scholarly journals Neuronal Aβ42 is enriched in small vesicles at the presynaptic side of synapses

2018 ◽  
Vol 1 (3) ◽  
pp. e201800028 ◽  
Author(s):  
Yang Yu ◽  
Daniel C Jans ◽  
Bengt Winblad ◽  
Lars O Tjernberg ◽  
Sophia Schedin-Weiss
Keyword(s):  
Hippocampal Neurons ◽  
Memory Function ◽  
Three Dimensional ◽  
Amyloid Β ◽  
Super Resolution ◽  
Long Term Potentiation ◽  
Synaptic Function ◽  
Amyloid Β Peptide ◽  
Term Potentiation ◽  
Super Resolution Microscopy

The amyloid β-peptide (Aβ) is a physiological ubiquitously expressed peptide suggested to be involved in synaptic function, long-term potentiation, and memory function. The 42 amino acid-long variant (Aβ42) forms neurotoxic oligomers and amyloid plaques and plays a key role in the loss of synapses and other pathogenic events of Alzheimer disease. Still, the exact localization of Aβ42 in neurons and at synapses has not been reported. Here, we used super-resolution microscopy and show that Aβ42 was present in small vesicles in presynaptic compartments, but not in postsynaptic compartments, in the neurites of hippocampal neurons. Some of these vesicles appeared to lack synaptophysin, indicating that they differ from the synaptic vesicles responsible for neurotransmitter release. The Aβ42-containing vesicles existed in presynapses connected to stubby spines and mushroom spines, and were also present in immature presynapses. These vesicles were scarce in other parts of the neurites, where Aβ42 was instead present in large, around 200–600 nm, vesicular structures. Three-dimensional super-resolution microscopy confirmed that Aβ42 was present in the presynapse and absent in the postsynapse.

scholarly journals Aberrant Synaptic PTEN in Symptomatic Alzheimer’s Patients May Link Synaptic Depression to Network Failure

2021 ◽  
Vol 13 ◽  
Author(s):  
Marta Díaz González ◽  
Assaf Buberman ◽  
Miguel Morales ◽  
Isidro Ferrer ◽  
Shira Knafo
Keyword(s):  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Amyloid Β ◽  
Long Term Potentiation ◽  
Synaptic Depression ◽  
Synaptic Function ◽  
Network Failure ◽  
Term Potentiation ◽  
Synaptic Failure

In Alzheimer’s disease (AD), Amyloid β (Aβ) impairs synaptic function by inhibiting long-term potentiation (LTP), and by facilitating long-term depression (LTD). There is now evidence from AD models that Aβ provokes this shift toward synaptic depression by triggering the access to and accumulation of PTEN in the postsynaptic terminal of hippocampal neurons. Here we quantified the PTEN in 196,138 individual excitatory dentate gyrus synapses from AD patients at different stages of the disease and from controls with no neuropathological findings. We detected a gradual increase of synaptic PTEN in AD brains as the disease progresses, in conjunction with a significant decrease in synaptic density. The synapses that remain in symptomatic AD patients are more likely to be smaller and exhibit fewer AMPA receptors (AMPARs). Hence, a high Aβ load appears to strongly compromise human hippocampal synapses, as reflected by an increase in PTEN, inducing a loss of AMPARs that may eventually provoke synaptic failure and loss.

scholarly journals A Super-Resolved View of the Alzheimer’s Disease-Related Amyloidogenic Pathway in Hippocampal Neurons

2021 ◽  
pp. 1-20
Author(s):  
Yang Yu ◽  
Yang Gao ◽  
Bengt Winblad ◽  
Lars Tjernberg ◽  
Sophia Schedin Weiss
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Hippocampal Neurons ◽  
Three Dimensional ◽  
Amyloid Β ◽  
Stimulated Emission ◽  
Amyloid Β Peptide ◽  
Primary Neurons ◽  
Amyloid Β Protein ◽  
Early Endosomes

Background: Processing of the amyloid-β protein precursor (AβPP) is neurophysiologically important due to the resulting fragments that regulate synapse biology, as well as potentially harmful due to generation of the 42 amino acid long amyloid β-peptide (Aβ 42), which is a key player in Alzheimer’s disease. Objective: Our aim was to clarify the subcellular locations of the amyloidogenic AβPP processing in primary neurons, including the intracellular pools of the immediate substrate, AβPP C-terminal fragment (APP-CTF) and the product (Aβ 42). To overcome the difficulties of resolving these compartments due to their small size, we used super-resolution microscopy. Methods: Mouse primary hippocampal neurons were immunolabelled and imaged by stimulated emission depletion (STED) microscopy, including three-dimensional, three-channel imaging and image analyses. Results: The first (β-secretase) and second (γ-secretase) cleavages of AβPP were localized to functionally and distally distinct compartments. The β-secretase cleavage was observed in early endosomes, where we were able to show that the liberated N- and C-terminal fragments were sorted into distinct vesicles budding from the early endosomes in soma. Lack of colocalization of Aβ 42 and APP-CTF in soma suggested that γ-secretase cleavage occurs in neurites. Indeed, APP-CTF was, in line with Aβ 42 in our previous study, enriched in the presynapse but absent from the postsynapse. In contrast, full-length AβPP was not detected in either the pre- or the postsynaptic side of the synapse. Furthermore, we observed that endogenously produced and endocytosed Aβ 42 were localized in different compartments. Conclusion: These findings provide critical super-resolved insight into amyloidogenic AβPP processing in primary neurons.

scholarly journals High levels of 27-hydroxycholesterol results in synaptic plasticity alterations in the hippocampus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Raul Loera-Valencia ◽  
Erika Vazquez-Juarez ◽  
Alberto Muñoz ◽  
Gorka Gerenu ◽  
Marta Gómez-Galán ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Memory Function ◽  
Long Term Potentiation ◽  
Synaptic Function ◽  
Cholesterol Homeostasis ◽  
Stratum Radiatum ◽  
Actin Binding ◽  
Ca1 Region ◽  
Hippocampal Ca1 Region ◽  
Term Potentiation

AbstractAlterations in brain cholesterol homeostasis in midlife are correlated with a higher risk of developing Alzheimer’s disease (AD). However, global cholesterol-lowering therapies have yielded mixed results when it comes to slowing down or preventing cognitive decline in AD. We used the transgenic mouse model Cyp27Tg, with systemically high levels of 27-hydroxycholesterol (27-OH) to examine long-term potentiation (LTP) in the hippocampal CA1 region, combined with dendritic spine reconstruction of CA1 pyramidal neurons to detect morphological and functional synaptic alterations induced by 27-OH high levels. Our results show that elevated 27-OH levels lead to enhanced LTP in the Schaffer collateral-CA1 synapses. This increase is correlated with abnormally large dendritic spines in the stratum radiatum. Using immunohistochemistry for synaptopodin (actin-binding protein involved in the recruitment of the spine apparatus), we found a significantly higher density of synaptopodin-positive puncta in CA1 in Cyp27Tg mice. We hypothesize that high 27-OH levels alter synaptic potentiation and could lead to dysfunction of fine-tuned processing of information in hippocampal circuits resulting in cognitive impairment. We suggest that these alterations could be detrimental for synaptic function and cognition later in life, representing a potential mechanism by which hypercholesterolemia could lead to alterations in memory function in neurodegenerative diseases.

scholarly journals Amyloid-β Peptide Is Needed for cGMP-Induced Long-Term Potentiation and Memory

2017 ◽  
Vol 37 (29) ◽  
pp. 6926-6937 ◽  
Author(s):  
Agostino Palmeri ◽  
Roberta Ricciarelli ◽  
Walter Gulisano ◽  
Daniela Rivera ◽  
Claudia Rebosio ◽  
...  
Keyword(s):  
Amyloid Β ◽  
Long Term Potentiation ◽  
Amyloid Β Peptide ◽  
Term Potentiation

scholarly journals Neuronal hibernation following hippocampal demyelination

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Selva Baltan ◽  
Safdar S. Jawaid ◽  
Anthony M. Chomyk ◽  
Grahame J. Kidd ◽  
Jacqueline Chen ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Three Dimensional ◽  
Long Term Potentiation ◽  
Synaptic Function ◽  
Mammalian Brain ◽  
Gene Transcript ◽  
Ca1 Neurons

AbstractCognitive dysfunction occurs in greater than 50% of individuals with multiple sclerosis (MS). Hippocampal demyelination is a prominent feature of postmortem MS brains and hippocampal atrophy correlates with cognitive decline in MS patients. Cellular and molecular mechanisms responsible for neuronal dysfunction in demyelinated hippocampi are not fully understood. Here we investigate a mouse model of hippocampal demyelination where twelve weeks of treatment with the oligodendrocyte toxin, cuprizone, demyelinates over 90% of the hippocampus and causes decreased memory/learning. Long-term potentiation (LTP) of hippocampal CA1 pyramidal neurons is considered to be a major cellular readout of learning and memory in the mammalian brain. In acute slices, we establish that hippocampal demyelination abolishes LTP and excitatory post-synaptic potentials of CA1 neurons, while pre-synaptic function of Schaeffer collateral fibers is preserved. Demyelination also reduced Ca2+-mediated firing of hippocampal neurons in vivo. Using three-dimensional electron microscopy, we investigated the number, shape (mushroom, stubby, thin), and post-synaptic densities (PSDs) of dendritic spines that facilitate LTP. Hippocampal demyelination did not alter the number of dendritic spines. Surprisingly, dendritic spines appeared to be more mature in demyelinated hippocampi, with a significant increase in mushroom-shaped spines, more perforated PSDs, and more astrocyte participation in the tripartite synapse. RNA sequencing experiments identified 400 altered transcripts in demyelinated hippocampi. Gene transcripts that regulate myelination, synaptic signaling, astrocyte function, and innate immunity were altered in demyelinated hippocampi. Hippocampal remyelination rescued synaptic transmission, LTP, and the majority of gene transcript changes. We establish that CA1 neurons projecting demyelinated axons silence their dendritic spines and hibernate in a state that may protect the demyelinated axon and facilitates functional recovery following remyelination.

scholarly journals MicroRNA-132 provides neuroprotection for tauopathies via multiple signaling pathways

2018 ◽  
Author(s):  
Rachid El Fatimy ◽  
Shaomin Li ◽  
Zhicheng Chen ◽  
Tasnim Mushannen ◽  
Sree Gongala ◽  
...  
Keyword(s):  
Rna Binding ◽  
Amyloid Β ◽  
Long Term Potentiation ◽  
Therapeutic Benefit ◽  
Glutamate Excitotoxicity ◽  
Amyloid Β Peptide ◽  
Neuroprotective Effects ◽  
Term Potentiation ◽  
Neuroprotective Function ◽  
Multiple Signaling

AbstractMicroRNAs (miRNA) regulate fundamental biological processes, including neuronal plasticity, stress response, and survival. Here we describe a neuroprotective function of miR-132, the miRNA most significantly down-regulated in Alzheimer’s disease. miR-132 protects mouse and human wild-type neurons and more vulnerable Tau-mutant primary neurons against amyloid β-peptide (Aβ) and glutamate excitotoxicity. It lowers the levels of total, phosphorylated, acetylated, and cleaved forms of Tau implicated in tauopathies, promotes neurite elongation and branching, and reduces neuronal death. Similarly, miR-132 attenuates PHF Tau pathology and neurodegeneration and enhances long-term potentiation in the P301S Tau transgenic mice. The neuroprotective effects are mediated by direct regulation of the Tau modifiers acetyltransferase EP300, kinase GSK3β, RNA-binding protein Rbfox1, and proteases Calpain 2 and Caspases 3/7. These data suggest miR-132 as a master regulator of neuronal health and indicate that miR-132 supplementation could be of therapeutic benefit for the treatment of Tau-associated neurodegenerative disorders.

DCP-LA neutralizes mutant amyloid β peptide-induced impairment of long-term potentiation and spatial learning

2010 ◽  
Vol 206 (1) ◽  
pp. 151-154 ◽  
Author(s):  
Tetsu Nagata ◽  
Takemi Tominaga ◽  
Hiroshi Mori ◽  
Takahiro Yaguchi ◽  
Tomoyuki Nishizaki
Keyword(s):  
Spatial Learning ◽  
Amyloid Β ◽  
Long Term Potentiation ◽  
Amyloid Β Peptide ◽  
Term Potentiation

scholarly journals Soluble Aβ Inhibits Specific Signal Transduction Cascades Common to the Insulin Receptor Pathway

2007 ◽  
Vol 282 (46) ◽  
pp. 33305-33312 ◽  
Author(s):  
Matthew Townsend ◽  
Tapan Mehta ◽  
Dennis J. Selkoe
Keyword(s):  
Protein Kinase ◽  
Alzheimer Disease ◽  
Insulin Receptor ◽  
Hippocampal Neurons ◽  
Amyloid Β ◽  
Principal Component ◽  
Long Term Potentiation ◽  
Amyloid Β Protein ◽  
Term Potentiation

Numerous studies have now shown that the amyloid β-protein (Aβ), the principal component of cerebral plaques in Alzheimer disease, rapidly and potently inhibits certain forms of synaptic plasticity. The amyloid (or Aβ) hypothesis proposes that the continuous disruption of normal synaptic physiology by Aβ contributes to the development of Alzheimer disease. However, there is little consensus about how Aβ mediates this inhibition at the molecular level. Using mouse primary hippocampal neurons, we observed that a brief treatment with cell-derived, soluble, human Aβ disrupted the activation of three kinases (Erk/MAPK, CaMKII, and the phosphatidylinositol 3-kinase-activated protein Akt/protein kinase B) that are required for long term potentiation, whereas two other kinases (protein kinase A and protein kinase C) were stimulated normally. An antagonist of the insulin receptor family of tyrosine kinases was found to mimic the pattern of Aβ-mediated kinase inhibition. We then found that soluble Aβ binds to the insulin receptor and interferes with its insulin-induced autophosphorylation. Taken together, these data demonstrate that physiologically relevant levels of naturally secreted Aβ interfere with insulin receptor function in hippocampal neurons and prevent the rapid activation of specific kinases required for long term potentiation.

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