bims-mecosi 2024-01-07 papers

bims-mecosi

Biomed News

on Membrane contact sites

Issue of 2024–01–07
ten papers selected by
Verena Kohler, Umeå University

Mitochondrial lipid dynamics regulated by MITOL-mediated ubiquitination.
The novel bacterial effector protein Cb EPF1 mediates ER-LD membrane contacts to regulate host lipid droplet metabolism.
Relevance of the endoplasmic reticulum-mitochondria axis in cancer diagnosis and therapy.
SYNJ2BP ameliorates intervertebral disc degeneration by facilitating mitochondria-associated endoplasmic reticulum membrane formation and mitochondrial Zn2+ homeostasis.
Deoxynivalenol induced intestinal barrier injury, mitochondrial dysfunction and calcium overload by inositol 1,4,5-triphosphate receptors (IP3Rs)-mitochondrial calcium uniporter (MCU) calcium axis.
IP3R-1 aggravates endotoxin-induced acute lung injury in mice by regulating MAM formation and mitochondrial function.
Disruption of MAM integrity in mutant FUS oligodendroglial progenitors from hiPSCs.
Mic19 depletion impairs endoplasmic reticulum-mitochondrial contacts and mitochondrial lipid metabolism and triggers liver disease.
MAPK1 Mediates MAM Disruption and Mitochondrial Dysfunction in Diabetic Kidney Disease via the PACS-2-Dependent Mechanism.
Vitamin D ameliorates age-induced nonalcoholic fatty liver disease by increasing the mitochondrial contact site and cristae organizing system (MICOS) 60 level.

J Biochem. 2023 Dec 29. pii: mvad117. [Epub ahead of print]

Mitochondrial lipid dynamics regulated by MITOL-mediated ubiquitination.

Koji Yamano, Hiroki Kinefuchi, Waka Kojima.

  Mitochondria-endoplasmic reticulum (ER) contact sites in mammals provide platforms for various reactions such as calcium signaling, lipid metabolism, organelle dynamics and autophagy. To fulfill these tasks, a number of proteins assemble at the contact sites including MITOL/MARCHF5, a critical mitochondrial ubiquitin ligase. How MITOL regulates mitochondrial function from the contact site, however, has been largely unresolved. Recently, a new role for MITOL in the active transport of phosphatidic acid from the ER to mitochondria was reported. In this commentary, we briefly summarize our current understanding of mitochondria-ER contact sites and discuss the recently elucidated mechanism of MITOL fine-tuning phospholipid transfer activity through ubiquitination.

Keywords:  contact site; mitochondria; phospholipid; ubiquitin; ubiquitin ligase

DOI:  https://doi.org/10.1093/jb/mvad117
bioRxiv. 2023 Dec 11. pii: 2023.12.11.571031. [Epub ahead of print]

The novel bacterial effector protein Cb EPF1 mediates ER-LD membrane contacts to regulate host lipid droplet metabolism.

Rajendra Kumar Angara, Arif Sadi, Stacey D Gilk.

Effective intracellular communication between cellular organelles is pivotal for maintaining cellular homeostasis. Tether proteins, which are responsible for establishing membrane contact sites between cell organelles, enable direct communication between organelles and ultimately influence organelle function and host cell homeostasis. While recent research has identified tether proteins in several bacterial pathogens, their functions have predominantly been associated with mediating inter-organelle communication specifically between the bacteria containing vacuole (BCV) and the host endoplasmic reticulum (ER). However, this study reveals a novel bacterial effector protein, Cb EPF1, which acts as a molecular tether beyond the confines of the BCV and facilitates interactions between host cell organelles. Coxiella burnetii , an obligate intracellular bacterial pathogen, encodes the FFAT motif-containing protein Cb EPF1 which localizes to host lipid droplets (LDs). Cb EPF1 establishes inter-organelle contact sites between host LDs and the ER through its interactions with VAP family proteins. Intriguingly, Cb EPF1 modulates growth of host LDs in a FFAT motif-dependent manner. These findings highlight the potential for bacterial effector proteins to impact host cellular homeostasis by manipulating inter-organelle communication beyond conventional BCVs.

DOI: https://doi.org/10.1101/2023.12.11.571031
Exp Mol Med. 2024 Jan 04.

Relevance of the endoplasmic reticulum-mitochondria axis in cancer diagnosis and therapy.

Garam An, Junho Park, Jisoo Song, Taeyeon Hong, Gwonhwa Song, Whasun Lim.

Dynamic interactions between organelles are responsible for a variety of intercellular functions, and the endoplasmic reticulum (ER)-mitochondrial axis is recognized as a representative interorganelle system. Several studies have confirmed that most proteins in the physically tethered sites between the ER and mitochondria, called mitochondria-associated ER membranes (MAMs), are vital for intracellular physiology. MAM proteins are involved in the regulation of calcium homeostasis, lipid metabolism, and mitochondrial dynamics and are associated with processes related to intracellular stress conditions, such as oxidative stress and unfolded protein responses. Accumulating evidence has shown that, owing to their extensive involvement in cellular homeostasis, alterations in the ER-mitochondrial axis are one of the etiological factors of tumors. An in-depth understanding of MAM proteins and their impact on cell physiology, particularly in cancers, may help elucidate their potential as diagnostic and therapeutic targets for cancers. For example, the modulation of MAM proteins is utilized not only to target diverse intracellular signaling pathways within cancer cells but also to increase the sensitivity of cancer cells to anticancer reagents and regulate immune cell activities. Therefore, the current review summarizes and discusses recent advances in research on the functional roles of MAM proteins and their characteristics in cancers from a diagnostic perspective. Additionally, this review provides insights into diverse therapeutic strategies that target MAM proteins in various cancer types.

DOI: https://doi.org/10.1038/s12276-023-01137-3
Free Radic Biol Med. 2023 Dec 27. pii: S0891-5849(23)01184-X. [Epub ahead of print]212 220-233

SYNJ2BP ameliorates intervertebral disc degeneration by facilitating mitochondria-associated endoplasmic reticulum membrane formation and mitochondrial Zn2+ homeostasis.

Yu Song, Wen Geng, Dingchao Zhu, Huaizhen Liang, Zhi Du, Bide Tong, Kun Wang, Shuai Li, Yong Gao, Xiaobo Feng, Zhiwei Liao, Rongcheng Mei, Cao Yang.

  Nucleus pulposus (NP) cell function-loss is one main contributor during intervertebral disc degeneration (IDD) progression. Both mitochondria and endoplasmic reticulum (ER) play vital roles in sustaining NP cell homeostasis, while the precise function of ER-mitochondria tethering and cross talk in IDD remain to be clarified. Here, we demonstrated that a notable disruption of mitochondria-associated ER membrane (MAM) was identified in degenerated discs and TBHP-induced NP cells, accompanied by mitochondrial Zn2+ overload and NP cell senescence. Importantly, experimental coupling of MAM contacts by MFN2, a critical regulator of MAM formation, could enhance NLRX1-SLC39A7 complex formation and mitochondrial Zn2+ homeostasis. Further using the sequencing data from TBHP-induced degenerative model of NP cells, combining the reported MAM proteomes, we demonstrated that SYNJ2BP loss was one critical pathological characteristic of NP cell senescence and IDD progression, which showed close relationship with MAM disruption. Overexpression of SYNJ2BP could facilitate MAM contact organization and NLRX1-SLC39A7 complex formation, thus promoted mitochondrial Zn2+ homeostasis, NP cell proliferation and intervertebral disc rejuvenation. Collectively, our present study revealed a critical role of SYNJ2BP in maintaining mitochondrial Zn2+ homeostasis in NP cells during IDD progression, partially via sustaining MAM contact and NLRX1-SLC39A7 complex formation.

Keywords:  Intervertebral disc degeneration; Mitochondria-associated ER membrane; NLRX1; Nucleus pulposus; SLC39A7; SYNJ2BP

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.12.028
Sci Total Environ. 2023 Dec 29. pii: S0048-9697(23)08359-6. [Epub ahead of print] 169729

Deoxynivalenol induced intestinal barrier injury, mitochondrial dysfunction and calcium overload by inositol 1,4,5-triphosphate receptors (IP3Rs)-mitochondrial calcium uniporter (MCU) calcium axis.

Xin Li, Feiyang Gou, Jiang Zhu, Qian Lin, Minjie Yu, Xiaodian Tu, Qihua Hong, Caihong Hu.

  Deoxynivalenol (DON) contamination is widespread in crops and could easily cause gut damage, which brings hazards to animals. Mitochondria are considered as an important target of DON, nevertheless, the mechanism is still unclear. Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) have gained arousing interest and are recognized as critical signaling hubs that control calcium signaling transduction between ER and mitochondria. This study aims to investigate the effects of DON on intestinal barrier, mitochondria, MAMs and inositol 1,4,5-triphosphate receptors (IP3Rs)-mitochondrial calcium uniporter (MCU) calcium axis in piglets and porcine intestinal epithelial cells (IPEC-J2). Furthermore, inhibition of IP3Rs or MCU was used to explore whether IP3Rs-MCU axis of MAMs was involved in the mitochondria dysfunction and intestinal epithelium barrier injury induced by DON in IPEC-J2. The data showed that DON induced intestinal barrier injury, mitochondrial dysfunction and ERS in piglets' jejunum and IPEC-J2. Moreover, DON increased MAMs by upregulating the protein level of Mitofusin 2 (Mfn2), increasing the percentage of mitochondria with MAMs/total mitochondria and the ratio of MAMs length/mitochondrial perimeter and shortening the distance between mitochondria and ER of MAMs. Importantly, DON influenced IP3Rs-glucose-regulated protein 75 (GRP75)-voltage-dependent anion channel 1 (VDAC1)-MCU calcium axis by increasing the protein levels of GRP75 and MCU and the interaction of VDAC1-GRP75-IP3Rs complex, which in turn induced mitochondrial calcium overload. Furthermore, inhibition of IP3Rs or MCU alleviated DON-induced intestinal epithelium barrier injury, mitochondrial dysfunction and mitochondrial calcium overload of IPEC-J2. The current investigation proposed that DON induced intestinal injury, mitochondrial dysfunction and calcium overload via IP3Rs-GRP75-VDAC1-MCU calcium axis.

Keywords:  Deoxynivalenol; Intestinal barrier; Mitochondria; Mitochondria-associated endoplasmic reticulum membranes; Piglets

DOI:  https://doi.org/10.1016/j.scitotenv.2023.169729
Exp Biol Med (Maywood). 2023 Dec 30. 15353702231220667

IP3R-1 aggravates endotoxin-induced acute lung injury in mice by regulating MAM formation and mitochondrial function.

Shuan Dong, Ya Wu, Yuan Zhang, Shaona Li, Qin Zhao, Shasha Liu, Yan Guo, Xiangyun Li, Kai Song, Lili Wu, Lina Wu, Jia Shi, Lirong Gong, Jianbo Yu.

  Acute lung injury (ALI) caused by endotoxin represents one of the common clinical emergencies. Mitochondria-associated endoplasmic reticulum membranes (MAM) serve as a critical link between mitochondria and endoplasmic reticulum (ER), which has an essential effect on maintaining intracellular homeostasis. As an important component of MAM, type-1 inositol-1,4,5-trisphosphate receptor (IP3R-1) mediates the ER-to-mitochondrial transport of Ca2+. This study explored the role of IP3R-1 and MAM in ALI. Besides the levels of inflammasome-associated components interleukin (IL)-6, tumor necrosis factor (TNF)-α, and malonyldialdehyde (MDA) were increased in both bronchoalveolar lavage fluid (BALF) and serum, increased cross-sectional area of mitochondria, elevated MAM formation, and decreased respiratory control ratio (RCR) were observed within lung tissues collected in lipopolysaccharide (LPS)-treated mice, accompanied by upregulation of IP3R-1 in total lung lysates and MAM. Ca2+ uptake level in the mitochondria, production of reactive oxygen species (ROS) in the mitochondria, and the formation of MAM were elevated within LPS-treated MLE-12 cells, and all those changes in response to LPS were partly inhibited by knocking down of IP3R-1 expression in MLE-12 cells. Collectively, IP3R-1 has a critical effect on MAM formation and mitochondrial dysfunction, which could be innovative therapeutic targets for ALI caused by endotoxin.

Keywords:  Ca2+; Endotoxin-induced acute lung injury; IP3R-1; MAM; mitochondria

DOI:  https://doi.org/10.1177/15353702231220667
Acta Neuropathol. 2024 Jan 03. 147(1): 6

Disruption of MAM integrity in mutant FUS oligodendroglial progenitors from hiPSCs.

Yingli Zhu, Thibaut Burg, Katrien Neyrinck, Tim Vervliet, Fatemeharefeh Nami, Ellen Vervoort, Karan Ahuja, Maria Livia Sassano, Yoke Chin Chai, Arun Kumar Tharkeshwar, Jonathan De Smedt, Haibo Hu, Geert Bultynck, Patrizia Agostinis, Johannes V Swinnen, Ludo Van Den Bosch, Rodrigo Furtado Madeiro da Costa, Catherine Verfaillie.

  Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and fatal neurodegenerative disorder, characterized by selective loss of motor neurons (MNs). A number of causative genetic mutations underlie the disease, including mutations in the fused in sarcoma (FUS) gene, which can lead to both juvenile and late-onset ALS. Although ALS results from MN death, there is evidence that dysfunctional glial cells, including oligodendroglia, contribute to neurodegeneration. Here, we used human induced pluripotent stem cells (hiPSCs) with a R521H or a P525L mutation in FUS and their isogenic controls to generate oligodendrocyte progenitor cells (OPCs) by inducing SOX10 expression from a TET-On SOX10 cassette. Mutant and control iPSCs differentiated efficiently into OPCs. RNA sequencing identified a myelin sheath-related phenotype in mutant OPCs. Lipidomic studies demonstrated defects in myelin-related lipids, with a reduction of glycerophospholipids in mutant OPCs. Interestingly, FUSR521H OPCs displayed a decrease in the phosphatidylcholine/phosphatidylethanolamine ratio, known to be associated with maintaining membrane integrity. A proximity ligation assay further indicated that mitochondria-associated endoplasmic reticulum membranes (MAM) were diminished in both mutant FUS OPCs. Moreover, both mutant FUS OPCs displayed increased susceptibility to ER stress when exposed to thapsigargin, and exhibited impaired mitochondrial respiration and reduced Ca2+ signaling from ER Ca2+ stores. Taken together, these results demonstrate a pathological role of mutant FUS in OPCs, causing defects in lipid metabolism associated with MAM disruption manifested by impaired mitochondrial metabolism with increased susceptibility to ER stress and with suppressed physiological Ca2+ signaling. As such, further exploration of the role of oligodendrocyte dysfunction in the demise of MNs is crucial and will provide new insights into the complex cellular mechanisms underlying ALS.

Keywords:  Amyotrophic lateral sclerosis; ER stress; FUS; Lipid defects; MAM disruption; Mitochondrial dysfunction

DOI:  https://doi.org/10.1007/s00401-023-02666-x
Nat Commun. 2024 Jan 02. 15(1): 168

Mic19 depletion impairs endoplasmic reticulum-mitochondrial contacts and mitochondrial lipid metabolism and triggers liver disease.

Jun Dong, Li Chen, Fei Ye, Junhui Tang, Bing Liu, Jiacheng Lin, Pang-Hu Zhou, Bin Lu, Min Wu, Jia-Hong Lu, Jing-Jing He, Simone Engelender, Qingtao Meng, Zhiyin Song, He He.

Endoplasmic reticulum (ER)-mitochondria contacts are critical for the regulation of lipid transport, synthesis, and metabolism. However, the molecular mechanism and physiological function of endoplasmic reticulum-mitochondrial contacts remain unclear. Here, we show that Mic19, a key subunit of MICOS (mitochondrial contact site and cristae organizing system) complex, regulates ER-mitochondria contacts by the EMC2-SLC25A46-Mic19 axis. Mic19 liver specific knockout (LKO) leads to the reduction of ER-mitochondrial contacts, mitochondrial lipid metabolism disorder, disorganization of mitochondrial cristae and mitochondrial unfolded protein stress response in mouse hepatocytes, impairing liver mitochondrial fatty acid β-oxidation and lipid metabolism, which may spontaneously trigger nonalcoholic steatohepatitis (NASH) and liver fibrosis in mice. Whereas, the re-expression of Mic19 in Mic19 LKO hepatocytes blocks the development of liver disease in mice. In addition, Mic19 overexpression suppresses MCD-induced fatty liver disease. Thus, our findings uncover the EMC2-SLC25A46-Mic19 axis as a pathway regulating ER-mitochondria contacts, and reveal that impairment of ER-mitochondria contacts may be a mechanism associated with the development of NASH and liver fibrosis.

DOI: https://doi.org/10.1038/s41467-023-44057-6
Int J Biol Sci. 2024 ;20(2): 569-584

MAPK1 Mediates MAM Disruption and Mitochondrial Dysfunction in Diabetic Kidney Disease via the PACS-2-Dependent Mechanism.

Shanshan Liu, Shuai Han, Cuili Wang, Hongjun Chen, Qiannan Xu, Shi Feng, Yucheng Wang, Jihong Yao, Qin Zhou, Xuanli Tang, Li Lin, Lidan Hu, Alan J Davidson, Bing Yang, Cunqi Ye, Fan Yang, Jianhua Mao, Chao Tong, Jianghua Chen, Hong Jiang.

  Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease (ESRD). Mitochondrial dysfunction in renal tubules, occurring early in the disease, is linked to the development of DKD, although the underlying pathways remain unclear. Here, we examine diabetic human and mouse kidneys, and HK-2 cells exposed to high glucose, to show that high glucose disrupts mitochondria-associated endoplasmic reticulum membrane (MAM) and causes mitochondrial fragmentation. We find that high glucose conditions increase mitogen-activated protein kinase 1(MAPK1), a member of the MAP kinase signal transduction pathway, which in turn lowers the level of phosphofurin acidic cluster sorting protein 2 (PACS-2), a key component of MAM that tethers mitochondria to the ER. MAPK1-induced disruption of MAM leads to mitochondrial fragmentation but this can be rescued in HK-2 cells by increasing PACS-2 levels. Functional studies in diabetic mice show that inhibition of MAPK1 increases PACS-2 and protects against the loss of MAM and the mitochondrial fragmentation. Taken together, these results identify the MAPK1-PACS-2 axis as a key pathway to therapeutically target as well as provide new insights into the pathogenesis of DKD.

Keywords:  MAPK1; PACS-2; diabetic kidney disease; mitochondria; mitochondria-associated endoplasmic reticulum membrane

DOI:  https://doi.org/10.7150/ijbs.89291
Exp Mol Med. 2024 Jan 04.

Vitamin D ameliorates age-induced nonalcoholic fatty liver disease by increasing the mitochondrial contact site and cristae organizing system (MICOS) 60 level.

Gyu Hee Kim, Hyeon-Ju Jeong, Yoo Jeong Lee, Hyeon Young Park, Soo Kyung Koo, Joo Hyun Lim.

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease. Despite intensive research, considerable information on NAFLD development remains elusive. In this study, we examined the effects of vitamin D on age-induced NAFLD, especially in connection with mitochondrial abnormalities. We observed the prevention of NAFLD in 22-month-old C57BL/6 mice fed a vitamin D3-supplemented (20,000 IU/kg) diet compared with mice fed a control (1000 IU/kg) diet. We evaluated whether vitamin D3 supplementation enhanced mitochondrial functions. We found that the level of mitochondrial contact site and cristae organizing system (MICOS) 60 (Mic60) level was reduced in aged mice, and this reduction was specifically restored by vitamin D3. In addition, depletion of Immt, the human gene encoding the Mic60 protein, induced changes in gene expression patterns that led to fat accumulation in both HepG2 and primary hepatocytes, and these alterations were effectively prevented by vitamin D3. In addition, silencing of the vitamin D receptor (VDR) decreased the Mic60 levels, which were recovered by vitamin D treatment. To assess whether VDR directly regulates Mic60 levels, we performed chromatin immunoprecipitation and reporter gene analysis. We discovered that VDR directly binds to the Immt 5' promoter region spanning positions -3157 to -2323 and thereby upregulates Mic60. Our study provides the first demonstration that a reduction in Mic60 levels due to aging may be one of the mechanisms underlying the development of aging-associated NAFLD. In addition, vitamin D3 could positively regulate Mic60 expression, and this may be one of the important mechanisms by which vitamin D could ameliorate age-induced NAFLD.

DOI: https://doi.org/10.1038/s12276-023-01125-7