Purification and polypeptide composition of corpora amylacea from aged human brain

From corpora amylacea to wasteosomes: History and perspectives

Corpora amylacea (CA) have been described in several human organs and have been associated with ageing and several pathological conditions. Although they were first discovered two centuries ago, their function and significance have not yet been identified. Here, we provide a chronological summary of the findings on CA in various organs and identify their similarities. After collecting and integrating these findings, we propose to consider CA as waste containers created by specific cells, which sequester waste products and foreign products, and assemble them within a glycan structure. The containers are then secreted into the external medium or interstitial spaces, in this latter case subsequently being phagocytosed by macrophages. This proposal explains, among others, why CA are so varied in content, why only some of them contain fibrillary amyloid proteins, why all of them contain glycan structures, why some of them contain neo-epitopes and are phagocytosed, and why they can be intracellular or extracellular structures. Lastly, in order to avoid the ambiguity of the term amyloid (which can indicate starch-like structures but also insoluble fibrillary proteins), we propose renaming CA as "wasteosomes", emphasising the waste products they entrap rather than their misleading amyloid properties.

Cerebral Corpora amylacea are dense membranous labyrinths containing structurally preserved cell organelles

Corpora amylacea are cell-derived structures that appear physiologically in the aged human brain. While their histological identification is straightforward, their ultrastructural composition and microenvironment at the nanoscale have remained unclear so far, as has their relevance to aging and certain disease states that involve the sequestration of toxic cellular metabolites. Here, we apply correlative serial block-face scanning electron microscopy and transmission electron tomography to gain three-dimensional insight into the ultrastructure and surrounding microenvironment of cerebral Corpora amylacea in the human brainstem and hippocampal region. We find that cerebral Corpora amylacea are composed of dense labyrinth-like sheets of lipid membranes, contain vesicles as well as morphologically preserved mitochondria, and are in close proximity to blood vessels and the glymphatic system, primarily within the cytoplasm of perivascular glial cells. Our results clarify the nature of cerebral Corpora amylacea and provide first hints on how they may arise and develop in the aging brain.

The polysaccharide scaffold of PrP 27-30 is a common compound of natural prions and consists of alpha-linked polyglucose

An inert polysaccharide scaffold identified as a 5-15% component of prion rods (PrP 27-30) is unambiguously distinguishable from the N-glycosyl groups and the GPI anchor of PrP, and consists predominantly of 1,4-linked glucose with some branching via 1,4,6-linked glucose. We show that this polysaccharide scaffold is a common secondary component of prions found in hamster full-length PrP(Sc), prion rods and in mouse ScN2a prions from cell culture. The preparation from prion rods was improved, resulting in a polysaccharide scaffold free of remaining infectivity. Furthermore, we determined the stereochemistry of the glycoside linkages as pre-dominantly if not entirely alpha-glycosidic. The origin of the polysaccharide, its interaction with PrP and its potential relation to glycogen and corpora amylacea are discussed.

The carbohydrate-binding domain of Lafora disease protein targets Lafora polyglucosan bodies

Lafora's disease (LD) is an autosomal recessive and fatal form of epilepsy with onset in late childhood or adolescence. One of the characteristic features of LD pathology is the presence of periodic acid-Schiff (PAS) positive Lafora inclusion bodies. Lafora bodies are present primarily in neurons, but they have also been found in other organs. Histochemical and biochemical studies have indicated that Lafora bodies are composed mainly of polysaccharides. The LD gene, EPM2A, encodes a 331 amino acid long protein named laforin that contains an N-terminal carbohydrate-binding domain (CBD) and a C-terminal dual-specificity phosphatase domain (DSPD). Here we demonstrate that the CBD of laforin targets the protein to Lafora inclusion bodies and this property could be evolutionarily conserved. We also tested in vitro the effects of five LD missense mutations on laforin's affinity to Lafora body. While the missense mutant W32G failed to bind to purified Lafora body, four other mutants (S25P, E28L, F88L, and R108C) did not show any effect on the binding affinity. Based on these observations we propose the existence of a laforin-mediated glycogen metabolic pathway regulating the disposal of pathogenic polyglucosan inclusions. This is the first report demonstrating a direct association between the LD gene product and the disease-defining storage product, the Lafora bodies.

Temporal lobe epilepsy and corpora amylacea in the hippocampus: clinicopathologic correlation

Corpora amylacea (CoA) have been found in about 60% of neurosurgical specimens showing hippocampal sclerosis (HS). To determine clinical and neuroimaging differences between HS with and without CoA, we studied 29 patients (21 male, 8 female; age at surgery, 12 to 49 years) who underwent anterior temporal lobectomy for intractable medial temporal lobe epilepsy. No CoA were noted in the hippocampus of 11 cases, and deposition of CoA was mild and limited to the subependymal and vestigial hippocampal sulcus regions in nine cases; in nine cases, moderate to marked deposition was noted in the pyramidal cell layer, accompanying severe neuronal loss. No significant differences were evident between these three groups for age at onset, frequency and duration of epileptic seizures, the average age at surgery, or surgical results. Hippocampal hyperintensity in fluid-attenuated inversion recovery magnetic resonance images tended to increase with increasing hippocampal deposition of CoA. Formation of CoA appears to be a response to neuronal loss in the pyramidal cell layer, being related to the epileptogenic process as a consequence rather than a cause.

S100 proteins in Corpora amylacea from normal human brain

Corpora amylacea (C.A.) also named polyglucosan bodies (P.B.) are one of the hallmarks of normal brain aging. Although their functions are not yet clear, C.A. increase in number in patients suffering from neurodegenerative diseases. C.A. contain 88% of hexoses and 4% of proteins. Most of the proteins in C.A. are aging or stress proteins such as heat shock proteins, ubiquitinated proteins and advanced glycation end products which are also proinflammatory products. Stimulated by the potential role played by some S100 proteins in the inflammatory process which may be triggered in C.A., we investigated, by immunohistochemistry, the presence of different S100 proteins (S100A1, S100A2, S100A3, S100A4, S100A5, S100A6, S100A8, S100A9, S100A12 and S100B) in C.A. from normal human brain. Among the ten S100 proteins analyzed, nine (S100A) were detected in C.A. Three S100 proteins (S100A8, S100A9, S100A12) which are highly expressed in activated macrophages and used as inflammatory markers were detected in C.A. S100A8 was, in addition, found in thick neuronal processes from the pons. One (S100B) could not be found in C.A. although it was highly expressed in astrocytes. In C.A., the staining intensity was estimated by computer-assisted microscopy and gave the following order: S100A1 congruent withS100A8 congruent with S100A9>S100A5> or =S100A4>S100A12>S100A6> S100A2=S100A3. The potential inflammatory role played by S100 proteins in C.A. is discussed.

Casein related amyloid, characterization of a new and unique amyloid protein isolated from bovine corpora amylacea

Amyloid bodies can be found in mammary secretory tissue of various species. These corpora amylacea (CA) have a lamellated structure, contain amyloid fibrils and are predominantly located in the alveolar lumina. The nature of the amyloid was not known, but CA were suggested to originate either from milk casein or mammary alveolar epithelial keratin. In the present report, bovine CA were analyzed histochemically. Furthermore, CA were isolated, analyzed and the amyloid was purified and characterized by amino acid sequencing. CA amyloid appeared to be potassium permanganate sensitive and tryptophan positive, and in this respect different from most other amyloid types except for AA and beta-2 microglobulin amyloid. Gel filtration of purified amyloid fibrils showed a HMW peak and a major 4 kD peak. N-terminal amino acid sequencing showed the amyloid to consist of tryptic-like peptides with an unusually high content of amino acids with bulky side chains. The amyloid protein was identified as derived from alpha-S2-casein. The fragments are of varying length (32, 33 and 45 amino acids), but all start at position 81 of alpha-S2-casein. We have identified a new and unique amyloid protein, and we propose to designate it as A alpha-S2C according to the guidelines for amyloid nomenclature.

Corpora-amylacea and the family of polyglucosan diseases

The history, characters, composition and topography of corpora amylacea (CA) in man and the analogous polyglucosan bodies (PGB) in other species are documented, noting particularly the wide variation in the numbers found with age and in neurological disease. Their origins from both neurons and glia and their probable migrations and ultimate fate are discussed. Their presence is also noted in other organs, particularly in the heart. The occurrence in isolated cases of occasional 'massive' usually focal accumulations of similar polyglucosan bodies in association with certain chronic neurological diseases is noted and the specific conditions Adult Polyglucosan body disease and type IV glycogenosis where they are found throughout the nervous system in great excess is discussed. The distinctive differences of CA from the PGB of Lafora body disease and Bielschowsky body disease are emphasised. When considering their functional roles, a parallel is briefly drawn on the one hand between normal CA and the bodies in the polyglucosan disorders and on the other with the lysosomal system and its associated storage diseases. It is suggested that these two systems are complementary ways by which large, metabolically active cells such as neurons, astrocytes, cardiac myocytes and probably many other cell types, dispose of the products of stressful metabolic events throughout life and the continuing underlying process of aging and degradation of long lived cellular proteins. Each debris disposal system must be regulated in its own way and must inevitably, a priori, be heir to metabolic defects that give rise in each to its own set of metabolic disorders.

Corpus amylaceum (polyglucosan body) in the peripheral olfactory system

Peripheral part of the olfactory system (bulb and tract) was investigated for the occurrence of corpus amylaceum (CA) (polyglucosan body) in 296 (281 pathological and 15 control cases) autopsied human brains. No significant differences were found in the incidence between the various age groups above 40 years or between different disease groups and the controls. The predominance of CA in the olfactory tract and its loose correlation with age at this localization over 40 years of age could be resulted by various factors, including the extremely rich astrocytic and capillary network in the intermediate zone, and the proximity of the olfactory tract to the external environment, which may result in the protective role of CA. The role of stress was proved by the HSP-60 positivity of CA.

Experimental induction of corpora amylacea-like inclusions in rat astroglia

Corpora amylacea (CA) are glycoproteinaceous inclusions that accumulate in the human central nervous system during normal ageing, and to an even greater extent in Alzheimer's disease and other neurodegenerative disorders. They are particularly prominent in subpial and subependymal regions, and are most commonly located within astrocytes and their processes. We previously demonstrated that human CA share many tinctorial and histochemical properties in common with Gomori-positive cytoplasmic granules which accumulate in periventricular astrocytes of the ageing vertebrate brain and in rat astroglial cultures exposed to the sulphydryl agent, cysteamine (CSH). In the present study, long-term exposure of neonatal rat astrocyte cultures to CSH resulted in the formation of large spherical, PAS-positive cytoplasmic inclusions which are highly reminiscent of, if not identical to, human CA. As in the case of human CA and Gomori-positive astrocyte granules, the CSH-induced CA-like inclusions exhibit non-enzymatic peroxidase activity and consistent immunolabelling with antibodies directed against the mitochondrial protein, sulphite oxidase. Taken together, our findings suggest that progressive mitochondrial damage and macroautophagy play an important role in the biogenesis of CA (and Gomori-positive granules) in astrocytes of the ageing periventricular brain.

A functional role for corpora amylacea based on evidence from complement studies

Few theories have been advanced for the production of corpora amylacea (CA) by the normal ageing brain and by the CNS under various neurological conditions. Proteins derived from neurons and oligodendrocytes are found in CA and to understand their origins brain tissue from patients with Alzheimer's disease (AD), multiple sclerosis (MS) and Pick's disease (PD) were tested for complement activity. All CA were immunopositive for antisera to classical pathway-specific components, the activation products C3d and the terminal complement complex (TCC), the C3 convertase regulator membrane cofactor protein (MCP) and the fluid phase regulators S-protein and clusterin. CA were immunonegative for the alternative complement pathway proteins and the complement regulators, decay accelerating factor (DAF) and CD59. Western immunoblotting of isolated solubilized CA from the same tissues demonstrated a weak band for MCP but TCC was more easily shown by immunoprecipitation. A filamentous fringe around CA, probably of astrocytic origin, was also immunopositive for complement factors. CA consist of an inert mucopolysaccharide matrix encasing ubiquitinated proteins, resulting from death of and damage to neurons, myelin and oligodendrocytes. A function of CA, therefore, could be to prevent the recognition of these immunogenic proteins by lymphocytes and microglia and thus protect the CNS from further injury.

X-ray microprobe analysis of corpora amylacea

Since corpora amylacea is concentrated in the high density fraction in the subcellular fractionation of autopsy brain. It is suspected that inorganic materials accumulate in corpora amylacea. Therefore, elemental analyses of partially purified corpora amylacea from autopsy brain from a patient with Alzheimer's disease and those from brain of a non-demented patient were performed by the X-ray microprobe method. Prominent peaks of sodium, phosphorus, sulphur and chloride were observed, and mapping analyses confirmed that these elements were actually contained within the corpora amylacea. A similar result was obtained using cryostat sections. Corpora amylacea are characteristically distributed along the margin of blood vessels, beneath the pial border of the hippocampus and in the subependymal zones of ventricles of aged brains, namely in the vicinity of blood and cerebrospinal fluid. From this distribution and from the results of the present paper, we suggest that corpora amylacea play a role in the absorption and accumulation of inorganic materials which have been extravasated from blood and cerebrospinal fluid (CSF) and taken up by astrocytes. This may reflect alteration of the blood-brain and blood-CSF barriers in the ageing brain.

Mitochondrial constituents of corpora amylacea and autofluorescent astrocytic inclusions in senescent human brain

Corpora amylacea (CA) are cytoplasmic inclusions that accumulate in human brain in the course of normal aging, and to an even greater extent, in Alzheimer's disease and other neurodegenerative conditions. In senescent and Alzheimer-diseased human brains, astrocytes in limbic and periventricular regions exhibit red autofluorescent inclusions, homologous to Gomori-positive astrocyte granules previously described in the brains of aging rodents and other vertebrates. We have shown that Gomori inclusions in situ and in culture are derived from autophagocytosed mitochondria exhibiting iron-mediated peroxidase activity. In the human brain, the autofluorescent inclusions share many properties with CA. Both types of inclusion progressively accumulate in periventricular regions with advancing age, are largely astrocytic in origin, and contain various heat shock proteins and ubiquitin. Using histochemistry in conjunction with cofocal microscopy, we demonstrated that both CA and the red autofluorescent granules exhibit non-enzymatic peroxidase activity and an affinity for CAH and PAS. The only major divergent histochemical feature between the Gomori-positive astrocyte granules and CA is the presence of orange-red autofluorescence in the former and the absence of endogenous fluorescence in the latter. On the basis of numerous shared topographic and histochemical features, we hypothesized that CA are largely derived from autofluorescent (Gomori-positive) astrocyte granules which reside in periventricular regions of the senescent CNS. Immunofluorescent labeling and laser scanning confocal microscopy demonstrated consistent colocalization of the mitochondrial proteins, sulfite oxidase, and heat shock protein 60, to both CA and the autofluorescent astroglial inclusions. In addition, both CA and the autofluorescent astrocyte granules exhibit staining for DNA which colocalizes to mitochondrial antigens and therefore likely represents mitochondrial nucleic acid in dual-labeled preparations. These observations suggest that a) Gomori-positive astrocyte granules in human brain are homologous to those described in rodents, b) Gomori-positive granules may be structural precursors of CA in senescent human brain, and c) in the aging human brain, degenerate mitochondria within periventricular astrocytes give rise to autofluorescent cytoplasmic granules and corpora amylacea.

Age-related fibrillar material in mouse brain. Assessing its potential as a biomarker of aging and as a model of human neurodegenerative disease

We have described the age-related deposition of fibrillar material in brains of B6 mice and SAM. Since in other inbred strains similar deposits were absent or occurred only occasionally and only in aged individuals, a genetic predisposition of B6 mice and SAM to accumulate the fibrillar material is suggested. The deposits are mostly associated with astrocytic processes and have been referred to as astrocytic inclusions. HSPG- and laminin-like molecules have been identified as components of the fibrillar material. The deposits have similarities with CA in humans, but they also show some important differences; thus there is presently insufficient evidence to consider the deposits the murine equivalent of CA. Although the physiological significance of the fibrillar material is not yet clear, the awareness of the deposits appears pertinent because they might contribute to various aspects of CNS function of susceptible strains of mice, and therefore could lead to possible misinterpretations of the results of studies employing these strains. Future directions of our research will determine the potential of the murine deposits to model aspects of human neuropathology, in particular, whether the deposits may mimic the deposition of ECM molecules as an early-event in the pathogenesis of amyloid plaque formation.

Isolation of pseudoperoxidase-positive astrocyte granules from intact rat brain and cysteamine-treated neuroglial cultures

A subpopulation of astrocytes in periventricular regions of aging brain and in cysteamine (CSH)-treated glial cultures contain autofluorescent cytoplasmic granules that exhibit an affinity for Gomori's chrome alum hematoxylin (CAH), and non-enzymatic peroxidase activity. Although shown to be histochemically distinct from lipofuscin, the lack of pure preparations of these glial inclusions has hindered the elucidation of their precise chemical constituents. Using sucrose gradient fractionation and density centrifugation on percoll, we obtained enriched preparations of astrocyte cytoplasmic granules from intact rat brain and CSH-treated astrocyte cultures. The presence and relative purity of these inclusions were confirmed by laser scanning confocal microscopy for red autofluorescent granules, diaminobenzidine histochemistry for non-enzymatic peroxidase activity and chrome alum hematoxylin (Gomori) staining. In the enriched fractions, the smaller granules (0.5-4.0 microns) were spherical and weakly autofluorescent, whereas larger inclusions (5.0-10.0 microns) tended to be intensely autofluorescent and pleomorphic. As in situ, the purified material was argyrophilic and did not stain for lipids. Isolation of these astrocytic inclusions should permit a more thorough characterization of their biochemical contents.

Immunochemical identification of ubiquitin and heat-shock proteins in corpora amylacea from normal aged and Alzheimer's disease brains

Corpora amylacea (CA) accumulation in the central nervous system (CNS) is associated with both normal aging and neurodegenerative conditions such as Alzheimer's disease (AD). CA is reported to be primarily composed of glucose polymers, but approximately 4% of the total weight of CA is consistently composed of protein. CA protein resolved on sodium dodecylsulfate-polyacrylamide gel electrophoresis showed a broad range of polypeptides ranging from 24 to 133 kDa, with four abundant bands. Immunoblots of the profile of polypeptides solubilized from purified CA, showed positive ubiquitin (Ub) immunoreactivity for all the bands. Antisera to heat-shock proteins (hsp) 28 and 70 reacted selectively with bands of 30 and 67 kDa. These results show that Ub is associated with the primary protein components of CA and that the polypeptides are likely to be Ub conjugates. Immunostaining experiments were performed to specifically characterize the protein components of CA in brain tissue sections as well as those of CA purified from both AD and normal aged brains. In all cases CA showed positive reactions with antibodies to Ub, with antibodies raised against either paired helical filaments or hsp 28 or 70, the most prominent staining being with antibodies to Ub, hsp 28 or hsp 70. The presence of Ub and hsp 28 and 70, which are actively induced after stress, suggests that accumulation of altered proteins, possibly attributed to an increased frequency of unusual post-translational modifications or to a sustained physiological stress (related to both normal aging and neurodegenerative process), may be involved in the pathogenesis of CA.

Hereditary branching enzyme dysfunction in adult polyglucosan body disease: a possible metabolic cause in two patients

We describe 2 unrelated patients with adult polyglucosan body disease (APBD) diagnosed by sural nerve biopsy. Both patients were offspring of consanguineous marriages. They presented clinically with late onset pyramidal tetraparesis, micturition difficulties, peripheral neuropathy, and mild cognitive impairment. Magnetic resonance imaging of the brain revealed extensive white matter abnormalities in both. In search of a possible metabolic defect, we evaluated glycogen metabolism in these patients and their clinically unaffected children. Branching enzyme activity in the patients' polymorphonuclear leukocytes was about 15% of control values, whereas their children displayed values of 50 to 60%, suggesting a possible autosomal recessive mode of transmission. This is the first report of an inherited metabolic defect in patients with adult polyglucosan body disease. We suggest that branching enzyme dysfunction may be implicated in the pathogenesis of some patients with adult polyglucosan body disease.

Heat shock protein expression in corpora amylacea in the central nervous system: clues to their origin

Small bodies expressing epitopes of the 72 kD heat shock protein (HSP) have been identified in the brain and spinal cord in normal and neurologically abnormal individuals. These bodies resemble the 'pre-corpora amylacea' (pre-CA), thought to be the primary structure in the development of the mature body. Corpora amylacea are laminated hyaline bodies composed of polyglucosans. They are found in larger numbers with increasing age in the brain and spinal cord. Mature, histologically 'classical', corpora amylacea express epitopes of HSP chiefly at the periphery of the corpus, whilst smaller immature 'pre-corpora' stain intensely throughout the entire structure. A heat shock or stress response in neurons and glial cells may be part of the cellular reaction to accumulation of abnormal products.

Ubiquitin is a component of polypeptides purified from corpora amylacea of aged human brain

Corpora amylacea (CA) are one of the conspicuous features of brain tissue in normal aging and neurodegenerative diseases. Quantitative protein determination of purified CA revealed a protein content of about 4% of total weight. Qualitative protein analysis revealed a broad range of polypeptides, with four being more abundant. High performance liquid chromatography (HPLC) fractionation of this protein material showed four peaks which are related to the four major polypeptides with molecular weights of 24 KD, 42 KD, 94 KD, and 133 KD. Amino acid content analysis of the 24 KD, 42 KD and 94 KD polypeptides indicated that distinct protein species are involved. N-terminal amino acid sequence analysis of the 24 KD and 42 KD polypeptides revealed in both cases homology with the N-terminal sequence of human ubiquitin.