bims-mecosi 2025-08-17 papers

bims-mecosi

Biomed News

on Membrane contact sites

Issue of 2025–08–17
eleven papers selected by
Verena Kohler, Umeå University

DJ-1 in Parkinson's disease: Its important role at endoplasmic reticulum-mitochondria contact sites.
Inter-Organellar Ca2+ Homeostasis in Plant and Animal Systems.
Endoplasmic reticulum: the target of chlamydial manipulation.
Targeting PDK4 to Mitigate Osimertinib-Induced Cardiotoxicity: Insights into Mitochondria-endoplasmic reticulum Crosstalk and Necroptosis.
GLP-1R associates with VAPB and SPHKAP at ERMCSs to regulate β-cell mitochondrial remodelling and function.
Deep mapping of the endomembrane system of cerebellar Purkinje neurons.
Mitochondrial ultrastructural pathology in diabetic cardiomyopathy: integrated analysis via scanning electron microscopy and 3D visualization imaging.
Cardioprotective effect of Yiqi Huoxue decoction on post-myocardial infarction injury mediated by Ca2+ flux through MAMs.
Gadolinium impairs male steroidogenesis: In vivo and in vitro.
The DRP1 inhibitory peptide P110 provides neuroprotection after subarachnoid hemorrhage by suppressing neuronal apoptosis and stabilizing the blood-brain barrier.
Application of STEM tomography to investigate smooth ER morphology under stress conditions.

Behav Brain Res. 2025 Aug 12. pii: S0166-4328(25)00362-6. [Epub ahead of print]495 115775

DJ-1 in Parkinson's disease: Its important role at endoplasmic reticulum-mitochondria contact sites.

Haohao Fan, Yuanyuan Li, Juan Huang, Jinyu Jiang, Fei Feng, Nanqu Huang, Yong Luo.

  Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting millions of people globally and causing significant impairments in motor and cognitive functions. The key pathological hallmarks of PD include the aggregation of α-synuclein (α-Syn), degeneration of dopaminergic neurons, and formation of Lewy bodies (LBs), leading to a range of clinical symptoms, such as rigidity, bradykinesia, and cognitive deficits. Although the exact causes of PD are not fully understood, factors such as oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress are implicated in its pathogenesis. The protein DJ-1 (PARK7), a highly conserved antioxidant, has been identified as a significant factor in PD, particularly because of its role in maintaining cellular homeostasis and regulating cellular responses to stress. The interaction of DJ-1 with endoplasmic reticulum-mitochondria contact sites (MERCs) is crucial for calcium regulation, autophagy, and the management of ER stress, all of which are related to PD progression. This review focuses on the function of DJ-1 within mitochondria-associated endoplasmic reticulum membranes (MAMs or ER-MAMs), aiming to provide insights into PD mechanisms and potential therapeutic targets.

Keywords:  DJ-1; Endoplasmic reticulum; Mitochondria; Mitochondria-associated endoplasmic reticulum membranes; Mitochondria-associated membranes; Parkinson's disease

DOI:  https://doi.org/10.1016/j.bbr.2025.115775
Cells. 2025 Aug 06. pii: 1204. [Epub ahead of print]14(15):

Inter-Organellar Ca2+ Homeostasis in Plant and Animal Systems.

Philip Steiner, Susanna Zierler.

  The regulation of calcium (Ca2+) homeostasis is a critical process in both plant and animal systems, involving complex interplay between various organelles and a diverse network of channels, pumps, and transporters. This review provides a concise overview of inter-organellar Ca2+ homeostasis, highlighting key regulators and mechanisms in plant and animal cells. We discuss the roles of key Ca2+ channels and transporters, including IP3Rs, RyRs, TPCs, MCUs, TRPMLs, and P2XRs in animals, as well as their plant counterparts. Here, we explore recent innovations in structural biology and advanced microscopic techniques that have enhanced our understanding of these proteins' structure, functions, and regulations. We examine the importance of membrane contact sites in facilitating Ca2+ transfer between organelles and the specific expression patterns of Ca2+ channels and transporters. Furthermore, we address the physiological implications of inter-organellar Ca2+ homeostasis and its relevance in various pathological conditions. For extended comparability, a brief excursus into bacterial intracellular Ca2+ homeostasis is also made. This meta-analysis aims to bridge the gap between plant and animal Ca2+ signaling research, identifying common themes and unique adaptations in these diverse biological systems.

Keywords:  IP3 receptors; TRPML channels; animal calcium signaling; calcium homeostasis; membrane contact sites; mitochondrial calcium uniporters; organelle communication; plant calcium signaling; ryanodine receptors; two-pore channels

DOI:  https://doi.org/10.3390/cells14151204
Arch Microbiol. 2025 Aug 11. 207(9): 219

Endoplasmic reticulum: the target of chlamydial manipulation.

Yating Wen, Wenbo Lei, Yi Liu, Yuqiong Sheng, Ranhui Li, Zhongyu Li.

  Chlamydia, as an obligate intracellular pathogen, causes significant human diseases such as trachoma, sexually transmitted infections, respiratory illnesses, and atherosclerosis. Understanding its unique survival strategies within host cells is crucial for developing effective treatments. The endoplasmic reticulum (ER) is a key target for intracellular pathogens due to its roles in fundamental cellular functions. Chlamydia forms membrane contact sites (MCSs) with the ER. This physical connection allows Chlamydia to obtain sphingomyelin and regulate calcium ion concentrations via the ER, thereby promoting inclusion formation and facilitating inclusion extrusion. Additionally, chlamydial infection triggers ER stress and downstream unfolded protein response (UPR), leading to autophagy, the expression of inflammatory factors, and oxidative stress (OS), all of which have dual roles in the survival and pathogenesis of Chlamydia. By focusing on the interactions between Chlamydia and the ER, we highlight the mechanisms underlying lipid acquisition, calcium signaling, and subversion of the UPR. These insights not only advance our understanding of Chlamydia's pathogenesis but also reveal potential therapeutic targets to treat chlamydial infections.

Keywords:   Chlamydia ; Calcium ion regulation; Endoplasmic reticulum; Membrane contact sites; Unfolded protein response

DOI:  https://doi.org/10.1007/s00203-025-04411-2
Free Radic Biol Med. 2025 Aug 09. pii: S0891-5849(25)00886-X. [Epub ahead of print]

Targeting PDK4 to Mitigate Osimertinib-Induced Cardiotoxicity: Insights into Mitochondria-endoplasmic reticulum Crosstalk and Necroptosis.

Jingwen Deng, Dan Wang, Keyi Jiang, Xueyan Lang, Yue Sun, Yilan Li.

   BACKGROUND: Osimertinib is a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) widely used in non-small cell lung cancer. However, its cardiotoxicity has raised increasing clinical concern. The underlying mechanisms remain unclear.
METHODS: We evaluated the effects of osimertinib on cardiac structure and function in mice and assessed cell viability, mitochondrial function, and cell death pathways in H9C2 and AC16 cardiomyocytes. Mitochondria-associated endoplasmic reticulum membranes (MAMs), mitochondrial calcium overload, and necroptosis were analyzed by immunofluorescence, transmission electron microscopy, calcium probes, and Western blotting. Genetic and pharmacologic modulation of pyruvate dehydrogenase kinase 4 (PDK4) was used to probe its functional role. Protein-protein interactions were examined by co-immunoprecipitation and molecular docking.
RESULTS: Osimertinib caused cardiac dysfunction and myocardial damage in vivo and triggered necroptosis in cardiomyocytes, characterized by increased phosphorylation of RIP3 and MLKL. Mechanistically, osimertinib upregulated PDK4, which promoted excessive MAM formation, mitochondrial calcium overload, and mitochondrial dysfunction. Co-immunoprecipitation revealed that PDK4 facilitated the interaction between BAP31 and FIS1, key tethering proteins at MAMs. Silencing PDK4 or inhibiting necroptosis with necrosulfonamide alleviated mitochondrial dysfunction and cell death. Conversely, PDK4 overexpression alone induced MAM formation, mitochondrial depolarization, and necroptotic signaling. Importantly, FIS1 knockdown mimicked the protective effects of PDK4 silencing. These results demonstrate that PDK4 contributes to osimertinib-induced cardiotoxicity by regulating MAM-associated necroptosis.
CONCLUSION: Our findings identify a novel role for PDK4 in mediating osimertinib-induced cardiomyocyte necroptosis via MAM formation and mitochondrial calcium overload. Targeting the PDK4-BAP31-FIS1 axis may offer a potential therapeutic strategy to mitigate the cardiotoxic effects of osimertinib.

Keywords:  Cardiotoxicity; Mitochondria-associated endoplasmic reticulum membranes; Necroptosis; Osimertinib; PDK4

DOI:  https://doi.org/10.1016/j.freeradbiomed.2025.08.017
bioRxiv. 2025 Jul 20. pii: 2024.04.28.591531. [Epub ahead of print]

GLP-1R associates with VAPB and SPHKAP at ERMCSs to regulate β-cell mitochondrial remodelling and function.

Gregory Austin, Affiong I Oqua, Liliane El Eid, Mingli Zhu, Yusman Manchanda, Priyanka Peres, Helena Coyle, Yelyzaveta Poliakova, Karim Bouzakri, Alex Montoya, Dominic J Withers, Michele Solimena, Ben Jones, Steven J Millership, Steffen Burgold, David C A Gaboriau, Endre Majorovits, Evelyn Garlick, Maria Lima, Inga Prokopenko, Jonathon Nixon-Abell, Andreas Müller, Alejandra Tomas.

Glucagon-like peptide-1 receptor (GLP-1R) agonists (GLP-1RAs) ameliorate mitochondrial health by increasing mitochondrial turnover in metabolically relevant tissues. Mitochondrial adaptation to metabolic stress is crucial to maintain pancreatic β-cell function and prevent type 2 diabetes (T2D) progression. While the GLP-1R is well-known to stimulate cAMP production leading to Protein Kinase A (PKA) and Exchange Protein Activated by cyclic AMP 2 (Epac2) activation, there is a lack of understanding of the molecular mechanisms linking GLP-1R signalling with mitochondrial and β-cell functional adaptation. Here, we present a comprehensive study in β-cell lines and primary islets that demonstrates that, following GLP-1RA stimulation, GLP-1R-positive endosomes associate with the endoplasmic reticulum (ER) membrane contact site (MCS) tether VAPB at ER-mitochondria MCSs (ERMCSs), where active GLP-1R engages with SPHKAP, an A-kinase anchoring protein (AKAP) previously linked to T2D and adiposity risk in genome-wide association studies (GWAS). The inter-organelle complex formed by endosomal GLP-1R, ER VAPB and SPHKAP triggers a pool of ERMCS-localised cAMP/PKA signalling via the formation of a PKA-RIα biomolecular condensate which leads to changes in mitochondrial contact site and cristae organising system (MICOS) complex phosphorylation, mitochondrial remodelling, and β-cell functional adaptation, with important consequences for the regulation of β-cell insulin secretion and survival to stress.

DOI: https://doi.org/10.1101/2024.04.28.591531
bioRxiv. 2025 Jul 14. pii: 2025.07.08.663701. [Epub ahead of print]

Deep mapping of the endomembrane system of cerebellar Purkinje neurons.

Matthias G Haberl, Silvia Viana da Silva, Sebastien Phan, Eric Bushong, Thomas Deerinck, Mark H Ellisman.

Neuronal function relies on the precise spatial organization of intracellular membrane-bounded organelles involved in anabolism and Ca 2+ sequestration, such as the Golgi apparatus, mitochondria and the endoplasmic reticulum (ER), along with structures involved in catabolism, such as lysosomes. Despite their known roles in energy supply, calcium homeostasis, and proteostasis, our understanding of how the anabolism-linked organelles are structurally arranged within neurons remains incomplete. Due to the tremendous complexity in the morphologies and fine structural features and interwoven nature of these intracellular organelles, particularly the ER, our understanding of their structural organization is limited, particularly, with regard to quantitative assessments of their sites of interaction and accurate measures of their volumetric proportions inside of a single large neuron. To approach this challenge, we used serial block-face scanning electron microscopy (SBEM) to generate large-scale 3D EM volumes and electron tomography on high-pressure frozen tissue of the rodent cerebellum, including the largest cells in the vertebrate brain, the cerebellar Purkinje neuron as well as the most abundant cell type in the vertebrate brain, the much smaller cerebellar granule neuron. We reconstructed the neuronal ultrastructure of these different cell types, focusing on the ER, mitochondria and membrane contact sites, to then characterize intracellular motifs and organization principles in detail, providing a first full map to quantitatively describe a neuronal endoarchitectome . At the gross level organization, we found that the intracellular composite of organelles are cell type specific features, with specific differences between Purkinje neurons and Granule cells. At the level of fine structure, we mapped ultrastructural domains within Purkinje neurons where ER and mitochondria associate directly. In addition to cell type specific differences, we observed significant subcellular regional variation, particularly within the axon initial segment (AIS) of Purkinje neurons, where we identified ultrastructural domains with sharply contrasting distributions of ER and mitochondria. These findings suggest a finely tuned spatial organization of organelles that may underpin the distinct functional demands along the axon. We expect that our subcellular map, along with the methods developed to obtain these maps, will facilitate future studies in health, aging and disease to characterize defined features, by developing a framework for quantitative analysis of the neuronal ultrastructure.

DOI: https://doi.org/10.1101/2025.07.08.663701
Cardiovasc Diabetol. 2025 Aug 13. 24(1): 331

Mitochondrial ultrastructural pathology in diabetic cardiomyopathy: integrated analysis via scanning electron microscopy and 3D visualization imaging.

Bo Wang, Linghao Dai, Haowei Liang, Jiayu He, Jiayi Zhou, Yang Guan, Hui Wang.

   BACKGROUND: Mitochondrial dysfunction plays a pivotal role in the onset and progression of diabetic cardiomyopathy (DCM). It is hypothesized that ultrastructural mitochondrial abnormalities, molecular dynamics imbalance, and bioenergetic impairments collectively contribute significantly to cardiac dysfunction. Consequently, investigating mitochondrial ultrastructural changes and metabolic disturbances is crucial for elucidating the mechanistic underpinnings of DCM.
OBJECTIVE: This study aims to comprehensively characterize alterations in mitochondrial ultrastructure and energy metabolism in DCM and examine the interplay between these two factors.
METHODS: High glucose-treated H9c2 cardiomyocytes and DCM model mice were analyzed via scanning electron microscopy (SEM) and 3D imaging. Three-dimensional morphometric parameters-such as Length3D, Thickness3D, Width3D, Area3D, Volume3D, Anisotropy, Flatness, and Elongation-were quantified to evaluate mitochondrial architecture. At the two-dimensional (2D) level, mitochondria-associated membrane (MAM) parameters were analyzed. Further, detailed statistical analysis was conducted on mitochondrial cristae, including cristae scores, count, width, gap size, and junction widths in myocardial tissues. Mitochondrial dynamics and autophagy-related protein expression (Mfn1, Mfn2, Opa1, p-Drp1(ser616), PINK1, Parkin1) in myocardial tissues were assessed by Western blot. Mitochondrial bioenergetics were measured by ATP content, membrane potential, mtDNA copy number, SOD levels, mitochondrial Ca2+ levels, and oxidative phosphorylation (OXPHOS) activity across Complexes I-V in myocardial tissue. Additionally, the oxygen consumption rate (OCR) of viable H9c2 cells was measured using the O2k system.
RESULTS: 3D reconstruction revealed key myocardial ultrastructures-including T-tubules, sarcoplasmic reticulum (SR), intercalated discs, and mitochondria-and demonstrated significant differences in mitochondrial morphology and 3D morphometric parameters across subpopulations. Under high glucose (HG) conditions, in vitro analysis showed a reduction in mitochondrial Length3D and Anisotropy in H9c2 cells, accompanied by increases in Thickness3D, Width3D, Flatness, and Elongation. HG exposure also led to an increase in the length of MAM contact sites and the MAM-to-mitochondria perimeter ratio. In vivo, the DCM group exhibited decreased 2D morphometric parameters (length, width, area, perimeter, and shape AP), as well as reductions in 3D measurements (Thickness3D, Width3D, and Volume3D) compared to controls. No significant differences were observed in Length3D, Area3D, Anisotropy, Flatness, and Elongation between groups. 3D surface analysis revealed rough mitochondrial surfaces in the DCM group, while controls displayed smooth surfaces. Control mitochondria exhibited well-aligned, well-defined cristae, whereas DCM mitochondria showed cristae dissolution, disorganized arrangements, and vacuolization within the cristae. The DCM group also had increased cristae junction width and spacing. Additionally, megamitochondria were observed in DCM samples. The DCM group showed a significant increase in MAM contact site length and MAM-to-mitochondria perimeter ratio in myocardial tissue. Molecular analysis revealed decreased expression of fusion proteins (Mfn1, Opa1) and increased levels of p-Drp1(ser616), alongside elevated autophagy markers (PINK1, Parkin1). Bioenergetic dysfunction was evident through decreased ATP production, mitochondrial membrane potential collapse (ΔΨm), reduced mtDNA copy number, decreased SOD levels, impaired activities of complexes I/III/IV/V, and diminished basal/maximal respiration, ATP-linked respiration, and spare respiratory capacity. Conversely, mitochondrial Ca2+ levels were elevated in the DCM group, along with increased proton leakage in H9c2 cells.
CONCLUSIONS: This study establishes a comprehensive framework linking "3D morphology-molecular regulation-metabolic dysfunction," highlighting the synergistic interplay between mitochondrial ultrastructural remodeling and bioenergetic failure as key drivers of DCM progression. These findings provide valuable insights into DCM pathogenesis and suggest potential therapeutic targets.

Keywords:  3D visualization imaging; Diabetic cardiomyopathy; Energy metabolism; Mitochondria; Scanning electron microscopy; Ultrastructure

DOI:  https://doi.org/10.1186/s12933-025-02884-5
Front Cardiovasc Med. 2025 ;12 1596757

Cardioprotective effect of Yiqi Huoxue decoction on post-myocardial infarction injury mediated by Ca2+ flux through MAMs.

Yufei Li, Tianhui Du, Yunshu Zhang, Yang Lu, Xinyi Li, Weibin Xie, Shuwen Guo.

   Background: Mitochondria-associated membranes (MAMs) regulate cellular Ca2+ and contribute to cardiovascular disease pathogenesis. The IP3R-GRP75-VDAC1 complex is the primary MAMs pathway regulating Ca2+ flux and cardiomyocyte calcium homeostasis. Yiqi Huoxue decoction (YQHX), a Traditional Chinese Medicine formula, shows potential for myocardial infarction (MI) prevention and treatment. However, YQHX's regulation of MAMs and associated Ca2+ mechanisms in MI remains unclear.
Methods: MI rat and oxygen-glucose deprivation cardiomyocytes model were used to mimic myocardial ischemia in human. in vivo, Rats were randomly divided into Sham, Model, YQHX (8.2 g/kg) and Perindopril (10 mg/kg) groups. 28 days after MI, echocardiography, HE, Masson staining and transmission electron microscopy detections were performed to observe cardiac functions and morphology. The effects of YQHX on H9c2 cell viability, mPTP and Ca2+ levels were examined in vitro. Proteins located at MAMs including Cyclophilin D (CypD), Mitochondrial Calcium Uniporter (MCU), Sigma-1 Receptor (Sig-1R), and Neurite Outgrowth Inhibitor B (NOGO-B) are abundantly expressed in myocardial tissue. Consequently, these proteins, along with components of the IP3Rs-GRP75-VDAC1 complex, were detected using WB and qPCR. Mitofusin 2 (Mfn2), which regulates mitochondrial function and Ca2+ flux and is widely expressed at MAMs, was assessed using immunofluorescence.MKT-077, an agent known to disrupt the IP3Rs-GRP75-VDAC1 complex, was employed to investigate the mechanism of YQHX on the complex.
Results: YQHX improved cardiac function and attenuated pathological changes in vivo. It ameliorated MAMs ultrastructure and function, enhancing CypD, MCU, Sig-1R, and NOGO-B expression while reducing IP3R2, GRP75, and VDAC1. in vitro, YQHX significantly increased viability, reduced oxygen-glucose deprivation-induced mPTP opening and Ca2+ levels, upregulated CypD, MCU, Sig-1R, and NOGO-B, and downregulated IP3R2, GRP75, and VDAC1. YQHX also restored MAMs morphology, decreased mPTP opening and Ca2+ levels, and reversed GRP75 downregulation blocked by MKT-077 under oxygen-glucose deprivation.
Conclusions: YQHX exerts cardioprotection against hypoxia by regulating Ca2+ homeostasis and preserving MAMs structure, function, and associated protein expression.

Keywords:  IP3Rs-GRP75-VDAC1 complex; MAMS; Yiqi Huoxue decoction (YQHX); cardiomyocytes; myocardial infarction (MI)

DOI:  https://doi.org/10.3389/fcvm.2025.1596757
Toxicology. 2025 Aug 10. pii: S0300-483X(25)00220-3. [Epub ahead of print]518 154261

Gadolinium impairs male steroidogenesis: In vivo and in vitro.

Sara Falvo, Giulia Grillo, Massimo Venditti, Gabriella Chieffi Baccari, Maria Maddalena Di Fiore, Tiziana Cappello, Mariachiara Galati, Maria Maisano, Giuseppe Petito, Rosalba Senese, Alessandra Santillo.

  The increasing use of gadolinium (Gd) in industrial and medical fields made it a hazardous environmental pollutant. Once ingested through water and/or food, Gd may potentially have toxic effects on all body districts. However, the effects of Gd on testicular function have been little explored. In the present study, adult male rats were allowed to drink GdCl3 or Gd2O3 (10-20-40 mg/Kg b.w.) for 4 weeks. Following Gd treatment, a significant decrease in steroidogenic-related protein (StAR, 3β-HSD, 17β-HSD, and 5α-Red) expressions, T and DHT levels, and spermatozoa concentration were observed. To clarify the cellular mechanisms underlying Gd-induced damage, we exposed mouse Leydig (TM3) cells to increasing concentrations (5-1000 µM) of GdCl3 or Gd2O3 for 24 h. The in vitro results showed a dose-dependent decrease in cell viability and confirmed that both Gd forms inhibited steroidogenesis-related protein expressions. Steroidogenesis is a multistep process taking place in mitochondria and endoplasmic reticulum, and Mitochondria-Associated Endoplasmic Reticulum Membranes (MAMs) play a key role. We found a decrease in MMP as well as in mitochondrial biogenesis (PGC1-α, NRF1, TFAM), fusion (MFN2), fission (DRP1) and MAMs (ATAD3, SOAT1, FACL4) marker expressions. The Gd-caused oxidative stress, as suggested by the increase in TBARS levels in GdCl3- or Gd2O3-treated TM3 cells, increased autophagy and apoptosis by inhibiting the Akt pathway. In conclusion, our study highlights for the first time the adverse effects, and the underlying intracellular mechanisms, of orally administred Gd on the testicular function, laying the foundation for further research to understand its impact on male fertility.

Keywords:  Apoptosis; Autophagy, Mitochondrial dysfunction, MAMs; Gadolinium; Male steroidogenesis; Oxidative stress

DOI:  https://doi.org/10.1016/j.tox.2025.154261
Free Radic Biol Med. 2025 Aug 08. pii: S0891-5849(25)00880-9. [Epub ahead of print]240 1-14

The DRP1 inhibitory peptide P110 provides neuroprotection after subarachnoid hemorrhage by suppressing neuronal apoptosis and stabilizing the blood-brain barrier.

Shuangying Hao, Junrui Luo, Shuai Yuan, Wenbo Chen, Xinhong Zhang, Cheng Zhao, Hao Xu, Zhiqiang Liu, Dingding Zhang.

  Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are key pathological features of early brain injury (EBI) following subarachnoid hemorrhage (SAH). Increasing evidence highlights mitochondria-associated ER membranes (MAMs) as central regulators of ER proteostasis and mitochondrial quality control. Given the dual role of dynamin-related protein 1 (DRP1) in modulating MAMs integrity and mitochondrial dynamics, we hypothesized that pharmacological inhibition of DRP1 would exert neuroprotective effects in SAH by preserving inter-organelle communication and restoring mitochondrial bioenergetics. To test this hypothesis, we employed an endovascular perforation model to induce SAH in mice and used oxyhemoglobin-treated HT22 hippocampal neurons to mimic SAH in vitro. Both models demonstrated a significant increase in DRP1 and phosphorylated DRP1 (p-DRP1) expression at 24 h and 72 h post-injury. Treatment with the selective DRP1 inhibitor P110 effectively reduced DRP1 and p-DRP1 levels, attenuated neuronal apoptosis and blood-brain barrier disruption, and improved neurological outcomes. Mechanistically, P110 treatment significantly mitigated SAH-induced inflammation, MAMs formation, mitochondrial calcium overload, reactive oxygen species production, ATP depletion and cytochrome c release. Collectively, these findings suggest that DRP1 inhibition via P110 confers neuroprotection after SAH by modulating inflammation, MAMs Formation, and mitochondrial dysfunction.

Keywords:  DRP1; Inflammation; Mitochondria-associated ER membranes; Neuroprotection; P110; Subarachnoid hemorrhage

DOI:  https://doi.org/10.1016/j.freeradbiomed.2025.08.011
J Microsc. 2025 Sep;299(3): 228-241

Application of STEM tomography to investigate smooth ER morphology under stress conditions.

V Heinz, R Rachel, C Ziegler.

  The endoplasmic reticulum (ER) is a highly dynamic organelle that undergoes significant morphological alterations in response to cellular stress. While conventional transmission electron microscopy (TEM) has provided valuable insights into these changes, such as the formation of crystalloid-ER and ER whorls, obtaining comprehensive three-dimensional (3D) information on these large structures within their cellular context has remained a challenge. To overcome these limitations, this study introduces an innovative application of dual-axis scanning transmission electron microscopy (STEM) tomography to investigate ER morphology under stress conditions in human embryonic kidney (HEK) cells overexpressing the cation channel polycystin-2 (PC-2). Benefitting from high-resolution, increased depth-of-focus, and reduced aberrations, STEM tomography enabled the detailed 3D reconstruction of large cellular subvolumes, providing unprecedented views of stress-induced ER structures. Our findings reveal distinct ultrastructural details of both crystalloid-ER and ER whorls. Crystalloid-ER exhibited a tubular architecture with potential interconnectedness, while ER whorls displayed a lamellar organisation and distinct membrane curvature. We observed the co-occurrence of these distinct smooth ER (sER) morphotypes within the same cell, yet they remained spatially separated, suggesting potential functional specialisation. Furthermore, we identified direct membrane contacts in mixed morphotypes, hinting at a shared origin or dynamic relationship between these structures. The study also elucidated the interactions of these organised smooth ER (OSER) structures with other organelles, such as mitochondria (MAM sites) and vesicles. In summary, the presented ultra-structural insights have a significant impact on our understanding of stress-related ER morphology changes. The ability to visualise the intricate 3D architecture and spatial relationships of these structures provides novel perspectives on the ER's adaptive responses to stress, including potential roles in lipid and protein biosynthesis and intracellular communication. These findings underscore the power of dual-axis STEM tomography for elucidating complex organellar organisation and dynamics in their native cellular context.

Keywords:  ER stress; ER whorls; crystalloid‐ER; endoplasmic reticulum (ER) morphology; scanning transmission electron microscopy (STEM); tomography

DOI:  https://doi.org/10.1111/jmi.70020