Dysfunctional ER-mitochondrion coupling is associated with ER stress-induced apoptosis and neurological deficits in a rodent model of severe head injury

Astragaloside IV ameliorated neuroinflammation and improved neurological functions in mice exposed to traumatic brain injury by modulating the PERK-eIF2α-ATF4 signaling pathway

Increasing evidence suggests that endoplasmic reticulum stress (ER stress) and neuroinflammation are involved in the complex pathological process of traumatic brain injury (TBI). However, the pathological mechanisms of their interactions in TBI remain incompletely elucidated. Therefore, investigating and ameliorating neuroinflammation and ER stress post-TBI may represent effective strategies for treating secondary brain injury. Astragaloside IV (AS-IV) has been reported as a potential neuroprotective and anti-inflammatory agent in neurological diseases. This study utilized a mouse TBI model to investigate the pathological mechanisms and crosstalk of ER stress, neuroinflammation, and microglial cell morphology in TBI, as well as the mechanisms and potential of AS-IV in improving TBI. The research revealed that post-TBI, inflammatory factors IL-6, IL-1β, and TNF-α increased, microglial cells were activated, and the specific inhibitor of PERK phosphorylation, GSK2656157, intervened to alleviate neuroinflammation and inhibit microglial cell activation. Post-TBI, levels of ER stress-related proteins (p-PERK, p-eIF2a, ATF4, ATF6, and p-IRE1a) increased. Following AS-IV treatment, neurological dysfunction in TBI mice improved. Levels of p-PERK, p-eIF2a, and ATF4 decreased, along with reductions in inflammatory factors IL-6, IL-1β, and TNF-α. Changes in microglial/macrophage M1/M2 polarization were observed. Additionally, the PERK activator CCT020312 intervention eliminated the impact of AS-IV on post-TBI inflammation and ER stress-related proteins p-PERK, p-eIF2a, and ATF4. These results indicate that AS-IV alleviates neuroinflammation and brain damage post-TBI through the PERK pathway, offering new directions and theoretical insights for TBI treatment.

Nandrolone Abuse Prior to Head Trauma Mitigates Endoplasmic Reticulum Stress, Mitochondrial Bioenergetic Deficits, and Markers of Neurodegeneration

The abuse of synthetic steroids, such as nandrolone decanoate (ND), is often associated with violent behavior, increasing the risk of traumatic brain injury (TBI). After a TBI, proteins like APP, β-amyloid peptide-42 (Aβ42), and phosphorylated tau (pTau) accumulate and trigger endoplasmic reticulum (ER) stress associated with an unfolded protein response (UPR). The involvement of mitochondrial bioenergetics in this context remains unexplored. We interrogate whether the abuse of ND before TBI alters the responses of ER stress and mitochondrial bioenergetics in connection with neurodegeneration and memory processing in mice. Male CF1 adult mice were administered ND (15 mg/kg) or vehicle (VEH) s.c. for 19 days, coinciding with the peak day of aggressive behavior, and then underwent cortical controlled impact (CCI) or sham surgery. Spatial memory was assessed through the Morris water maze task (MWM) post-TBI. In synaptosome preparations, i) we challenged mitochondrial complexes (I, II, and V) in a respirometry assay, employing metabolic substrates, an uncoupler, and inhibitors; and ii) assessed molecular biomarkers through Western blot. TBI significantly increased APP, Aβ42, and pTauSer396 levels, along with ER-stress proteins, GRP78, ATF6, and CHOP, implying it primed apoptotic signaling. Concurrently, TBI reduced mitochondrial Ca2+ efflux in exchange with Na+, disturbed the formation/dissipation of membrane potential, increased H2O2 production, decreased biogenesis (PGC-1⍺ and TOM20), and ATP biosynthesis coupled with oxygen consumption. Unexpectedly, ND abuse before TBI attenuated the elevations in APP, Aβ42, and pTauSer396, accompanied by a decrease in GRP78, ATF6, and CHOP levels, and partial normalization of mitochondrial-related endpoints. A principal component analysis revealed a key hierarchical signature featuring mitochondrial Ca2+ efflux, CHOP, GRP78, TOM20, H2O2, and bioenergetic efficiency as a unique variable (PC1) able to explain the memory deficits caused by TBI, as well as the preservation of memory fitness induced by prior ND abuse.

Identification and Validation of Endoplasmic Reticulum Stress-Related Gene in Traumatic Brain Injury

Endoplasmic reticulum stress (ERS) plays an essential role in the development of traumatic brain injury (TBI). We aimed to identify and validate the potential ERS-related genes of TBI through bioinformatics analysis and in vitro cell experiment. A total of 19 TBI and ERS-related genes were obtained from the GeneCards database and Comparative Toxicogenomics Database (CTD). Enrichment analysis primarily enriched in apoptosis. NFE2L2 was identified as a hub gene based on the protein-protein interactions (PPI) network that combined seven ranked methods included in cytoHubba. To further explore the effect of Nrf2, the protein encoded by NFE2L2, on ERS-induced apoptosis, we conducted cell experiments with tert-butylhydroquinone (tBHQ), the classical inducer of Nrf2. Western blot suggested tBHQ pretreatment could diminish ERS and reduce the protein expressions of apoptosis in the primary cultured neuron injury model. These data may establish some theoretical basis for the treatment of TBI and provide inspiration and innovative ideas for clinicians and pathologists to understand TBI comprehensively.

Focused ultrasound-induced cell apoptosis for the treatment of tumours

Cancer is a serious public health problem worldwide. Traditional treatments, such as surgery, radiotherapy, chemotherapy, and immunotherapy, do not always yield satisfactory results; therefore, an efficient treatment for tumours is urgently needed. As a convenient and minimally invasive modality, focused ultrasound (FUS) has been used not only as a diagnostic tool but also as a therapeutic tool in an increasing number of studies. FUS can help treat malignant tumours by inducing apoptosis. This review describes the three apoptotic pathways, apoptotic cell clearance, and how FUS affects these three apoptotic pathways. This review also discusses the role of thermal and cavitation effects on apoptosis, including caspase activity, mitochondrial dysfunction, and Ca2+ elease. Finally, this article reviews various aspects of FUS combination therapy, including sensitization by radiotherapy and chemotherapy, gene expression upregulation, and the introduction of therapeutic gases, to provide new ideas for clinical tumour therapy.

The correlation between mitochondria-associated endoplasmic reticulum membranes (MAMs) and Ca2+ transport in the pathogenesis of diseases

Mitochondria and the endoplasmic reticulum (ER) are vital organelles that influence various cellular physiological and pathological processes. Recent evidence shows that about 5%-20% of the mitochondrial outer membrane is capable of forming a highly dynamic physical connection with the ER, maintained at a distance of 10-30 nm. These interconnections, known as MAMs, represent a relatively conserved structure in eukaryotic cells, acting as a critical platform for material exchange between mitochondria and the ER to maintain various aspects of cellular homeostasis. Particularly, ER-mediated Ca2+ release and recycling are intricately associated with the structure and functionality of MAMs. Thus, MAMs are integral in intracellular Ca2+ transport and the maintenance of Ca2+ homeostasis, playing an essential role in various cellular activities including metabolic regulation, signal transduction, autophagy, and apoptosis. The disruption of MAMs observed in certain pathologies such as cardiovascular and neurodegenerative diseases as well as cancers leads to a disturbance in Ca2+ homeostasis. This imbalance potentially aggravates pathological alterations and disease progression. Consequently, a thorough understanding of the link between MAM-mediated Ca2+ transport and these diseases could unveil new perspectives and therapeutic strategies. This review focuses on the changes in MAMs function during disease progression and their implications in relation to MAM-associated Ca2+ transport.

Hydronidone induces apoptosis in activated hepatic stellate cells through endoplasmic reticulum stress-associated mitochondrial apoptotic pathway

BACKGROUND AND AIM

Hydronidone (HDD) is a novel pirfenidone derivative developed initially to reduce hepatotoxicity. Our previous studies in animals and humans have demonstrated that HDD treatment effectively attenuates liver fibrosis, yet the underlying mechanism remains unclear. This study aimed to investigate whether HDD exerts its anti-fibrotic effect by inducing apoptosis in activated hepatic stellate cells (aHSCs) through the endoplasmic reticulum stress (ERS)-associated mitochondrial apoptotic pathway.

METHODS

The carbon tetrachloride (CCl4)- and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced liver fibrosis models were used for in vivo studies. In vitro studies were conducted using the human hepatic stellate cell line LX-2. The apoptotic effect of HDD on aHSCs was examined using TUNEL and flow cytometry assays. The small interfering RNA (siRNA) technique was employed to downregulate the expression of interest genes.

RESULTS

HDD treatment significantly promoted apoptosis in aHSCs in both the CCl4- and DDC-induced liver fibrosis in mice and LX-2 cells. Mechanistic studies revealed that HDD triggered ERS and subsequently activated the IRE1α-ASK1-JNK pathway. Furthermore, the influx of cytochrome c from the mitochondria into the cytoplasm was increased, leading to mitochondrial dysfunction and ultimately triggering apoptosis in aHSCs. Notably, inhibition of IRE1α or ASK1 by siRNA partially abrogated the pro-apoptotic effect of HDD in aHSCs.

CONCLUSIONS

The findings of both in vivo and in vitro studies suggest that HDD induces apoptosis in aHSCs via the ERS-associated mitochondrial apoptotic pathway, potentially contributing to the amelioration of liver fibrosis.

Potential Role of Endoplasmic Reticulum Stress in Modulating Protein Homeostasis in Oligodendrocytes to Improve White Matter Injury in Preterm Infants

Preterm white matter injury (WMI) is a demyelinating disease with high incidence and mortality in premature infants. Oligodendrocyte cells (OLs) are a specialized glial cell that produces myelin proteins and adheres to the axons providing energy and metabolic support which susceptible to endoplasmic reticulum protein quality control. Disruption of cellular protein homeostasis led to OLs dysfunction and cell death, immediately, the unfolded protein response (UPR) activated to attempt to restore the protein homeostasis via IRE1/XBP1s, PERK/eIF2α and ATF6 pathway that reduced protein translation, strengthen protein-folding capacity, and degraded unfolding/misfolded protein. Moreover, recent works have revealed the conspicuousness function of ER signaling pathways in regulating influenced factors such as calcium homeostasis, mitochondrial reactive oxygen generation, and autophagy activation to regulate protein hemostasis and improve the myelination function of OLs. Each of the regulation modes and their corresponding molecular mechanisms provides unique opportunities and distinct perspectives to obtain a deep understanding of different actions of ER stress in maintaining OLs' health and function. Therefore, our review focuses on summarizing the current understanding of ER stress on OLs' protein homeostasis micro-environment in myelination during white matter development, as well as the pathophysiology of WMI, and discussing the further potential experimental therapeutics targeting these factors that restore the function of the UPR in OLs myelination function.

A Modern Approach to the Treatment of Traumatic Brain Injury

Background: Traumatic brain injury manifests itself in various forms, ranging from mild impairment of consciousness to severe coma and death. Traumatic brain injury remains one of the leading causes of morbidity and mortality. Currently, there is no therapy to reverse the effects associated with traumatic brain injury. New neuroprotective treatments for severe traumatic brain injury have not achieved significant clinical success. Methods: A literature review was performed to summarize the recent interdisciplinary findings on management of traumatic brain injury from both clinical and experimental perspective. Results: In the present review, we discuss the concepts of traditional and new approaches to treatment of traumatic brain injury. The recent development of different drug delivery approaches to the central nervous system is also discussed. Conclusions: The management of traumatic brain injury could be aimed either at the pathological mechanisms initiating the secondary brain injury or alleviating the symptoms accompanying the injury. In many cases, however, the treatment should be complex and include a variety of medical interventions and combination therapy.

Phthalates Induce Neurotoxicity by Disrupting the Mfn2-PERK Axis-Mediated Endoplasmic Reticulum-Mitochondria Interaction

Di-(2-ethylhexyl) phthalate (DEHP), as the most common phthalate, has been extensively used as a plasticizer to improve the plasticity of agricultural products, which pose severe harm to human health. Mitochondrial dynamics and endoplasmic reticulum (ER) homeostasis are indispensable for maintaining mitochondria-associated ER membrane (MAM) integrity. In this study, we aimed to explore the effect of DEHP on the nervous system and its association with the ER-mitochondria interaction. Here, we showed that DEHP caused morphological changes, motor deficits, cognitive impairments, and blood-brain barrier disruption in the brain. DEHP triggered ER stress, which is mainly mediated by protein kinase R-like endoplasmic reticulum kinase (PERK) signaling. Moreover, DEHP-induced mitofusin-2 (Mfn2) downregulation results in imbalance of the mitochondrial dynamics. Interestingly, DEHP exposure impaired MAMs by inhibiting the Mfn2-PERK interaction. Above all, this study elucidates the disruption of the Mfn2-PERK axis-mediated ER-mitochondria interaction as a phthalate-induced neurotoxicity that could be potentially developed as a novel therapy for neurological diseases.

Endoplasmic Reticulum Stress Promotes Neuronal Damage in Neonatal Hypoxic-Ischemic Brain Damage by Inducing Ferroptosis

Hypoxic-ischemic brain damage (HIBD) poses a significant risk of neurological damage in newborns. This study investigates the impact of endoplasmic reticulum stress (ERS) on neuronal damage in neonatal HIBD and its underlying mechanisms. HIBD neonatal rat model was constructed and pre-treated with 4-phenylbutiric acid (4-PBA). Nissl and TUNEL staining were utilised to assess neuronal damage and apoptosis in rat brains. HIBD cell model was established by inducing oxygen-glucose deprivation (OGD) in rat H19-7 neurons, which were then pre-treated with Thapsigargin (TG), Ferrostatin-1 (Fer-1), or both. Cell viability and apoptosis of H19-7 neurons were analysed using cell counting kit-8 assay and TUNEL staining. GRP78-PERK-CHOP pathway activity and glutathione peroxidase-4 (GPX4) expression in rat brains and H19-7 neurons were assessed using Western blot. Ferroptosis-related indicators, including glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA) and iron content, were measured using commercial kits in both rat brains and H19-7 neurons. GRP78-PERK-CHOP pathway was overactivated in HIBD neonatal rats' brains, which was mitigated by 4-PBA treatment. 4-PBA treatment demonstrated a reduction in neuronal damage and apoptosis in HIBD-affected neonatal rat brains. Furthermore, it attenuated ferroptosis in rats by increasing GPX4, GSH and SOD while decreasing MDA and iron content. In the OGD-induced H19-7 neurons, Fer-1 treatment counteracted the suppressive effects of TG on viability, the exacerbation of apoptosis, the promotion of ferroptosis and the activation of the GRP78-PERK-CHOP pathway. Overall, ERS facilitates neuronal damage in neonatal HIBD by inducing ferroptosis. Consequently, the suppression of ERS may represent a promising therapeutic strategy for treating neonatal HIBD.

Endoplasmic reticulum stress: molecular mechanism and therapeutic targets

The endoplasmic reticulum (ER) functions as a quality-control organelle for protein homeostasis, or "proteostasis". The protein quality control systems involve ER-associated degradation, protein chaperons, and autophagy. ER stress is activated when proteostasis is broken with an accumulation of misfolded and unfolded proteins in the ER. ER stress activates an adaptive unfolded protein response to restore proteostasis by initiating protein kinase R-like ER kinase, activating transcription factor 6, and inositol requiring enzyme 1. ER stress is multifaceted, and acts on aspects at the epigenetic level, including transcription and protein processing. Accumulated data indicates its key role in protein homeostasis and other diverse functions involved in various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, achromatopsia, cataracts, ocular tumors, ocular surface diseases, and myopia. This review summarizes the molecular mechanisms underlying the aforementioned ocular diseases from an ER stress perspective. Drugs (chemicals, neurotrophic factors, and nanoparticles), gene therapy, and stem cell therapy are used to treat ocular diseases by alleviating ER stress. We delineate the advancement of therapy targeting ER stress to provide new treatment strategies for ocular diseases.

Neutrophil extracellular traps aggravate neuronal endoplasmic reticulum stress and apoptosis via TLR9 after traumatic brain injury

Endoplasmic reticulum (ER) stress and ER stress-mediated apoptosis play an important role during secondary brain damage after traumatic brain injury (TBI). Increased neutrophil extracellular traps (NETs) formation has been demonstrated to be associated with neurological damage after TBI. However, the correlation between ER stress and NETs remains unclear, and the specific function of NETs in neurons has not been defined. In this study, we found that the levels of NETs circulating biomarkers were remarkably elevated in the plasma of TBI patients. We then inhibited NETs formation by peptidylarginine deiminase 4 (PAD4, a critical enzyme for NETs formation) deficiency and discovered that ER stress activation and ER stress-mediated neuronal apoptosis were reduced. The degradation of NETs via DNase I showed similar outcomes. Furthermore, overexpression of PAD4 aggravated neuronal ER stress and ER stress-associated apoptosis, while TLR9 antagonist administration abrogated the damage caused by NETs. In addition to in vivo experiments, in vitro experiments revealed that treatment with a TLR9 antagonist alleviated NETs-induced ER stress and apoptosis in HT22 cells. Collectively, our results indicated that ER stress as well as the accompanying neuronal apoptosis can be ameliorated by disruption of NETs and that suppression of the TLR9-ER stress signaling pathway may contribute to positive outcomes after TBI.

Endoplasmic reticulum homeostasis: a potential target for diabetic nephropathy

The endoplasmic reticulum (ER) is the most vigorous organelle in intracellular metabolism and is involved in physiological processes such as protein and lipid synthesis and calcium ion transport. Recently, the abnormal function of the ER has also been reported to be involved in the progression of kidney disease, especially in diabetic nephropathy (DN). Here, we reviewed the function of the ER and summarized the regulation of homeostasis through the UPR and ER-phagy. Then, we also reviewed the role of abnormal ER homeostasis in residential renal cells in DN. Finally, some ER stress activators and inhibitors were also summarized, and the possibility of maintaining ER homeostasis as a potential therapeutic target for DN was discussed.

The ER-mitochondria interface, where Ca2+ and cell death meet

Endoplasmic reticulum (ER)-mitochondria contact sites are crucial to allow Ca²⁺ flux between them and a plethora of proteins participate in tethering both organelles together. Inositol 1,4,5-trisphosphate receptors (IP₃Rs) play a pivotal role at such contact sites, participating in both ER-mitochondria tethering and as Ca²⁺-transport system that delivers Ca²⁺ from the ER towards mitochondria. At the ER-mitochondria contact sites, the IP₃Rs function as a multi-protein complex linked to the voltage-dependent anion channel 1 (VDAC1) in the outer mitochondrial membrane, via the chaperone glucose-regulated protein 75 (GRP75). This IP₃R-GRP75-VDAC1 complex supports the efficient transfer of Ca²⁺ from the ER into the mitochondrial intermembrane space, from which the Ca²⁺ ions can reach the mitochondrial matrix through the mitochondrial calcium uniporter. Under physiological conditions, basal Ca²⁺ oscillations deliver Ca²⁺ to the mitochondrial matrix, thereby stimulating mitochondrial oxidative metabolism. However, when mitochondrial Ca²⁺ overload occurs, the increase in [Ca²⁺] will induce the opening of the mitochondrial permeability transition pore, thereby provoking cell death. The IP₃R-GRP75-VDAC1 complex forms a hub for several other proteins that stabilize the complex and/or regulate the complex's ability to channel Ca²⁺ into the mitochondria. These proteins and their mechanisms of action are discussed in the present review with special attention for their role in pathological conditions and potential implication for therapeutic strategies.

Traumatic Brain Injury Alters Cerebral Concentrations and Redox States of Coenzymes Q9 and Q10 in the Rat

To date, there is no information on the effect of TBI on the changes in brain CoQ levels and possible variations in its redox state. In this study, we induced graded TBIs (mild TBI, mTBI and severe TBI, sTBI) in male rats, using the weight-drop closed-head impact acceleration model of trauma. At 7 days post-injury, CoQ₉, CoQ₁₀ and α-tocopherol were measured by HPLC in brain extracts of the injured rats, as well as in those of a group of control sham-operated rats. In the controls, about the 69% of total CoQ was in the form of CoQ₉ and the oxidized/reduced ratios of CoQ₉ and CoQ₁₀ were, respectively, 1.05 ± 0.07 and 1.42 ± 0.17. No significant changes in these values were observed in rats experiencing mTBI. Conversely, in the brains of sTBI-injured animals, an increase in reduced and a decrease in oxidized CoQ₉ produced an oxidized/reduced ratio of 0.81 ± 0.1 (p < 0.001 compared with both controls and mTBI). A concomitant decrease in both reduced and oxidized CoQ₁₀ generated a corresponding oxidized/reduced ratio of 1.38 ± 0.23 (p < 0.001 compared with both controls and mTBI). An overall decrease in the concentration of the total CoQ pool was also found in sTBI-injured rats (p < 0.001 compared with both controls and mTBI). Concerning α-tocopherol, whilst no differences compared with the controls were found in mTBI animals, a significant decrease was observed in rats experiencing sTBI (p < 0.01 compared with both controls and mTBI). Besides suggesting potentially different functions and intracellular distributions of CoQ₉ and CoQ₁₀ in rat brain mitochondria, these results demonstrate, for the first time to the best of knowledge, that sTBI alters the levels and redox states of CoQ₉ and CoQ₁₀, thus adding a new explanation to the mitochondrial impairment affecting ETC, OXPHOS, energy supply and antioxidant defenses following sTBI.

Mitochondria associated ER membrane and cerebral ischemia: molecular mechanisms and therapeutic strategies

Endoplasmic reticulum (ER) and mitochondria are two important organelles that are highly dynamic in mammalian cells. The physical connection between them is mitochondria associated ER membranes (MAM). In recent years, studies on endoplasmic reticulum and mitochondria have shifted from independent division to association and comparison, especially MAM has gradually become a research hotspot. MAM connects the two organelles, not only to maintain their independent structure and function, but also to promote metabolism and signal transduction between them. This paper reviews the morphological structure and protein localization of MAM, and briefly analyzes the functions of MAM in regulating Ca²⁺ transport, lipid synthesis, mitochondrial fusion and fission, endoplasmic reticulum stress and oxidative stress, autophagy and inflammation. Since ER stress and mitochondrial dysfunction are important pathological events in neurological diseases including ischemic stroke, MAM is likely to play an important role in cerebral ischemia by regulating the signaling of the two organelles and the crosstalk of the two pathological events.

The Missing Piece? A Case for Microglia's Prominent Role in the Therapeutic Action of Anesthetics, Ketamine, and Psychedelics

There is much excitement surrounding recent research of promising, mechanistically novel psychotherapeutics - psychedelic, anesthetic, and dissociative agents - as they have demonstrated surprising efficacy in treating central nervous system (CNS) disorders, such as mood disorders and addiction. However, the mechanisms by which these drugs provide such profound psychological benefits are still to be fully elucidated. Microglia, the CNS's resident innate immune cells, are emerging as a cellular target for psychiatric disorders because of their critical role in regulating neuroplasticity and the inflammatory environment of the brain. The following paper is a review of recent literature surrounding these neuropharmacological therapies and their demonstrated or hypothesized interactions with microglia. Through investigating the mechanism of action of psychedelics, such as psilocybin and lysergic acid diethylamide, ketamine, and propofol, we demonstrate a largely under-investigated role for microglia in much of the emerging research surrounding these pharmacological agents. Among others, we detail sigma-1 receptors, serotonergic and γ-aminobutyric acid signalling, and tryptophan metabolism as pathways through which these agents modulate microglial phagocytic activity and inflammatory mediator release, inducing their therapeutic effects. The current review includes a discussion on future directions in the field of microglial pharmacology and covers bidirectional implications of microglia and these novel pharmacological agents in aging and age-related disease, glial cell heterogeneity, and state-of-the-art methodologies in microglial research.

Potential role of mitochondria-associated endoplasmic reticulum membrane proteins in diseases

Mitochondria-associated endoplasmic reticulum membranes (MAMs) are dynamic membrane coupling regions formed by the coupling of the mitochondrial outer membrane and endoplasmic reticulum (ER). MAMs are involved in the mitochondrial dynamics, mitophagy, Ca²⁺ exchange, and ER stress. A large number of studies indicate that many proteins are involved in the formation of MAMs, including dynamic-related protein 1 (Drp1), DJ-1, PTEN-induced putative kinase 1 (PINK), α-synuclein (α-syn), sigma-1 receptor (S1R), mitofusin-2 (Mfn2), presenilin-1 (PS1), protein kinase R (PKR)-like ER kinase (PERK), Parkin, Cyclophilin D (CypD), glucose-related protein 75 (Grp75), FUN14 domain containing 1 (Fundc1), vesicle-associated membrane-protein-associated protein B (VAPB), phosphofurin acidic cluster sorting protein 2 (PACS-2), ER oxidoreductin 1 (Ero1), and receptor expression-enhancing protein 1 (REEP1). These proteins play an important role in the structure and functions of the MAMs. Abnormalities in these MAM proteins further contribute to the occurrence and development of related diseases, such as neurodegenerative diseases, non-alcoholicfattyliverdisease (NALFD), type 2 diabetes mellitus (T2DM), and diabetic kidney (DN). In this review, we introduce important proteins involved in the structure and the functions of the MAMs. Furthermore, we effectively summarize major insights about these proteins that are involved in the physiopathology of several diseases through the effect on MAMs.