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Medicine and Science in Sports and... Jun 2024The unfolded protein response (UPR) is a proteostatic process that is activated in response to endoplasmic reticulum stress. It is currently unclear how aging influences...
BACKGROUND
The unfolded protein response (UPR) is a proteostatic process that is activated in response to endoplasmic reticulum stress. It is currently unclear how aging influences the chronic and adaptive UPR in human skeletal muscle. Here we determined the effect of aging on UPR activation at rest, in response to exercise, and the associations with muscle function.
METHODS
Thirty young (20-35 yrs) and 50 older (65-85 yrs) individuals were enrolled. Vastus lateralis biopsies were performed at rest and 3 hrs and 48 hrs after a single bout of resistance exercise. The abundance of UPR-related transcripts and proteins were measured by RNA sequencing and Western blotting, respectively. Fractional synthetic rates (FSR) of muscle protein were determined by mass spectrometry following intravenous infusion of 13C6 phenylalanine.
RESULTS
Older adults demonstrated elevated transcriptional and proteomic markers of UPR activation in resting muscle. Resting UPR gene expression was negatively associated with muscle strength and power in older adults. The UPR is similarly activated by acute resistance exercise in young and older adults and positively associated with muscle function but not the anabolic response to exercise.
CONCLUSIONS
Skeletal muscle from older adults exhibits chronically activated UPR, which accompanies functional decline. The adaptive UPR is a proteostatic mechanism that is upregulated in response to exercise in young and older adults and positively associated with muscle function.
PubMed: 38934509
DOI: 10.1249/MSS.0000000000003508 -
Biochemical Society Transactions Jun 2024Neurons are highly specialised cells that need to relay information over long distances and integrate signals from thousands of synaptic inputs. The complexity of...
Neurons are highly specialised cells that need to relay information over long distances and integrate signals from thousands of synaptic inputs. The complexity of neuronal function is evident in the morphology of their plasma membrane (PM), by far the most intricate of all cell types. Yet, within the neuron lies an organelle whose architecture adds another level to this morphological sophistication - the endoplasmic reticulum (ER). Neuronal ER is abundant in the cell body and extends to distant axonal terminals and postsynaptic dendritic spines. It also adopts specialised structures like the spine apparatus in the postsynapse and the cisternal organelle in the axon initial segment. At membrane contact sites (MCSs) between the ER and the PM, the two membranes come in close proximity to create hubs of lipid exchange and Ca2+ signalling called ER-PM junctions. The development of electron and light microscopy techniques extended our knowledge on the physiological relevance of ER-PM MCSs. Equally important was the identification of ER and PM partners that interact in these junctions, most notably the STIM-ORAI and VAP-Kv2.1 pairs. The physiological functions of ER-PM junctions in neurons are being increasingly explored, but their molecular composition and the role in the dynamics of Ca2+ signalling are less clear. This review aims to outline the current state of research on the topic of neuronal ER-PM contacts. Specifically, we will summarise the involvement of different classes of Ca2+ channels in these junctions, discuss their role in neuronal development and neuropathology and propose directions for further research.
PubMed: 38934485
DOI: 10.1042/BST20230819 -
Neural Regeneration Research Jun 2024The N-terminal EF-hand calcium-binding proteins 1-3 (NECAB1-3) constitute a family of predominantly neuronal proteins characterized by the presence of at least one...
The N-terminal EF-hand calcium-binding proteins 1-3 (NECAB1-3) constitute a family of predominantly neuronal proteins characterized by the presence of at least one EF-hand calcium-binding domain and a functionally less well characterized C-terminal antibiotic biosynthesis monooxygenase domain. All three family members were initially discovered due to their interactions with other proteins. NECAB1 associates with synaptotagmin-1, a critical neuronal protein involved in membrane trafficking and synaptic vesicle exocytosis. NECAB2 interacts with predominantly striatal G-protein-coupled receptors, while NECAB3 partners with amyloid-beta A4 precursor protein-binding family A members 2 and 3, key regulators of β-amyloid production. This demonstrates the capacity of the family for interactions with various classes of proteins. NECAB proteins exhibit distinct subcellular localizations: NECAB1 is found in the nucleus and cytosol, NECAB2 resides in endosomes and the plasma membrane, and NECAB3 is present in the endoplasmic reticulum and Golgi apparatus. The antibiotic biosynthesis monooxygenase domain, an evolutionarily ancient component, is akin to atypical heme oxygenases in prokaryotes but is not well-characterized in vertebrates. Prokaryotic antibiotic biosynthesis monooxygenase domains typically form dimers, suggesting that calcium-mediated conformational changes in NECAB proteins may induce antibiotic biosynthesis monooxygenase domain dimerization, potentially activating some enzymatic properties. However, the substrate for this enzymatic activity remains uncertain. Alternatively, calcium-mediated conformational changes might influence protein interactions or the subcellular localization of NECAB proteins by controlling the availability of protein-protein interaction domains situated between the EF hands and the antibiotic biosynthesis monooxygenase domain. This review summarizes what is known about genomic organization, tissue expression, intracellular localization, interaction partners, and the physiological and pathophysiological role of the NECAB family.
PubMed: 38934399
DOI: 10.4103/NRR.NRR-D-24-00094 -
PNAS Nexus Jun 2024The unfolded protein response (UPR) is a widespread signal transduction pathway triggered by endoplasmic reticulum (ER) stress. Because calcium (Ca) is a key factor in...
The unfolded protein response (UPR) is a widespread signal transduction pathway triggered by endoplasmic reticulum (ER) stress. Because calcium (Ca) is a key factor in the maintenance of ER homeostasis, massive Ca depletion of the ER is a potent inducer of ER stress. Although moderate changes in ER Ca drive the ubiquitous Ca signaling pathways, a possible incremental relationship between UPR activation and Ca changes has yet to be described. Here, we determine the sensitivity and time-dependency of activation of the three ER stress sensors, inositol-requiring protein 1 alpha (IRE1α), protein kinase R-like ER kinase (PERK), and activating transcription factor 6 alpha (ATF6α) in response to controlled changes in the concentration of ER Ca in human cultured cells. Combining Ca imaging, fluorescence recovery after photobleaching experiments, biochemical analyses, and mathematical modeling, we uncover a nonlinear rate of activation of the IRE1α branch of UPR, as compared to the PERK and ATF6α branches that become activated gradually with time and are sensitive to more important ER Ca depletions. However, the three arms are all activated within a 1 h timescale. The model predicted the deactivation of PERK and IRE1α upon refilling the ER with Ca. Accordingly, we showed that ER Ca replenishment leads to the complete reversion of IRE1α and PERK phosphorylation in less than 15 min, thus revealing the highly plastic character of the activation of the upstream UPR sensors. In conclusion, our results reveal a dynamic and dose-sensitive Ca-dependent activation/deactivation cycle of UPR induction, which could tightly control cell fate upon acute and/or chronic stress.
PubMed: 38933930
DOI: 10.1093/pnasnexus/pgae229 -
Frontiers in Medicine 2024Links have been established between SARS-CoV-2 and endoplasmic reticulum stress (ERS). However, the relationships between inflammation, ERS, and the volume of organ...
INTRODUCTION
Links have been established between SARS-CoV-2 and endoplasmic reticulum stress (ERS). However, the relationships between inflammation, ERS, and the volume of organ damage are not well known in humans. The aim of this study was to explore whether ERS explains lung damage volume (LDV) among COVID-19 patients admitted to the intensive care unit (ICU).
MATERIALS AND METHODS
We conducted a single-center retrospective study (ancillary analysis of a prospective cohort) including severe COVID-19 ICU patients who had a chest computed tomography (CT) scan 24 h before/after admission to assess LDV. We performed two multivariate linear regression models to identify factors associated with plasma levels of 78 kDa-Glucose-Regulated Protein (GRP78; ERS marker) and Interleukin-6 (IL-6; inflammation marker) at admission.
RESULTS
Among 63 patients analyzed, GRP78 plasma level was associated with LDV in both multivariate models (β = 22.23 [4.08;40.38]; = 0.0179, β = 20.47 [0.74;40.20]; = 0.0423) but not with organ failure (Sequential Organ Failure Assessment (SOFA) score) at admission (r = 0.03 [-0.22;0.28]; = 0.2559). GRP78 plasma level was lower among ICU survivors (1539.4 [1139.2;1941.1] vs. 1714.2 [1555.2;2579.1] pg./mL. respectively; = 0.0297). IL-6 plasma level was associated with SOFA score at admission in both multivariate models (β = 136.60 [65.50;207.70]; = 0.0003, β = 193.70 [116.60;270.90]; < 0.0001) but not with LDV ( = 0.13 [-0.14;0.39]; = 0.3219). IL-6 plasma level was not different between ICU survivors and non-survivors (12.2 [6.0;43.7] vs. 30.4 [12.9;69.7] pg./mL. respectively; = 0.1857). There was no correlation between GRP78 and IL-6 plasma levels ( = 0.13 [-0.13;0.37]; = 0.3106).
CONCLUSION
Among severe COVID-19 patients, ERS was associated with LDV but not with systemic inflammation, while systemic inflammation was associated with organ failure but not with LDV.
PubMed: 38933109
DOI: 10.3389/fmed.2024.1368031 -
BioEssays : News and Reviews in... Jun 2024Various lipid transfer proteins (LTPs) mediate the inter-organelle transport of lipids. By working at membrane contact zones between donor and acceptor organelles, LTPs...
Various lipid transfer proteins (LTPs) mediate the inter-organelle transport of lipids. By working at membrane contact zones between donor and acceptor organelles, LTPs achieve rapid and accurate inter-organelle transfer of lipids. This article will describe the emerging paradigm that the action of LTPs at organelle contact zones generates metabolic channeling events in lipid metabolism, mainly referring to how ceramide synthesized in the endoplasmic reticulum is preferentially metabolized to sphingomyelin in the distal Golgi region, how cholesterol and phospholipids receive specific metabolic reactions in mitochondria, and how the hijacking of host LTPs by intracellular pathogens may generate new channeling-like events. In addition, the article will discuss how the function of LTPs is regulated, exemplified by a few representative LTP systems, and will briefly touch on experiments that will be necessary to establish the paradigm that LTP-mediated inter-organelle transport of lipids is one of the mechanisms of compartmentalization-based metabolic channeling events.
PubMed: 38932642
DOI: 10.1002/bies.202400045 -
Viruses Jun 2024Antiretroviral treatments have notably extended the lives of individuals with HIV and reduced the occurrence of comorbidities, including ocular manifestations. The...
Antiretroviral treatments have notably extended the lives of individuals with HIV and reduced the occurrence of comorbidities, including ocular manifestations. The involvement of endoplasmic reticulum (ER) stress in HIV-1 pathogenesis raises questions about its correlation with cellular senescence or its role in initiating senescent traits. This study investigated how ER stress and dysregulated autophagy impact cellular senescence triggered by HIV-1 Tat in the MIO-M1 cell line (human Müller glial cells). Cells exposed to HIV-1 Tat exhibited increased vimentin expression combined with markers of ER stress (BiP, p-eIF2α), autophagy (LC3, Beclin-1, p62), and the senescence marker p21 compared to control cells. Western blotting and staining techniques like SA-β-gal were employed to examine these markers. Additionally, treatments with ER stress inhibitor 4-PBA before HIV-1 Tat exposure led to a decreased expression of ER stress, senescence, and autophagy markers. Conversely, pre-treatment with the autophagy inhibitor 3-MA resulted in reduced autophagy and senescence markers but did not alter ER stress markers compared to control cells. The findings suggest a link between ER stress, dysregulated autophagy, and the initiation of a senescence phenotype in MIO-M1 cells induced by HIV-1 Tat exposure.
Topics: Humans; Autophagy; Cellular Senescence; Endoplasmic Reticulum Stress; tat Gene Products, Human Immunodeficiency Virus; HIV-1; Cell Line; Ependymoglial Cells; HIV Infections
PubMed: 38932195
DOI: 10.3390/v16060903 -
Viruses May 2024Despite their small and simple structure compared with their hosts, virus particles can cause severe harm and even mortality in highly evolved species such as humans. A...
Despite their small and simple structure compared with their hosts, virus particles can cause severe harm and even mortality in highly evolved species such as humans. A comprehensive quantitative biophysical understanding of intracellular virus replication mechanisms could aid in preparing for future virus pandemics. By elucidating the relationship between the form and function of intracellular structures from the host cell and viral components, it is possible to identify possible targets for direct antiviral agents and potent vaccines. Biophysical investigations into the spatio-temporal dynamics of intracellular virus replication have thus far been limited. This study introduces a framework to enable simulations of these dynamics using partial differential equation (PDE) models, which are evaluated using advanced numerical mathematical methods on leading supercomputers. In particular, this study presents a model of the replication cycle of a specific RNA virus, the hepatitis C virus. The diffusion-reaction model mimics the interplay of the major components of the viral replication cycle, including non structural viral proteins, viral genomic RNA, and a generic host factor. Technically, surface partial differential equations (sufPDEs) are coupled on the 3D embedded 2D endoplasmic reticulum manifold with partial differential equations (PDEs) in the 3D membranous web and cytosol volume. The membranous web serves as a viral replication factory and is formed on the endoplasmic reticulum after infection and in the presence of nonstructural proteins. The coupled sufPDE/PDE model was evaluated using realistic cell geometries based on experimental data. The simulations incorporate the effects of non structural viral proteins, which are restricted to the endoplasmic reticulum surface, with effects appearing in the volume, such as host factor supply from the cytosol and membranous web dynamics. Because the spatial diffusion properties of genomic viral RNA are not yet fully understood, the model allows for viral RNA movement on the endoplasmic reticulum as well as within the cytosol. Visualizing the simulated intracellular viral replication dynamics provides insights similar to those obtained by microscopy, complementing data from in vitro/in vivo viral replication experiments. The output data demonstrate quantitative consistence with the experimental findings, prompting further advanced experimental studies to validate the model and refine our quantitative biophysical understanding.
Topics: Virus Replication; Humans; Computer Simulation; Hepacivirus; Endoplasmic Reticulum; RNA, Viral; Models, Biological; Spatio-Temporal Analysis
PubMed: 38932132
DOI: 10.3390/v16060840 -
Pharmaceutics Jun 2024The objective of the present investigation was to evidence the skin retardation phenomenon of lidocaine by gluconic acid as an inactive ingredient involved in...
The objective of the present investigation was to evidence the skin retardation phenomenon of lidocaine by gluconic acid as an inactive ingredient involved in citrate-crosslinking chitosan nanoparticles. Lidocaine hydrochloride was loaded in nanoparticles based on chitosan, fabricated by using a water-in-oil microemulsion as a template and citric acid as an ionic cross-linker. Gluconic acid (pentahydroxy hexanoic acid) was added during the fabrication and compared with caproic acid, a non-hydroxy hexanoic acid. The chitosan nanoparticulate systems were characterized for mean particle size, particle size distribution, and zeta potential. The pentahydroxy hexanoic acid decreased the zeta potential to a significantly lower value than those obtained from both plain citrate and citrate-hexanoic acid formulations. The relatively lower value implies that gluconate ions are partly attached to the nanoparticle's surface and mask its positively charged groups. It was also noted that the in vitro percutaneous permeation flux of lidocaine significantly decreased when gluconate-containing chitosan nanoparticles were applied, i.e., 6.1 ± 1.5 μg‧cm‧h without gluconic acid to 3.4 ± 2.3 μg‧cm‧h with gluconic acid. According to this result, it is suggested that gluconate ions played a role in retarding drug permeation through the skin, probably by calcium chelation in the , which in turn stimulated lamellar body secretion, lipid synthesis, and intracellular release of Ca from the endoplasmic reticulum.
PubMed: 38931951
DOI: 10.3390/pharmaceutics16060831 -
Pharmaceutics May 2024We describe the design, synthesis, and activity of a potent thiourea-bridged backbone cyclic peptidomimetic known as Clarstatin, comprising a 5-amino acid sequence...
We describe the design, synthesis, and activity of a potent thiourea-bridged backbone cyclic peptidomimetic known as Clarstatin, comprising a 5-amino acid sequence (Q/D)-(R/K)-X-X-A-(Gln/Asp)-(Arg/Lys)-AA-AA-Ala-based on a motif called "shared epitope (SE)", specifically present in specific alleles of the gene. This SE binds to a particular site within the proline reach domain (P-domain) of the cell surface-calreticulin (CS-CRT). CS-CRT is a multifunctional endoplasmic reticulum (ER) calcium-binding protein that is located on the cell surface of T cells and triggers innate immune signaling, leading to the development of inflammatory autoimmune diseases. The development of Clarstatin was based on the parent peptide W-G-D-K-S-G-A- derived from the active region of the SE. Following the design based on the cycloscan method, the synthesis of Clarstatin was performed by the Fmoc solid phase peptide synthesis (SPPS) method, purified by HPLC to 96% homogeneity, and its structure was confirmed by LC-MS. Clarstatin reduced calcium levels in Jurkat lymphocyte cultures, ameliorated uveitis in vivo in the experimental autoimmune uveitis (EAU) mice model, and was safe upon acute toxicity evaluation. These findings identify Clarstatin as a promising lead compound for future drug development as a novel class of therapeutic agents in the therapy of uveitis.
PubMed: 38931845
DOI: 10.3390/pharmaceutics16060723