bims-mecosi 2024-04-21 papers

bims-mecosi

Biomed News

on Membrane contact sites

Issue of 2024–04–21
nine papers selected by
Verena Kohler, Umeå University

Endoplasmic reticulum - condensate interactions in protein synthesis and secretion.
Altered GM1 catabolism affects NMDAR-mediated Ca2+ signaling at ER-PM junctions and increases synaptic spine formation in a GM1-gangliosidosis model.
Endothelial Mitochondria-Associated Membranes (MAMs) Isolation by Percoll Step Gradients.
Unraveling the CLCC1 interactome: Impact of the Asp25Glu variant and its interaction with SigmaR1 at the Mitochondrial-Associated ER Membrane (MAM).
Ip3r-Grp75-Vdac and relevant Ca2+ signaling regulate dietary palmitic acid-induced de novo lipogenesis by mitochondria-associated ER membrane (MAM) recruiting Seipin in yellow catfish.
Exploring the role of Prx II in mitigating endoplasmic reticulum stress and mitochondrial dysfunction in neurodegeneration.
Non-vesicular phosphatidylinositol transfer plays critical roles in defining organelle lipid composition.
Accumulation of APP C-terminal fragments causes endolysosomal dysfunction through the dysregulation of late endosome to lysosome-ER contact sites.
Progression of herpesvirus infection remodels mitochondrial organization and metabolism.

Curr Opin Cell Biol. 2024 Apr 15. pii: S0955-0674(24)00036-X. [Epub ahead of print]88 102357

Endoplasmic reticulum - condensate interactions in protein synthesis and secretion.

Dan T M Nguyen, Max Koppers, Ginny G Farías.

In the past decade, a growing amount of evidence has demonstrated that organelles do not act autonomously and independently but rather communicate with each other to coordinate different processes for proper cellular function. With a highly extended network throughout the cell, the endoplasmic reticulum (ER) plays a central role in interorganelle communication through membrane contact sites. Here, we highlight recent evidence indicating that the ER also forms contacts with membrane-less organelles. These interactions contribute to the dynamic assembly and disassembly of condensates and controlled protein secretion. Additionally, emerging evidence suggests their involvement in mRNA localization and localized translation. We further explore exciting future directions of this emerging theme in the organelle contact site field.

DOI: https://doi.org/10.1016/j.ceb.2024.102357
Cell Rep. 2024 Apr 16. pii: S2211-1247(24)00445-5. [Epub ahead of print]43(5): 114117

Altered GM1 catabolism affects NMDAR-mediated Ca2+ signaling at ER-PM junctions and increases synaptic spine formation in a GM1-gangliosidosis model.

Jason A Weesner, Ida Annunziata, Diantha van de Vlekkert, Camenzind G Robinson, Yvan Campos, Ashutosh Mishra, Leigh E Fremuth, Elida Gomero, Huimin Hu, Alessandra d'Azzo.

  Endoplasmic reticulum-plasma membrane (ER-PM) junctions mediate Ca2+ flux across neuronal membranes. The properties of these membrane contact sites are defined by their lipid content, but little attention has been given to glycosphingolipids (GSLs). Here, we show that GM1-ganglioside, an abundant GSL in neuronal membranes, is integral to ER-PM junctions; it interacts with synaptic proteins/receptors and regulates Ca2+ signaling. In a model of the neurodegenerative lysosomal storage disease, GM1-gangliosidosis, pathogenic accumulation of GM1 at ER-PM junctions due to β-galactosidase deficiency drastically alters neuronal Ca2+ homeostasis. Mechanistically, we show that GM1 interacts with the phosphorylated N-methyl D-aspartate receptor (NMDAR) Ca2+ channel, thereby increasing Ca2+ flux, activating extracellular signal-regulated kinase (ERK) signaling, and increasing the number of synaptic spines without increasing synaptic connectivity. Thus, GM1 clustering at ER-PM junctions alters synaptic plasticity and worsens the generalized neuronal cell death characteristic of GM1-gangliosidosis.

Keywords:  CP: Cell biology; CP: Neuroscience; Ca(2+) signaling; ER-PM junctions; GM1-gangliosidosis; NMDAR; dendritic spines; lysosomal storage disease; membrane contact sites; synapse

DOI:  https://doi.org/10.1016/j.celrep.2024.114117
Methods Mol Biol. 2024 ;2782 113-122

Endothelial Mitochondria-Associated Membranes (MAMs) Isolation by Percoll Step Gradients.

Margaret Baldini, Cheng Zhang, Jun Yu.

  Mitochondria-associated membranes (MAMs) are regions where the endoplasmic reticulum (ER) interacts with mitochondria and regulate lipid trafficking, calcium signaling, ER stress, and inflammation activation. Isolation of MAMs from endothelial cells is vital for studying insight into the immune regulation of many inflammatory diseases. Endothelial cells (ECs) are critical innate immune cells due to their paracrine function of secreting interleukins, chemokines, cytokines, and growth factors, as well as expressing levels of pattern recognition receptors including toll-like receptors (TLRs). Furthermore, ECs regulate and recruit monocytes by expressing adhesion molecules including vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), P-selectin, and E-selectin, to facilitate monocyte diapedesis in areas of damage and inflammation. This protocol consists of step-by-step instructions on isolating pure MAMs and other subcellular fractions from endothelial cells, which is critical to understanding ER and mitochondria crosstalks in endothelial functions in health and disease.

Keywords:  Endoplasmic reticulum; Endothelial cells; Immunity; Inflammation; Mitochondria; Mitochondria-associated membranes; Subcellular fractions

DOI:  https://doi.org/10.1007/978-1-0716-3754-8_8
Neurosci Lett. 2024 Apr 13. pii: S0304-3940(24)00155-1. [Epub ahead of print] 137778

Unraveling the CLCC1 interactome: Impact of the Asp25Glu variant and its interaction with SigmaR1 at the Mitochondrial-Associated ER Membrane (MAM).

Ilaria D'Atri, Emily-Rose Martin, Liming Yang, Elizabeth Sears, Emma Baple, Andrew H Crosby, John K Chilton, Asami Oguro-Ando.

  The endoplasmic reticulum (ER) plays an indispensable role in cellular processes, including maintenance of calcium homeostasis, and protein folding, synthesized and processing. Disruptions in these processes leading to ER stress and the accumulation of misfolded proteins can instigate the unfolded protein response (UPR), culminating in either restoration of balanced proteostasis or apoptosis. A key player in this intricate balance is CLCC1, an ER-resident chloride channel, whose essential role extends to retinal development, regulation of ER stress, and UPR. The importance of CLCC1 is further underscored by its interaction with proteins localized to mitochondria-associated endoplasmic reticulum membranes (MAMs), where it participates in UPR induction by MAM proteins. In previous research, we identified a p.(Asp25Glu) pathogenic CLCC1 variant associated with retinitis pigmentosa (RP) (CLCC1 hg38 NC_000001.11; NM_001048210.3, c.75C > A; UniprotKB Q96S66). In attempt to decipher the impact of this variant function, we leveraged liquid chromatography-mass spectrometry (LC-MS) to identify likely CLCC1-interacting proteins. We discovered that the CLCC1 interactome is substantially composed of proteins that localize to ER compartments and that the Asp25Glu variant results in noticeable loss and gain of specific protein interactors. Intriguingly, the analysis suggests that the CLCC1Asp25Glu mutant protein exhibits a propensity for increased interactions with cytoplasmic proteins compared to its wild-type counterpart. To corroborate our LC-MS data, we further scrutinized two novel CLCC1 interactors, Calnexin and SigmaR1, chaperone proteins that localize to the ER and MAMs. Through microscopy, we demonstrate that CLCC1 co-localizes with both proteins, thereby validating our initial findings. Moreover, our results reveal that CLCC1 co-localizes with SigmaR1 not merely at the ER, but also at MAMs. These findings reinforce the notion of CLCC1 interacting with MAM proteins at the ER-mitochondria interface, setting the stage for further exploration into how these interactions impact ER or mitochondria function and lead to retinal degenerative disease when impaired.

Keywords:  CLCC1; Endoplasmic reticulum; MAM; Retinitis pigmentosa; SigmaR1

DOI:  https://doi.org/10.1016/j.neulet.2024.137778
J Nutr. 2024 Apr 17. pii: S0022-3166(24)00224-4. [Epub ahead of print]

Ip3r-Grp75-Vdac and relevant Ca2+ signaling regulate dietary palmitic acid-induced de novo lipogenesis by mitochondria-associated ER membrane (MAM) recruiting Seipin in yellow catfish.

Yu-Feng Song, Zhen-Yu Bai, Xiao-Hong Lai, Zhi Luo, Christer Hogstrand.

   BACKGROUND: The mitochondria-associated endoplasmic reticulum membrane membranes (MAM), is the central hub for endoplasmic reticulum and mitochondria functional communicate. It plays a crucial role in hepatic lipid homeostasis. However, even though MAM has been acknowledged to be enriched in enzymes that contribute to lipid biosynthesis, no study has yet investigated the exact role of MAM on hepatic neutral lipid synthesis.
OBJECTIVES: To address these gaps, this study investigated the systemic control mechanisms for MAM in neutral lipids synthesis by recruiting Seipin, focusing on the role of the Ip3r-Grp75-Vdac complex and their relevant Ca2+ signaling in this process.
METHODS: To this end, a model animal for lipid metabolism, yellow catfish (Pelteobagrus fulvidraco), were fed six different diets containing a range of palmitic acid (PA) concentrations from 0 g/kg to 150 g/kg in vivo for 10 weeks. In vitro experiments were also conducted to intercept the MAM-mediated Ca2+ signaling in isolated hepatocytes by transfecting them with si-mitochondrial calcium uniporter (mcu). Since mcu was resided in the inner mitochondrial membrane (IMM), si-mcu cannot disrupt MAM's structural integrity.
RESULTS: 1. Hepatocellular MAM sub-proteome analysis indicated excessive dietary PA intake enhanced hepatic MAM structural join by activating Ip3r-Grp75-voltage-dependent anion channel (Vdac) complexes. 2. Dietary PA intake induced hepatic neutral lipid accumulation through MAM recruiting Seipin, which activated lipid droplet biogenesis. Our findings also revealed a previously unidentified mechanism whereby MAM recruited Seipin and controlled hepatic lipid homeostasis, depending on Ip3r-Grp75-Vdac-controlled Ca2+ signaling but not only MAM's structural integrity.
CONCLUSIONS: These results offer a novel insight into the MAM-recruited Seipin in controlling hepatic lipid synthesis in a MAM structural integrity-dependent and Ca2+ signaling-dependent manner, highlighting the critical contribution of MAM in maintaining hepatic neutral lipid homeostasis.

Keywords:  Ca(2+) signaling; Hepatic lipogenesis; Ip3r-Grp75-Vdac complex; Mitochondria-associated endoplasmic reticulum membrane (MAM); Seipin

DOI:  https://doi.org/10.1016/j.tjnut.2024.04.021
Cell Commun Signal. 2024 Apr 18. 22(1): 231

Exploring the role of Prx II in mitigating endoplasmic reticulum stress and mitochondrial dysfunction in neurodegeneration.

Mei-Hua Jin, Lin Feng, Hong-Yi Xiang, Hu-Nan Sun, Ying-Hao Han, Taeho Kwon.

   BACKGROUND: Neurodegenerative diseases are increasingly recognized for their association with oxidative stress, which leads to progressive dysfunction and loss of neurons, manifesting in cognitive and motor impairments. This study aimed to elucidate the neuroprotective role of peroxiredoxin II (Prx II) in counteracting oxidative stress-induced mitochondrial damage, a key pathological feature of neurodegeneration.
METHODS: We investigated the impact of Prx II deficiency on endoplasmic reticulum stress and mitochondrial dysfunction using HT22 cell models with knocked down and overexpressed Prx II. We observed alcohol-treated HT22 cells using transmission electron microscopy and monitored changes in the length of mitochondria-associated endoplasmic reticulum membranes and their contact with endoplasmic reticulum mitochondria contact sites (EMCSs). Additionally, RNA sequencing and bioinformatic analysis were conducted to identify the role of Prx II in regulating mitochondrial transport and the formation of EMCSs.
RESULTS: Our results indicated that Prx II preserves mitochondrial integrity by facilitating the formation of EMCSs, which are essential for maintaining mitochondrial Ca2+ homeostasis and preventing mitochondria-dependent apoptosis. Further, we identified a novel regulatory axis involving Prx II, the transcription factor ATF3, and miR-181b-5p, which collectively modulate the expression of Armcx3, a protein implicated in mitochondrial transport. Our findings underscore the significance of Prx II in protecting neuronal cells from alcohol-induced oxidative damage and suggest that modulating the Prx II-ATF3-miR-181b-5p pathway may offer a promising therapeutic strategy against neurodegenerative diseases.
CONCLUSIONS: This study not only expands our understanding of the cytoprotective mechanisms of Prx II but also offers necessary data for developing targeted interventions to bolster mitochondrial resilience in neurodegenerative conditions.

Keywords:  Endoplasmic reticulum-mitochondrial interactions; Mitochondrial damage; Neurodegenerative diseases; Peroxiredoxin II; Reactive oxygen species

DOI:  https://doi.org/10.1186/s12964-024-01613-x
EMBO J. 2024 Apr 16.

Non-vesicular phosphatidylinositol transfer plays critical roles in defining organelle lipid composition.

Yeun Ju Kim, Joshua G Pemberton, Andrea Eisenreichova, Amrita Mandal, Alena Koukalova, Pooja Rohilla, Mira Sohn, Andrei W Konradi, Tracy T Tang, Evzen Boura, Tamas Balla.

  Phosphatidylinositol (PI) is the precursor lipid for the minor phosphoinositides (PPIns), which are critical for multiple functions in all eukaryotic cells. It is poorly understood how phosphatidylinositol, which is synthesized in the ER, reaches those membranes where PPIns are formed. Here, we used VT01454, a recently identified inhibitor of class I PI transfer proteins (PITPs), to unravel their roles in lipid metabolism, and solved the structure of inhibitor-bound PITPNA to gain insight into the mode of inhibition. We found that class I PITPs not only distribute PI for PPIns production in various organelles such as the plasma membrane (PM) and late endosomes/lysosomes, but that their inhibition also significantly reduced the levels of phosphatidylserine, di- and triacylglycerols, and other lipids, and caused prominent increases in phosphatidic acid. While VT01454 did not inhibit Golgi PI4P formation nor reduce resting PM PI(4,5)P2 levels, the recovery of the PM pool of PI(4,5)P2 after receptor-mediated hydrolysis required both class I and class II PITPs. Overall, these studies show that class I PITPs differentially regulate phosphoinositide pools and affect the overall cellular lipid landscape.

Keywords:  Golgi Complex; Membrane Contact Sites; Non-Vesicular Lipid Transport; Phosphatidylinositol; Phospholipase C

DOI:  https://doi.org/10.1038/s44318-024-00096-3
Dev Cell. 2024 Apr 12. pii: S1534-5807(24)00199-0. [Epub ahead of print]

Accumulation of APP C-terminal fragments causes endolysosomal dysfunction through the dysregulation of late endosome to lysosome-ER contact sites.

Marine Bretou, Ragna Sannerud, Abril Escamilla-Ayala, Tom Leroy, Céline Vrancx, Zoë P Van Acker, Anika Perdok, Wendy Vermeire, Inge Vorsters, Sophie Van Keymolen, Michelle Maxson, Benjamin Pavie, Keimpe Wierda, Eeva-Liisa Eskelinen, Wim Annaert.

  Neuronal endosomal and lysosomal abnormalities are among the early changes observed in Alzheimer's disease (AD) before plaques appear. However, it is unclear whether distinct endolysosomal defects are temporally organized and how altered γ-secretase function or amyloid precursor protein (APP) metabolism contribute to these changes. Inhibiting γ-secretase chronically, in mouse embryonic fibroblast and hippocampal neurons, led to a gradual endolysosomal collapse initiated by decreased lysosomal calcium and increased cholesterol, causing downstream defects in endosomal recycling and maturation. This endolysosomal demise is γ-secretase dependent, requires membrane-tethered APP cytoplasmic domains, and is rescued by APP depletion. APP C-terminal fragments (CTFs) localized to late endosome/lysosome-endoplasmic reticulum contacts; an excess of APP-CTFs herein reduced lysosomal Ca2+ refilling from the endoplasmic reticulum, promoting cholesterol accretion. Tonic regulation by APP-CTFs provides a mechanistic explanation for their cellular toxicity: failure to timely degrade APP-CTFs sustains downstream signaling, instigating lysosomal dyshomeostasis, as observed in prodromal AD. This is the opposite of substrates such as Notch, which require intramembrane proteolysis to initiate signaling.

Keywords:  APP proteolysis; APP-CTF; endolysosomal homeostasis; late endosome/lysosome-endoplasmic reticulum contact sites; lysosomal Ca(2+); presenilins; primary hippocampal neurons; γ-secretase; γ-secretase inhibitor

DOI:  https://doi.org/10.1016/j.devcel.2024.03.030
PLoS Pathog. 2024 Apr 15. 20(4): e1011829

Progression of herpesvirus infection remodels mitochondrial organization and metabolism.

Simon Leclerc, Alka Gupta, Visa Ruokolainen, Jian-Hua Chen, Kari Kunnas, Axel A Ekman, Henri Niskanen, Ilya Belevich, Helena Vihinen, Paula Turkki, Ana J Perez-Berna, Sergey Kapishnikov, Elina Mäntylä, Maria Harkiolaki, Eric Dufour, Vesa Hytönen, Eva Pereiro, Tony McEnroe, Kenneth Fahy, Minna U Kaikkonen, Eija Jokitalo, Carolyn A Larabell, Venera Weinhardt, Salla Mattola, Vesa Aho, Maija Vihinen-Ranta.

Viruses target mitochondria to promote their replication, and infection-induced stress during the progression of infection leads to the regulation of antiviral defenses and mitochondrial metabolism which are opposed by counteracting viral factors. The precise structural and functional changes that underlie how mitochondria react to the infection remain largely unclear. Here we show extensive transcriptional remodeling of protein-encoding host genes involved in the respiratory chain, apoptosis, and structural organization of mitochondria as herpes simplex virus type 1 lytic infection proceeds from early to late stages of infection. High-resolution microscopy and interaction analyses unveiled infection-induced emergence of rough, thin, and elongated mitochondria relocalized to the perinuclear area, a significant increase in the number and clustering of endoplasmic reticulum-mitochondria contact sites, and thickening and shortening of mitochondrial cristae. Finally, metabolic analyses demonstrated that reactivation of ATP production is accompanied by increased mitochondrial Ca2+ content and proton leakage as the infection proceeds. Overall, the significant structural and functional changes in the mitochondria triggered by the viral invasion are tightly connected to the progression of the virus infection.

DOI: https://doi.org/10.1371/journal.ppat.1011829