, normal endothelial cell organization was lacking. The data suggest Piezo1 channels as pivotal integrators of vascular architacture with physiological mechanical force.
Project description:A key pathogenic agent in Alzheimer’s disease (AD) is the amyloid β-protein (Aβ), which self-assembles into a variety of neurotoxic structures. Establishing structure-activity relationships for these assemblies is critical for proper therapeutic target identification and design. We examined the effects of Aβ monomers, dimers, higher-order oligomers, and fibrils on gene expression in primary rat hippocampal neurons. As opposed to “reverse” Aβ or non-Aβ peptides typically used as controls in such studies, we designed novel scrambled Aβ peptides predicted to behave distinctly from native Aβ. Significant changes in gene expression were observed for all peptide assemblies, but fibrils induced the largest changes. Significant changes in gene expression were observed for all peptide assemblies, but fibrils induced the largest changes. Weighted gene co-expression network analysis (WGCNA) revealed two predominant gene modules related to Aβ treatment. Many genes within these modules were associated with inflammatory signaling pathways