Yuri Miura

Pancreatic ductal adenocarcinoma (PDAC) exhibits diverse phenotypes, including epithelial and mesenchymal characteristics, yet these features have not been effectively translated into clinical applications. Mucins are implicated in tumor progression and therapeutic resistance and are considered potential diagnostic and therapeutic targets. In this study, five epithelial and three mesenchymal PDAC cell lines were cultured under two-dimensional (2D) and three-dimensional (3D) conditions to investigate mucin expression. Proteomic analysis identified five mucins (MUC1, MUC4, MUC5B, MUC19, and MUC20) in 2D culture and eight (including MUC2, MUC5AC, and MUC13) in 3D culture. Candidate mucins were further validated by immunocytochemistry with H-score assessment. MUC1 was consistently expressed in all PDAC cell lines and showed marked upregulation in several lines under 3D culture. In mesenchymal PDAC cell lines, mucin expression was largely restricted to MUC1, whereas epithelial lines displayed broad 3D-induced reorganization. Notably, MUC5AC was absent in 2D culture but robustly induced in all epithelial PDAC cell lines under 3D conditions. Other mucins, including MUC2, MUC4, MUC5B, MUC13, MUC19, and MUC20, were variably upregulated, with epithelial lines demonstrating higher diversity and intensity of expression. These findings demonstrate that 3D culture effectively reveals the plasticity and heterogeneity of mucin expression in PDAC, highlighting its potential as a platform for biomarker discovery and the development of therapeutic strategies.

A higher Japan Science and Technology Agency Index of Competence (JST-IC) score—an index of higher-level functional ability among older Japanese adults—was associated with a lower long-term risk of a...

Neuronal aging and neurodegenerative diseases are accompanied by proteostasis collapse, while the cellular factors that trigger it have not been identified. Impaired mitochondrial transport in the axon is another feature of aging and neurodegenerative diseases. Using Drosophila , we found that genetic depletion of axonal mitochondria causes dysregulation of protein degradation. Axons with mitochondrial depletion showed abnormal protein accumulation and autophagic defects. Lowering neuronal ATP levels by blocking glycolysis did not reduce autophagy, suggesting that autophagic defects are associated with mitochondrial distribution. We found that eIF2β was increased by the depletion of axonal mitochondria via proteome analysis. Phosphorylation of eIF2α, another subunit of eIF2, was lowered, and global translation was suppressed. Neuronal overexpression of eIF2β phenocopied the autophagic defects and neuronal dysfunctions, and lowering eIF2β expression rescued those perturbations caused by depletion of axonal mitochondria. These results indicate the mitochondria-eIF2β axis maintains proteostasis in the axon, of which disruption may underlie the onset and progression of age-related neurodegenerative diseases.

Aging affects tissue glycan profiles, which may alter cellular functions and increase the risk of age-related diseases. Glycans are biosynthesized by glycosyltransferases using the corresponding nucleotide sugar, and the availability of nucleotide sugars affects glycosylation efficiency. However, the effects of aging on nucleotide sugar profiles and contents are yet to be elucidated. Therefore, this study aimed to investigate the effects of aging on nucleotide sugars using a new LC-MS/MS method. Specifically, the new method was used to determine the nucleotide sugar contents of various tissues (brain, liver, heart, skeletal muscle, kidney, lung, and colon) of male C57BL/6NCr mice (7- or 26-month-old). Characteristic age-associated nucleotide sugar changes were observed in each tissue sample. Particularly, there was a significant decrease in UDP-glucuronic acid content in the kidney of aged mice and a decrease in the contents of several nucleotide sugars, including UDP-N-acetylgalactosamine, in the brain of aged mice. Additionally, there were variations in nucleotide sugar profiles among the tissues examined regardless of the age. The kidneys had the highest concentration of UDP-glucuronic acid among the seven tissues. In contrast, the skeletal muscle had the lowest concentration of total nucleotide sugars among the tissues; however, CMP-N-acetylneuraminic acid and CDP-ribitol were relatively enriched. Conclusively, these findings may contribute to the understanding of the roles of glycans in tissue aging.

Obesity has been increasing worldwide and is well-known as a risk factor for cognitive decline. It has been reported that oxidative stress in the brain is deeply involved in cognitive dysfunction in rodent models. While there are many studies on oxidation in the liver and adipose tissue of obese mice, the relationship between obesity-induced cognitive dysfunction and brain oxidation has not been elucidated. Here, we show that obesity induced by a high-fat, high-sucrose diet (HFSD) alters cognitive function in C57BL/6 male mice, and it may involve the acceleration of brain oxidation. Tocotrienols (T3s), which are members of the vitamin E family, can prevent HFSD-induced cognitive changes. To elucidate these mechanisms, respiratory metabolism, locomotor activity, temperature around brown adipose tissue, and protein profiles in the cerebrum cortex were measured. Contrary to our expectation, respiratory metabolism was decreased, and temperature around brown adipose tissue was increased in the feeding of HFSD. The proteins that regulate redox balance did not significantly change, but 12 proteins, which were changed by HFSD feeding and not changed by T3s-treated HFSD compared to control mice, were identified. Our results indicated that HFSD-induced obesity decreases mouse learning ability and that T3s prevent its change. Additionally, feeding of HFSD significantly increased brain oxidation. However, further study is needed to elucidate the mechanisms of change in oxidative stress in the brain by obesity.

Protein acylation is a vital post-translational modification that regulates various protein functions. In particular, protein succinylation has attracted significant attention because of its potential relationship with various biological events and diseases. In this report, we establish a new method for the comprehensive detection and analysis of potentially succinylated proteins using a chemical tagging technology. The newly synthesized alkyne-containing succinyl substrate successfully labeled lysine residues of proteins through intracellular metabolic labeling independent of other acylation pathways such as protein malonylation. Furthermore, reporter molecules such as biotin moieties and fluorescent dyes were conjugated to alkyne-tagged succinylated proteins via Click reactions, permitting enrichment for proteomic analysis and fluorescence imaging of the labeled proteins. We successfully analyzed and identified numerous potential succinylated proteins associated with various biological processes using gel electrophoresis, proteomic and bioinformatic analyses, and their visualization in cells.

Aim: Heart failure is increasing in Japan, in particular that with preserved ejection fraction (HFpEF) prevalent in older‐aged patients. The purpose of this study was to investigate the pathophysiology during the early stage of left ventricular (LV) diastolic dysfunction by the quantitative proteome analysis of human myocardium.Methods: Among 331 post‐mortem autopsy patients, we selected 23 patients (aged 79 ± 9.6 years) with echocardiographic data and without major comorbidities, except hypertension. Cryopreserved autopsy tissue of the LV myocardium was subjected to proteome analysis. LV diastolic function was evaluated by echocardiographic data. Thirteen patients were classified into the impaired diastolic function (IDF) group, and 10 the normal cardiac function group. We performed comparative proteome analysis between the IDF and normal groups by isobaric tags for relative and absolute quantitation (iTRAQ) using nano‐liquid chromatography–tandem mass spectrometry.Results: The iTRAQ‐based proteome analysis revealed 57 differentially expressed proteins in the IDF group. Molecular network analysis of differentially expressed proteins indicated that endoplasmic reticulum (ER) stress was a potentially important event. Furthermore, the expressions of proteins associated with the ER stress response, such as glucose‐regulated protein 78 kDa, inositol‐requiring kinase 1α and spliced X‐box binding protein 1, were significantly decreased in the IDF group.Conclusions: This study suggested that reduced ER stress responses were involved during the early stage of LV diastolic dysfunction. Geriatr Gerontol Int ••; ••: ••–•• Geriatr Gerontol Int 2021; 21: 577–583.

Serine-threonine kinase 38 (STK38) is a member of the protein kinase A (PKA)/PKG/PKC-family implicated in the regulation of cell division and morphogenesis. However, the molecular mechanisms underlying STK38 stability remain largely unknown. Here, we show that treatment of cells with either heat or the calcium ionophore A23187 induced STK38 degradation. The calpain inhibitor calpeptin suppressed hyperthermia-induced degradation or the appearance of A23187-induced cleaved form of STK38. An in vitro cleavage assay was then used to demonstrate that calpain I directly cleaves STK38 at the proximal N-terminal region. Deletion of the N-terminal region of STK38 increased its stability against hyperthermia. We further demonstrated that the MAPKK kinase (MAP3K) MEKK2 prevented both heat- and calpain-induced cleavage of STK38. MEKK2 knockdown enhanced hyperthermia-induced degradation of STK38. We performed an in vitro MEKK2 assay and identified the key regulatory site in STK38 phosphorylated by MEKK2. Experiments with a phosphorylation-defective mutant demonstrated that phosphorylation of Ser 91 is important for STK38 stability, as the enzyme is susceptible to degradation by the calpain pathway unless this residue is phosphorylated. In summary, we demonstrated that STK38 is a calpain substrate and revealed a novel role of MEKK2 in the process of STK38 degradation by calpain.