Synaptic AMPA Receptor Plasticity and Behavior

The ability to change behavior likely depends on the selective strengthening and weakening of brain synapses. The cellular models of synaptic plasticity, long-term potentiation (LTP) and depression (LTD) of synaptic strength, can be expressed by the synaptic insertion or removal of AMPA receptors (AMPARs), respectively. We here present an overview of studies that have used animal models to show that such AMPAR trafficking underlies several experience-driven phenomena—from neuronal circuit formation to the modification of behavior. We argue that monitoring and manipulating synaptic AMPAR trafficking represents an attractive means to study cognitive function and dysfunction in animal models

Immunocytochemistry by Electron Spectroscopic Imaging Using Well Defined Boronated Monovalent Antibody Fragments

Contributing to the rapidly developing field of immunoelectron microscopy a new kind of markers has been created. The element boron, incorporated as very stable carborane clusters into different kinds of peptides, served as a marker detectable by electron spectroscopic imaging (ESI) - an electron microscopic technique with high-resolution potential. Covalently linked immunoreagents conspicuous by the small size of both antigen recognizing part and marker moiety are accessible by using peptide concepts for label construction and their conjugation with Fab\u27 fragments. Due to a specific labeling of the free thiol groups of the Fab\u27 fragments, the antigen binding capacity was not affected by the attachment of the markers and the resulting immunoprobes exhibited an elongated shape with the antigen combining site and the label located at opposite ends. The labeling densities observed with these reagents were found to be significantly higher than those obtained by using conventional colloidal gold methods. Combined with digital image processing and analysis systems, boron-based ESI proved to be a powerful approach in ultrastructural immunocytochemistry employing pre-and post-embedding methods

Engineering of specific bacteriophages for early diagnosis of Alzheimer′s disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease affecting a large proportion of the human population worldwide with great impact on social and economic level. At molecular level, AD is characterized by an increased deposition of plaques, which consist of amyloid-beta however, it is not the amyloid-beta in plaques, but amyloid-beta in soluble oligomeric form that impairs synaptic function and memory encoding. The limitations imposed by the blood-brain barrier (BBB) have hindered the development of new diagnostic/therapeutic techniques. Also, AD-treatments that target plaques have proven to be ineffective, therefore it is important to find diagnostic and therapeutic tools that selectively target amyloid-beta in oligomeric form. Peptie ligands that selectively recognize AB-oligomers are available, however they are not able to cross the BBB. To overcome this limitation, the development and application of viruses has become a very interesting tool. Bacteriophages (or phages – virus that only infect bacterial cells) can bypass the BBB and can be genetically and chemically manipulated in order to recognize and target specific biomarkers commonly used for AD diagnostic. The present work describes the development of a bacteriophage-based system that can be capable of diagnose AD at an early stage by shuttling amyloid-beta specific ligands across the BBB. Phages were genetically engineered with two peptide sequences described to selectively recognize amyloid-beta oligomers in order to target and visualize amyloid-beta aggregates in the brain. Future work will be devoted to test this system in AD-mouse models for diagnosis purposes at an early stage of the disease. If successful, this approach will provide the neuroscience community with a promising tool for AD early diagnose

GluR1 links structural and functional plasticity at excitatory synapses

Long-term potentiation (LTP), a cellular model of learning and memory, produces both an enhancement of synaptic function and an increase in the size of the associated dendritic spine. Synaptic insertion of AMPA receptors is known to play an important role in mediating the increase in synaptic strength during LTP, whereas the role of AMPA receptor trafficking in structural changes remains unexplored. Here, we examine how the cell maintains the correlation between spine size and synapse strength during LTP. We found that cells exploit an elegant solution by linking both processes to a single molecule: the AMPA-type glutamate receptor subunit 1 (GluR1). Synaptic insertion of GluR1 is required to permit a stable increase in spine size, both in hippocampal slice cultures and in vivo. Synaptic insertion of GluR1 is not sufficient to drive structural plasticity. Although crucial to the expression of LTP, the ion channel function of GluR1 is not required for the LTP-driven spine size enhancement. Remarkably, a recombinant cytosolic C-terminal fragment (C-tail) of GluR1 is driven to the postsynaptic density after an LTP stimulus, and the synaptic incorporation of this isolated GluR1 C-tail is sufficient to permit spine enlargement even when postsynaptic exocytosis of endogenous GluR1 is blocked. We conclude that during plasticity, synaptic insertion of GluR1 has two functions: the established role of increasing synaptic strength via its ligand-gated ion channel, and a novel role through the structurally stabilizing effect of its C terminus that permits an increase in spine size

A bacteriophage-based platform for early diagnosis of Alzheimers disease

Book of Abstracts of CEB Annual Meeting 2017[Excerpt] Alzheimer’s disease (AD) is the most common neurodegenerative disease affecting a large proportion of the human population worldwide. One hallmark of AD is the increased deposition of plaques, which consist of amyloid-beta (AB) peptide, a key molecule to cause AD onset and progression. However, it is not AB immobilized in plaques, but in the still-soluble oligomeric/fibrillar form that impairs synaptic function and memory encoding. It is therefore important to develop tools that selectively target AB in oligomeric/fibrillar form, to diagnose and neutralize these detrimental AB-clusters during the early stages of the disease. Homing peptides that selectively recognize AB-oligomers and fibrils have been described: AB30-39, reactive for AB fibrils and AB33-42, reactive to fibrils and oligomers [1]. However, these peptides are unable to cross the blood-brain barrier (BBB) by themselves. To overcome this limitation, viruses became a very interesting tool given their versatility to be modified through genetic or chemical manipulation. Bacteriophages (phages), are viruses that only infect bacteria (a major advantage in terms of safety when therapeutic use in humans is envisaged). M13KE is one of the most widely used phage which has been reported as capable to cross the BBB [2]. [...]info:eu-repo/semantics/publishedVersio

New ultrahigh vacuum setup and advanced diagnostic techniques for studying a-Si:H film growth by radical beams

A new ultrahigh vacuum setup is presented which is designed for studying the surface science aspects of a-Si:H film growth using various advanced optical diagnostic techniques. The setup is equipped with plasma and radical sources which produce well-defined radicals beams such that the a-Si:H deposition process can be mimicked. In this paper the initial experiments with respect to deposition of a-Si:H using a hot wire source and etching of a-Si:H by atomic hydrogen are presented. These processes are monitored by real time spectroscopic ellipsometry and the etch yield of Si by atomic hydrogen is quantified to be 0.005±0.002 Si atoms per incoming H atom