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Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models.

ABSTRACT: It is well-established that subcompartments of endoplasmic reticulum (ER) are in physical contact with the mitochondria. These lipid raft-like regions of ER are referred to as mitochondria-associated ER membranes (MAMs), and they play an important role in, for example, lipid synthesis, calcium homeostasis, and apoptotic signaling. Perturbation of MAM function has previously been suggested in Alzheimer's disease (AD) as shown in fibroblasts from AD patients and a neuroblastoma cell line containing familial presenilin-2 AD mutation. The effect of AD pathogenesis on the ER-mitochondria interplay in the brain has so far remained unknown. Here, we studied ER-mitochondria contacts in human AD brain and related AD mouse and neuronal cell models. We found uniform distribution of MAM in neurons. Phosphofurin acidic cluster sorting protein-2 and ?1 receptor, two MAM-associated proteins, were shown to be essential for neuronal survival, because siRNA knockdown resulted in degeneration. Up-regulated MAM-associated proteins were found in the AD brain and amyloid precursor protein (APP)Swe/Lon mouse model, in which up-regulation was observed before the appearance of plaques. By studying an ER-mitochondria bridging complex, inositol-1,4,5-triphosphate receptor-voltage-dependent anion channel, we revealed that nanomolar concentrations of amyloid ?-peptide increased inositol-1,4,5-triphosphate receptor and voltage-dependent anion channel protein expression and elevated the number of ER-mitochondria contact points and mitochondrial calcium concentrations. Our data suggest an important role of ER-mitochondria contacts and cross-talk in AD pathology.

SUBMITTER: Hedskog L

PROVIDER: S-EPMC3651455 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature

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Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models.

Hedskog Louise L Pinho Catarina Moreira CM Filadi Riccardo R Rönnbäck Annica A Hertwig Laura L Wiehager Birgitta B Larssen Pia P Gellhaar Sandra S Sandebring Anna A Westerlund Marie M Graff Caroline C Winblad Bengt B Galter Dagmar D Behbahani Homira H Pizzo Paola P Glaser Elzbieta E Ankarcrona Maria M

Proceedings of the National Academy of Sciences of the United States of America 20130425 19

It is well-established that subcompartments of endoplasmic reticulum (ER) are in physical contact with the mitochondria. These lipid raft-like regions of ER are referred to as mitochondria-associated ER membranes (MAMs), and they play an important role in, for example, lipid synthesis, calcium homeostasis, and apoptotic signaling. Perturbation of MAM function has previously been suggested in Alzheimer's disease (AD) as shown in fibroblasts from AD patients and a neuroblastoma cell line containin ...[more]

PMID: 23620518

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Project description:Currently, more than 55 million people around the world suffer from dementia, and Alzheimer's disease-related dementia (ADRD) accounts for nearly 60-70% of all those cases. The spread of AD pathology and progressive neurodegeneration in the hippocampus and cerebral cortex is strongly correlated with cognitive decline in AD patients; however, the molecular underpinning of the ADRD causality is still unclear. Studies of postmortem AD brains and animal models of AD suggest that elevated endoplasmic reticulum (ER) stress may have a role in ADRD pathology through altered neurocellular homeostasis in brain regions associated with learning and memory. To study the ER stress-associated neurocellular response and its effects on neurocellular homeostasis and neurogenesis, we modeled an ER stress challenge using Thapsigargin (TG), a specific inhibitor of sarco/endoplasmic reticulum Ca2+ ATPase (SERCA), in induced pluripotent stem cell (iPSC)-derived neural stem cells (NSCs) of two individuals from our Mexican American Family Study (MAFS). High-content screening and transcriptomic analysis of the control and ER stress-challenged NSCs showed that NSC’s ER stress response resulted in a significant decline in NSC self-renewal and an increase in apoptosis and cellular oxidative stress. A total of 2300 genes were significantly (moderated t statistics FDR corrected p-value ≤ 0.05 and Fold Change absolute ≥ 2.0) differentially expressed (DE). Pathway enrichment and gene network analysis of DE genes suggests that all three unfolded protein response (UPR) pathways (PERK, IRE1, and ATF6) were significantly activated and cooperatively regulated the NSC’s transcriptional response to ER stress. Our results show that IRE1/XBP1 mediated transcriptional regulation of E2F1 and its downstream targets have a dominant role in inducing G1/S-phase cell cycle arrest in the ER stress-challenged NSCs. The ER stress-challenged NSCs also showed activation of CHOP-mediated apoptosis and dysregulation of synaptic plasticity and neurotransmitter homeostasis-associated genes. Overall, our results suggest that ER stress-associated attenuation of NSC self-renewal, increased apoptosis, and dysregulated synaptic plasticity and neurotransmitter homeostasis plausibly play a role in the causation of ADRD.

Project description:SEPN1-related myopathy (SEPN1-RM) is a muscle disorder due to mutations of the SEPN1 gene, which is characterized by muscle weakness and fatigue leading to scoliosis and life-threatening respiratory failure. Core lesions, focal areas of mitochondria depletion in skeletal muscle fibers, are the most common histopathological lesion. SEPN1-RM underlying mechanisms and the precise role of SEPN1 in muscle remained incompletely understood, hindering the development of biomarkers and therapies for this untreatable disease. To investigate the pathophysiological pathways in SEPN1-RM, we performed metabolic studies, calcium and ATP measurements, super-resolution and electron microscopy on in vivo and in vitro models of SEPN1 deficiency as well as muscle biopsies from SEPN1-RM patients. Mouse models of SEPN1 deficiency showed marked alterations in mitochondrial physiology and energy metabolism, suggesting that SEPN1 controls mitochondrial bioenergetics. Moreover, we found that SEPN1 was enriched at the mitochondria-associated membranes (MAM), and was needed for calcium transients between ER and mitochondria, as well as for the integrity of ER-mitochondria contacts. Consistently, loss of SEPN1 in patients was associated with alterations in body composition which correlated with the severity of muscle weakness, and with impaired ER-mitochondria contacts and low ATP levels. Our results indicate a role of SEPN1 as a novel MAM protein involved in mitochondrial bioenergetics. They also identify a systemic bioenergetic component in SEPN1-RM and establish mitochondria as a novel therapeutic target. This role of SEPN1 contributes to explain the fatigue and core lesions in skeletal muscle as well as the body composition abnormalities identified as part of the SEPN1-RM phenotype. Finally, these results point out to an unrecognized interplay between mitochondrial bioenergetics and ER homeostasis in skeletal muscle. They could therefore pave the way to the identification of biomarkers and therapeutic drugs for SEPN1-RM and for other disorders in which muscle ER-mitochondria cross-talk are impaired.

Dataset Information

Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models.

Publications

Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models.

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