Shelley F. Newman

An increase in S-glutathionylated proteins in the Alzheimer's disease inferior parietal lobule, a proteomics approach

Alzheimers disease (AD) is a neurodegenerative disorder characterized by neurofibrillary tangles, senile plaques, and loss of synapses. Many studies support the notion that oxidative stress plays an important role in AD pathogenesis. Previous studies from our laboratory employed redox proteomics to identify oxidatively modified proteins in the AD inferior parietal lobule (IPL) and hippocampus. The proteins were consistent with biochemical or pathological alterations in AD and have been central to further investigations of the disease. The present study focused on the identification of specific targets of protein S‐glutathionylation in AD and control IPL by using a redox proteomics approach. For AD IPL, we identified deoxyhemoglobin, α‐crystallin B, glyceraldehyde phosphate dehydrogenase (GAPDH), and α‐enolase as significantly S‐glutathionylated relative to these brain proteins in control IPL. GAPDH and α‐enolase were also shown to have reduced activity in the AD IPL. This study demonstrates that specific proteins are sensitive to S‐glutathionylation, which most likely is due to their sensitivity to cysteine oxidation initiated by the increase in oxidative stress in the AD brain.

Pin1 in Alzheimer's disease

Proteolytic processing and phosphorylation of amyloid precursor protein (APP), and hyperphosphorylation of tau protein, have been shown to be increased in Alzheimers disease (AD) brains, leading to increased production of β‐amyloid (Aβ) peptides and neurofibrillary tangles, respectively. These observations suggest that phosphorylation events are critical to the understanding of the pathogenesis and treatment of this devastating disease. Pin‐1, one of the peptidyl‐prolyl isomerases (PPIase), catalyzes the isomerization of the peptide bond between pSer/Thr‐Pro in proteins, thereby regulating their biological functions which include protein assembly, folding, intracellular transport, intracellular signaling, transcription, cell cycle progression and apoptosis. A number of previous studies have shown that Pin1 is co‐localized with phosphorylated tau in AD brain, and shows an inverse relationship to the expression of tau. Pin1 protects neurons under in vitro conditions. Moreover, recent studies demonstrate that APP is a target for Pin1 and thus, in Aβ production. Furthermore, Pin1 was found to be oxidatively modified and to have reduced activity in the hippocampus in mild cognitive impairment (MCI) and AD. Because of the diverse functions of Pin1, and the discovery that this protein is one of the oxidized proteins common to both MCI and AD brain, the question arises as to whether Pin1 is one of the driving forces for the initiation or progression of AD pathogenesis, finally leading to neurodegeneration and neuronal apoptosis. In the present review, we discuss the role of Pin1 with respect to Alzheimers disease.

REVIEW: Pin1 in Alzheimer's disease

Proteolytic processing and phosphorylation of amyloid precursor protein (APP), and hyperphosphorylation of tau protein, have been shown to be increased in Alzheimers disease (AD) brains, leading to increased production of β‐amyloid (Aβ) peptides and neurofibrillary tangles, respectively. These observations suggest that phosphorylation events are critical to the understanding of the pathogenesis and treatment of this devastating disease. Pin‐1, one of the peptidyl‐prolyl isomerases (PPIase), catalyzes the isomerization of the peptide bond between pSer/Thr‐Pro in proteins, thereby regulating their biological functions which include protein assembly, folding, intracellular transport, intracellular signaling, transcription, cell cycle progression and apoptosis. A number of previous studies have shown that Pin1 is co‐localized with phosphorylated tau in AD brain, and shows an inverse relationship to the expression of tau. Pin1 protects neurons under in vitro conditions. Moreover, recent studies demonstrate that APP is a target for Pin1 and thus, in Aβ production. Furthermore, Pin1 was found to be oxidatively modified and to have reduced activity in the hippocampus in mild cognitive impairment (MCI) and AD. Because of the diverse functions of Pin1, and the discovery that this protein is one of the oxidized proteins common to both MCI and AD brain, the question arises as to whether Pin1 is one of the driving forces for the initiation or progression of AD pathogenesis, finally leading to neurodegeneration and neuronal apoptosis. In the present review, we discuss the role of Pin1 with respect to Alzheimers disease.

Protective effect of the xanthate, D609, on Alzheimer's amyloid β-peptide (1-42)-induced oxidative stress in primary neuronal cells

Tricyclodecan-9-yl-xanthogenate (D609) is an inhibitor of phosphatidylcholine-specific phospholipase C, and this agent also has been reported to protect rodents against oxidative damage induced by ionizing radiation. Previously, we showed that D609 mimics glutathione (GSH) functions and that a disulfide is formed upon oxidation of D609 and the resulting dixanthate is a substrate for GSH reductase, regenerating D609. Considerable attention has been focused on increasing the intracellular GSH levels in many diseases, including Alzheimers disease (AD). Amyloid β-peptide [Aβ(1–42)], elevated in AD brain, is associated with oxidative stress and toxicity. The present study aimed to investigate the protective effects of D609 on Aβ(1–42)-induced oxidative cell toxicity in cultured neurons. Decreased cell survival in neuronal cultures treated with Aβ(1–42) correlated with increased free radical production measured by dichlorofluorescein fluorescence and an increase in protein oxidation (protein carbonyl, 3-nitrotyrosine) and lipid peroxidation (4-hydroxy-2-nonenal) formation. Pretreatment of primary hippocampal cultures with D609 significantly attenuated Aβ(1–42)-induced cytotoxicity, intracellular ROS accumulation, protein oxidation, lipid peroxidation and apoptosis. Methylated D609, with the thiol functionality no longer able to form the disulfide upon oxidation, did not protect neuronal cells against Aβ(1–42)-induced oxidative stress. Our results suggest that D609 exerts protective effects against Aβ(1–42) toxicity by modulating oxidative stress. These results may be of importance for the treatment of AD and other oxidative stress-related diseases.

Redox proteomic analysis of carbonylated brain proteins in mild cognitive impairment and early Alzheimer's disease.

Previous studies indicated increased levels of protein oxidation in brain from subjects with Alzheimers disease (AD), raising the question of whether oxidative damage is a late effect of neurodegeneration or precedes and contributes to the pathogenesis of AD. Hence, in the present study we used a parallel proteomic approach to identify oxidatively modified proteins in inferior parietal lobule (IPL) from subjects with mild cognitive impairment (MCI) and early stage-AD (EAD). By comparing to age-matched controls, we reasoned that such analysis could help in understanding potential mechanisms involved in upstream processes in AD pathogenesis. We have identified four proteins that showed elevated levels of protein carbonyls: carbonic anhydrase II (CA II), heat shock protein 70 (Hsp70), mitogen-activated protein kinase I (MAPKI), and syntaxin binding protein I (SBP1) in MCI IPL. In EAD IPL we identified three proteins: phosphoglycerate mutase 1 (PM1), glial fibrillary acidic protein, and fructose bisphospate aldolase C (FBA-C). Our results imply that some of the common targets of protein carbonylation correlated with AD neuropathology and suggest a possible involvement of protein modifications in the AD progression.

Protective effect of D609 against amyloid-beta1-42-induced oxidative modification of neuronal proteins: redox proteomics study.

Oxidative stress has been implicated in the pathophysiology of a number of diseases, including neurodegenerative disorders such as Alzheimers disease (AD), a neurodegenerative disorder associated with cognitive decline and enhanced oxidative stress. Amyloid‐beta peptide1–42 (Aβ1–42), one of the main component of senile plaques, can induce in vitro and in vivo oxidative damage to neuronal cells through its ability to produce free radicals. The aim of this study was to investigate the protective effect of the xanthate D609 on Aβ1–42‐induced protein oxidation by using a redox proteomics approach. D609 was recently found to be a free radical scavenger and antioxidant. In the present study, rat primary neuronal cells were pretreated with 50 μM of D609, followed by incubation with 10 μM Aβ1–42 for 24 hr. In the cells treated with Aβ1–42 alone, four proteins that were significantly oxidized were identified: glyceraldehyde‐3‐phosphate dehydrogenase, pyruvate kinase, malate dehydrogenase, and 14‐3‐3 zeta. Pretreatment of neuronal cultures with D609 prior to Aβ1–42 protected all the identified oxidized proteins in the present study against Aβ1–42‐mediated protein oxidation. Therefore, D609 may ameliorate the Aβ1–42‐induced oxidative modification. We discuss the implications of these Aβ1–42‐mediated oxidatively modified proteins for AD pathology and for potential therapeutic intervention in this dementing disorder.

Redox proteomics in some age-related neurodegenerative disorders or models thereof

SummaryNeurodegenerative diseases cause memory loss and cognitive impairment. Results from basic and clinical scientific research suggest a complex network of mechanisms involved in the process of neurodegeneration. Progress in treatment of such disorders requires researchers to better understand the functions of proteins involved in neurodegenerative diseases, to characterize their role in pathogenic disease mechanisms, and to explore their roles in the diagnosis, treatment, and prevention of neurodegenerative diseases. A variety of conditions of neurodegenerative diseases often lead to post-translational modifications of proteins, including oxidation and nitration, which might be involved in the pathogenesis of neurodegenerative diseases. Redox proteomics, a subset of proteomics, has made possible the identification of specifically oxidized proteins in neurodegenerative disorders, providing insight into a multitude of pathways that govern behavior and cognition and the response of the nervous system to injury and disease. Proteomic analyses are particularly suitable to elucidate post-translational modifications, expression levels, and protein—protein interactions of thousands of proteins at a time. Complementing the valuable information generated through the integrative knowledge of protein expression and function should enable the development of more efficient diagnostic tools and therapeutic modalities. Here we review redox proteomic studies of some neurodegenerative diseases.

Detection of Carbonylated Proteins in 2-D SDS Page Separations

Protein carbonyls are an index of protein oxidation which, in turn, reflects the interplay of oxidative stress and degradation of oxidatively modified proteins. Protein carbonyls are increased in brain proteins in aging and age-related neurodegenerative disorders, including Alzheimers disease. In this chapter, we outline methods to detect protein carbonyls following two dimensional-based separation of brain proteins.

REVIEW: Pin1 in Alzheimer's disease: Pin1 in Alzheimer's disease

Proteolytic processing and phosphorylation of amyloid precursor protein (APP), and hyperphosphorylation of tau protein, have been shown to be increased in Alzheimers disease (AD) brains, leading to increased production of β‐amyloid (Aβ) peptides and neurofibrillary tangles, respectively. These observations suggest that phosphorylation events are critical to the understanding of the pathogenesis and treatment of this devastating disease. Pin‐1, one of the peptidyl‐prolyl isomerases (PPIase), catalyzes the isomerization of the peptide bond between pSer/Thr‐Pro in proteins, thereby regulating their biological functions which include protein assembly, folding, intracellular transport, intracellular signaling, transcription, cell cycle progression and apoptosis. A number of previous studies have shown that Pin1 is co‐localized with phosphorylated tau in AD brain, and shows an inverse relationship to the expression of tau. Pin1 protects neurons under in vitro conditions. Moreover, recent studies demonstrate that APP is a target for Pin1 and thus, in Aβ production. Furthermore, Pin1 was found to be oxidatively modified and to have reduced activity in the hippocampus in mild cognitive impairment (MCI) and AD. Because of the diverse functions of Pin1, and the discovery that this protein is one of the oxidized proteins common to both MCI and AD brain, the question arises as to whether Pin1 is one of the driving forces for the initiation or progression of AD pathogenesis, finally leading to neurodegeneration and neuronal apoptosis. In the present review, we discuss the role of Pin1 with respect to Alzheimers disease.