Hsp70 and hsp40 chaperones can inhibit self-assembly of polyglutamine proteins into amyloid-like fibrils

Requirement of an intact microtubule cytoskeleton for aggregation and inclusion body formation by a mutant huntingtin fragment

Huntington's disease is caused by the expansion of CAG repeats coding for a polyglutamine tract in the huntingtin protein. The major pathological feature found in Huntington's disease neurons is the presence of detergent-insoluble ubiquitinated inclusion bodies composed of the huntingtin protein. However, the mechanisms that underlie inclusion body formation, and the precise relationship between inclusion bodies and events that initiate toxicity, remain unclear. Here, we analyzed the effects of drugs or genetic mutations that disrupt the microtubule cytoskeleton in a Saccharomyces cerevisiae model of the aggregation of an amino-terminal polyglutamine-containing fragment of huntingtin exon 1 (HtEx1). Treatment of yeast with drugs that disrupt microtubules resulted in less than 2% of the detergent-insoluble HtEx1 observed in mock-treated cells and prevented the formation of large juxtanuclear inclusion bodies. Disruption of microtubules also unmasked a potent glutamine length-dependent toxicity of HtEx1 under conditions where HtEx1 exists in an entirely detergent-soluble nonaggregated form. Results from the yeast model paralleled those from neuronal pheochromocytoma cells, where disruption of microtubules eliminated the formation of juxtanuclear and intranuclear inclusion bodies by HtEx1. Our results suggest that active transport along microtubules may be required for inclusion body formation by HtEx1 and that inclusion body formation may have evolved as a cellular mechanism to promote the sequestration or clearance of soluble species of HtEx1 that are otherwise toxic to cells.

Occurrence of glutamate receptor subunit 1-containing aggresome-like structures during normal development of rat spinal cord interneurons

During a developmental study of the expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) -type glutamate receptor subunits in rat spinal cord, we observed the existence of cytoplasmic inclusion bodies with positive immunoreactivity to glutamate receptor subunit 1 (GluR1) but not to other glutamate receptor subunits. GluR1-positive bodies have a diameter of between 1 and 3 microm and can be seen widely distributed throughout spinal cord gray matter, with the exception of the ventral horn region. They transiently appear within a definite developmental time-period between embryonic day 19 and postnatal day 17 and are only associated with neuronal cells. Ultrastructural analysis revealed that these inclusions were located adjacent to the nucleus and consisted of amorphous material without any limiting membrane. Immunocytochemical analysis revealed that the inclusions displayed positive immunoreactivity to ubiquitin, HSP70, and 20S proteasome. All these data indicate that GluR1-containing inclusions display all the ultrastructural and immunocytochemical characteristics of the recently described structure, which have been given the name aggresomes. Further studies are needed to determine the biological significance of these normally occurring aggresome-like inclusions, because aggresomes are usually considered in a pathologic context.

Chaperone suppression of cellular toxicity of huntingtin is independent of polyglutamine aggregation

Polyglutamine protein aggregation is associated with eight inherited neurodegenerative disorders. In Huntington's disease, N-terminal fragments of mutant huntingtin form intracellular aggregates and mediate cellular toxicity. Recent studies have shown that chaperones inhibit polyglutamine-mediated aggregation and cellular toxicity. Because chaperones also inhibit caspase activation to protect cells from death, it remains unclear whether the protective effect of chaperones on polyglutamine-mediated cellular toxicity is dependent on their inhibition of protein aggregation. In this study, we show that several chaperones including HSP 40, HSP 70, and N-ethylmaleimide-sensitive factor can inhibit cellular toxicity caused by N-terminal mutant huntingtin fragments. However, only HSP 40 is able to inhibit huntingtin aggregation. Furthermore, time-course study suggests that the protection of chaperones against huntingtin toxicity is not the result of their suppression of huntingtin aggregation. Chaperones inhibit caspase-3 and caspase-9 activation mediated by mutant huntingtin, and this inhibition is independent of huntingtin aggregation. We propose that the inhibition of caspase activity by chaperones is involved in their suppression of polyglutamine toxicity.

Inhibition of polyglutamine aggregation in R6/2 HD brain slices-complex dose-response profiles

Huntington's disease (HD) is a late onset neurodegenerative disorder caused by a CAG/polyglutamine (polyQ) repeat expansion. PolyQ aggregates can be detected in the nuclei and processes of neurons in HD patients and mouse models prior to the onset of symptoms. The misfolding and aggregation pathway is an important therapeutic target. To better test the efficacy of aggregation inhibitors, we have developed an organotypic slice culture system. We show here that the formation of polyQ aggregates in hippocampal slices established from the R6/2 mouse follows the same prescribed sequence as occurs in vivo. Using this assay, we show that Congo red and chrysamine G can modulate aggregate formation, but show complex dose-response curves. Oral administration of creatine has been shown to delay the onset of all aspects of the phenotype and neuropathology in R6/2 mice. We show here that creatine can similarly inhibit aggregate formation in the slice culture assay.

Altered transcription in yeast expressing expanded polyglutamine

Expanded polyglutamine tracts are responsible for at least eight fatal neurodegenerative diseases. In mouse models, proteins with expanded polyglutamine cause transcriptional dysregulation before onset of symptoms, suggesting that this dysregulation may be an early event in polyglutamine pathogenesis. Transcriptional dysregulation and cellular toxicity may be due to interaction between expanded polyglutamine and the histone acetyltransferase CREB-binding protein. To determine whether polyglutamine-mediated transcriptional dysregulation occurs in yeast, we expressed polyglutamine tracts in Saccharomyces cerevisiae. Gene expression profiles were determined for strains expressing either a cytoplasmic or nuclear protein with 23 or 75 glutamines, and these profiles were compared to existing profiles of mutant yeast strains. Transcriptional induction of genes encoding chaperones and heat-shock factors was caused by expression of expanded polyglutamine in either the nucleus or cytoplasm. Transcriptional repression was most prominent in yeast expressing nuclear expanded polyglutamine and was similar to profiles of yeast strains deleted for components of the histone acetyltransferase complex Spt/Ada/Gcn5 acetyltransferase (SAGA). The promoter from one affected gene (PHO84) was repressed by expanded polyglutamine in a reporter gene assay, and this effect was mitigated by the histone deacetylase inhibitor, Trichostatin A. Consistent with an effect on SAGA, nuclear expanded polyglutamine enhanced the toxicity of a deletion in the SAGA component SPT3. Thus, an early component of polyglutamine toxicity, transcriptional dysregulation, is conserved in yeast and is pharmacologically antagonized by a histone deacetylase inhibitor. These results suggest a therapeutic approach for treatment of polyglutamine diseases and provide the potential for yeast-based screens for agents that reverse polyglutamine toxicity.

Are there CAG repeat expansion-related disorders outside the central nervous system?

Expansions of poly-glutamine tracts in proteins that are expressed in the central nervous system cause neurodegenerative diseases. The altered proteins accumulate over long periods of time, forming nuclear inclusions, and lead to neuronal cell death. A similar mechanism could also be operant in non-dividing cells outside the central nervous system because nuclear inclusions are not limited to neurons. In addition, variations of the repeat length within the normal range may affect cellular function as it has been shown for the androgen receptor that is involved in neoplastic degeneration of several tissues. We have identified a poly-glutamine/poly-proline repeat in the homeobox gene DLX6. DLX genes are expressed in non-proliferative cells of the apical ectodermal ridge of developing limbs. Ablation of these cells leads to limb malformation. We propose that CAG triplet expansions in this gene could lead to cell death in the apical ectodermal ridge causing limb malformations. Indeed, autosomal dominant limb malformations with increasing severity in successive generations have been linked to the chromosomal region that contains DLX6. The analysis of a limited number of patients affected by split hand/foot malformation so far revealed only a slight modifier effect of repeat length within the normal range and no expansions have been detected.

Association of plasma antibodies against the inducible Hsp70 with hypertension and harsh working conditions

Autoantibodies against certain stress or heat shock proteins (Hsps) may play a role in the pathogenesis and/ or prognosis of some diseases. Using immunoblotting with human recombinant Hsps and univariate and multivariate logistic regression models, we have investigated the presence of antibodies against Hsp70, the inducible member of the 70-kDa family of heat shock proteins, and analyzed its possible association with hypertension and working conditions. Plasma and serum were collected from 764 steel mill workers from 6 work sites exposed to (1) severe noise; (2) severe noise and dust; (3) noise, dust, and heat; (4) noise and heat; (5) severe noise and heat; and (6) office conditions (control). Workers with prolonged exposure to stresses such as noise, dust, and high temperature and a combination of these in the workplace had a high incidence (26.6% to 40.2%) of antibodies to Hsp70 compared to the lowest incidence (18.6%) of antibodies to Hsp70 in the control group of office workers. Moreover, there was a statistical association of antibodies against Hsp70 with hypertension. The statistical correlation between the presence of antibodies to Hsp70 and hypertension is higher in the group of workers with blood pressure of 160/95 mmHg than in the 140/90-mmHg group after excluding possible effects of the workplace stresses. These results suggest that harsh workplace conditions can increase the production of antibodies against Hsp70 and that the presence of antibodies to this stress protein may be associated with hypertension. The precise mechanism for the elevation of antibodies against Hsps by environmental and workplace stresses and their relation to hypertension remains to be established.

Initial process of polyglutamine aggregate formation in vivo

BACKGROUND

Polyglutamine expansion in protein is responsible for several inherited neuro-degenerative diseases. The expansion has toxic effects on neural cells as well as results in forming aggregates. Using yeast, we examined the initial process of polyglutamine aggregate formation in vivo.

RESULTS

Following expression, polyglutamine tracts were of a soluble form during a lag period, and then formed insoluble complexes. The lag was prolonged and the formation of insoluble complex became slower by decreasing the number of polyglutamine tracts and by a treatment with guanidine hydrochloride. Gel filtration analysis revealed that the soluble polyglutamine existed in a small form. Formation of polyglutamine aggregates appeared to follow similar kinetics reported in the in vitro studies, where polyglutamine tracts self-aggregate in a length-, concentration- and time-dependent manner. However, in vivo, Hsp104 was required for the conversion from a soluble to an insoluble state. Without Hsp104, polyglutamine tracts tended to remain in a small soluble form, prolonging the lag. Moreover, the dependency on Hsp104 for aggregate formation was strong with the short polyglutamine tract, and decreased with the long polyglutamine tract.

CONCLUSION

For polyglutamine aggregate formation, a balance of parameters including the length of the polyglutamine tract, Hsp104, and level of polyglutamine expression determined its efficiency.

Analysis of heat shock transcription factor for suppression of polyglutamine toxicity

Individually over-expressed chaperones can interfere with cytotoxicity and aggregation of polyglutamine proteins in disease models. As chaperones cooperate, the analysis of suppression or reversal of polyglutamine pathology may require ways to up-regulate multiple chaperone coding genes. This condition might be achieved by exogenous expression of de-repressed forms of heat shock transcription factor 1 (HSF1), which mediates induction of several genes coding cytosolic and nuclear chaperones. Here we present the rationale behind this possible approach and the caveats, and employ a non-neuronal cell system to test whether Ataxin-1 aggregation can be modulated by de-repressed HSF1 mutants through augmented expression of chaperone coding genes. In our experiments, HSF1 mutants have induced heat shock protein 70 and Human DnaJ (HDJ)-1 to intermediate levels. Cells expressing such mutants also showed partial reduction of Ataxin-1 [31Q] aggregation. A consolidated positive outcome of these tests in cellular models would encourage experiments in transgenic mice and prospects for pharmacological modulation of HSF1 activity or delivery.

Nuclear aggregation of huntingtin is not prevented by deletion of chaperone Hsp104

Polyglutamine expansion causes the disease proteins to aggregate, resulting in stable insoluble aggregates in the nucleus. The in vitro aggregation and cellular toxicity of polyglutamine proteins are reduced by chaperone heat shock proteins (Hsp). In polyglutamine disease animal models, however, polyglutamine inclusions remain in the nucleus despite the suppression of neurodegeneration by Hsp. Studies using yeast genetic approach revealed that the balance of Hsp is important for regulating protein aggregation in the cytoplasm of yeast cells. Here we report that N-terminal fragments of huntingtin with an expanded polyglutamine tract form aggregates only in the cytoplasm of yeast cells and, when tagged with nuclear localization sequences (NLS), are able to aggregate in the nucleus. Deletion of the Hsp104 gene prevents the aggregation of huntingtin in the cytoplasm but is unable to eliminate the aggregation of NLS-tagged huntingtin in the nucleus. The inhibitory effect of Hsp104 deletion on the cytoplasmic aggregation of huntingtin only occurs in viable yeast cells, as aggregates can be formed in Hsp104 deletion cells that have been frozen for 72 h. Fresh cytosolic extracts of the Hsp104 deletion strain inhibit the aggregation of huntingtin in vitro, suggesting that the deletion of Hsp104 may alter the activities of other cytoplasmic factors to inhibit polyglutamine aggregation in the cytoplasm. We propose that the regulatory effects of chaperones may mainly be restricted to the cytoplasm and have much less influence on polyglutamine-containing aggregates in the nucleus.

Accumulation of mutant huntingtin fragments in aggresome-like inclusion bodies as a result of insufficient protein degradation

The huntingtin exon 1 proteins with a polyglutamine repeat in the pathological range (51 or 83 glutamines), but not with a polyglutamine tract in the normal range (20 glutamines), form aggresome-like perinuclear inclusions in human 293 Tet-Off cells. These structures contain aggregated, ubiquitinated huntingtin exon 1 protein with a characteristic fibrillar morphology. Inclusion bodies with truncated huntingtin protein are formed at centrosomes and are surrounded by vimentin filaments. Inhibition of proteasome activity resulted in a twofold increase in the amount of ubiquitinated, SDS-resistant aggregates, indicating that inclusion bodies accumulate when the capacity of the ubiquitin-proteasome system to degrade aggregation-prone huntingtin protein is exhausted. Immunofluorescence and electron microscopy with immunogold labeling revealed that the 20S, 19S, and 11S subunits of the 26S proteasome, the molecular chaperones BiP/GRP78, Hsp70, and Hsp40, as well as the RNA-binding protein TIA-1, the potential chaperone 14-3-3, and alpha-synuclein colocalize with the perinuclear inclusions. In 293 Tet-Off cells, inclusion body formation also resulted in cell toxicity and dramatic ultrastructural changes such as indentations and disruption of the nuclear envelope. Concentration of mitochondria around the inclusions and cytoplasmic vacuolation were also observed. Together these findings support the hypothesis that the ATP-dependent ubiquitin-proteasome system is a potential target for therapeutic interventions in glutamine repeat disorders.

Multiple Gln/Asn-rich prion domains confer susceptibility to induction of the yeast [PSI(+)] prion

The yeast prion [PSI(+)] results from self-propagating aggregates of Sup35p. De novo formation of [PSI(+)] requires an additional non-Mendelian trait, thought to result from a prion form of one or more unknown proteins. We find that the Gln/Asn-rich prion domains of two proteins, New1p and Rnq1p, can control susceptibility to [PSI(+)] induction as well as enhance aggregation of a human glutamine expansion disease protein. [PSI(+)] inducibility results from gain-of-function properties of New1p and Rnq1p aggregates rather than from inactivation of the normal proteins. These studies suggest a molecular basis for the epigenetic control of [PSI(+)] inducibility and may reveal a broader role for this phenomenon in the physiology of protein aggregation.

Mechanism of prion loss after Hsp104 inactivation in yeast

In vivo propagation of [PSI(+)], an aggregation-prone prion isoform of the yeast release factor Sup35 (eRF3), has previously been shown to require intermediate levels of the chaperone protein Hsp104. Here we perform a detailed study on the mechanism of prion loss after Hsp104 inactivation. Complete or partial inactivation of Hsp104 was achieved by the following approaches: deleting the HSP104 gene; modifying the HSP104 promoter that results in low level of its expression; and overexpressing the dominant-negative ATPase-inactive mutant HSP104 allele. In contrast to guanidine-HCl, an agent blocking prion proliferation, Hsp104 inactivation induced relatively rapid loss of [PSI(+)] and another candidate yeast prion, [PIN(+)]. Thus, the previously hypothesized mechanism of prion dilution in cell divisions due to the blocking of prion proliferation is not sufficient to explain the effect of Hsp104 inactivation. The [PSI(+)] response to increased levels of another chaperone, Hsp70-Ssa, depends on whether the Hsp104 activity is increased or decreased. A decrease of Hsp104 levels or activity is accompanied by a decrease in the number of Sup35(PSI+) aggregates and an increase in their size. This eventually leads to accumulation of huge agglomerates, apparently possessing reduced prion forming capability and representing dead ends of the prion replication cycle. Thus, our data confirm that the primary function of Hsp104 in prion propagation is to disassemble prion aggregates and generate the small prion seeds that initiate new rounds of prion propagation (possibly assisted by Hsp70-Ssa).

Proteasome inhibition in oxidative stress neurotoxicity: implications for heat shock proteins

Recent studies have demonstrated that inhibition of the proteasome, an enzyme responsible for the majority of intracellular proteolysis, may contribute to the toxicity associated with oxidative stress. In the present study we demonstrate that exposure to oxidative injury (paraquat, H(2)O(2), FeSO(4)) induces a rapid increase in reactive oxygen species (ROS), loss of mitochondrial membrane potential, inhibition of proteasome activity, and induction of cell death in neural SH-SY5Y cells. Application of proteasome inhibitors (MG115, epoxomycin) mimicked the effects of oxidative stressors on mitochondrial membrane potential and cell viability, and increased vulnerability to oxidative injury. Neural SH-SY5Y cells stably transfected with human HDJ-1, a member of the heat shock protein family, were more resistant to the cytotoxicity associated with oxidative stressors. Cells expressing increased levels of HDJ-1 displayed similar degrees of ROS formation following oxidative stressors, but demonstrated a greater preservation of mitochondrial function and proteasomal activity following oxidative injury. Cells transfected with HDJ-1 were also more resistant to the toxicity associated with proteasome inhibitor application. These data support a possible role for proteasome inhibition in the toxicity of oxidative stress, and suggest heat shock proteins may confer resistance to oxidative stress, by preserving proteasome function and attenuating the toxicity of proteasome inhibition.

The protective role of HSP90 against 3-hydroxykynurenine-induced neuronal apoptosis

3-hydroxykynurenine (3HK), an endogenous metabolite of tryptophan in the kynurenine pathway, is a potential neurotoxin in several neurodegenerative disorders. Stabilizing protein structure, heat shock proteins (HSPs) have diverse roles as molecular chaperones to mediate stress tolerance. In the present study, we investigated the possible protective role of HSPs against 3HK induced neuronal cell death. Here we report that 3HK induced in a dose- and time-dependent manner neuronal cell death in neuroblastoma SK-N-SH cells. The cell death showed characteristic apoptotic features such as cell shrinkage, plasma membrane blebbing, chromatin condensation, and nuclear condensation and fragmentation. Furthermore, SK-N-SN cells were protected from 3HK induced cytotoxicity by prior elevation of HSPs expression. Our results show that the protective effect was abolished by HSP90 anti-sense oligonucleotides while not by HSP27 and HSP70 anti-sense oligonucleotides. Also, our result shows that HSP90 effectively inhibits caspases activities leading to the apoptosis. These results suggest that 3HK induces apoptosis in neuroblastoma SK-N-SN cells and that HSP90 is major contributing protein component of protection against 3HK induced apoptosis.

Therapeutic opportunities in polyglutamine disease

Polyglutamine diseases comprise a class of familial neurodegenerative disorders caused by expression of proteins containing expanded polyglutamine tracts. Great progress has been made in elucidating the molecular mechanisms contributing to polyglutamine pathology, and in identifying potential drug targets. Although much remains to be learned, these advances provide an opportunity for rational approaches to target-based drug discovery.

Huntington's disease: from gene to potential therapy

Huntington's disease (HD) is a progressive, late-onset neurodegenerative illness with autosomal dominant inheritance that affects one in 10 000 individuals in Western Europe. The disease is caused by a polyglutamine repeat expansion located in the N-terminal region of the huntingtin protein. The mutation is likely to act by a gain of function, but the molecular mechanisms by which it leads to neuronal dysfunction and cell death are not yet known. The normal function of huntingtin in cell metabolism is also unclear. There is no therapy for HD. Research on HD should help elucidate the pathogenetic mechanism of this illness in order to develop successful treatments to prevent or slow down symptoms. This article presents new results in HD research focusing on in vivo and in vitro model systems, potential molecular mechanisms of HD, and the development of therapeutic strategies.

In situ proteolytic digestion of inclusion body polypeptides occurs as a cascade process

Misfolded proteins undergo a preferent degradation ruled by the housekeeping bacterial proteolytic system, but upon precipitation as inclusion bodies their stability dramatically increases. The susceptibility of aggregated polypeptides to proteolytic attack remains essentially unexplored in bacteria and also in eukaryotic cells. We have studied here the in vitro proteolysis of beta-galactosidase fusion proteins by trypsin treatment of purified inclusion bodies. A cascade digestion process similar to that occurring in vivo has been observed in the insoluble fraction of the digestion reaction. This suggests that major protease target sites are not either lost or newly generated by protein precipitation and that the digestion occurs in situ probably on solvent-exposed surfaces of inclusion bodies. In addition, the sequence of the proteolytic attack is influenced by protein determinants other than amino acid sequence, the early digestion steps having a dramatic influence on the further cleavage susceptibility of the intermediate degradation fragments. These observations indicate unexpected conformational changes of inclusion body proteins during their site-limited digestion, that could promote protein release from aggregates, thus partially accounting for the plasticity of in vivo protein precipitation and solubilization in bacteria.

Mutation processes at the protein level: is Lamarck back?

The experimental evidence accumulated for the last half of the century clearly suggests that inherited variation is not restricted to the changes in genomic sequences. The prion model, originally based on unusual transmission of certain neurodegenerative diseases in mammals, provides a molecular mechanism for the template-like reproduction of alternative protein conformations. Recent data extend this model to protein-based genetic elements in yeast and other fungi. Reproduction and transmission of yeast protein-based genetic elements is controlled by the "prion replication" machinery of the cell, composed of the protein helpers responsible for the processes of assembly and disassembly of protein structures and multiprotein complexes. Among these, the stress-related chaperones of Hsp100 and Hsp70 groups play an important role. Alterations of levels or activity of these proteins result in "mutator" or "antimutator" affects in regard to protein-based genetic elements. "Protein mutagens" have also been identified that affect formation and/or propagation of the alternative protein conformations. Prion-forming abilities appear to be conserved in evolution, despite the divergence of the corresponding amino acid sequences. Moreover, a wide variety of proteins of different origins appear to possess the ability to form amyloid-like aggregates, that in certain conditions might potentially result in prion-like switches. This suggests a possible mechanism for the inheritance of acquired traits, postulated in the Lamarckian theory of evolution. The prion model also puts in doubt the notion that cloned animals are genetically identical to their genome donors, and suggests that genome sequence would not provide a complete information about the genetic makeup of an organism.

Protein aggregation as bacterial inclusion bodies is reversible

Inclusion bodies are refractile, intracellular protein aggregates usually observed in bacteria upon targeted gene overexpression. Since their occurrence has a major economical impact in protein production bio-processes, in vitro refolding strategies are under continuous exploration. In this work, we prove spontaneous in vivo release of both beta-galactosidase and P22 tailspike polypeptides from inclusion bodies resulting in their almost complete disintegration and in the concomitant appearance of soluble, properly folded native proteins with full biological activity. Since, in particular, the tailspike protein exhibits an unusually slow and complex folding pathway involving deep interdigitation of beta-sheet structures, its in vivo refolding indicates that bacterial inclusion body proteins are not collapsed into an irreversible unfolded state. Then, inclusion bodies can be observed as transient deposits of folding-prone polypeptides, resulting from an unbalanced equilibrium between in vivo protein precipitation and refolding that can be actively displaced by arresting protein synthesis. The observation that the formation of big inclusion bodies is reversible in vivo can be also relevant in the context of amyloid diseases, in which deposition of important amounts of aggregated protein initiates the pathogenic process.

Deranged expression of molecular chaperones in brains of patients with Alzheimer's disease

Alzheimer's disease (AD) is one of the disorders caused by protein conformational changes and recent studies have shown that several chaperone proteins are involved in this process. As information of chaperone expression in AD brain is limited, we aimed to study the expressional pattern of chaperones in several brain regions, as this may be essential to understand how folding defects can lead to disease. We studied the concomitant expressional patterns of molecular chaperones in seven brain regions of adults with AD using two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-associated laser desorption ionization mass spectroscopy (MALDI-MS). We unambiguously identified and quantified nine different chaperone proteins. Six chaperone proteins, heat shock protein 60 (HSP 60), HSP 70 RY, heat shock cognate (HSC) 71, alpha crystallin B chain, glucose regulated protein (GRP) 75, and GRP 94 showed aberrant expressional patterns depending on brain region. HSP 70.1, GRP 78 and T-complex 1 (TCP-1) epsilon subunit did not show any significant expressional change. These findings are compatible with neuropathological and biochemical abnormalities in AD brain and this report presents the first approach to quantify nine different chaperones simultaneously at the protein level in individual AD brain regions providing evidence for the relevance of aberrant chaperone expression to AD neuropathology.

Molecular genetics: unmasking polyglutamine triggers in neurodegenerative disease

Two decades ago, molecular genetic analysis provided a new approach for defining the roots of inherited disorders. This strategy has proved particularly powerful because, with only a description of the inheritance pattern, it can uncover previously unsuspected mechanisms of pathogenesis that are not implicated by known biological pathways or by the disease manifestations. Nowhere has the impact of molecular genetics been more evident than in the dominantly inherited neurodegenerative disorders, where eight unrelated diseases have been revealed to possess the same type of mutation--an expanded polyglutamine encoding sequence--affecting different genes.