Gephyrin palmitoylation and oligomerization in synaptic plasticity, membrane recruitment and proteostasis

Efficient signal transmission in the central nervous system is essential for higher brain functions. Inhibitory signaling in the brain primarily takes place at GABAergic (γ-aminobutyric acid) synapses and balances the activity of excitatory synapses. GABA type A receptors (GABAARs) are clustered at the synapse by a scaffold with the peripheral membrane protein gephyrin as major postsynaptic protein. One key feature of synapses is their ability to adapt in response to neuronal network activities, though underlying mechanisms how these changes are orchestrated under normal and pathological conditions are poorly understood. The first part of the study focuses on gephyrin’s membrane association in neurons with the aim to elucidate the molecular mechanisms and significance of membrane tethering. Gephyrin from Sf9 insect cells, but not E. coli, bound to liposomes and specifically to phosphatidylinositol 4-phosphate in protein-lipid overlay assays. Furthermore, gephyrin was identified to be mainly associated with cholesterol-rich membrane microdomains in mouse brains. Posttranslational lipid modifications of synaptic proteins regulate their trafficking and membrane localization and contribute to synaptic plasticity. Using different experimental approaches, gephyrin was identified to be palmitoylated in vivo. Palmitoylation of gephyrin was crucial for its localization at synapses and influenced the size of gephyrin clusters and the architecture of the inhibitory synapse. Membrane release of gephyrin upon inhibition of palmitoylation led to reduced surface quantities of synaptic GABAAR subunits. Additionally, the membrane detachment made gephyrin more susceptible to cleavage by the protease calpain I resulting in an accelerated turnover of the protein. Gephyrin palmitoylation was identified to be regulated by GABAAR activity leading to rapid changes in gephyrin palmitoylation levels. Palmitoylation screens in hippocampal neurons identified the neurite-localized palmitoyl transferase DHHC12 and Golgi-resident DHHC16 as gephyrin palmitoylating enzymes, which increase gephyrin cluster size and its amount in synapses. Gephyrin was also identified to be physiologically S-nitrosylated by NO, which is produced by neuronal nitric oxide synthase (nNOS). Pharmacological nNOS activity modulation in HEK-293 cells and hippocampal neurons reciprocally regulated gephyrin palmitoylation. Together, these findings identify differential modification of gephyrin by palmitoylation and nitrosylation and suggest that palmitoylation dynamics of gephyrin contribute to the regulation of GABAergic activity-dependent plasticity. Inhibitory signaling is crucial to counterbalance excitatory transmission. Anomalous inhibitory circuits and particularly irregular gephyrin expression have been linked to epileptic disorders. Patients with idiopathic generalized epilepsy have been screened for mutations in the GPHN gene. In the second part, a patient was identified with a hemizygous mutation in GPHN resulting in the expression of a truncated gephyrin variant that failed to oligomerize at inhibitory synapses. This pathogenic variant acted dominant-negatively on regular gephyrin and disrupted the normal gephyrin scaffold and synaptic GABAAR clustering in hippocampal neurons. The results suggest that mutations in genes coding for proteins of the inhibitory synapse is an important mechanism in the pathophysiology of monogenetic epilepsy forms

The Question of Re-turning: Toward or Away from the Virtual?

It is by now generally understood that the nature of events are central to Deleuze’s philosophical endeavour. This has not meant, however, that the process mapped out by this concept has been adequately grasped. Indeed, the lines mapping out events are obscured, theoretical, even otherworldly, whenever the complexities of the creating of the virtual and the actual as the created, are reductively conceived as giving way to two separated domains; two separated domains whereby the repeater would be forever condemned to be the result of an otherworldly will that “works through it,” one that would signal that they would never be capable of becoming worthy of the events that make a life.[i] The perspectival reality of the virtual with respect to the actual, which despite its fragmentary nature is in its entirety encompassed in each singular event, requires of us that we grasp what it is that Antonin Artaud’s points to when saying, I “am my son, my father, my mother, and myself.” It is not as though events perceived in the form of a virtual complex render beings inconsequential; instead, events are capable of ousting the verb “to be” in a double sense, because they enfold what is most affirmative in the activity of beings, the being of becoming whereby a life is born, always yet again, and as a function of which, as Alfred North Whitehead notes, what an actual being is, is how that entity becomes. It is adequate to its becoming. The actual as present-being expresses the verb “to be” in an ephemeral sense, or it is expressed by it in a restrictive way, while when affirmed as indistinct from the virtual, being, the verb “to be,” implies nothing else than the return of becoming. It is an untimely instant in which what is affirmed is the continuation of becoming; an instant that makes each event be the infinite becoming-finite of an actual being. So as to explore the nature of events in Deleuze’s philosophy, it is this displacement, the ousting of the verb “to be,” that I focus in on in this paper

The Paradox of Sense, or On the Event of Thought in Giles Deleuze's Philosophy

Written under the double heading The Paradox of Sense, or on the Event of Thought, this dissertation is a study of the doubled pathway of articulation in Gilles Deleuze’s philosophy. With the repetition of the heading, we want to suggest that, in fact, these two pathways unfold with respect to the same Event. The question which way do we turn, away or towards the virtual, is equivalent to the question, what difference is there. The double pathway defines the central problematic of this dissertation: in the first place, the line of articulation leads to the expression of sense in the proposition, meanwhile with the repetition of difference, another pathway of articulation is retraced that revolves around speaking the event. With the event the question becomes: What does it mean to speak the event once beings are taken to be events

Decoding of Multiple Wrist and Hand Movements Using a Transient EMG Classifier

: The design of prosthetic controllers by means of neurophysiological signals still poses a crucial challenge to bioengineers. State of the art of electromyographic (EMG) continuous pattern recognition controllers rely on the questionable assumption that repeated muscular contractions produce repeatable patterns of steady-state EMG signals. Conversely, we propose an algorithm that decodes wrist and hand movements by processing the signals that immediately follow the onset of contraction (i.e., the transient EMG). We collected EMG data from the forearms of 14 non-amputee and 5 transradial amputee participants while they performed wrist flexion/extension, pronation/supination, and four hand grasps (power, lateral, bi-digital, open). We firstly identified the combination of wrist and hand movements that yielded the best control performance for the same participant (intra-subject classification). Then, we assessed the ability of our algorithm to classify participant data that were not included in the training set (cross-subject classification). Our controller achieved a median accuracy of ~96% with non-amputees, while it achieved heterogeneous outcomes with amputees, with a median accuracy of ~89%. Importantly, for each amputee, it produced at least one acceptable combination of wrist-hand movements (i.e., with accuracy >85%). Regarding the cross-subject classifier, while our algorithm obtained promising results with non-amputees (accuracy up to ~80%), they were not as good with amputees (accuracy up to ~35%), possibly suggesting further assessments with domain-adaptation strategies. In general, our offline outcomes, together with a preliminary online assessment, support the hypothesis that the transient EMG decoding could represent a viable pattern recognition strategy, encouraging further online assessments

A SiGe 8-Channel Comparator for Application in a Synthetic Aperture Radiometer

We present a high-speed low-power 8-channel comparator tailored for the application of sampling antenna signals in a cross-correlator system for space-borne synthetic aperture radiometer instruments. Features like clock return path, per-channel offset calibration and bias current tuning make the comparator adaptable and gives the possibility to adjust the comparator for low power consumption, while keeping performance within the requirements of the cross-correlator system. The comparator has been implemented and fabricated in a 130-nm SiGe BiCMOS process. Measurements show that the comparator can perform sampling at a rate of 4.5 GS/s with a power consumption of 48 mW/channel or 1 GS/s with a power consumption of 17 mW/channel

A model for implementing vibration and sound heatmaps in smart cities based on crowdsensing data

This paper aims to establish a model that can utilize vibration and sound heatmaps in smart traffic using Internet of things, mobile and web technologies. The developed system should be able to monitor and collect information using crowdsensing technology, as well as provide the current status of the environment. The final objective of the model is to generate visual heat maps related to perceptual attributes (e.g. ‘calm’, ‘pleasant’, ‘unbearable‘) with collected vibrations and sounds as a starting point. The proposed system is developed through these main stages: (1) Vibration and sound sources recognition (2) Profiling of the sources (3) Prediction of perceptual measures divided by the area (4) Implementation of vibration and sound heatmaps. This research is specifically focusing on the last two stages (predictions and implementation). These stages are broken down into smaller phases with methodology and processes described in detail. The model of the developed system was realized through measured vibrations and sound data in urban transportation in Novi Sad city. Finally, we present the research results from the analysis paradigm and provide suggestions for its implementation

Possible role of TGF-B pathways in schizophrenia

© 2016, University of Kragujevac, Faculty of Science. All Rights Reserved. The phenomenological uniqueness of each patient with schizophrenia is determined by complex symptomatology, particularly the overlapping of symptoms and their prominence in certain phases of this mental disorder. Establishing biological markers is an important step in the further objectivisation and quantification of schizophrenia. Identifying the cytokine profiles that precede a psychotic episode could direct the strategies for relapse prevention and be useful in predicting disease progression and treatment response. In the context of inflammation, TGF-β exerts potent anti-inflammatory and immunosuppressive functions by inhibiting pro-inflammatory cytokine synthesis, but it can also have pro-inflammatory functions through its stimulatory effects on inflammatory 17 cells. It has been shown that the T helper cell type-1 and type-17 responses are reduced and type-2 response is increased in patients with schizophrenia. Both data from the literature and our results also indicate the presence of an anti-inflammatory response through production of the TGF-β regulatory cytokine. A meta-analysis of plasma cytokine alterations suggested that TGF-β is the state marker for acute exacerbation of schizophrenia, and we showed that TGF-β can also be a valuable marker for psychosis. Hyperactivity of TGF-β signalling pathways in schizophrenia may be both a neuroprotective mechanism and a possible therapeutic target

A 183-GHz Schottky diode receiver with 4 dB noise figure

Atmospheric science based on space-borne\ua0millimeter wave measurements require reliable and state-of-the art\ua0receivers. In particular, the water vapor line at 183.3 GHz\ua0motivates the development of sensitive mixers at this frequency.\ua0Traditional assembly techniques employed in the production of\ua0Schottky diode receivers involve flip-chip mounting and soldering\ua0of discrete dies, which prohibit the implementation of reliable and\ua0repeatable production processes. In this work, we present a\ua0subharmonic 183 GHz mixer implementing a repeatable assembly\ua0method using beamlead Schottky diodes. The mixer was\ua0integrated with a InP HEMT MMIC low noise intermediate\ua0frequency amplifier resulting in a record-low receiver noise\ua0temperature of 450 K at 1 mW of local oscillator power measured\ua0at room-temperature. The measured Allan time was 10 s and the\ua0third order local oscillator spurious power was less than -60 dBm.\ua0The proposed assembly method is of particular importance for\ua0space-borne missions but also applicable to a wide range of\ua0terahertz applications

Decoding of Multiple Wrist and Hand Movements Using a Transient EMG Classifier

The design of prosthetic controllers by means of neurophysiological signals still poses a crucial challenge to bioengineers. State of the art of electromyographic (EMG) continuous pattern recognition controllers rely on the questionable assumption that repeated muscular contractions produce repeatable patterns of steady-state EMG signals. Conversely, we propose an algorithm that decodes wrist and hand movements by processing the signals that immediately follow the onset of contraction (i.e., the \textit {transient} EMG). We collected EMG data from the forearms of 14 non-amputee and 5 transradial amputee participants while they performed wrist flexion/extension, pronation/supination, and four hand grasps (power, lateral, bi-digital, open). We firstly identified the combination of wrist and hand movements that yielded the best control performance for the same participant (intra-subject classification). Then, we assessed the ability of our algorithm to classify participant data that were not included in the training set (cross-subject classification). Our controller achieved a median accuracy of 96% with non-amputees, while it achieved heterogeneous outcomes with amputees, with a median accuracy of 89%. Importantly, for each amputee, it produced at least one \textit {acceptable} combination of wrist-hand movements (i.e., with accuracy >85%). Regarding the cross-subject classifier, while our algorithm obtained promising results with non-amputees (accuracy up to 80%), they were not as good with amputees (accuracy up to 35%), possibly suggesting further assessments with domain-adaptation strategies. In general, our offline outcomes, together with a preliminary online assessment, support the hypothesis that the transient EMG decoding could represent a viable pattern recognition strategy, encouraging further online assessments