Genome-wide kinase-MAM interactome screening reveals the role of CK2A1 in MAM Ca2+ dynamics linked to DEE66.

The endoplasmic reticulum (ER) and mitochondria form a unique subcellular compartment called mitochondria-associated ER membranes (MAMs). Disruption of MAMs impairs Ca2+ homeostasis, triggering pleiotropic effects in the neuronal system. Genome-wide kinase-MAM interactome screening identifies casein kinase 2 alpha 1 (CK2A1) as a regulator of composition and Ca2+ transport of MAMs. CK2A1-mediated phosphorylation of PACS2 at Ser207/208/213 facilitates MAM localization of the CK2A1-PACS2-PKD2 complex, regulating PKD2-dependent mitochondrial Ca2+ influx. We further reveal that mutations of PACS2 (E209K and E211K) associated with developmental and epileptic encephalopathy-66 (DEE66) impair MAM integrity through the disturbance of PACS2 phosphorylation at Ser207/208/213. This, in turn, causes the reduction of mitochondrial Ca2+ uptake and the dramatic increase of the cytosolic Ca2+ level, thereby, inducing neurotransmitter release at the axon boutons of glutamatergic neurons. In conclusion, our findings suggest a molecular mechanism that MAM alterations induced by pathological PACS2 mutations modulate Ca2+-dependent neurotransmitter release.

The Alzheimer's disease-associated C99 fragment of APP regulates cellular cholesterol trafficking.

The link between cholesterol homeostasis and cleavage of the amyloid precursor protein (APP), and how this relationship relates to Alzheimer's disease (AD) pathogenesis, is still unknown. Cellular cholesterol levels are regulated through crosstalk between the plasma membrane (PM), where most cellular cholesterol resides, and the endoplasmic reticulum (ER), where the protein machinery that regulates cholesterol levels resides. The intracellular transport of cholesterol from the PM to the ER is believed to be activated by a lipid-sensing peptide(s) in the ER that can cluster PM-derived cholesterol into transient detergent-resistant membrane domains (DRMs) within the ER, also called the ER regulatory pool of cholesterol. When formed, these cholesterol-rich domains in the ER maintain cellular homeostasis by inducing cholesterol esterification as a mechanism of detoxification while attenuating its de novo synthesis. In this manuscript, we propose that the 99-aa C-terminal fragment of APP (C99), when delivered to the ER for cleavage by γ-secretase, acts as a lipid-sensing peptide that forms regulatory DRMs in the ER, called mitochondria-associated ER membranes (MAM). Our data in cellular AD models indicates that increased levels of uncleaved C99 in the ER, an early phenotype of the disease, upregulates the formation of these transient DRMs by inducing the internalization of extracellular cholesterol and its trafficking from the PM to the ER. These results suggest a novel role for C99 as a mediator of cholesterol disturbances in AD, potentially explaining early hallmarks of the disease.

Characterization of mitochondria-associated ER membranes in the enteric nervous system under physiological and pathological conditions.

Alterations in endoplasmic reticulum (ER)-mitochondria associations and in mitochondria-associated ER membrane (MAM) behavior have been reported in the brain in several neurodegenerative diseases. Despite the emerging role of the gut-brain axis in neurodegenerative disorders, the biology of MAM in the enteric nervous system (ENS) has not previously been studied. Therefore, we set out to characterize the MAM in the distal colon of wild-type C57BL/6J mice and senescence-accelerated mouse prone 8 (SAMP8), a mouse model of age-related neurodegeneration. We showed for the first time that MAMs are widely present in enteric neurons and that their association is altered in SAMP8 mice. We then examined the functions of MAMs in a primary culture model of enteric neurons and showed that calcium homeostasis was altered in SAMP8 mice when compared with control animals. These findings provide the first detailed characterization of MAMs in the ENS under physiological conditions and during age-associated neurodegeneration. Further investigation of MAM modifications in the ENS in disease may provide valuable information about the possible role of enteric MAMs in neurodegenerative diseases.NEW & NOTEWORTHY Our work shows for the first time the presence of contacts between endoplasmic reticulum and mitochondria in the enteric neurons and that the dynamic of these contacts is affected in these cells from an age-related neurodegeneration mouse model. It provides new insights into the potential role of enteric mitochondria-associated endoplasmic reticulum membrane in neurodegenerative disorders.

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.

[Effect and mechanism of Linggui Zhugan Decoction in regulating Sig1R on Angâ ¡-induced cardiomyocyte hypertrophy].

This study aims to explore the mechanism of Linggui Zhugan Decoction(LGZGD) in inhibiting Angiotensin Ⅱ(AngⅡ)-induced cardiomyocyte hypertrophy by regulating sigma-1 receptor(Sig1R). The model of H9c2 cardiomyocyte hypertrophy induced by AngⅡ in vitro was established by preparing LGZGD-containing serum and blank serum. H9c2 cells were divided into normal group, AngⅡ model group, 20% normal rat serum group(20% NSC), and 20% LGZGD-containing serum group. After the cells were incubated with AngⅡ(1 µmol·L~(-1)) or AngⅡ with serum for 72 h, the surface area of cardiomyocytes was detected by phalloidine staining, and the activities of Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase were detected by micromethod. The mitochondrial Ca~(2+) levels were detected by flow cytometry, and the expression levels of atrial natriuretic peptide(ANP), brain natriuretic peptide(BNP), Sig1R, and inositol 1,4,5-triphosphate receptor type 2(IP_3R_2) were detected by Western blot. The expression of Sig1R was down-regulated by transfecting specific siRNA for investigating the efficacy of LGZGD-containing serum on cardiomyocyte surface area, Na~+-K~+-ATPase activity, Ca~(2+)-Mg~(2+)-ATPase activity, mitochondrial Ca~(2+), as well as ANP, BNP, and IP_3R_2 protein expressions. The results showed that compared with the normal group, AngⅡ could significantly increase the surface area of cardiomyocytes and the expression of ANP and BNP(P<0.01), and it could decrease the activities of Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase, the concentration of mitochondrial Ca~(2+), and the expression of Sig1R(P<0.01). In addition, IP_3R_2 protein expression was significantly increased(P<0.01). LGZGD-containing serum could significantly decrease the surface area of cardiomyocytes and the expression of ANP and BNP(P<0.05, P<0.01), and it could increase the activities of Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase, the concentration of mitochondrial Ca~(2+ )(P<0.01), and the expression of Sig1R(P<0.05). In addition, IP_3R_2 protein expression was significantly decreased(P<0.05). However, after Sig1R was down-regulated, the effects of LGZGD-containing serum were reversed(P<0.01). These results indicated that the LGZGD-containing serum could inhibit cardiomyocyte hypertrophy induced by AngⅡ, and its pharmacological effect was related to regulating Sig1R, promoting mitochondrial Ca~(2+ )inflow, restoring ATP synthesis, and protecting mitochondrial function.

SIRT3 ameliorates diabetes-associated cognitive dysfunction via regulating mitochondria-associated ER membranes.

BACKGROUND: Diabetes is associated with an increased risk of cognitive decline and dementia. These diseases are linked with mitochondrial dysfunction, most likely as a consequence of excessive formation of mitochondria-associated membranes (MAMs). Sirtuin3 (SIRT3), a key mitochondrial NAD+-dependent deacetylase, is critical responsible for mitochondrial functional homeostasis and is highly associated with neuropathology. However, the role of SIRT3 in regulating MAM coupling remains unknown. METHODS: Streptozotocin-injected diabetic mice and high glucose-treated SH-SY5Y cells were established as the animal and cellular models, respectively. SIRT3 expression was up-regulated in vivo using an adeno-associated virus in mouse hippocampus and in vitro using a recombinant lentivirus vector. Cognitive function was evaluated using behavioural tests. Hippocampus injury was assessed using Golgi and Nissl staining. Apoptosis was analysed using western blotting and TUNEL assay. Mitochondrial function was detected using flow cytometry and confocal fluorescence microscopy. The mechanisms were investigated using co-immunoprecipitation of VDAC1-GRP75-IP3R complex, fluorescence imaging of ER and mitochondrial co-localisation and transmission electron microscopy of structural analysis of MAMs. RESULTS: Our results demonstrated that SIRT3 expression was significantly reduced in high glucose-treated SH-SY5Y cells and hippocampal tissues from diabetic mice. Further, up-regulating SIRT3 alleviated hippocampus injuries and cognitive impairment in diabetic mice and mitigated mitochondrial Ca2+ overload-induced mitochondrial dysfunction and apoptosis. Mechanistically, MAM formation was enhanced under high glucose conditions, which was reversed by genetic up-regulation of SIRT3 via reduced interaction of the VDAC1-GRP75-IP3R complex in vitro and in vivo. Furthermore, we investigated the therapeutic effects of pharmacological activation of SIRT3 in diabetic mice via honokiol treatment, which exhibited similar effects to our genetic interventions. CONCLUSIONS: In summary, our findings suggest that SIRT3 ameliorates cognitive impairment in diabetic mice by limiting aberrant MAM formation. Furthermore, targeting the activation of SIRT3 by honokiol provides a promising therapeutic candidate for diabetes-associated cognitive dysfunction. Overall, our study suggests a novel role of SIRT3 in regulating MAM coupling and indicates that SIRT3-targeted therapies are promising for diabetic dementia patients.

Mitochondria associated ER membranes 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.

Functional diversity of apolipoprotein E: from subcellular localization to mitochondrial function.

Human apolipoprotein E (APOE), originally known for its role in lipid metabolism, is polymorphic with three major allele forms, namely, APOEε2, APOEε3, and APOEε4, leading to three different human APOE isoforms. The ε4 allele is a genetic risk factor for Alzheimer's disease (AD); therefore, the vast majority of APOE research focuses on its role in AD pathology. However, there is increasing evidence for other functions of APOE through the involvement in other biological processes such as transcriptional regulation, mitochondrial metabolism, immune response, and responsiveness to dietary factors. Therefore, the aim of this review is to provide an overview of the potential novel functions of APOE and their characterization. The detection of APOE in various cell organelles points to previously unrecognized roles in mitochondria and others, although it is actually considered a secretory protein. Furthermore, numerous interactions of APOE with other proteins have been detected, providing indications for new metabolic pathways involving APOE. The present review summarizes the current evidence on APOE beyond its original role in lipid metabolism, to change the perspective and encourage novel approaches to future research on APOE and its isoform-dependent role in the cellular metabolism.

Impact of ER Stress and ER-Mitochondrial Crosstalk in Huntington's Disease.

Accumulation of misfolded proteins is a common phenomenon of several neurodegenerative diseases. The misfolding of proteins due to abnormal polyglutamine (PolyQ) expansions are linked to the development of PolyQ diseases including Huntington's disease (HD). Though the genetic basis of PolyQ repeats in HD remains prominent, the primary molecular basis mediated by PolyQ toxicity remains elusive. Accumulation of misfolded proteins in the ER or disruption of ER homeostasis causes ER stress and activates an evolutionarily conserved pathway called Unfolded protein response (UPR). Protein homeostasis disruption at organelle level involving UPR or ER stress response pathways are found to be linked to HD. Due to dynamic intricate connections between ER and mitochondria, proteins at ER-mitochondria contact sites (mitochondria associated ER membranes or MAMs) play a significant role in HD development. The current review aims at highlighting the most updated information about different UPR pathways and their involvement in HD disease progression. Moreover, the role of MAMs in HD progression has also been discussed. In the end, the review has focused on the therapeutic interventions responsible for ameliorating diseased states via modulating either ER stress response proteins or modulating the expression of ER-mitochondrial contact proteins.

Ethanol Induces Extracellular Vesicle Secretion by Altering Lipid Metabolism through the Mitochondria-Associated ER Membranes and Sphingomyelinases.

Recent evidence pinpoints extracellular vesicles (EVs) as key players in intercellular communication. Given the importance of cholesterol and sphingomyelin in EV biology, and the relevance of mitochondria-associated endoplasmic reticulum membranes (MAMs) in cholesterol/sphingomyelin homeostasis, we evaluated if MAMs and sphingomyelinases (SMases) could participate in ethanol-induced EV release. EVs were isolated from the extracellular medium of BV2 microglia treated or not with ethanol (50 and 100 mM). Radioactive metabolic tracers combined with thin layer chromatography were used as quantitative methods to assay phospholipid transfer, SMase activity and cholesterol uptake/esterification. Inhibitors of SMase (desipramine and GW4869) and MAM (cyclosporin A) activities were also utilized. Our data show that ethanol increases the secretion and inflammatory molecule concentration of EVs. Ethanol also upregulates MAM activity and alters lipid metabolism by increasing cholesterol uptake, cholesterol esterification and SMase activity in microglia. Notably, the inhibition of either SMase or MAM activity prevented the ethanol-induced increase in EV secretion. Collectively, these results strongly support a lipid-driven mechanism, specifically via SMases and MAM, to explain the effect of ethanol on EV secretion in glial cells.

The silence of the fats: A MAM's story about Alzheimer.

The discovery of contact sites was a breakthrough in cell biology. We have learned that an organelle cannot function in isolation, and that many cellular functions depend on communication between two or more organelles. One such contact site results from the close apposition of the endoplasmic reticulum (ER) and mitochondria, known as mitochondria-associated ER membranes (MAMs). These intracellular lipid rafts serve as hubs for the regulation of cellular lipid and calcium homeostasis, and a growing body of evidence indicates that MAM domains modulate cellular function in both health and disease. Indeed, MAM dysfunction has been described as a key event in Alzheimer disease (AD) pathogenesis. Our most recent work shows that, by means of its affinity for cholesterol, APP-C99 accumulates in MAM domains of the ER and induces the uptake of extracellular cholesterol as well as its trafficking from the plasma membrane to the ER. As a result, MAM functionality becomes chronically upregulated while undergoing continual turnover. The goal of this review is to discuss the consequences of C99 elevation in AD, specifically the upregulation of cholesterol trafficking and MAM activity, which abrogate cellular lipid homeostasis and disrupt the lipid composition of cellular membranes. Overall, we present a novel framework for AD pathogenesis that can be linked to the many complex alterations that occur during disease progression, and that may open a door to new therapeutic strategies.

MAMs are attractive targets for bacterial repurposing of the host cell: MAM-functions might be key for undermining an infected cell.

Pathogenic bacteria frequently target the endoplasmic reticulum (ER) and mitochondria in order to exploit host functions. ER-mitochondria inter-organelle communication is topologically sub-compartmentalized at mitochondria-associated ER membranes (MAMs). MAMs are specific membranous microdomains with unique regulatory functions such as lipid synthesis and trafficking, calcium homeostasis, mitochondrial morphology, inflammasome activation, autophagosome formation, and apoptosis. These important cellular processes are all modulated by pathogens to subvert host functions and promote infection, thus it is tempting to assume that pathogenic bacteria target MAMs to subvert these different pathways in their hosts. First lines of evidence that support this hypothesis come from Legionella pneumophila. This intracellular bacterium secretes an effector that exhibits sphingosine-1 phosphate lyase activity (LpSpl) that seems to target MAMs to modulate the autophagy response to infection. Here we thus propose the concept that MAMs could be targeted by pathogenic bacteria to undermine key host cellular processes.

Potential Roles of Mitochondria-Associated ER Membranes (MAMs) in Traumatic Brain Injury.

The endoplasmic reticulum (ER) and mitochondria have both been shown to be critical in cellular homeostasis. The functions of the ER and mitochondria are independent but interrelated. These two organelles could form physical interactions, known as MAMs, to regulate physiological functions between ER and mitochondria to maintain Ca2+, lipid, and metabolite exchange. Several proteins are located in MAMs, including RNA-dependent protein kinase (PKR)-like ER kinase, inositol 1,4,5-trisphosphate receptors, phosphofurin acidic cluster sorting protein-2 and sigma-1 receptor to ensure regulation. Recent studies indicated that MAMs participate in inflammation and apoptosis in various conditions. All of these functions are crucial in determining cell fate following traumatic brain injury (TBI). We hypothesized that MAMs may associate with TBI and could contribute to mitochondrial dysfunction, ER stress, autophagy dysregulation, dysregulation of Ca2+ homeostasis, and oxidative stress. In this review, we summarize the latest understanding of MAM formation and their potential regulatory role in TBI pathophysiology.

Role of mitochondrial dysfunction and dysregulation of Ca2+ homeostasis in the pathophysiology of insulin resistance and type 2 diabetes.

Metabolic diseases such as obesity, type 2 diabetes (T2D) and insulin resistance have attracted great attention from biomedical researchers and clinicians because of the astonishing increase in its prevalence. Decrease in the capacity of oxidative metabolism and mitochondrial dysfunction are a major contributor to the development of these metabolic disorders. Recent studies indicate that alteration of intracellular Ca2+ levels and downstream Ca2+-dependent signaling pathways appear to modulate gene transcription and the activities of many enzymes involved in cellular metabolism. Ca2+ uptake into mitochondria modulates a number of Ca2+-dependent proteins and enzymes participating in fatty acids metabolism, tricarboxylic acid cycle, oxidative phosphorylation and apoptosis in response to physiological and pathophysiological conditions. Mitochondrial calcium uniporter (MCU) complex has been identified as a major channel located on the inner membrane to regulate Ca2+ transport into mitochondria. Recent studies of MCU complex have increased our understanding of the modulation of mitochondrial function and retrograde signaling to the nucleus via regulation of the mitochondrial Ca2+ level. Mitochondria couple cellular metabolic state by regulating not only their own Ca2+ levels, but also influence the entire network of cellular Ca2+ signaling. The mitochondria-associated ER membranes (MAMs), which are specialized structures between ER and mitochondria, are responsible for efficient communication between these organelles. Defects in the function or structure of MAMs have been observed in affected tissue cells in metabolic disease or neurodegenerative disorders. We demonstrated that dysregulation of intracellular Ca2+ homeostasis due to mitochondrial dysfunction or defects in the function of MAMs are involved in the pathogenesis of insulin insensitivity and T2D. These observations suggest that mitochondrial dysfunction and disturbance of Ca2+ homeostasis warrant further studies to assist the development of therapeutics for prevention and medication of insulin resistance and T2D.

Alzheimer Disease.

The most widely accepted hypothesis to explain the pathogenesis of Alzheimer disease (AD) is the amyloid cascade, in which the accumulation of extraneuritic plaques and intracellular tangles plays a key role in driving the course and progression of the disease. However, there are other biochemical and morphological features of AD, including altered calcium, phospholipid, and cholesterol metabolism and altered mitochondrial dynamics and function that often appear early in the course of the disease, prior to plaque and tangle accumulation. Interestingly, these other functions are associated with a subdomain of the endoplasmic reticulum (ER) called mitochondria-associated ER membranes (MAM). MAM, which is an intracellular lipid raft-like domain, is closely apposed to mitochondria, both physically and biochemically. These MAM-localized functions are, in fact, increased significantly in various cellular and animal models of AD and in cells from AD patients, which could help explain the biochemical and morphological alterations seen in the disease. Based on these and other observations, a strong argument can be made that increased ER-mitochondria connectivity and increased MAM function are fundamental to AD pathogenesis.

Alterations in Ca2+ Signalling via ER-Mitochondria Contact Site Remodelling in Cancer.

Inter-organellar contact sites establish microdomains for localised Ca2+-signalling events. One of these microdomains is established between the ER and the mitochondria. Importantly, the so-called mitochondria-associated ER membranes (MAMs) contain, besides structural proteins and proteins involved in lipid exchange, several Ca2+-transport systems, mediating efficient Ca2+ transfer from the ER to the mitochondria. These Ca2+ signals critically control several mitochondrial functions, thereby impacting cell metabolism, cell death and survival, proliferation and migration. Hence, the MAMs have emerged as critical signalling hubs in physiology, while their dysregulation is an important factor that drives or at least contributes to oncogenesis and tumour progression. In this book chapter, we will provide an overview of the role of the MAMs in cell function and how alterations in the MAM composition contribute to oncogenic features and behaviours.

Contacting the gut: Mitochondria-associated Endoplasmic Reticulum Membranes in the Enteric Nervous System.

Changes in the connections between the endoplasmic reticulum (ER) and mitochondria, as well as alterations in mitochondria-associated ER membrane (MAM) signalling, have been documented in various neurodegenerative diseases affecting the brain. Despite the growing recognition of the significance of the gut-brain axis in neurodegenerative conditions, there has been no prior investigation into the biology of MAM within the enteric nervous system (ENS). Our recent research reveals, for the first time, the existence of connections between the ER and mitochondria within enteric neurons. Additionally, we observed alterations in the dynamics of these connections in the enteric neurons from a mouse model exhibiting age-related neurodegeneration. These findings provide the first detailed characterization of MAM in the ENS under physiological conditions and in a mouse model of age-associated neurodegeneration and shed new light on the potential role of enteric MAM in the context of neurodegenerative disorders.

Phillyrin promotes autophagosome formation in A53T-αSyn-induced Parkinson's disease model via modulation of REEP1.

BACKGROUND: The preservation of autophagosome formation presents a promising strategy for tackling neurological disorders, such as Parkinson's disease (PD). Mitochondria-associated endoplasmic reticulum (ER) membranes (MAM) serve not only as a focal point linked to various neurological disorders but also play a crucial role in supporting the biogenesis of autophagosomes. PURPOSE: This investigation aimed to elucidate the neuroprotective properties of phillyrin against PD and its underlying mechanisms in promoting autophagosome formation. METHODS: ER and mitochondria co-localization was assessed via fluorescent staining. Annexin V-fluorescein isothiocyanate (FITC) fluorescence was employed to quantify accessible cardiolipin (CL) on mitochondrial surfaces. The levels of CL within the MAM fraction of SH-SY5Y cells were evaluated using a CL probe assay kit. Monodansylcadaverine staining was utilized to detect autophagosome formation in SH-SY5Y cells. In an A53T-alpha-synuclein (αSyn)-induced PD mouse model, the anti-PD properties of phillyrin were assessed using open field, pole climbing, and rotarod tests, as well as immunohistochemistry staining of TH+ neurons in the brain sections. RESULTS: In A53T-αSyn-treated SH-SY5Y cells, phillyrin facilitated autophagosome formation by suppressing CL externalization and restoring MAM integrity. Phillyrin enhanced the localization of receptor expression-enhancing protein 1 (REEP1) within MAM and mitochondria, bolstering MAM formation. Increased REEP1 levels in mitochondria, attributed to phillyrin, enhanced the interaction between REEP1 and NDPK-D, thereby reducing CL externalization. Furthermore, phillyrin exhibited a dose-dependent enhancement of motor function in mice, accompanied by an increase in the abundance of dopaminergic neurons within the substantia nigra. CONCLUSIONS: These findings illuminate phillyrin's ability to enhance MAM formation through upregulation of REEP1 expression within MAM, while concurrently attenuating CL externalization via the REEP1-NDPK-D interaction. These mechanisms bolster autophagosome biogenesis, offering resilience against A53T-αSyn-induced PD. Thus, our study advances the understanding of phillyrin's complex mechanisms and underscores its potential as a therapeutic approach for PD, opening new avenues in natural product pharmacology.

The Role of Alpha-Synuclein in Synucleinopathy: Impact on Lipid Regulation at Mitochondria-ER Membranes.

The protein alpha-synuclein (αSyn) plays a critical role in the pathogenesis of synucleinopathy, which includes Parkinson's disease and multiple system atrophy, and mounting evidence suggests that lipid dyshomeostasis is a critical phenotype in these neurodegenerative conditions. Previously, we identified that αSyn localizes to mitochondria-associated endoplasmic reticulum membranes (MAMs), temporary functional domains containing proteins that regulate lipid metabolism, including the de novo synthesis of phosphatidylserine. In the present study, we have analyzed the lipid composition of postmortem human samples, focusing on the substantia nigra pars compacta of Parkinson's disease and controls, as well as three less affected brain regions of Parkinson's donors. To further assess synucleinopathy-related lipidome alterations, similar analyses were performed on the striatum of multiple system atrophy cases. Our data show region-and disease-specific changes in the levels of lipid species. Specifically, our data revealed alterations in the levels of specific phosphatidylserine species in brain areas most affected in Parkinson's disease. Some of these alterations, albeit to a lesser degree, are also observed multiples system atrophy. Using induced pluripotent stem cell-derived neurons, we show that αSyn contributes to regulating phosphatidylserine metabolism at MAM domains, and that αSyn dosage parallels the perturbation in phosphatidylserine levels. Our results support the notion that αSyn pathophysiology is linked to the dysregulation of lipid homeostasis, which may contribute to the vulnerability of specific brain regions in synucleinopathy. These findings have significant therapeutic implications.

Progress of mitochondrial and endoplasmic reticulum-associated signaling and its regulation of chronic liver disease by Chinese medicine.

The endoplasmic reticulum (ER) is connected to mitochondria through mitochondria-associated ER membranes (MAMs). MAMs provide a framework for crosstalk between the ER and mitochondria, playing a crucial role in regulating cellular calcium balance, lipid metabolism, and cell death. Dysregulation of MAMs is involved in the development of chronic liver disease (CLD). In CLD, changes in MAMs structure and function occur due to factors such as cellular stress, inflammation, and oxidative stress, leading to abnormal interactions between mitochondria and the ER, resulting in liver cell injury, fibrosis, and impaired liver function. Traditional Chinese medicine has shown some research progress in regulating MAMs signaling and treating CLD. This paper reviews the literature on the association between mitochondria and the ER, as well as the intervention of traditional Chinese medicine in regulating CLD.