Localization and regulation of yeast aldehyde dehydrogenase Ald4p structures.

Previously, we identified yeast strains, namely SWORD, showing more robust Ald4p-GFP filament formation than the typical strains. Here, we report that Ald4p-GFP in SWORD strains favorably polymerize into gigantic structures in the cytoplasm, despite the enzyme being established as a mitochondrial resident. In addition, we have found that nocodazole, a microtubule destabilizer, has no effect on Ald4p high-order assembly, suggesting no direct association between microtubule dynamics and Ald4p structure formation.

Extracellular Fe and Fe modulate osteocytic viability, expression of SOST, RANKL and FGF23, and fluid flow-induced YAP1 nuclear translocation.

Iron overload negatively affects bone mass and strength. However, the impact of iron excess on osteocytes-important bone cells for mechanotransduction and remodeling-is poorly understood. Herein, we examined the effects of iron exposure on osteocytes during their maturation process.

Robust assembly of the aldehyde dehydrogenase Ald4p in Saccharomyces cerevisiae.

As part of our studies of yeast aldehyde dehydrogenase (Ald4p) assembly, we identified a population of transformants (SWORD strain) that show more robust filament formation of GFP-tagged Ald4p (Ald4p-GFP) than that of a wild type ALD4::GFP strain. Sequencing of the ALD4 gene in the SWORD strain showed that the increased assembly was not due to changes to the ALD4 coding sequence, suggesting that a second mutation site was altering Ald4p assembly. Using short-read whole-genome sequencing, we identified spontaneous mutations in FLO9.

Analysis of Influenza A virus infection in human induced pluripotent stem cells (hiPSCs) and their derivatives.

Influenza A virus (IAV) infection in pregnant women is a major public health concern. However, the effect of IAV infection on human embryogenesis is still unclear. Here we show that human induced pluripotent stem cells (hiPSCs) and hiPSC-derived ectodermal, mesodermal and endodermal cells are susceptible to IAV infection.

Nuclear targeted Saccharomyces cerevisiae asparagine synthetases associate with the mitotic spindle regardless of their enzymatic activity.

Recently, human asparagine synthetase has been found to be associated with the mitotic spindle. However, this event cannot be seen in yeast because yeast takes a different cell division process via closed mitosis (there is no nuclear envelope breakdown to allow the association between any cytosolic enzyme and mitotic spindle). To find out if yeast asparagine synthetase can also (but hiddenly) have this feature, the coding sequences of green fluorescent protein (GFP) and nuclear localization signal (NLS) were introduced downstream of ASN1 and ASN2, encoding asparagine synthetases Asn1p and Asn2p, respectively, in the yeast genome having mCherrry coding sequence downstream of TUB1 encoding alpha-tubulin, a building block of the mitotic spindle.

Analysis of Tembusu virus infection of human cell lines and human induced pluripotent stem cell derived hepatocytes.

Tembusu virus (TMUV) causes disease in poultry, especially in ducks, resulting in abnormality in egg production and with high morbidity and mortality, resulting in great loss in duck farming industry in China and Southeast Asia. Previous studies on the pathogenesis of TMUV infection have been mostly conducted in poultry, with a few studies being undertaken in mice. While TMUV does not cause disease in humans, it has been reported that antibodies against TMUV have been found in serum samples from duck farmers, and thus data on TMUV infection in humans is limited, and the pathogenesis is unclear.

Coupled regulations of enzymatic activity and structure formation of aldehyde dehydrogenase Ald4p.

Previously, we have developed an extramitochondrial assembly system, where mitochondrial targeting signal (MTS) can be removed from a given mitochondrial enzyme, which could be used to characterize the regulatory factors involved in enzyme assembly/disassembly Here, we demonstrate that addition of exogenous acetaldehyde can quickly induce the supramolecular assembly of MTS-deleted aldehyde dehydrogenase Ald4p in yeast cytoplasm. Also, by using PCR-based modification of the yeast genome, cytoplasmically targeted Ald4p cannot polymerize into long filaments when key functional amino acid residues are substituted, as shown by N192D, S269A, E290K and C324A mutations. This study has confirmed that extramitochondrial assembly could be a powerful external system for studying mitochondrial enzyme assembly, and its regulatory factors outside the mitochondria.

Saccharomyces cerevisiae ASN1 and ASN2 are asparagine synthetase paralogs that have diverged in their ability to polymerize in response to nutrient stress.

Recent work has found that many metabolic enzymes have the ability to polymerize in response to metabolic changes or environmental stress. This ability to polymerize is well conserved for the few metabolic enzyme paralogs that have been studied in yeast. Here we describe the first set of paralogs, Asn1p and Asn2p, that have differential assembly behavior.

Nevirapine induced mitochondrial dysfunction in HepG2 cells.

Nevirapine (NVP) is a non-nucleoside reverse transcriptase inhibitor frequently used in combination with other antiretroviral agents for highly active antiretroviral therapy (HAART) of patients infected with the human immunodeficiency virus type 1 (HIV-1). However NVP can cause serious, life-threatening complications. Hepatotoxicity is one of the most severe adverse effects, particularly in HIV patients with chronic hepatitis C virus co-infection as these patients can develop liver toxicity after a relatively short course of treatment.

Titration of individual strains in trivalent live-attenuated influenza vaccine without neutralization.

Formulation and quality control of trivalent live-attenuated influenza vaccine requires titration of infectivity of individual strains in the trivalent mix. This is usually performed by selective neutralization of two of the three strains and titration of the un-neutralized strain in cell culture or embryonated eggs. This procedure requires standard sera with high neutralizing titer against each of the three strains.

Viral load of the highly pathogenic avian influenza H5N1 virus in infected human tissues.

The highly pathogenic avian influenza A (H5N1) virus is a virulent virus that causes an acute febrile respiratory disease with high mortality in humans. To gain a better insight of H5N1 viral distributions in infected human tissues, the levels of viral RNA were determined in the autopsy tissues from two patients who were infected with H5N1 virus by using real-time reverse transcription-polymerase chain reaction. In one patient who died on day 6 of the illness, the viral load in the lung was extremely high, whereas the levels of viral RNA in the other organs were more than 6 log lower.