Pro-apoptotic protein–protein interactions of the extended N-AChE terminus

The N-terminally extended “synaptic” acetylcholinesterase variant N-AChE-S operates to promote apoptosis; however, the protein partners involved in this function remain unknown. Here, we report that when microinjected to fertilized mouse oocytes, N-AChE-S caused embryonic death as early as the zygotic stage. To identify the putative protein partners involved, we first tried yeast two hybrid screening, but this approach failed, probably because of the N-AChE-S-induced lethality. In contrast, sequence analysis and a corresponding peptide array revealed possible partners, which were validated by co-immunoprecipitation. These include the kinases GSK3, Aurora and GAK, the membrane integrin receptors, and the death receptor FAS. Each of these could potentially modulate N-AChE-S-induced apoptosis with possible therapeutic value for the treatment of Alzheimer’s disease.     

Adaptor protein interactions: modulators of amyloid precursor protein metabolism and Alzheimer's disease risk?

The cytoplasmic C-terminus of APP plays critical roles in its cellular trafficking and delivery to proteases. Adaptor proteins with phosphotyrosine-binding (PTB) domains, including those in the X11, Fe65, and c-Jun N-terminal kinase (JNK)-interacting protein (JIP) families, bind specifically to the absolutely conserved -YENPTY- motif in the APP C-terminus to regulate its trafficking and processing. Compounds that modulate APP-adaptor protein interactions may inhibit Abeta generation by specifically targeting the substrate (APP) instead of the enzyme (beta- or gamma-secretase). Genetic polymorphisms in (or near) adaptor proteins may influence risk of sporadic AD by interacting with APP in vivo to modulate its trafficking and processing to Abeta.     

Divalent cation tolerance protein binds to β-secretase and inhibits the processing of amyloid precursor protein

The deposition of amyloid-beta is a pathological hallmark of Alzheimer’s disease. Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by β-secretase (beta-site amyloid precursor protein-cleaving enzyme 1) and γ-secretase. To further elucidate the roles of beta-site amyloid precursor protein-cleaving enzyme 1 in the development of Alzheimer’s disease, a yeast two-hybrid system was used to screen a human embryonic brain cDNA library for proteins directly interacting with the intracellular domain of beta-site amyloid precursor protein-cleaving enzyme 1. A potential beta-site amyloid precursor protein-cleaving enzyme 1- interacting protein identified from the positive clones was divalent cation tolerance protein. Immunoprecipitation studies in the neuroblastoma cell line N2a showed that exogenous divalent cation tolerance protein interacts with endogenous beta-site amyloid precursor protein-cleaving enzyme 1. The overexpression of divalent cation tolerance protein did not affect beta-site amyloid precursor protein-cleaving enzyme 1 protein levels, but led to increased amyloid precursor protein levels in N2a/APP695 cells, with a concomitant reduction in the processing product amyloid precursor protein C-terminal fragment, indicating that divalent cation tolerance protein inhibits the processing of amyloid precursor protein. Our experimental findings suggest that divalent cation tolerance protein negatively regulates the function of beta-site amyloid precursor protein-cleaving enzyme 1. Thus, divalent cation tolerance protein could play a protective role in Alzheimer’s disease.     

Mitochondrial protein associated neurodegeneration – Case report

Neurodegeneration with brain iron accumulation (NBIA) is a group of genetic disorders with a progressive extrapyramidal syndrome and excessive iron deposition in the brain, particularly in the globus pallidus and substantia nigra. We present the case of a 31-year-old woman with mitochondrial protein associated neurodegeneration (MPAN). MPAN is a new identified subtype of NBIA, caused by mutations in C19orf12 gene. The typical features are speech and gait disturbances, dystonia, parkinsonism and pyramidal signs. Common are psychiatric symptoms such as impulsive or compulsive behavior, depression and emotional lability. In almost all cases, the optic atrophy has been noted and about 50% of cases have had a motor axonal neuropathy. In the MRI on T2- and T2*-weighted images, there are hypointense lesions in the globus palidus and substantia nigra corresponding to iron accumulation.     

Are neurodegenerative diseases "protein cancers"?

In the last 30 years, the elucidation of the molecular pathogenesis of neurodegenerative diseases has undergone remarkable progress, including the discoveries of the causative genes and risk factors of Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. However, the fundamental questions of why different neurons degenerate in different diseases and why these diseases are progressive have received little attention. I have proposed the "protein cancer" hypothesis, which states that abnormal or malignant proteins--such as prion proteins--generated in a cell grow and propagate from cell to cell by converting normal proteins, and this propagation causes disease progression, analogous to the metastasis of cancer cells to multiple different tissues during cancer progression. Intracellular filamentous inclusions composed of amyloid-like proteins, such as tau, α-synuclein, and TDP-43, are common neuropathological features of many neurodegenerative disorders, and the extent of the abnormal protein pathologies is closely related to disease progression. Recent results of experimental model studies as well as biochemical analyses of abnormal proteins in patients have provided support for this hypothesis. Therefore, small molecules or antibodies that can inhibit the intra- and intercellular propagation of abnormal proteins are expected to be promising candidates for clinical therapy.     

The impact of a novel apolipoprotein E and amyloid-β protein precursor-interacting protein on the production of amyloid-β

Alzheimer's disease (AD) is characterized by disrupted metabolism of the amyloid-β protein precursor (AβPP) and deposition of a byproduct, the amyloid-β (Aβ) peptide, into plaques. AD is also genetically linked to the gene for apolipoprotein E (apoE). We have identified a novel apoE-binding protein (TMCC2) that also forms a complex with AβPP. TMCC2 is a neuronal, predominantly ER-localized, protein that co-migrated with AβPP during native gel electrophoresis of rat brain extracts, and co-immunoprecipitated with AβPP from transfected human cell lysates. TMCC2 bound apoE in an isoform-specific manner in vitro and co-immunoprecipitated with apoE from cell lysates. Co-expression of apoE and TMCC2 stimulated Aβ production from the "Swedish" variant of AβPP (K595 M/N596L) by up to 1.5-fold (p < 0.05), and also from the 99-amino acid C-terminal fragment of AβPP (AβPP-C99) that is the direct precursor to Aβ by 1.5- to 2-fold (p < 0.0005), this effect was greater with apoE4 than apoE3 (p = 0.02); both apoE3 and apoE4 stimulated a greater increase in Aβ1-42 than Aβ1-40 production from AβPP-C99 in the presence of TMCC2. The interaction between TMCC2 and apoE may therefore contribute to disrupted AβPP metabolism and altered Aβ production, as observed in AD.     

Amyloid precursor protein compartmentalization restricts β-amyloid production

Alzheimer's disease (AD) is defined by deposits of the 42-residue amyloid-beta peptide (Abeta42) in the brain. Abeta42 is a minor metabolite of the amyloid precursor protein (APP), but its relative levels are increased by mutations on APP and presenilins 1 and 2 linked to familial AD. beta-secretase (BACE-1), an aspartyl protease, cleaves approx 10% of the APP in neuronal cells on the N-terminal side of Abeta to produce the C-terminal fragment (CTFbeta), which is cleaved by gamma-secretase to produce mostly Abeta of 40 residues (90%) and approx10% Abeta42. A third enzyme, alpha-secretase, cleaves APP after Abeta16 to secrete sAPPalpha and CTFalpha, the major metabolites of APP. Moreover, previous studies have demonstrated that phorbol esters stimulate processing of APP by alpha-secretase. Because alpha-secretase and BACE-1 cleave APP within the secretory pathway, it is likely that the two enzymes compete for the APP substrate. This type of competition can explain the failure to saturate the minor BACE-1 pathway by overexpressing APP in the cell. In this study, we demonstrate that inhibition of constitutive alpha-secretase processing in a human neuroblastoma cell line does not increase the yield of Abeta, suggesting that the APP substrate targeted for alpha-secretase processing is not diverted to the BACE-1 pathway. However, when phorbol ester-induced alpha-secretase was similarly inhibited, we detected an increase in BACE-1 processing and AB yield. We explain these results compartmentalization of BACE-1 and alpha-secretase with processing depending on sorting of APP to the two compartments. The simplest explanation for the detection of competition between the two pathways upon phorbol ester stimulation is the partial failure of this compartmentalization by phorbol ester-induced release of secretory vesicles.     

Expression of anti-apoptotic protein Bcl-2 and proapoptotic protein Bax after delayed paraplegia induced by ischemia/reperfusion injury

INTRODUCTION Apoptosis is known to occur in the central nervous system during de- velopment and in pathological settings such as ischemia reperfusion (IR) injury[1]. Apoptosis requires an active commitment of the cell to degrade its own DNA, according to …     

Colocalization of prion protein and β protein in the same amyloid plaques in patients with Gerstmann-Sträussler Syndrome

Summary We examined paraffin-embedded brain sections from three patients with Creutzfeldt-Jakob disease (CJD) and four patients with Gerstmann-Sträussler syndrome (GSS) who also had protein deposits in the brains. Immunostaining using anti-prion protein (PrP) and anti- protein coupled with formic acid pretreatment, revealed PrP deposits and protein deposits, respectively. In all four GSS patients examined, sequential double immunostaining and single immunostaining in serial sections or simultaneous double immunofluorescence revealed the colocalization of PrP and protein in the same amyloid plaques. The plaques labeled with both antibodies were designated as -PrP plaques. Small kuru plaques of less than 15 m in diameter were rarely found to coexist with deposits. The percentages of -PrP plaques in larger kuru plaques were not constant among the four GSS patients. The colocalization patterns of both deposits were observed as being roughly of two types as follows: (1) diffuse protein deposits located around the PrP core; and (2) a protein core and PrP core simultaneously existing in one amyloid plaque. Under an electron microscope, we were able to confirm the presence of both protein and PrP in a single plaque in four GSS patients older than 60 years old. In contrast, no colocalization of either deposits was seen in the amyloid plaque core fractions of a young GSS patient who had no protein deposits, even at the electron microscopic level. Therefore, the colocalization of both proteins in a single plaque is believed to be age-related and incidental in GSS patients but suggests a similar morphogenesis of both amyloid deposits.Supported in part by a Grant-in-Aid for Scientific Research (02454245, 03454171) from the Ministry of Education, Science and Culture of Japan     

Nogo,a star protein in reticulon family

1 Introduction In higher vertebrate animals, from amphibian to mammalian, when the central nervous system (CNS) is injured, the neural tissue itself is difficult for most animals to regenerate. Earlier functional studies indicated that in- hibitory proteins, such as myelin-associated glycoprotein (MAG)[1], oligodendrocyte-myelin glycoprotein (OMgp)[2 ] and Nogo[3], are enriched in myelin and oligodendrocytes. Among these proteins, Nogo has attracted more and more interest, although the fun…     

Regulation of β cleavage of amyloid precursor protein

Alzheimer’s disease ranks the first cause for senile dementia. The amyloid cascade is proposed to contribute to the pathogenesis of this disease. In this cascade, amyloid β peptide (Aβ) is produced through a sequential cleavage of amyloid precursor protein (APP) by β and γ secretases, while its cleavage by α secretase precludes Aβ production and generates neurotrophic sAPPα. Thus, enhancing αsecretase activity or suppressing βand γcleavage may reduce A βformation and ameliorate the pathological process of the disease. Several regulatory mechanisms of APP cleavage have been established. The present review mainly summarizes the signaling pathways pertinent to the regulation of APP β cleavage.     

Exploring the mechanistic insights of Cas scaffolding protein family member 4 with protein tyrosine kinase 2 in Alzheimer’s disease by evaluating protein interactions through molecular docking and dynamic simulations

Cas scaffolding protein family member 4 and protein tyrosine kinase 2 are signaling proteins, which are involved in neuritic plaques burden, neurofibrillary tangles, and disruption of synaptic connections in Alzheimer’s disease. In the current study, a computational approach was employed to explore the active binding sites of Cas scaffolding protein family member 4 and protein tyrosine kinase 2 proteins and their significant role in the activation of downstream signaling pathways. Sequential and structural analyses were performed on Cas scaffolding protein family member 4 and protein tyrosine kinase 2 to identify their core active binding sites. Molecular docking servers were used to predict the common interacting residues in both Cas scaffolding protein family member 4 and protein tyrosine kinase 2 and their involvement in Alzheimer’s disease-mediated pathways. Furthermore, the results from molecular dynamic simulation experiment show the stability of targeted proteins. In addition, the generated root mean square deviations and fluctuations, solvent-accessible surface area, and gyration graphs also depict their backbone stability and compactness, respectively. A better understanding of CAS and their interconnected protein signaling cascade may help provide a treatment for Alzheimer’s disease. Further, Cas scaffolding protein family member 4 could be used as a novel target for the treatment of Alzheimer’s disease by inhibiting the protein tyrosine kinase 2 pathway.     

Clinicopathologic characteristics of sporadic Japanese Creutzfeldt–Jakob disease classified according to prion protein gene polymorphism and prion protein type

We analyzed neuropathologic features of 23 Japanese patients with sporadic Creutzfeldt–Jakob disease (sCJD) by means of prion protein (PrP) immunolabeling associated with codon 129 polymorphism of the PrP gene and western blot analysis of protease-resistant PrP (PrP type). Clinical features, particularly age at onset, disease duration, periodic synchronous discharge and presence of myoclonus, were also analyzed. This study included 11 cases of subacute spongiform encephalopathy (SSE), 10 cases of panencephalopathic (PE)-type sCJD and two cases of thalamic-type sCJD, classified according to cerebral pathology findings. According to PrP gene polymorphism and PrP type, 18 cases were classified as MM1-type, two as MV1-type, two as MM2-type and one as MM1 + 2-type sCJD. SSE and PE-type sCJD showed similar clinical features, with the exception of disease duration, codon 129 polymorphism and PrP type. Thalamic-type sCJD showed different clinical features and PrP type. We suggest that SSE and PE-type sCJD comprise the sCJD subtype and that PE-type sCJD is a prolonged pathologic phenotype of SSE. When we compare our results with those from a series of Caucasian sCJD patients, the percentages of codon 129 polymorphisms differed, as did classification based on PrP gene polymorphism and PrP type; our series included many PE-type sCJD cases and disease duration was relatively long and MM2-type cases showed clinicopathologic variability.     

Cerebrospinal fluid protein biomarkers for Alzheimer’s disease

The introduction of acetylcholine esterase (AChE) inhibitors as a symptomatic treatment of Alzheimer’s disease (AD) has made patients seek medical advice at an earlier stage of the disease. This has highlighted the importance of diagnostic markers for early AD. However, there is no clinical method to determine which of the patients with mild cognitive impairment (MCI) will progress to AD with dementia, and which have a benign form of MCI without progression. In this paper, the performance of cerebrospinal fluid (CSF) protein biomarkers for AD is reviewed. The diagnostic performance of the three biomarkers, total tau, phospho-tau, and the 42 amino acid form of β-amyloid have been evaluated in numerous studies and their ability to identify incipient AD in MCI cases has also been studied. Some candidate AD biomarkers including ubiquitin, neurofilament proteins, growth-associated protein 43 (neuromodulin), and neuronal thread protein (AD7c) show interesting results but have been less extensively studied. It is concluded that CSF biomarkers may have clinical utility in the differentiation between AD and several important differential diagnoses, including normal aging, depression, alcohol dementia, and Parkinson’s disease, and also in the identification of Creutzfeldt-Jakob disease in cases with rapidly progressive dementia. Early diagnosis of AD is not only of importance to be able to initiate symptomatic treatment with AChE inhibitors, but will be the basis for initiation of treatment with drugs aimed at slowing down or arresting the degenerative process, such as γ-secretase inhibitors, if these prove to affect AD pathology and to have a clinical effect.     

Genistein protects hippocampal neurons against injury by regulating calcium/calmodulin dependent protein kinase Ⅳ protein levels in Alzheimer's disease model rats

Genistein has a neuroprotective effect in Alzheimer's disease, but its mechanism of action needs further clarification. Accumulating evidence suggests that excessive phosphorylation of tau protein causes production of neurofibrillary tangles, which is one of the main pathological characteristics of Alzheimer's disease, and tau protein can be phosphorylated by calcium/calmodulin dependent protein kinase IV(CAMK4). After 7 days of pre-administration of genistein(90 mg/kg), an Alzheimer's disease rat model was established using an intraperitoneal injection of D-galactose combined with an intracerebral injection of amyloid-β peptide(25–35). The rat was then continuously administered genistein(90 mg/kg) for 42 days. The Morris water maze test, western blotting and hematoxylin-eosin staining results showed that genistein significantly decreased the escape latency and increased the number of times crossing the platform, reduced p-tau, CALM, CAMKK1 and p-CAMK4 protein levels in the hippocampus, and alleviated hippocampal neuron damage. These findings indicate that genistein may play a neuroprotective role in Alzheimer's disease through regulating CAMK4 to modulate tau hyperphosphorylation.     

Secreted form of β-amyloid precursor protein activates protein kinase C and phospholipase Cγ1 in cultured embryonic rat neocortical cells

The secreted form of β-amyloid precursor protein (sAPP) has been reported to exert various biological activities in cultured neurons. The signal transduction mechanisms underlying these physiological functions of sAPP remain unclear. We now report that treatment of neural cells with the secreted form of APP695 (sAPP695) leads to dose- and time-dependent increase in phosphorylation of the endogenous substrates with a molecular mass of 80, 57 and 43 kDa. Pretreatment of cells with protein kinase C (PKC) inhibitor H-7 reduced phosphorylation of the 80- and 43-kDa proteins in a dose-dependent manner. The effect of sAPP695 on the phosphorylation is mimicked by phorbol 12-myristate-13-acetate (PMA). Downregulation of PKC by prolonged treatment of cells with PMA abolished sAPP695-enhanced phosphorylation of the 80- and 43-kDa proteins, indicating PKC is involved in the sAPP695-enhanced phosphorylation of these proteins in the cells. We also suggest that the 80- and 43-kDa proteins phosphorylated by sAPP695-stimulation are the major PKC substrates myristoylated alanine-rich C-kinase substrate and growth-associated protein-43. Furthermore, we demonstrate that tyrosine phosphorylation of phospholipase Cγ1 and formation of inositol 1,4,5-trisphosphate were increased by sAPP695-stimulation. These observations suggest that sAPP695 induces the activation of the signaling pathways through a stimulation of phosphoinositide–PKC cascade.     

Can galanin also be considered as growth-associated protein 3.2?

A recent study has shown that mice containing a loss-of-function mutation in the gene encoding galanin exhibit decreased peripheral nerve regeneration after a lesion. This major advance indicates, for the first time, that the large increases in galanin expression that occur in axotomized peripheral neurons have functional consequences for regeneration. Hopefully, similar functional consequences will soon be found for other peptides induced in these neurons after axotomy, such as vasoactive intestinal peptide and pituitary adenylate cyclase-activating peptide.     

Deposition of amyloid β protein in non-Alzheimer dementias: evidence for a neuronal origin of parenchymal deposits of β protein in neurodegenerative disease

Summary In two elderly patients with frontal lobe dementia and in two others with progressive aphasia an inverse relationship between the severity of protein deposition and the principal pathology of these disorders was noted. Deposition of protein occurred only in areas of cortex where functional (viable) neurones were still present and was absent where neuronal decimation had taken place. Such findings suggest that the presence of functional neurones is necessary for protein deposition to occur and, therefore, that neurones may be the source of the amyloid protein that is deposited within brain parenchyma not only in these disorders but also in other conditions, particularly Alzheimer's disease.Supported by a grant from the North Western Regional Health Authority (DJ) and a B.Sc Intercalated Studentship from the MRC (PWS)