Biology subjects

Chang, H.-C.

Publications and source records attributed to Chang, H.-C..

23 records · Page 2Linked to original sources

bioRxiv2021

Laser Ablation and Fluid Flows Show a Single Force Mechanism Governs Spindle Positioning

Few techniques are available for elucidating the nature of forces that drive subcellular behaviors. Here we develop two complementary ones: 1) femtosecond stereotactic laser ablation (FESLA), which rapidly creates complex cuts of subcellular structures, thereby allowing precise dissection of when, where, and in what direction forces are generated; and 2) assessment of subcellular fluid flows, by comparing direct flow measurements, using microinjected fluorescent nanodiamonds, to large-scale fluid-structure simulations of different models of force transduction. We apply these to study centrosomes in Caenorhabditis elegans early embryos, and use the data to construct a biophysically-based model of centrosome dynamics. Taken together, we demonstrate that cortical pulling forces provide a general explanation for many behaviors mediated by centrosomes, including pronuclear migration/centration and rotation, metaphase spindle positioning, asymmetric spindle elongation and spindle oscillations. In sum, this work establishes new methodologies for disentangling the forces responsible for cell biological phenomena.

biophysics↗

bioRxiv2021

Aging is associated with increased brain iron through brain-derived hepcidin expression

Iron is an essential molecule for biological processes, but its accumulation can lead to oxidative stress and cellular death. Due to its oxidative effects, iron accumulation is implicated in the process of aging and neurodegenerative diseases. However, the mechanism for this increase in iron with aging, and whether this increase is localized to specific cellular compartment(s), are not known. Here, we measured the levels of iron in different tissues of aged mice, and demonstrate that while cytosolic non-heme iron is increased in the liver and muscle tissue, only the aged brain exhibits an increase in both the cytosolic and mitochondrial non-heme iron. This increase in brain iron is associated with elevated levels of local hepcidin mRNA and protein in the brain. We also demonstrate that the increase in hepcidin is associated with increased ubiquitination and reduced levels of the only iron exporter, feroportin-1 (FPN1). Overall, our studies provide a potential mechanism for iron accumulation in the brain through increased local expression of hepcidin, and subsequent iron accumulation due to decreased iron export. Additionally, our data support that aging is associated with mitochondrial and cytosolic iron accumulation only in the brain and not in other tissues.

cell biology↗

bioRxiv2020

Augmenter of Liver Regeneration Regulates Cellular Iron by Modulating Mitochondrial Transport of ATP-Binding Cassette B8

Chronic loss of Augmenter of Liver Regeneration (ALR) results in mitochondrial myopathy with cataracts, however, the mechanism for this disorder remains unclear. Here, we demonstrate that loss of ALR, a principal component of the MIA40/ALR protein import pathway, results in impaired cytosolic Fe/S cluster biogenesis in mammalian cells. Mechanistically, MIA40/ALR facilitates the mitochondrial import of ATP binding cassette (ABC)-B8, an inner mitochondrial membrane protein required for cytoplasmic Fe/S cluster maturation, through physical interaction with ABCB8. Downregulation of ALR impairs mitochondrial ABCB8 import, reduces cytoplasmic Fe/S cluster maturation, and increases cellular iron through the iron regulatory protein-iron response element system. Our finding provides a mechanistic link between MIA40/ALR import machinery and cytosolic Fe/S cluster maturation through the mitochondrial import of ABCB8, and offers a potential explanation for the pathology seen in patients with ALR mutations.

cell biology↗

bioRxiv2019

Dynamic-ultrastructural cell volume (3D) correlative microscopy facilitated by intracellular fluorescent nanodiamonds as multi-modal probes

Three-dimensional correlative light and electron microscopy (3D CLEM) are attaining popularity as a potential technique to explore the functional aspects of a cell together with high-resolution ultrastructural details across the cell volume. In order to perform such a 3D CLEM experiment, there is an imperative requirement for multi-modal probes that are both fluorescent and electron-dense. These multi-modal probes will serve as landmarks in matching up the large full cell volume datasets acquired by different imaging modalities. Fluorescent nanodiamonds (FNDs) are a unique nanosized, fluorescent, and electron-dense material from the nanocarbon family. We hereby propose a novel and straightforward method for executing 3D CLEM using FNDs as multi-modal landmarks. We demonstrate that FNDs is biocompatible and easily identified both in living cell fluorescence imaging and in serial block-face scanning electron microscopy (SB-EM). We illustrate the 3D CLEM method by registering multi-modal datasets.

cell biology↗

bioRxiv2019

Mechanistic and compositional studies of the autophagy-inducing areca nut ingredient

Areca nut (AN) is a popular chewing carcinogen worldwide causing a variety of diseases such as oral and esophageal carcinomas. We previously found that the partially purified 30-100 kDa fraction of AN extract (ANE 30-100K) induces autophagy in oral carcinoma OECM-1 cells and some other different types of cells. Since autophagy is known to play important roles in tumor establishment and development, the underlying mechanisms of ANE 30-100K-induced autophagy (AIA) is worthy of further investigation. In this study, we further demonstrated that the cytotoxic concentration of ANE 30-100K induces some typical autophagy hallmarks in esophageal carcinoma (CE81T/VGH) cells in an Atg5-dependent manner. Furthermore, the endocytosis inhibitor (methyl-{beta}-cyclodextrin) and two caveolin shRNAs, as well as two proteasome inhibitors (lactacystin and epoxomicin), were shown to attenuate ANE 30-100K-induced cytotoxicity and LC3-II accumulation significantly in OECM-1 and CE81T/VGH cells. Finally, we also analyzed the carbohydrate compositions of ANE 30-100K by phenol-sulfuric acid method and high performance anion exchange chromatography with pulse amperic detector. The results showed that ANE 30-100K contains about 67% carbohydrate and is composed of fucose (5.938%), arabinose (24.631%), glucosamine (8.066%), galactose (26.820%), glucose (21.388%), and mannose (13.157%). Collectively, these results suggest that caveolin-mediated endocytosis and proteasome are required for AIA and the major components of ANE 30-100K are carbohydrates. This study may have provided new knowledges of the action mechanisms and compositions of ANE 30-100K.

cancer biology↗