Biology subjects

Lin, S.-S.

Publications and source records attributed to Lin, S.-S..

10 recordsLinked to original sources

bioRxiv2026

P2X7 receptor-mediated astrocytic atrophy in the hippocampus of mice after status epilepticus

Genetic deletion or pharmacological blockade of P2X7 receptors (Rs) counteract status epilepticus (SE) in animal models of epilepsy. It is, however, unclear whether P2X7Rs are localized at astrocytes or neurons, and the reason for astrocytic atrophy arising in consequence of SE is also ambiguous. We conducted a combined morphological/electrophysiological study in order to investigate these issues. It has been shown that kainic acid (KA)-induced SE in mice led to the atrophy of hippocampal astrocytes and at the same time to the decrease of ezrin immunoreactivity and its co-expression with mCherry, whose synthesis has been initiated by the injection of a virus complex. mCherry expression in astrocytes enabled us to study changes in cell somata and processes brought about by KA-injection. Ezrin is a plasmalemmal-cytoskeleton linker; its grade of expression indicates changes in the existence/function of small peripheral astrocytic processes. Pretreatment of mice with the blood-brain barrier-permeable P2X7R antagonist JNJ-47965567 prevented the SE-induced damage of astrocytes. KA caused a potentiation of dibenzoyl-ATP (Bz-ATP) currents in astrocytes but not neurons of the hippocampus. This effect was also abolished by pre-treatment of mice with JNJ-47965567 before applying KA, although no similar changes occurred in hippocampal CA1 neurons. The measurement of spontaneous postsynaptic currents (sPSCs) and spontaneous excitatory postsynaptic currents (sEPSCs) indicated a presynaptic facilitation of neurotransmitter release by Bz-ATP. In conclusion, we suggest that astrocytic P2X7Rs are the primary target of ATP release from damaged CNS cells in the hippocampus which simultaneously causes damage to astrocytic somata and processes.

neuroscience↗

bioRxiv2025

The PXBAR-domain protein SNX9 selectively sequesters PI(3,4)P2 lipid and protects it from hydrolysis at the plasma membrane

Plasma membrane remodeling processes are tightly regulated by the spatiotemporal distribution and dynamic conversion of phosphoinositidyl lipids (PIPs). This regulation is controlled by the recruitment of proteins such as sorting nexin 9 (SNX9), a key mediator of late-stage endocytosis and macropinocytosis. Using live cell imaging, in vitro reconstitution assays, and molecular dynamics simulations, we investigated how SNX9 distinguishes between PI(3,4)P2 and PI(4,5)P2, and the physiological relevance of this selectivity. Our results revealed that during macropinocytic membrane ruffling, SNX9 is recruited in a spatiotemporally coordinated manner with PI(3,4)P2, but not with PI(4,5)P2. While SNX9 induces comparably weak mechanical remodeling on model membranes containing either PIP2 species, it exhibits a clear selective binding to PI(3,4)P2, mediated by a non-canonical interface. Through mutational analysis of key residues involved in this sequestration, we further demonstrated that SNX9 protects PI(3,4)P2 from hydrolysis. Together, these results reveal a previously unrecognized mechanism of SNX9-PIP2 lipid interaction that underscores SNX9s pivotal role in coordinating membrane remodeling processes. TeaserCurvature sensing BAR protein SNX9 selectively sequesters PI(3,4)P2 lipids, acting as a checkpoint in cell membrane remodeling.

biophysics↗

bioRxiv2024

Astrocyte ezrin defines resilience to stress-induced depressive behaviours in mice

Astrocyte atrophy is the main histopathological hallmark of major depressive disorder (MDD) in humans and in animal models of depression. Here we demonstrated that manipulating with ezrin expression specifically in astrocytes significantly increases the resilience of mice to chronic unpredictable mild stress (CUMS). Overexpression of ezrin in astrocytes from prefrontal cortex (PFC) rescued depressive-like behaviours induced by CUMS, whereas down-regulation of ezrin in astrocytes from PFC increased mice susceptibility to CUMS and promoted depressive-like behaviours. These behavioural changes correlated with astrocytic morphology. Astrocytes from PFC of mice sensitive to CUMS demonstrated significant atrophy; similar atrophy was found in astrocytes from animals with down-regulated ezrin expression. To the contrary morphology remains unchanged astrocytes in animals resistant to CUMS and in animals with astrocytic overexpression of ezrin. Morphological changes also correlated with ezrin immunoreactivity which was low in mice with depressive-like behaviours and high in mice resistant to stress. We conclude that Ezrin-dependent morphological remodelling of astrocytes defines the sensitivity of mice to stress: high ezrin expression renders them stress resilient, whereas low ezrin expression promotes depressive-like behaviour in response to chronic stress.

neuroscience↗

bioRxiv2024

Cellular mechanotransduction of human osteoblasts in microgravity

Astronauts experience significant and rapid bone loss as a result of an extended stay in space, making the International Space Station (ISS) the perfect laboratory for studying osteoporosis due to the accelerated nature of bone loss on the ISS. This prompts the question, how does the lack of load due to zero-gravity propagate to bone-forming cells, human fetal osteoblasts (hFOBs), altering their maturation to mineralization? Here, we aim to study the mechanotransduction mechanisms by which bone loss occurs in microgravity. Two automated experiments, 4 microfluidic chips capable of measuring single-cell mechanics of hFOBs via aspiration and cell spheroids incubated in pressure-controlled chambers, were each integrated into a CubeLab deployed to the ISS National Laboratory. For the first experiment, we report protrusion measurements of aspirated cells after exposure to microgravity at the ISS and compare these results to ground control conducted inside the CubeLab. Our analysis revealed slightly elongated protrusions for space samples compared to ground samples indicating softening of hFOB cells in microgravity. In the second experiment, we encapsulated osteoblast spheroids in collagen gel and incubated the samples in pressure-controlled chambers. We found that microgravity significantly reduced filamentous actin levels in the hFOB spheroids. When subjected to pressure, the spheroids exhibited increased pSMAD1/5/9 expression, regardless of the microgravity condition. Moreover, microgravity reduced YAP expression, while pressure increased YAP levels, thus restoring YAP expression for spheroids in microgravity. Our study provides insights into the influence of microgravity on the mechanical properties of bone cells and the impact of compressive pressure on cell behavior and signaling in space.

cell biology↗

bioRxiv2023

Matrix stiffness modulates 3D spheroid sorting and burst-like collective migration

While it is known that cells with differential adhesion tend to segregate and preferentially sort, the physical forces governing sorting and invasion in heterogeneous tumors remain poorly understood. To investigate this, we tune matrix confinement, mimicking changes in the stiffness and confinement of the tumor microenvironment, to explore how physical confinement influences individual and collective cell migration in 3D spheroids. High levels of confinement lead to cell sorting while reducing matrix confinement triggers the collective fluidization of cell motion. Cell sorting, which depends on cell-cell adhesion, is crucial to this phenomenon. Burst-like migration does not occur for spheroids that have not undergone sorting, regardless of the degree of matrix confinement. Using computational Self-Propelled Voronoi modeling, we show that spheroid sorting and invasion into the matrix depend on the balance between cell-generated forces and matrix resistance. The findings support a model where matrix confinement modulates 3D spheroid sorting and unjamming in an adhesion-dependent manner, providing insights into the mechanisms of cell sorting and migration in the primary tumor and toward distant metastatic sites.

biophysics↗

bioRxiv2023

Electroacupuncture prevents astrocyte atrophy to alleviate depression

Astrocyte atrophy is the main histopathological hallmark of the major depressive disorder (MDD) in humans and in animal models of depression. Here we show that electroacupuncture prevents astrocyte atrophy in the prefrontal cortex and alleviates depressive-like behaviour in mice subjected to the chronic unpredictable mild stress (CUMS). Treatment of mice with CUMS induced depressive-like phenotypes as confirmed by sucrose preference test, tail suspension test, and forced swim test. These behavioural changes were paralleled with morphological atrophy of astrocytes in the prefrontal cortex, revealed by analysis of 3D reconstructions of confocal Z-stack images of mCherry expressing astrocytes. This morphological atrophy was accompanied with a decrease in expression of cytoskeletal linker Ezrin, associated with formation of astrocytic leaflets, which form astroglial synaptic cradle. Electroacupuncture at the acupoint ST36 as well as treatment with anti-depressant fluoxetine prevented depressive-like behaviours, astrocytic atrophy and down-regulation of astrocytic ezrin. In conclusion, our data further strengthen the notion of a primary role of astrocytic atrophy in depression and reveal astrocytes as cellular target for electroacupuncture in treatment of depressive disorders.

neuroscience↗

bioRxiv2022

Compressive stress drives adhesion-dependent unjamming transitions in breast cancer cell migration

Cellular unjamming is the collective fluidization of cell motion and has been linked to many biological processes, including development, wound repair, and tumor growth. In tumor growth, the uncontrolled proliferation of cancer cells in a confined space generates mechanical compressive stress. However, because multiple cellular and molecular mechanisms may be operating simultaneously, the role of compressive stress in unjamming transitions during cancer progression remains unknown. Here we investigate which mechanism dominates in a dense, mechanically stressed monolayer. We find that long-term mechanical compression triggers cell arrest in benign epithelial cells and enhances cancer cell migration in transitions correlated with cell shape, leading us to examine the contributions of cell-cell adhesion and substrate traction in shape-dependent unjamming transitions. We show that cadherin-mediated cell-cell adhesion regulates differential cellular responses to compressive stress and predominantly controls unjamming transitions in dense monolayers. Importantly, compressive stress does not induce the epithelial--mesenchymal transition in unjammed cells. Using traction force microscopy, traction forces are attenuated in compressed cells in the bulk of the monolayer regardless of cell type and motility. Intercellular adhesion thus is the dominant regulator of compression-induced unjamming transitions and may impact collective cell motion in tumor development and breast cancer progression.

biophysics↗

bioRxiv2020

Dynamin-2 regulates synaptic podosome maturation to facilitate neuromuscular junction development

Neuromuscular junctions (NMJs) govern rapid and efficient neuronal communication with muscle cells, which relies on the proper architecture of specialized postsynaptic compartments. However, the intrinsic mechanism in muscle cells contributing to elaborate NMJ development has been unclear. In this study, we reveal that the GTPase dynamin-2 (Dyn2), best-known for catalyzing synaptic vesicle endocytosis at the presynaptic membrane, is also involved in postsynaptic morphogenesis. We demonstrate that Dyn2 is enriched in the postsynaptic membrane of muscle cells and is involved in the maturation of neurotransmitter receptor clusters via its actin bundling ability. Dyn2 functions as a molecular girdle to regulate synaptic podosome turnover and promote morphogenesis of the postsynaptic apparatus. In Drosophila NMJs, Dyn2 is required to organize the postsynaptic actin cytoskeleton and to mediate its electrophysiological activities. Mechanistically, the actin binding, self-assembly, GTP hydrolysis ability, and Y597 phosphorylation of Dyn2 all regulate its actin bundling activity. Together, our study uncovers a role for Dyn2 in cytoskeleton remodeling and organization at the postsynaptic membrane of NMJs.

molecular biology↗

bioRxiv2019

Chromatin organization in early land plants reveals an ancestral association between H3K27me3, transposons, and constitutive heterochromatin

Genome packaging by nucleosomes is a hallmark of eukaryotes. Histones and the pathways that deposit, remove, and read histone modifications are deeply conserved. Yet, we lack information regarding chromatin landscapes in extant representatives of ancestors of the main groups of eukaryotes and our knowledge of the evolution of chromatin related processes is limited. We used the bryophyte Marchantia polymorpha, which diverged from vascular plants 400 Mya, to obtain a whole chromosome genome assembly and explore the chromatin landscape and three-dimensional organization of the genome of early land plants. Based on genomic profiles of ten chromatin marks, we conclude that the relationship between active marks and gene expression is conserved across land plants. In contrast, we observed distinctive features of transposons and repeats in Marchantia compared with flowering plants. Silenced transposons and repeats did not accumulate around centromeres, and a significant proportion of transposons were marked by H3K27me3, which is otherwise dedicated to the transcriptional repression of protein coding genes in flowering plants. Chromatin compartmentalization analyses of Hi-C data revealed that chromatin regions belonging to repressed heterochromatin were densely decorated with H3K27me3 but not H3K9 or DNA methylation as reported in flowering plants. We conclude that in early plants, H3K27me3 played an essential role in heterochromatin function, suggesting an ancestral role of this mark in transposon silencing.

molecular biology↗

bioRxiv2019

Acute decrease in plasma membrane tension induces macropinocytosis via PLD2 activation

Internalization of macromolecules and membrane into cells through endocytosis is critical for cellular growth, signaling, and membrane tension homeostasis. Although endocytosis is responsive to both biochemical and physical stimuli, how physical cues modulate endocytic pathways is less understood. In contrary to the accumulating discoveries on effects of increased membrane tension on endocytosis, little is known about how a drop of tension impacts membrane trafficking. Here we reveal that acute reduction of plasma membrane tension results in phosphatidic acid, F-actin and dynamin 2-enriched dorsal membrane ruffling and subsequent macropinocytosis in myoblast. The membrane flaccidity-induced local phosphatidic acid production depends on phospholipase D2 (PLD2) that is activated via lipid raft disruption. Furthermore, the \"membrane flaccidity-PLD2-macropinocytosis\" pathway is dominant in myotube, reflecting a potential mechanism of membrane tension homeostasis upon intensive muscle stretching and relaxation. Together, we identify a new mechanotransduction pathway which converts acute tension drop into PA production and subsequently initiates macropinocytosis via actin and dynamin activities.\n\nSummaryWe reveal a mechanical induction of macropinocytosis that is elicited by acute decrease of plasma membrane tension, followed by lipid raft destabilization, PLD2 activation and PA production.

cell biology↗