Neuronal Cytoskeletal Proteins Research Articles

Biomarkers of mature neuronal differentiation and related diseases.

The nervous system regulates perception, cognition and behavioral responses by serving as the body's primary communication system for receiving, regulating and transmitting information. Neurons are the fundamental structures and units of the nervous system. Their differentiation and maturation processes rely on the expression of specific biomarkers. Neuron-specific intracellular markers can be used to determine the degree of neuronal maturation. Neuronal cytoskeletal proteins dictate the shape and structure of neurons, while synaptic plasticity and signaling processes are intricately associated with neuronal synaptic markers. Furthermore, abnormal expression levels of biomarkers can serve as diagnostic indicators for nervous system diseases. This article reviews the markers of mature neuronal differentiation and their relationship with nervous system diseases.

Lyssavirus M protein degrades neuronal microtubules by reprogramming mitochondrial metabolism.

Infection with neurotropic viruses may result in changes in host behavior, which are closely associated with degenerative changes in neurons. The lyssavirus genus comprises highly neurotropic viruses, including the rabies virus (RABV), which has been shown to induce degenerative changes in neurons, marked by the self-destruction of axons. The underlying mechanism by which the RABV degrades neuronal cytoskeletal proteins remains incomplete. In this study, we show that infection with RABV or overexpression of its M protein can disrupt mitochondrial metabolism by binding to Slc25a4. This leads to a reduction in NAD+ production and a subsequent influx of Ca2+ from the endoplasmic reticulum and mitochondria into the cytoplasm of neuronal cell lines, activating Ca2+-dependent proteinase calpains that degrade α-tubulin. We further screened the M proteins of different lyssaviruses and discovered that the M protein of the dog-derived RABV strain (DRV) does not degrade α-tubulin. Sequence analysis of the DRV M protein and that of the lab-attenuated RABV strain CVS revealed that the 57th amino acid is vital for M-induced microtubule degradation. We generated a recombinant RABV with a mutation at the 57th amino acid position in its M protein and showed that this mutation reduces α-tubulin degradation in vitro and axonal degeneration in vivo. This study elucidates the mechanism by which lyssavirus induces neuron degeneration.IMPORTANCEPrevious studies have suggested that RABV (rabies virus, the representative of lyssavirus) infection induces structural abnormalities in neurons. But there are few articles on the mechanism of lyssavirus' effect on neurons, and the mechanism of how RABV infection induces neurological dysfunction remains incomplete. The M protein of lyssavirus can downregulate cellular ATP levels by interacting with Slc25a4, and this decrease in ATP leads to a decrease in the level of NAD+ in the cytosol, which results in the release of Ca2+ from the intracellular calcium pool, the endoplasmic reticulum, and mitochondria. The presence of large amounts of Ca2+ in the cytoplasm activates Ca2+-dependent proteases and degrades microtubule proteins. The amino acid 57 of M protein is the key site determining its disruption of mitochondrial metabolism and subsequent neuron degeneration.

Neurofilament Light Chain in Aqueous Humor as a Marker of Neurodegeneration in Glaucoma.

Neurofilament light chain (NfL) is a neuronal cytoskeletal protein that has been identified as a marker of neurodegeneration in diseases of the central nervous system. In this study, we investigated whether NfL in the aqueous humor (AH) can serve as a marker of neurodegeneration in glaucoma in a racially diverse North American population. Single-center, case-control study. We enrolled patients with various types and stages of glaucoma undergoing planned ophthalmic surgery as part of their routine care and compared them with patients without glaucoma undergoing phacoemulsification for age-related cataract. We collected AH from 39 glaucoma patients and 10 patients without glaucoma. AH NfL was quantified using the Single-Molecule Array (Simoa)® NF-light assay (Quanterix). Demographic information, such as age, body mass index, sex, and self-reported race, as well as clinical information, such as pre-operative intraocular pressure (IOP), maximum IOP, and number of pre-operative glaucoma medications, was obtained by reviewing the medical record. Levels of AH NfL. In a model controlling for age and body mass index (BMI), NfL was significantly elevated in AH from glaucoma patients (mean: 429 pg/mL; standard deviation [SD]: 1136 pg/mL) compared to AH from patients without glaucoma (mean: 3.1 pg/mL; SD: 1.9 pg/mg): P = 0.002. Higher AH NfL was associated with higher maximum IOP (R = 0.44, P = 0.005), higher pre-operative IOP (R = 0.46, P = 0.003), and more pre-operative glaucoma medications (Rs = 0.61, P < 0.001). There was no association between AH NfL and Humphrey visual field mean deviation (R = -0.20, P = 0.220), retinal nerve fiber layer thickness as measured with optical coherence tomography (R = 0.07, P = 0.694), or glaucoma stage (Rs = 0.015, P = 0.935). Our findings suggest that AH NfL may have clinical utility as a marker of glaucomatous neurodegeneration.

Agent Orange Causes Metabolic Dysfunction and Molecular Pathology Reminiscent of Alzheimer's Disease.

Agent Orange, an herbicide used during the Vietnam War, contains 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Agent Orange has teratogenic and carcinogenic effects, and population-based studies suggest Agent Orange exposures lead to higher rates of toxic and degenerative pathologies in the peripheral and central nervous system (CNS). This study examines the potential contribution of Agent Orange exposures to neurodegeneration. Human CNS-derived neuroepithelial cells (PNET2) treated with 2,4-D and 2,4,5-T were evaluated for viability, mitochondrial function, and Alzheimer's disease (AD)-related proteins. Treatment with 250μg/ml 2,4-D or 2,4,5-T significantly impaired mitochondrial function, caused degenerative morphological changes, and reduced viability in PNET2 cells. Correspondingly, glyceraldehyde-3-phosphate dehydrogenase expression which is insulin-regulated and marks the integrity of carbohydrate metabolism, was significantly inhibited while 4-hydroxy-2-nonenal, a marker of lipid peroxidation, was increased. Tau neuronal cytoskeletal protein was significantly reduced by 2,4,5-T, and relative tau phosphorylation was progressively elevated by 2,4,5-T followed by 2,4-D treatment relative to control. Amyloid-β protein precursor (AβPP) was increased by 2,4,5-T and 2,4-D, and 2,4,5-T caused a statistical trend (0.05 < p<0.10) increase in Aβ. Finally, altered cholinergic function due to 2,4,5-T and 2,4-D exposures was marked by significantly increased choline acetyltransferase and decreased acetylcholinesterase expression, corresponding with responses in early-stage AD. Exposures to Agent Orange herbicidal chemicals rapidly damage CNS neurons, initiating a path toward AD-type neurodegeneration. Additional research is needed to understand the permanency of these neuropathologic processes and the added risks of developing AD in Agent Orange-exposed aging Vietnam Veterans.

Phosphorylated Neurofilament Heavy Chain in the Cerebrospinal Fluid Is a Suitable Biomarker of Acute and Chronic Blast-Induced Traumatic Brain Injury.

Blast-induced traumatic brain injury (bTBI) has been documented as a significant concern for both military and civilian populations in response to the increased use of improvised explosive devices. Identifying biomarkers that could aid in the proper diagnosis and assessment of both acute and chronic bTBI is in urgent need since little progress has been made towards this goal. Addressing this knowledge gap is especially important in military veterans who are receiving assessment and care often years after their last blast exposure. Neuron-specific phosphorylated neurofilament heavy chain protein (pNFH) has been successfully evaluated as a reliable biomarker of different neurological disorders, as well as brain trauma resulting from contact sports and acute stages of brain injury of different origin. In the present study, we have evaluated the utility of pNFH levels measured in the cerebrospinal fluid (CSF) as an acute and chronic biomarker of brain injury resulting from single and tightly coupled repeated blast exposures using experimental rats. The pNFH levels increased at 24 h, returned to normal levels at 1 month, but increased again at 6 months and 1 year post-blast exposures. No significant changes were observed between single and repeated blast-exposed groups. To determine whether the observed increase of pNFH in CSF corresponded with its levels in the brain, we performed fluorescence immunohistochemistry in different brain regions at the four time-points evaluated. We observed decreased pNFH levels in those brain areas at 24 h, 6 months, and 1 year. The results suggest that blast exposure causes axonal degeneration at acute and chronic stages resulting in the release of pNFH, the abundant neuronal cytoskeletal protein. Moreover, the changes in pNFH levels in the CSF negatively correlated with the neurobehavioral functions in the rats, reinforcing suggestions that CSF levels of pNFH can be a suitable biomarker of bTBI.

Tributyltin Alters Calcium Levels, Mitochondrial Dynamics, and Activates Calpains Within Dorsal Root Ganglion Neurons.

Tributyltin (TBT) remains a global health concern. The primary route of human exposure to TBT is either through ingestion or skin absorption, but TBT's effects on the peripheral nervous system have still not been investigated. Therefore, we exposed in vitro sensory dorsal root ganglion (DRG) neurons to TBT at a concentration of 50-200 nM, which is similar to the observed concentrations of TBT in human blood samples. We observed that TBT causes extensive axon degeneration and neuronal death in the DRG neurons. Furthermore, we discovered that TBT causes an increase in both cytosolic and mitochondrial calcium levels, disrupts mitochondrial dynamics, decreases neuronal ATP levels, and leads to the activation of calpains. Additional experiments demonstrated that inhibition of calpain activation prevented TBT-induced fragmentation of neuronal cytoskeletal proteins and neuronal cell death. Thus, we conclude that calpain activation is the key executioner of TBT-induced peripheral neurodegeneration.

Ganoderma lucidum Modulates Neuronal Distorted Cytoskeletal Proteomics and Protein-Protein Interaction in Alzheimer’s disease Model Animals

Background: Alzheimer’s disease (AD) is the leading neurodegenerative disorder affecting memory, learning and behavior. Altered expression of proteins involved in neuronal structure and function is a recent observation of AD pathogenesis. Modulation of altered protein expression seems promising in AD therapeutics. In the present experiment, AD ameliorating effect of medicinal mushroom Ganoderma lucidum had been evaluated through its effect on neuronal cytoskeletal structure and function related protein expression pattern in AD model rats. Methods: Wistar male rats (120 ± 5gm) were divided into three groups: control (C), AD (A) and G. lucidum hot water extract (HWE) fed AD (AE), each group containing 15 rats. AD model rats were prepared by infusing Aβ1-42 (ab120959, abcam, USA) into the cerebral ventricles. Protein extraction from the brain samples was performed following homogenization of the hippocampus (50 mg ) with lysis buffer (1ml) using a homogenizer (Polytron PT 1200, Kinematica). Protein separation through SDS-PAGE and protein quantification through LC-chip MS/MS Q-TOF had been performed for label-free relative quantification. For statistical analyses, the data were exported to the Mass Profiler Professional (MPP) software and ANOVA (P&lt;0.05) had been performed to overcome the complications of false discovery associated with multiple test analyses. Functional interaction networks of the proteins were identified using the STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) database (version 10.0; http://string-db.org/). For further identifying over-representing pathways and biological functions, the ingenuity pathway analysis (IPA), build version: 389077M, content version: 27821452, (Release date: 2016-06-14) was used (https://www.ingenuity.com/wp-content/themes/ingenuity-qiagen). Datasets of the proteins significantly expressed (P&lt;0.05) and having log fold change of 1.5 and higher were uploaded (AD versus C, AD versus AE and C versus AE). Results: Among 2,212 proteins identified in the present study, 819 had been found to be differentially expressed. Of the differentially expressed ones, 9 proteins had been linked with neuronal cytoskeletal structure and function regulation such as tubulin, β-actin, dihydropyrimidinase-related protein 2 (DRP-2), keratin, glial fibrillary acidic protein (GFAP), Rho A proteins, septin, cofilin, gelsolin and dynamin. AD rats manifested altered expression of proteins associated with neuronal structure and function. G. lucidum hot water treatment ameliorated the altered expression of those proteins. Conclusions: Altered expression of hippocampal proteins is a hallmark of AD. Neuroproteomics regulatory approach towards AD amelioration seems promising. Inclusion of G. lucidum for proteomics based AD therapeutics in regulation of the proteins involved in neuronal structure and function seem apt. Thus, G. lucidum could be considered as an AD therapeutic agent.

Plasma Neurofilament Light Chain as a Translational Biomarker of Aging and Neurodegeneration in Dogs.

Age is a primary risk factor for multiple comorbidities including neurodegenerative diseases. Pet dogs and humans represent two populations that have experienced a significant increase in average life expectancy over the last century. A higher prevalence of age-related neurodegenerative diseases has been observed across both species, and human diseases, such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS), have canine analogs, canine cognitive dysfunction (CCD), and degenerative myelopathy (DM) respectively. In humans, protein biomarkers have proved useful in the prediction and diagnosis of neurodegeneration. Molecular signatures of many proteins are highly conserved across species. In this study, we explored the potential of the neuronal cytoskeletal protein neurofilament light chain (NfL) as a biomarker of neuro-aging in dogs using an ultrasensitive single-molecule array assay to measure plasma concentrations. Healthy dogs of different ages and dogs affected with CCD and DM were evaluated. The mean plasma NfL concentrations in the different age groups of the healthy population were as follows: 4.55 ± 1.70pg/mL in puppy/junior group (0.43-2years), 13.51 ± 6.8pg/mL in adult/mature group (2.1-9years), and 47.1 ± 12.68pg/mL in geriatric/senior group (9.3-14.5years). Concentrations in dogs with DM (7.5-12.6years) and CCD (11.0-15.6years) were 84.17 ± 53.57pg/mL and 100.73 ± 83.72pg/mL, respectively. Plasma NfL increases in an age-dependent manner and is significantly elevated in dogs diagnosed with neurodegenerative disease. This work identified plasma NfL as a key clinical index of neuro-aging and neurodegeneration in pet dogs. Our findings mirror recent reports from human neurodegenerative diseases.

Ganoderma lucidum Modulates Neuronal Distorted Cytoskeletal Proteomics and Protein-Protein Interaction in Alzheimer's Disease Model Animals

Background: Alzheimer’s disease (AD) is the leading neurodegenerative disorder affecting memory, learning and behavior. Altered expression of proteins involved in neuronal structure and function is a recent observation of AD pathogenesis. Modulation of altered protein expression seems promising in AD therapeutics. In the present experiment, AD ameliorating effect of medicinal mushroom Ganoderma lucidum (GL) had been evaluated through its effect on neuronal cytoskeletal structure and function related protein expression pattern in AD model rats. Methods: Wistar male rats (120 ± 5 gm) were divided into three groups: control rat (CR), Alzheimer’s Disease Model Rat (ADMR) and G. lucidum Hot Water Extract (GHWE) fed ADMR, each group containing 15 rats. AD model rats were prepared by infusing Aβ1-42 (ab120959, abcam, USA) into the cerebral ventricles. Protein extraction from the brain samples was performed following homogenization of the hippocampus (50 mg) with lysis buffer (1 ml) using a homogenizer (Polytron PT 1200, Kinematica). Protein separation through SDS-PAGE and protein quantification through LC-chip MS/MS Q-TOF had been performed for label-free relative quantification. For statistical analyses, the data were exported to the Mass Profiler Professional (MPP) software and ANOVA (P<0.05) had been performed to overcome the complications of false discovery associated with multiple test analyses. Functional interaction networks of the proteins were identified using the STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) database (version 10.0; http://string-db.org/). For further identifying over-representing pathways and biological functions, the Ingenuity Pathway Analysis (IPA), build version: 389077M, content version: 27821452, (Release date: 2016-06-14) was used (https://www.ingenuity.com/wp-content/themes/ingenuity-qiagen). Datasets of the proteins significantly expressed (P<0.05) and having log FC (fold change) of 1.5 and higher were uploaded (ADMR versus CR, ADMR versus GHWE fed ADMR and CR versus GHWE fed ADMR). Results: Among 2,212 proteins identified in the present study, 819 had been found to be differentially expressed. Of the differentially expressed ones, 9 proteins had been linked with neuronal cytoskeletal structure and function regulation such as tubulin, β-actin, dihydropyrimidinase-related protein 2 (DRP-2), keratin, Glial Fibrillary Acidic Protein (GFAP), Rho A proteins, septin, cofilin, gelsolin and dynamin. AD rats manifested altered expression of proteins associated with neuronal structure and function. G. lucidum Hot Water Treatment ameliorated the altered expression of those proteins. Conclusion: Altered expression of hippocampal proteins is a hallmark of AD. Neuroproteomics regulatory approach towards AD amelioration seems promising. Inclusion of G. lucidum for proteomics based AD therapeutics in regulation of the proteins involved in neuronal structure and function seem apt. Thus, G. lucidum could be considered as an AD therapeutic agent species.

Neuroprotective effects of human neural stem cells over-expressing choline acetyltransferase in a middle cerebral artery occlusion model

Stroke is one of the most-devastating brain diseases causing acute death or permanent disability. Although tissue-type plasminogen activator was approved by Food and Drug Administration for early reperfusion of the occluded vessels, oxidative injury may cause extensive brain infarction. Accordingly, there is a need for effective neuroprotection during reperfusion, and stem cell-based therapeutic approaches should fulfill this requirement. We established human neural stem cells (NSCs) encoding gene of choline acetyltransferase (F3.ChAT), an acetylcholine-synthesizing enzyme, and investigated whether infusion of the F3.ChAT cells attenuate the ischemia-reperfusion brain damage in a rat model of middle cerebral artery occlusion (MCAO). F3.ChAT cells were found to produce much higher amounts of ChAT as well as neuroprotective and anti-inflammatory neurotrophins than their parental F3 NSCs. After 2-h occlusion, the artery was reperfused, along with intravenous infusion of the stem cells (1 × 106 cells/rat). Administration of the F3.ChAT cells markedly reduced the infarction volume and improved both the cognitive dysfunction and behavioural deficits of MCAO animals, in which F3.ChAT cells were superior to F3 cells. F3.ChAT cells not only restored microtubule-associated protein-2, a neuronal cytoskeletal protein, and preserved microvessels, but also suppressed lipid peroxidation, pro-inflammatory cytokines, glial fibrillary acidic protein, and intercellular adhesion molecule-1 in the brain tissues. The results demonstrate that early intravenous infusion of NSCs expressing ChAT and neurotrophins attenuate brain and capillary injuries and restore neurobehavioural functions via neuroprotective and anti-inflammatory activities, and that F3.ChAT cells could be a candidate for the neuroprotection and functional recovery of acute stroke patients.

Clinical outcomes, ultrastructure and immunohistochemical features of canine high-grade olfactory neuroblastoma.

Olfactory neuroblastoma (ONB) is a rare intranasal neoplasm in both dogs and humans. Similar clinical presentation and overlapping histologic and immunohistochemical features of ONB with other intranasal neoplasms can make diagnosis and treatment of intranasal neoplasia challenging. Furthermore, in part because of their rarity, there is a lack of reporting on therapeutic regimen for these neoplasms. In humans, initial debulking surgery is usually followed by radiation therapy. Here we report on the histologic, immunohistochemical, and ultrastructural characteristics of canine ONB and report on the clinical progression of cases treated with radiation therapy. In all nine canine ONB examined here, neoplastic cells were arranged in a lobular manner amidst a prominent neurofibrillary matrix and had features consistent with Grade III (high grade) ONB. The neoplastic cells demonstrated positive immunohistochemical staining for TuJ-1, a Class III beta-tubulin neuronal cytoskeletal protein, and variable staining for other markers, including chromogranin, synaptophysin, AE1/AE3 and MAP2. The longest surviving case was treated with a regimen similar to that used in humans, consisting of debulking surgery followed by definitive radiation therapy. Our study found that TuJ-1 is a useful marker for ONB and that radiation therapy, even in cases of advanced disease, may result in prolonged survival.

The Role of Calpain and Proteasomes in the Degradation of Carbonylated Neuronal Cytoskeletal Proteins in Acute Experimental Autoimmune Encephalomyelitis.

The present study was designed to investigate the role of calpain and the proteasome in the removal of oxidized neuronal cytoskeletal proteins in myelin basic protein-induced experimental autoimmune encephalomyelitis (EAE). To this end, EAE rats received a single intrathecal injection of calpeptin or epoxomicin at the first sign of clinical disease. Forty-eight hours later, animals were sacrificed and lumbar spinal cord segments were dissected and used for biochemical analyses. The results show that calpain and proteasome activity is specifically, but partially, inhibited with calpeptin and epoxomicin, respectively. Calpain inhibition causes an increase in total protein carbonylation and in the amount of neurofilament proteins (NFPs), β-tubulin and β-actin that were spared from degradation, but no changes are seen in the oxidation of any of three NFPs. By contrast, proteasome inhibition has no effect on total protein carbonylation or cytoskeletal protein degradation but increases the amount of oxidized NFH and NFM. These results suggest that while the proteasome may contribute to removal of oxidized NFPs, calpain is the main protease involved in degradation of neuronal cytoskeleton and does not preferentially targets oxidized NFPs species in acute EAE. Different results were obtained in a cell-free system, where calpain inhibition rises the amount of oxidized NFH, and proteasome inhibition fails to change the oxidation state of the NFPs. The later finding suggests that the preferential degradation of oxidized NFH and NFM in vivo by the proteasome occurs via the 26S and not the 20S particle.

Selective targeting of 3 repeat Tau with brain penetrating single chain antibodies for the treatment of neurodegenerative disorders.

Alzheimer's disease (AD) is the most common form of dementia in the elderly affecting more than 5 million people in the U.S. AD is characterized by the accumulation of β-amyloid (Aβ) and Tau in the brain, and is manifested by severe impairments in memory and cognition. Therefore, removing tau pathology has become one of the main therapeutic goals for the treatment of AD. Tau (tubulin-associated unit) is a major neuronal cytoskeletal protein found in the CNS encoded by the gene MAPT. Alternative splicing generates two major isoforms of tau containing either 3 or 4 repeat (R) segments. These 3R or 4RTau species are differentially expressed in neurodegenerative diseases. Previous studies have been focused on reducing Tau accumulation with antibodies against total Tau, 4RTau or phosphorylated isoforms. Here, we developed a brain penetrating, single chain antibody that specifically recognizes a pathogenic 3RTau. This single chain antibody was modified by the addition of a fragment of the apoB protein to facilitate trafficking into the brain, once in the CNS these antibody fragments reduced the accumulation of 3RTau and related deficits in a transgenic mouse model of tauopathy. NMR studies showed that the single chain antibody recognized an epitope at aa 40-62 of 3RTau. This single chain antibody reduced 3RTau transmission and facilitated the clearance of Tau via the endosomal-lysosomal pathway. Together, these results suggest that targeting 3RTau with highly specific, brain penetrating, single chain antibodies might be of potential value for the treatment of tauopathies such as Pick's Disease.

Alterations in neuronal cytoskeletal and astrocytic proteins content in the brain of the autistic-like mouse strain C58/J

Autism spectrum disorder (ASD) is a neurodevelopment disorder characterized by deficient social interaction, impaired communication as well as repetitive behaviors. ASD subjects present connectivity and neuroplasticity disturbances associated with morphological alterations in axons, dendrites, and dendritic spines. Given that the neuronal cytoskeleton and astrocytes have an essential role in regulating several mechanisms of neural plasticity, the aim of this work was to study alterations in the content of neuronal cytoskeletal components actin and tubulin and their associated proteins, as well as astrocytic proteins GFAP and TSP-1 in the brain of a C58/J mouse model of ASD. We determined the expression and regulatory phosphorylation state of cytoskeletal components in the prefrontal cortex, hippocampus, and cerebellum of C58/J mice by means of Western blotting. Our results show that autistic-like mice present: 1) region-dependent altered expression and phosphorylation patterns of Tau isoforms, associated with anomalous microtubule depolymerization; 2) reduced MAP2 A content in prefrontal cortex; 3) region-dependent changes in cofilin expression and phosphorylation, associated with abnormal actin filament depolymerizing dynamics; 4) diminished synaptopodin levels in the hippocampus; and 5) reduced content of the astrocyte-secreted protein TSP-1 in the prefrontal cortex and hippocampus. Our work demonstrates changes in the expression and phosphorylation of cytoskeletal proteins as well as in TSP-1 in the brain of the autistic-like mice C58/J, shedding light in one of the possible molecular mechanisms underpinning neuroplasticity alterations in the ASD brain and laying the foundation for future investigations in this topic.

LOSS OF F-ACTIN IN SYNAPTOSOMES CORRELATES WITH COGNITIVE DYSFUNCTION (BRAAK STAGING, B-AMYLOID LOAD AND TANGLE LOAD) IN PATIENTS WITH MCI AND AD

Alzheimer's disease (AD) has been described by its biological signatures that mediate synaptic dysfunction and loss of dendritic spines. Neuronal cytoskeletal protein, such as F-actin (filamentous actin) are critical modulator of dendritic spine morphology and also regulates its function. Thus, maintaining the ratio of F-actin and G-actin within the dendritic spines is essential for optimal synaptic function. Our aim was to determine the status of synaptic F-actin levels in postmortem tissue from patients with no cognitive impairment (NCI), mild cognitive impairment (MCI) and AD patients. Autopsy human brain tissues were obtained from Rush Alzheimer's Disease Center, Chicago, IL, USA. Total of 36 brains were examined (12 each of NCI, MCI and AD). Frontal neocortical tissue from each human brain was thawed on ice and used for the preparation of synaptosomes. Further, we used an innovative method to isolate highly enriched F-Actin and G-Actin fractions from synaptosomes. F-actin levels in synaptosomes prepared from NCI, MCI and AD postmortem tissue showed graded decrease were significantly correlated. Furthermore, significant correlation was also seen between the decrease in synaptosomal F-actin and poor performance in several cognitive tests (Global cognitive score, Episodic memory score, Working memory score) as also reflected Braak staging, b-amyloid load and tangle load. Our findings provide evidence that loss of F-actin at the synapse correlates with the histopathological and behavioral dysfunctions seen in patients with mild cognitive impairment (MCI) and AD.

Time courses of post-injury mitochondrial oxidative damage and respiratory dysfunction and neuronal cytoskeletal degradation in a rat model of focal traumatic brain injury

Traumatic brain injury (TBI) results in rapid reactive oxygen species (ROS) production and oxidative damage to essential brain cellular components leading to neuronal dysfunction and cell death. It is increasingly appreciated that a major player in TBI-induced oxidative damage is the reactive nitrogen species (RNS) peroxynitrite (PN) which is produced in large part in injured brain mitochondria. Once formed, PN decomposes into highly reactive free radicals that trigger membrane lipid peroxidation (LP) of polyunsaturated fatty acids (e.g. arachidonic acid) and protein nitration (3-nitrotyrosine, 3-NT) in mitochondria and other cellular membranes causing various functional impairments to mitochondrial oxidative phosphorylation and calcium (Ca2+) buffering capacity. The LP also results in the formation of neurotoxic reactive aldehyde byproducts including 4-hydroxynonenal (4-HNE) and propenal (acrolein) which exacerbates ROS/RNS production and oxidative protein damage in the injured brain. Ultimately, this results in intracellular Ca2+ overload that activates proteolytic degradation of α-spectrin, a neuronal cytoskeletal protein. Therefore, the aim of this study was to establish the temporal evolution of mitochondrial dysfunction, oxidative damage and cytoskeletal degradation in the brain following a severe controlled cortical impact (CCI) TBI in young male adult rats. In mitochondria isolated from an 8 mm diameter cortical punch including the 5 mm wide impact site and their respiratory function studied ex vivo, we observed an initial decrease in complex I and II mitochondrial bioenergetics within 3 h (h). For complex I bioenergetics, this partially recovered by 12–16 h, whereas for complex II respiration the recovery was complete by 12 h. During the first 24 h, there was no evidence of an injury-induced increase in LP or protein nitration in mitochondrial or cellular homogenates. However, beginning at 24 h, there was a gradual secondary decline in complex I and II respiration that peaked at 72 h. post-TBI that coincided with progressive peroxidation of mitochondrial and cellular lipids, protein nitration and protein modification by 4-HNE and acrolein. The oxidative damage and respiratory failure paralleled an increase in Ca2+-induced proteolytic degradation of the neuronal cytoskeletal protein α-spectrin indicating a failure of intracellular Ca2+ homeostasis. These findings of a surprisingly delayed peak in secondary injury, suggest that the therapeutic window and needed treatment duration for certain antioxidant treatment strategies following CCI-TBI in rodents may be longer than previously believed.

Quantitative proteomic analysis of HIV-1 Tat-induced dysregulation in SH-SY5Y neuroblastoma cells.

Despite affecting up to 70% of HIV-positive patients and being the leading cause of dementia in patients under 40 years, the molecular mechanisms involved in the onset of HIV-associated neurocognitive disorders (HAND) are not well understood. To address this, we performed SILAC-based quantitative proteomic analysis on HIV-Tat treated SH-SY5Y neuroblastoma cells. Isolated protein was fractionated by SDS-PAGE and analyzed by nLC-MS/MS on an Orbitrap Velos. Using MaxQuant, we identified and quantified 3077 unique protein groups, of which 407 were differentially regulated. After applying an additional standard deviation-based cutoff, 29 of these were identified as highly significantly and stably dysregulated. GO term analysis shows dysregulation in both protein translation machinery as well as cytoskeletal regulation that have both been implicated in other dementias. In addition, several key cytoskeletal regulatory proteins such as ARHGEF17, the Rho GTPase, SHROOM3, and CMRP1 are downregulated. Together, these data demonstrate that HIV-Tat can dysregulate neuronal cytoskeletal regulatory proteins that could lead to the major HAND clinical manifestation-synapse loss.

Novel basic cell biological approaches to prevent the neuropathological disease symptoms and behavior

The biology of neurodegeneration program evolved from our laboratory studying the basic biology of neuronal cytoskeletal protein phosphorylation during development and normal function in the adult. To understand the molecular basis of neurodegeneration our major focus has been to study the regulation of compartment-specific patterns of cytoskeletal protein phosphorylation in neuronal perikarya and axons. We have demonstrated that phosphorylation of the numerous acceptor sites on such proteins as Tau and neurofilament are tightly and topographically regulated and generally confined to the axonal compartment under physiological conditions. However, during neuronal insults, it is deregulated induces neuropathology. During our course of studies to understand the biology of this regulation we identified cyclin dependent kinase5 (Cdk5); a neuron specific kinase involved in the nervous system development, function and survival. It was recognized that in neurodegenerative disorders such as Alzheimer’s disease (AD), Parkinson’s (PD) and Amyotrophic lateral sclerosis (ALS) the pathology was characterized by aberrant and hyper activation of Cdk5 and accumulation of aberrantly hyper phosphorylated cytoskeletal proteins in cell bodies, suggesting that topographic regulation had been compromised. This led inevitably into studies of neurodegeneration in cell culture and model mice with emphasis on Cdk5, that targets numerous neuronal proteins including cytoskeletal protein regulation by phosphorylation, which when deregulated, is responsible for the pathology seen in neurodegenerative diseases. In cell systems, neuronal stress leads to deregulated kinases. Recently we have discovered peptides derived from, p35, and a neuron specific activator of Cdk5, which rescue cells in vitro from stress induced pathology. The questions currently being investigated are (1) how is cytoskeletal protein phosphorylation topographically regulated in neurons? (2) What factors are responsible for the deregulation of Cdk5 in neurons? (3) Can mouse models of AD, PD and ALS be treated therapeutically with peptides that inhibit deregulated Cdk5?

Plasma neurofilament heavy chain is not a useful biomarker in Charcot-Marie-Tooth disease.

The negative results in trials of vitamin C in Charcot-Marie-Tooth disease (CMT) type 1A have highlighted the lack of sensitive outcome measures. Neurofilaments are abundant neuronal cytoskeletal proteins, and their concentration in blood is likely to reflect axonal breakdown. We therefore examined plasma neurofilament heavy-chain (NfH) concentration as a potential biomarker in CMT. Blood samples were collected from healthy controls and patients with CMT over a 2-year period. Disease severity was measured using the CMT Examination Score. An in-house enzyme-linked immunoabsorbent assay was used to measure plasma NfH levels. There was no significant difference in plasma NfH concentrations between CMT patients and controls (P = 0.449). There was also no significant difference in plasma NfH levels in the CMT group over 1 year (mean difference = -0.02, SEM = 4.44, P = 0.98). Plasma NfH levels are not altered in patients with CMT and are not a suitable biomarker of disease activity. Muscle Nerve 53: 972-975, 2016.

MP30-01 IDENTIFYING A SENSITIVE AND SPECIFIC PANEL OF DNA METHYLATION MARKERS IN MODELS OF CYSTITIS

stimulation of the pudendal nerve upregulates neurotrophin expression and improves recovery in a rat model of SUI. METHODS: Rats received 1 hour of electrical stimulation (20 Hz, 0.3 mA, 0.1 ms pulse) or sham stimulation of the pudendal nerve immediately after simulated birth injury, consisting of vaginal distension and pudendal nerve crush. A separate cohort of rats received sham injury and no treatment. All rats underwent stimulation or sham stimulation for 1 hour twice per week for 2 weeks. Brain derived neurotrophic factor (BDNF) and bII-tubulin (neuronal cytoskeletal protein and marker of neuroregenerative response) expression in Onuf’s nucleus was measured with RT-PCR. Leak point pressure (LPP) and external urethral sphincter electromyography (EUS EMG) was performed. Data was analyzed with a two-way ANOVA and Student-Newman-Keuls posthoc pairwise comparisons with p<0.05 statistically significant. RESULTS: Compared to sham stimulation, electrical stimulation significantly increased both BDNF and bII-tubulin expression in Onuf’s nucleus, demonstrating an increased neuroregenerative response. Both LPP and baseline EUS EMG amplitude decreased significantly after injury compared to sham injury and increased significantly with stimulation compared to sham stimulation. During voiding, EUS EMG burst frequency, burst duration, and interburst interval were significantly decreased by injury compared to sham and after injury were significantly increased with electrical stimulation compared to sham. CONCLUSIONS: Pudendal nerve electrical stimulation appears to promote SUI recovery via strengthening the neuroregenerative response by upregulating BDNF expression in pudendal nerve cell bodies. Electrical stimulation may shorten postpartum SUI duration and could potentially serve as a preventative treatment for later SUI development.