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Biomedical subjects

Henry L Paulson

Publications and source records attributed to Henry L Paulson.

At least 19 recordsLinked to original sources
PubMed2025

Caregiver experiences after the death of a person with dementia with Lewy bodies: A mixed-methods analysis.

BackgroundDementia with Lewy bodies (DLB) is a common degenerative dementia, but no studies investigate bereaved caregiver experiences.ObjectiveTo investigate the experiences of caregivers three months after the death of persons with DLB using a mixed-methods approach.MethodsDyads of individuals with moderate-advanced DLB and their primary informal caregivers were followed prospectively every 6 months until the person with DLB died. Caregivers completed a study visit with questionnaires and a semi-structured interview ∼3 months later. Spearman correlation coefficients and Wilcoxon rank-sum tests evaluated the relationships of post-death measures with pre-death patient and caregiver variables. Thematic analysis was used to analyze the interviews.ResultsSeventy-three caregivers completed visits (mean 3.5 months post-death). Most of the caregivers were women (82.2%) and spouses (76.7%) or adult children (17.8%). Over 40% had scores indicating risk for clinical depression. Post-death caregiver experiences (depression, quality of life, grief, resilience) correlated with pre-death caregiver experiences. Post-death experiences did not associate with patient characteristics, disease-related symptoms, or healthcare services used in the last 6 months of life. Trajectories for caregiver measures from pre- to post-death visits varied widely. Interview themes included grief and sadness, anger, guilt and regret, relief, appreciation/gratitude, and adjusting to a new normal.ConclusionsThe finding that pre-death caregiving experiences have the strongest association with post-death experiences emphasizes the critical importance of accessible and evidence-based caregiver support before and after the death of a person with DLB. Research is needed to develop interventions for current and bereaved caregivers of individuals with DLB.Trial registration informationNCT04829656 (submitted 2021-03-22).

Caregivers↗
PubMed2006

A novel route for F-box protein-mediated ubiquitination links CHIP to glycoprotein quality control.

In SCF (Skp1/Cullin/F-box protein) ubiquitin ligases, substrate specificity is conferred by a diverse array of F-box proteins. Only in fully assembled SCF complexes, it is believed, can substrates bound to F-box proteins become ubiquitinated. Here we show that Fbx2, a brain-enriched F-box protein implicated in the ubiquitination of glycoproteins discarded from the endoplasmic reticulum, binds the co-chaperone/ubiquitin ligase CHIP (C terminus of Hsc-70-interacting protein) through a unique N-terminal PEST domain in Fbx2. CHIP facilitates the ubiquitination and degradation of Fbx2-bound glycoproteins, including unassembled NMDA receptor subunits. These findings indicate that CHIP acts with Fbx2 in a novel ubiquitination pathway that links CHIP to glycoprotein quality control in neurons. In addition, they expand the repertoire of pathways by which F-box proteins can regulate ubiquitination and suggest a new role for PEST domains as a protein interaction motif.

Amino Acid Sequence↗
PubMed2005

Silencing primary dystonia: lentiviral-mediated RNA interference therapy for DYT1 dystonia.

DYT1 is the most common inherited dystonia. Currently, there are no preventive or curative therapies for this dominantly inherited disease. DYT1 dystonia is caused by a common three-nucleotide deletion in the TOR1A gene that eliminates a glutamic acid residue from the protein torsinA. Recent studies suggest that torsinA carrying the disease-linked mutation, torsinA(DeltaE) acts through a dominant-negative effect by recruiting wild-type torsinA [torsinA(wt)] into oligomeric structures in the nuclear envelope. Therefore, suppressing torsinA(DeltaE) expression through RNA interference (RNAi) could restore the normal function of torsinA(wt), representing a potentially effective therapy regardless of the biological role of torsinA. Here, we have generated short hairpin RNAs (shRNAs) that mediate allele-specific suppression of torsinA(DeltaE) and rescue cells from its dominant-negative effect, restoring the normal distribution of torsinA(wt). In addition, delivery of this shRNA by a recombinant feline immunodeficiency virus effectively silenced torsinA(DeltaE) in a neural model of the disease. We further establish the feasibility of this viral-mediated RNAi approach by demonstrating significant suppression of endogenous torsinA in mammalian neurons. Finally, this silencing of torsinA is achieved without triggering an interferon response. These results support the potential use of viral-mediated RNAi as a therapy for DYT1 dystonia and establish the basis for preclinical testing in animal models of the disease.

Animals↗
PubMed2005

CHIP suppresses polyglutamine aggregation and toxicity in vitro and in vivo.

Huntington's disease (HD) and other polyglutamine (polyQ) neurodegenerative diseases are characterized by neuronal accumulation of the disease protein, suggesting that the cellular ability to handle abnormal proteins is compromised. As both a cochaperone and ubiquitin ligase, the C-terminal Hsp70 (heat shock protein 70)-interacting protein (CHIP) links the two major arms of protein quality control, molecular chaperones, and the ubiquitin-proteasome system. Here, we demonstrate that CHIP suppresses polyQ aggregation and toxicity in transfected cell lines, primary neurons, and a novel zebrafish model of disease. Suppression by CHIP requires its cochaperone function, suggesting that CHIP acts to facilitate the solubility of mutant polyQ proteins through its interactions with chaperones. Conversely, HD transgenic mice that are haploinsufficient for CHIP display a markedly accelerated disease phenotype. We conclude that CHIP is a critical mediator of the neuronal response to misfolded polyQ protein and represents a potential therapeutic target in this important class of neurodegenerative diseases.

Animals↗
PubMed2005

Brain structure in preclinical Huntington's disease.

BACKGROUND: Huntington's disease (HD) is traditionally conceptualized as a degenerative disease of the striatum. Recent scientific advances, however, have suggested neurodevelopmental contributions and extrastriatal brain abnormalities. This study was designed to assess the morphology of the brain in participants who had previously undergone elective DNA analyses for the HD mutation who did not currently have a clinical diagnosis of HD (preclinical HD subjects). METHODS: Twenty-four preclinical participants with the gene expansion for HD underwent brain magnetic resonance imaging and were compared with a group of 24 healthy control subjects, matched by gender and age. RESULTS: Huntington's disease preclinical participants had substantial morphologic differences from controls throughout the cerebrum. Volume of the cerebral cortex was significantly increased in preclinical HD, whereas the basal ganglia and cerebral white matter volume were substantially decreased. CONCLUSIONS: In individuals with the HD gene mutation who are considered healthy (preclinical for manifest disease), the morphology of the brain is substantially altered compared with matched control subjects. Although decreased volumes of the striatum and cerebral white matter could represent early degenerative changes, the novel finding of enlarged cortex suggests that developmental pathology occurs in HD.

Adult↗
PubMed2005

Defining the role of ubiquitin-interacting motifs in the polyglutamine disease protein, ataxin-3.

Polyglutamine (polyQ) expansions cause neurodegeneration that is associated with protein misfolding and influenced by functional properties of the host protein. The polyQ disease protein, ataxin-3, has predicted ubiquitin-specific protease and ubiquitin-binding domains, which suggest that ataxin-3 functions in ubiquitin-dependent protein surveillance. Here we investigate direct links between the ubiquitin-proteasome pathway and ataxin-3. In neural cells we show that, through its ubiquitin interaction motifs (UIMs), normal or expanded ataxin-3 binds a broad range of ubiquitinated proteins that accumulate when the proteasome is inhibited. The expression of a catalytically inactive ataxin-3 (normal or expanded) causes ubiquitinated proteins to accumulate in cells, even in the absence of proteasome inhibitor. This accumulation of ubiquitinated proteins occurs primarily in the cell nucleus in transfected cells and requires intact UIMs in ataxin-3. We further show that both normal and expanded ataxin-3 can undergo oligoubiquitination. Although this post-translational modification occurs in a UIM-dependent manner, it becomes independent of UIMs when the catalytic cysteine residue of ataxin-3 is mutated, suggesting that ataxin-3 ubiquitination is itself regulated in trans by its own de-ubiquitinating activity. Finally, pulse-chase labeling reveals that ataxin-3 is degraded by the proteasome, with expanded ataxin-3 being as efficiently degraded as normal ataxin-3. Mutating the UIMs does not alter degradation, suggesting that UIM-mediated oligoubiquitination of ataxin-3 modulates ataxin-3 function rather than stability. The function of ataxin-3 as a de-ubiquitinating enzyme, its post-translational modification by ubiquitin, and its degradation via the proteasome link this polyQ protein to ubiquitin-dependent pathways already implicated in disease pathogenesis.

Amino Acid Motifs↗
PubMed2005

Breaks in coordination: DNA repair in inherited ataxia.

Genetic defects in DNA repair are increasingly recognized as being able to cause degenerative ataxia syndromes. It remains a mystery, however, why disruption of a process fundamental to proliferating cells can be selectively toxic to postmitotic neurons. Recent studies now reveal that an ataxia gene, tyrosyl phosphodiesterase 1 (TDP1), repairs single-stranded DNA breaks in nondividing cells. Here we review the implications of this and other findings for a growing list of hereditary ataxias.

Animals↗
PubMed2005

RNA interference improves motor and neuropathological abnormalities in a Huntington's disease mouse model.

Huntington's disease (HD) is a fatal, dominant neurogenetic disorder. HD results from polyglutamine repeat expansion (CAG codon, Q) in exon 1 of HD, conferring a toxic gain of function on the protein huntingtin (htt). Currently, no preventative treatment exists for HD. RNA interference (RNAi) has emerged as a potential therapeutic tool for treating dominant diseases by directly reducing disease gene expression. Here, we show that RNAi directed against mutant human htt reduced htt mRNA and protein expression in cell culture and in HD mouse brain. Importantly, htt gene silencing improved behavioral and neuropathological abnormalities associated with HD. Our data provide support for the further development of RNAi for HD therapy.

Animals↗
PubMed2005

Ataxin-3 suppresses polyglutamine neurodegeneration in Drosophila by a ubiquitin-associated mechanism.

Two central issues in polyglutamine-induced neurodegeneration are the influence of the normal function of the disease protein and modulation by protein quality control pathways. By using Drosophila, we now directly link host protein function and disease pathogenesis to ubiquitin pathways in the polyglutamine disease spinocerebellar ataxia type 3 (SCA3). Normal human ataxin-3--a polyubiquitin binding protein with ubiquitin protease activity--is a striking suppressor of polyglutamine neurodegeneration in vivo. This suppressor activity requires ubiquitin-associated activities of the protein and is dependent upon proteasome function. Our results highlight the critical importance of host protein function in SCA3 disease and a potential therapeutic role of ataxin-3 activity for polyglutamine disorders.

Animals↗
PubMed2005

RNA interference in neuroscience: progress and challenges.

1.RNA interference (RNAi) is a recently discovered biological pathway that mediates post-transcriptional gene silencing. The process of RNAi is orchestrated by an increasingly well-understood cellular machinery. 2. The common entry point for both natural and engineered RNAi are double stranded RNA molecules known as short interfering RNAs (siRNAs), that mediate the sequence-specific identification and degradation of the targeted messenger RNA (mRNA). The study and manipulation of these siRNAs has recently revolutionized biomedical research. 3. In this review, we first provide a brief overview of the process of RNAi, focusing on its potential role in brain function and involvement in neurological disease. We then describe the methods developed to manipulate RNAi in the laboratory and its applications to neuroscience. Finally, we focus on the potential therapeutic application of RNAi to neurological disease.

Animals↗
PubMed2004

RNAi suppresses polyglutamine-induced neurodegeneration in a model of spinocerebellar ataxia.

The dominant polyglutamine expansion diseases, which include spinocerebellar ataxia type 1 (SCA1) and Huntington disease, are progressive, untreatable, neurodegenerative disorders. In inducible mouse models of SCA1 and Huntington disease, repression of mutant allele expression improves disease phenotypes. Thus, therapies designed to inhibit expression of the mutant gene would be beneficial. Here we evaluate the ability of RNA interference (RNAi) to inhibit polyglutamine-induced neurodegeneration caused by mutant ataxin-1 in a mouse model of SCA1. Upon intracerebellar injection, recombinant adeno-associated virus (AAV) vectors expressing short hairpin RNAs profoundly improved motor coordination, restored cerebellar morphology and resolved characteristic ataxin-1 inclusions in Purkinje cells of SCA1 mice. Our data demonstrate in vivo the potential use of RNAi as therapy for dominant neurodegenerative disease.

Adenoviridae↗
PubMed2004

Aberrant cellular behavior of mutant torsinA implicates nuclear envelope dysfunction in DYT1 dystonia.

Torsion dystonia-1 (DYT1) dystonia, the most common inherited form of dystonia, is caused by a three base pair deletion that eliminates a single amino acid from the disease protein, torsinA. TorsinA is an "AAA" protein thought to reside in the endoplasmic reticulum (ER), yet both its cellular function and the basis for neuronal dysfunction in DYT1 remain unknown. A clue to disease pathogenesis is the fact that mutant, but not wild-type, torsinA forms membranous inclusions in cell culture. To explore the pathobiology of DYT1 dystonia, we generated PC12 neural cell lines that inducibly express wild-type or mutant torsinA. Although in this model torsinA displays some properties consistent with ER localization, mutant torsinA also accumulates in the nuclear envelope (NE), a structure contiguous with cytoplasmic ER. Consistent with this, membranous inclusions formed by mutant torsinA are shown to derive not from the ER, as thought previously, but from the NE. We demonstrate further that torsinA forms different disulfide-linked complexes that may be linked functionally to subcellular localization in the NE versus cytoplasmic ER. Despite mutant TA accumulation in NE structures, nucleocytoplasmic transport of a reporter protein was unaffected. These findings, together with parallel studies failing to demonstrate perturbation of ER function, implicate the NE as a primary site of dysfunction in DYT1. DYT1 dystonia can be added to the growing list of inherited neurological disorders involving the NE.

Active Transport, Cell Nucleus↗
PubMed2004

Targeting Alzheimer's disease genes with RNA interference: an efficient strategy for silencing mutant alleles.

Tau and amyloid precursor protein (APP) are key proteins in the pathogenesis of sporadic and inherited Alzheimer's disease. Thus, developing ways to inhibit production of these proteins is of great research and therapeutic interest. The selective silencing of mutant alleles, moreover, represents an attractive strategy for treating inherited dementias and other dominantly inherited disorders. Here, using tau and APP as model targets, we describe an efficient method for producing small interfering RNA (siRNA) against essentially any targeted region of a gene. We then use this approach to develop siRNAs that display optimal allele-specific silencing against a well-characterized tau mutation (V337M) and the most widely studied APP mutation (APPsw). The allele-specific RNA duplexes identified by this method then served as templates for constructing short hairpin RNA (shRNA) plasmids that successfully silenced mutant tau or APP alleles. These plasmids should prove useful in experimental and therapeutic studies of Alzheimer's disease. Our results suggest guiding principles for the production of allele-specific siRNA, and the general method described here should facilitate the production of gene-specific siRNAs.

Alleles↗
PubMed2004

Destabilization of a non-pathological variant of ataxin-3 results in fibrillogenesis via a partially folded intermediate: a model for misfolding in polyglutamine disease.

Ataxin-3 is a member of the polyglutamine family of proteins, which are associated with at least nine different neurodegenerative diseases. In the disease state, expansion of the polyglutamine tract leads to dysfunction and death of neurons, as well as formation of proteinaceous aggregates known as nuclear inclusions. Intriguingly, both expanded and non-expanded forms of ataxin-3 are observed within these nuclear inclusions. Ataxin-3 is the smallest of the polyglutamine disease proteins and in its expanded form causes the neurodegenerative disorder Machado-Joseph disease. Using a non-pathological variant containing 28 residues in its polyglutamine tract, we have probed the folding and misfolding pathways of ataxin-3. We describe here the first equilibrium folding pathway delineated for any polyglutamine protein and show that ataxin-3 folds reversibly via a single intermediate species. We have also explored further the misfolding potential of the protein and found that partial destabilization of ataxin-3 by chemical denaturation leads to the formation of fibrillar aggregates by the non-pathological variant. These results provide an insight into the possible mechanisms by which polyglutamine expansion may affect the stability and conformation of the protein. The implications of this are considered in the wider context of the development and pathogenesis of polyglutamine diseases.

Ataxin-3↗
PubMed2004

Molecular medicine for the brain: silencing of disease genes with RNA interference.

The recent discovery of RNA interference (RNAi) has revolutionised biological research and now holds promise as a potential therapy for human diseases. Currently untreatable neurological diseases are especially attractive targets. Scientists have already succeeded in using RNAi to suppress dominant disease genes in vitro; in some cases, this suppression has been allele-specific, silencing the disease-causing allele while maintaining expression of the normal allele. The challenge now is to bring this powerful technology in vivo to animal models to suppress disease genes and correct disease phenotypes. In the confrontation of this challenge, research should benefit from recent advances in viral and non-viral delivery of therapy to the brain.

Animals↗
PubMed2004

Caspase-mediated proteolysis of the polyglutamine disease protein ataxin-3.

Spinocerebellar ataxia type-3, also known as Machado-Joseph Disease, is one of many inherited neurodegenerative disorders caused by polyglutamine-encoding CAG repeat expansions in otherwise unrelated disease genes. Polyglutamine disorders are characterized by disease protein misfolding and aggregation; often within the nuclei of affected neurons. Although the precise mechanism of polyglutamine-mediated cell death remains elusive, evidence suggests that proteolysis of polyglutamine disease proteins by caspases contributes to pathogenesis. Using cellular models we now show that the endogenous spinocerebellar ataxia type-3 disease protein, ataxin-3, is proteolyzed in apoptotic paradigms, resulting in the loss of full-length ataxin-3 and the corresponding appearance of an approximately 28-kDa fragment containing the glutamine repeat. Broad-spectrum caspase inhibitors block ataxin-3 proteolysis and studies suggest that caspase-1 is a primary mediator of cleavage. Site-directed mutagenesis experiments eliminating three, six or nine potential caspase cleavage sites in the protein suggest redundancy in the site(s) at which cleavage can occur, as previously described for other disease proteins; but also map a major cleavage event to a cluster of aspartate residues within the ubiquitin-binding domain of ataxin-3 near the polyglutamine tract. Finally, caspase-mediated cleavage of expanded ataxin-3 resulted in increased ataxin-3 aggregation, suggesting a potential role for caspase-mediated proteolysis in spinocerebellar ataxia type-3 pathogenesis.

Adult↗
PubMed2003

Poly-ubiquitin binding by the polyglutamine disease protein ataxin-3 links its normal function to protein surveillance pathways.

In at least nine inherited diseases polyglutamine expansions cause neurodegeneration associated with protein misfolding and the formation of ubiquitin-conjugated aggregates. Although expanded polyglutamine triggers disease, functional properties of host polyglutamine proteins also must influence pathogenesis. Using complementary in vitro and cell-based approaches we establish that the polyglutamine disease protein, ataxin-3, is a poly-ubiquitin-binding protein. In stably transfected neural cell lines, normal and expanded ataxin-3 both co-precipitate with poly-ubiquitinated proteins that accumulate when the proteasome is inhibited. In vitro pull-down assays show that this reflects direct interactions between ataxin-3 and higher order ubiquitin conjugates; ataxin-3 binds K48-linked tetraubiquitin but not di-ubiquitin or mono-ubiquitin. Further studies with domain-deleted and site-directed mutants map tetra-ubiquitin binding to ubiquitin interaction motifs situated near the polyglutamine domain. In surface plasmon resonance binding analyses, normal and expanded ataxin-3 display similar submicromolar dissociation constants for tetra-ubiquitin. Binding kinetics, however, are markedly influenced by the surrounding protein context; ataxin-3 that lacks the highly conserved, amino-terminal josephin domain shows significantly faster association and dissociation rates for tetra-ubiquitin binding. Our results establish ataxin-3 as a poly-ubiquitin-binding protein, thereby linking its normal function to protein surveillance pathways already implicated in polyglutamine pathogenesis.

Amino Acid Motifs↗