Stefano Musardo

Endocytosis of synaptic ADAM10 in neuronal plasticity and Alzheimer’s disease

A disintegrin and metalloproteinase 10 (ADAM10), a disintegrin and metalloproteinase that resides in the postsynaptic densities (PSDs) of excitatory synapses, has previously been shown to limit β-amyloid peptide (Aβ) formation in Alzheimers disease (AD). ADAM10 also plays a critical role in regulating functional membrane proteins at the synapse. Using human hippocampal homogenates, we found that ADAM10 removal from the plasma membrane was mediated by clathrin-dependent endocytosis. Additionally, we identified the clathrin adaptor AP2 as an interacting partner of a previously uncharacterized atypical binding motif in the ADAM10 C-terminal domain. This domain was required for ADAM10 endocytosis and modulation of its plasma membrane levels. We found that the ADAM10/AP2 association was increased in the hippocampi of AD patients compared with healthy controls. Long-term potentiation (LTP) in hippocampal neuronal cultures induced ADAM10 endocytosis through AP2 association and decreased surface ADAM10 levels and activity. Conversely, long-term depression (LTD) promoted ADAM10 synaptic membrane insertion and stimulated its activity. ADAM10 interaction with the synapse-associated protein-97 (SAP97) was necessary for LTD-induced ADAM10 trafficking and required for LTD maintenance and LTD-induced changes in spine morphogenesis. These data identify and characterize a mechanism controlling ADAM10 localization and activity at excitatory synapses that is relevant to AD pathogenesis.

Cocaine-evoked negative symptoms require AMPA receptor trafficking in the lateral habenula

Addictive substances mediate positive and negative states promoting persistent drug use. However, substrates for aversive effects of drugs remain elusive. We found that, in mouse lateral habenula (LHb) neurons targeting the rostromedial tegmental nucleus, cocaine enhanced glutamatergic transmission, reduced K+ currents and increased excitability. GluA1 trafficking in LHb was instrumental for these cocaine-evoked modifications and drug-driven aversive behaviors. Altogether, our results suggest that long-lasting adaptations in LHb shape negative symptoms after drug taking.

Modeling Alzheimer's disease: from past to future

Alzheimer’s disease (AD) is emerging as the most prevalent and socially disruptive illness of aging populations, as more people live long enough to become affected. Although AD is placing a considerable and increasing burden on society, it represents the largest unmet medical need in neurology, because current drugs improve symptoms, but do not have profound disease-modifying effects. Although AD pathogenesis is multifaceted and difficult to pinpoint, genetic and cell biological studies led to the amyloid hypothesis, which posits that amyloid β (Aβ) plays a pivotal role in AD pathogenesis. Amyloid precursor protein (APP), as well as β- and γ-secretases are the principal players involved in Aβ production, while α-secretase cleavage on APP prevents Aβ deposition. The association of early onset familial AD with mutations in the APP and γ-secretase components provided a potential tool of generating animal models of the disease. However, a model that recapitulates all the aspects of AD has not yet been produced. Here, we face the problem of modeling AD pathology describing several models, which have played a major role in defining critical disease-related mechanisms and in exploring novel potential therapeutic approaches. In particular, we will provide an extensive overview on the distinct features and pros and contras of different AD models, ranging from invertebrate to rodent models and finally dealing with computational models and induced pluripotent stem cells.

ADAM10 in Synaptic Physiology and Pathology

Background: Generation of amyloid-β peptide is at the beginning of a cascade that leads to Alzheimers disease. Amyloid precursor protein (APP) as well as β- and γ-secretases are the principal players involved in amyloid-β (Aβ) production, while α-secretase cleavage on APP prevents Aβ deposition. A disintegrin and metalloproteinase 10 (ADAM10) has been demonstrated to act as α-secretase in neurons. Objective: Although localization of ADAM10 in the synaptic membrane is the key for its shedding activity, currently, very little is known about the mechanisms that control the synaptic abundance of ADAM10. Results: Two established forms of long-term activity-dependent plasticity, i.e. long-term potentiation and long-term depression (LTD), differentially regulate the synaptic availability and activity of ADAM10. Long-term potentiation decreases ADAM10 surface levels and activity by promoting its endocytosis. This process is mediated by activity-regulated association of ADAM10 with the clathrin adaptor protein 2 (AP2) complex. Conversely, LTD fosters ADAM10 insertion in the membrane and stimulates its activity. Furthermore, ADAM10 interaction with synapse-associated protein 97 (SAP97) is necessary for LTD-induced ADAM10 trafficking and required for LTD maintenance and LTD-induced spine morphology changes. Conclusions: Regulated interaction of ADAM10 with SAP97 and AP2 discloses a novel physiological mechanism of ADAM10 activity regulation at the synapses. This phenomenon produces a situation whereby synaptically regulated ADAM10 activity is positioned to modulate synaptic functioning.

Ring finger protein 10 is a novel synaptonuclear messenger encoding activation of NMDA receptors in hippocampus

Synapses and nuclei are connected by bidirectional communication mechanisms that enable information transfer encoded by macromolecules. Here, we identified RNF10 as a novel synaptonuclear protein messenger. RNF10 is activated by calcium signals at the postsynaptic compartment and elicits discrete changes at the transcriptional level. RNF10 is enriched at the excitatory synapse where it associates with the GluN2A subunit of NMDA receptors (NMDARs). Activation of synaptic GluN2A-containing NMDARs and induction of long term potentiation (LTP) lead to the translocation of RNF10 from dendritic segments and dendritic spines to the nucleus. In particular, we provide evidence for importin-dependent long-distance transport from synapto-dendritic compartments to the nucleus. Notably, RNF10 silencing prevents the maintenance of LTP as well as LTP-dependent structural modifications of dendritic spines. DOI: http://dx.doi.org/10.7554/eLife.12430.001

Synaptic dysfunction in Alzheimer's disease: From the role of amyloid β-peptide to the α-secretase ADAM10

Alzheimers disease (AD) is emerging as the most prevalent and socially disruptive illness of aging populations as more people live long enough to become affected. Although AD is placing a considerable and increasing burden on patients, caregivers and society, it represents the largest unmet medical need in neurology, because it is currently incurable. In the last few years, the amyloid hypothesis, which points to amyloid β-peptide (Aβ) as the initiating factor in AD, had a central role in the development of therapeutic strategies for AD. However, the recent clinical trials targeting Aβ have been disappointing. The need to obtain a comprehensive picture of AD pathogenesis is strong as ever. In this framework, this review focuses on Aβ effects on the synapses and on ADAM10, the enzyme able to prevent Aβ formation, analysing its function in the synapse, its contribution to AD pathology and discussing its potential as pharmacological target.

Sperm protein 17 and AKAP-associated sperm protein cancer/testis antigens are expressed in ciliated hepatic foregut cysts

Ciliated hepatic foregut cysts (CHFCs) are retained benign lesions of the liver. However, a case of squamous cell metaplasia and five cases of squamous cell carcinoma arising from a CHFC have been described. The potential of malignant transformation makes the identification of new biomarkers necessary. As the cancer/testis antigen sperm protein 17 (Sp17) has been detected in oral and oesophageal squamous cell carcinomas, the aim of this study was to investigate the expression of Sp17 and AKAP‐associated sperm protein (ASP), which has a shared N‐terminal sequence with Sp17, in four surgically resected CHFCs.

The Metrizer: an innovative device for achieving virtual hepatic biopsies

The last few years have brought rapid growth in the number of Virtual Microscopes (VM) and the promotion of digital histology. In this digital era, it is natural to assist in the transportation of histology imaging into computer technology support. We have also assisted in a quick and precise race towards improved technology capable of acquiring detailed digital images which realistically report the original slide for easy consultation [1,2]. The advanced technology herein proposed aims at being a sophisticated imaging archive. Digitally scanning slides however, does not give additional information to the vision of tissue structures, even with high resolution or improved colour and image precision. We can now say that high enlargement microscopic observation can only give same details to structures visible to the eye directly through the microscope. This means that when VMs are used in a correct manner they are capable of giving significant progress to highlighting, not quantifying, a critical field in applying technology specific to computerised measuring. The potential to improve precision and objectivity of measurements can be achieved with additional technical equipment. The aim of this study is to present a machine invented with a calculation potential to facilitate the work of the observer in a medical practice, not only in terms of easy retrieval of images but also as an instrument for the automatic analysis of digital histology. The “Metrizer” aims at supplying precise and objective descriptions and measurements of the specimen under observation. These descriptions do not substitute the pathologist but they should assist him/her to assert with objectivity and safety the entity of the observed pathology [3-8]. Material and methods The “Metrizer” (Figure 1) is an automatic, compact machine composed of a lens for microscopic observation, digital cameras, a movement device and a computer complete with software to control machine movement and image analysis. With these components the machine facilitates consultation of histological preparations (virtual microscop e-s lide scanner function) and supplies objective numeric data regarding the state of the tissue harbouring diverse diseases without causing fatigue or human error. Using the Slide Scanner function it enables to automatically digitalise the entire histological slide in high definition and makes it easily accessible in the digital archive.

Pituitary tumor transforming gene 1 in the liver

We read with interest and appreciate the paper by Fujii et al.,1 but feel it is necessary to make the following observations. Despite advances in our cellular and molecular knowledge, hepatocellular carcinoma (HCC) remains one of the major public health problems throughout the world. It is now known to be highly heterogeneous as it encompasses various pathological entities and a wide range of clinical behaviors, and is underpinned by a complex array of gene alterations that affect supra-molecular processes.2 Pituitary tumour transforming gene 1 (PTTG-1) is an oncogene expressed in various human neoplasms and cell lines.3-8 Although its pathogenetic implications in HCC are still unknown, it has been shown that its over-expression in hepatoma cell lines negatively regulates the ability of p53 to induce apoptosis, and that its silencing by means of short interference RNA may be an efficient way of treating liver cancer.8 The expression of tumor-associated antigens is mainly investigated at the gene level by means of quantitative real-time PCR (qrt-PCR). However, the information provided by this approach is limited by the fact that the phenomena observed at each level of anatomical organization (i.e., genes, sub-cellular entities, cells, tissues, organs, apparatuses and organisms) have properties that do not exist at lower or higher levels: qrt-PCR offers an adequate quantitative description of small-scale structures, but this is likely to be inapplicable when it comes to large-scale features.9 We used an immunoperoxidase-based staining assay to investigate the expression of PTTG-1 (anti-PTTG-1 polyclonal antibodies, Zymed Laboratory Inc., San Francisco, CA) in liver tissues taken from patients affected by chronic HCV-related hepatitis and primary HCC, and found that there were four immunopositive cell types: (a) hepatocytes recognized in hepatitic tissue in which the protein was located near the biliary pole (Fig. 1A); (B) Kupffer cells identified in hepatic tissue and surrounding the cancerous lesion (Fig. 1B); (c) some T lymphocytes situated in the portal spaces (Fig. 1C); and (d) a proportion of neoplastic liver cells (Fig. 1D). Primary colon cancer tissues were used as a positive control (Fig. 1E), and tissues incubated with rabbit immunoglobulin fraction (Dako, Milan, Italy) as a negative control (Fig. 1F). All of our findings demonstrate broader PTTG-1 expression in the liver than that reported by Fujii et al.1 Furthermore, on the basis of the above microscopic observations, it is possible to say: 1. The qrt-PCR detection of mRNA encoding PTTG-1 in HCC tissue and the surrounding non-cancerous hepatic parenchyma does not distinguish the cell types expressing the protein or its relative quantitative contribution to the total amount of detected mRNA. 2. The presence of PTTG-1 in tumoral and non-tumoral cells may actually be considered a shared characteristic that makes it possible to group different cell types in a single category. 3. The detection of PTTG-1 expression in some intrahepatic T lymphocytes extends previous findings showing its enhanced expression in circulating activated T cells.10 In conclusion, the paper of Fujii et al. discusses important points but, although the clinical application seems to be remarkable, we and other morphologists need additional details if we are to replicate the results.

Sex Difference: What does cannabis do to the brain before birth?

Being exposed to cannabinoids in the womb has different consequences for male and female rats.