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- Bortolini, Giacomo, 1996-, et al.
(author)
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The spatially resolved star formation history of the dwarf spiral galaxy NGC 5474
- 2024
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In: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 527:3, s. 5339-5355
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Journal article (peer-reviewed)abstract
- We study the resolved stellar populations and derive the star formation history of NGC 5474, a peculiar star-forming dwarf galaxy at a distance of ∼7 Mpc, using Hubble Space Telescope Advanced Camera for Surveys data from the Legacy Extragalactic UV Survey (LEGUS) programme. We apply an improved colour–magnitude diagram fitting technique based on the code SFERA and use the latest PARSEC–COLIBRI stellar models. Our results are the following. The off-centre bulge-like structure, suggested to constitute the bulge of the galaxy, is dominated by star formation (SF) activity initiated 14 Gyr ago and lasted at least up to 1 Gyr ago. Nevertheless, this component shows clear evidence of prolonged SF activity (lasting until ∼10 Myr ago). We estimate the total stellar mass of the bulge-like structure to be (5.0 ± 0.3) × 108 M⊙. Such a mass is consistent with published suggestions that this structure is in fact an independent system orbiting around and not within NGC 5474’s disc. The stellar overdensity located to the South–West of the bulge-like structure shows a significant SF event older than 1 Gyr, while it is characterized by two recent peaks of SF, around ∼10 and ∼100 Myr ago. In the last Gyr, the behaviour of the stellar disc is consistent with what is known in the literature as ‘gasping’. The synchronized burst at 10–35 Myr in all components might hint to the recent gravitational interaction between the stellar bulge-like structure and the disc of NGC 5474.
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| 2. |
- Dutta, Tanmoy, 1998, et al.
(author)
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Mitochondrial amidoxime-reducing component 1 p.Ala165Thr increases protein degradation mediated by the proteasome.
- 2024
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In: Liver international. - 1478-3223. ; 44:5, s. 1219-1232
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Journal article (peer-reviewed)abstract
- Metabolic dysfunction-associated steatotic liver disease (MASLD) is a global health concern with no effective and specific drug treatment available. The rs2642438 minor allele in mitochondrial amidoxime-reducing component 1 (MARC1) results in an aminoacidic substitution (p.Ala165Thr) and associates with protection against MASLD. However, the mechanisms behind this protective effect are unknown. In this study, we examined the consequences of this aminoacidic substitution on protein stability and subcellular localization.We overexpressed the human MARC1 A165 (wild-type) or 165T (mutant) invivo in mice and invitro in human hepatoma cells (HepG2 and HuH-7), generated several mutants at position 165 by insitu mutagenesis and then examined protein levels. We also generated HepG2 cells stably overexpressing MARC1 A165 or 165T to test the effect of this substitution on MARC1 subcellular localization.MARC1 165T overexpression resulted in lower protein levels than A165 both invivo and invitro. Similarly, any mutant at position 165 showed lower protein levels compared to the wild-type protein. We showed that the 165T mutant protein is polyubiquitinated and its degradation is accelerated through lysine-48 ubiquitin-mediated proteasomal degradation. We also showed that the 165T substitution does not affect the MARC1 subcellular localization.This study shows that alanine at position 165 in MARC1 is crucial for protein stability, and the threonine substitution at this position leads to a hypomorphic protein variant due to lower protein levels. Our result supports the notion that lowering hepatic MARC1 protein level may be a successful therapeutic strategy for treating MASLD.
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