Valosin Containing Protein Disease Research Articles

Valosin-Containing Protein (VCP): A Review of Its Diverse Molecular Functions and Clinical Phenotypes.

In this review we examine the functionally diverse ATPase associated with various cellular activities (AAA-ATPase), valosin-containing protein (VCP/p97), its molecular functions, the mutational landscape of VCP and the phenotypic manifestation of VCP disease. VCP is crucial to a multitude of cellular functions including protein quality control, endoplasmic reticulum-associated degradation (ERAD), autophagy, mitophagy, lysophagy, stress granule formation and clearance, DNA replication and mitosis, DNA damage response including nucleotide excision repair, ATM- and ATR-mediated damage response, homologous repair and non-homologous end joining. VCP variants cause multisystem proteinopathy, and pathology can arise in several tissue types such as skeletal muscle, bone, brain, motor neurons, sensory neurons and possibly cardiac muscle, with the disease course being challenging to predict.

Remote respiratory resistance exercise training improves respiratory function in individuals with VCP multisystem proteinopathy

Valosin-containing protein (VCP) disease is an autosomal dominant multisystem proteinopathy associated with hereditary inclusion body myopathy, Paget disease of bone, and frontotemporal dementia. Myopathy frequently results in respiratory muscle weakness, leading to early mortality due to respiratory failure. We investigated the effects of a remotely administered inspiratory muscle training program in individuals with VCP disease. Nine adults with VCP mutation-positive familial myopathy without evidence of dementia were recruited for a 40-week remotely administered study. Baseline performance was established during the first 8 weeks, followed by 32 weeks of inspiratory muscle training. The primary outcome was maximum inspiratory pressure (MIP). The secondary and exploratory endpoints included spirometry, grip strength, Inclusion Body Myopathy Functional Rating Scale (IBMFRS), Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS), timed up and go, and six-minute walk test (6MWT). During the treatment phase, MIP increased significantly by a weekly mean of 0.392cm. H2O (p=0.023). In contrast, grip strength and ALSFRS significantly decreased by 0.088 lbs. (p=0.031) and 0.043 points (p=0.004) per week, respectively, as expected from the natural progression of this disease. A remotely administered inspiratory muscle training program is therefore feasible, safe, and well-tolerated in individuals with VCP disease and results in improved inspiratory muscle strength.

Provisional practice recommendation for the management of myopathy in VCP-associated multisystem proteinopathy.

Valosin-containing protein (VCP)-associated multisystem proteinopathy (MSP) is a rare genetic disorder with abnormalities in the autophagy pathway leading to various combinations of myopathy, bone diseases, and neurodegeneration. Ninety percent of patients with VCP-associated MSP have myopathy, but there is no consensus-based guideline. The goal of this working group was to develop a best practice set of provisional recommendations for VCP myopathy which can be easily implemented across the globe. As an initiative by Cure VCP Disease Inc., a patient advocacy organization, an online survey was initially conducted to identify the practice gaps in VCP myopathy. All prior published literature on VCP myopathy was reviewed to better understand the different aspects of management of VCP myopathy, and several working group sessions were conducted involving international experts to develop this provisional recommendation. VCP myopathy has a heterogeneous clinical phenotype and should be considered in patients with limb-girdle muscular dystrophy phenotype, or any myopathy with an autosomal dominant pattern of inheritance. Genetic testing is the only definitive way to diagnose VCP myopathy, and single-variant testing in the case of a known familial VCP variant, or multi-gene panel sequencing in undifferentiated cases can be considered. Muscle biopsy is important in cases of diagnostic uncertainty or lack of a definitive pathogenic genetic variant since rimmed vacuoles (present in ~40% cases) are considered a hallmark of VCP myopathy. Electrodiagnostic studies and magnetic resonance imaging can also help rule out disease mimics. Standardized management of VCP myopathy will optimize patient care and help future research initiatives.

Prevalence of Frontotemporal Dementia in Females of 5 Hispanic Families With R159H VCP Multisystem Proteinopathy.

Missense variants of the valosin-containing protein (VCP) gene cause a progressive, autosomal dominant disease termed VCP multisystem proteinopathy (MSP1). The disease is a constellation of clinical features including inclusion body myopathy (IBM), Paget disease of bone (PDB), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS), typically reported at a frequency of 90%, 42%, 30%, and 9%, respectively. The Hispanic population is currently underrepresented in previous reports of VCP myopathy. We expand our genotype-phenotype studies in 5 Hispanic families with the c.476G>A, p.R159H VCP variant. We report detailed clinical findings of 11 patients in 5 Hispanic families with the c.476G > A, p.R159H VCP variant. In addition, we report frequencies of the main manifestations in 28 additional affected members of the extended family members. We also compared our findings with an existing larger cohort of patients with VCP MSP1. FTD was the most prevalent feature reported, particularly frequent in females. PDB was only seen in 1 patient in contrast to the earlier reported cohorts. The overall frequency of the different manifestations: myopathy, PDB, FTD, and ALS in these 5 families was 39%, 3%, 72%, and 8%, respectively. The atypical phenotype and later onset of manifestations in these families resulted in a noticeable delay in the diagnosis of VCP disease. Studying each VCP variant in the context of ethnic backgrounds is pivotal in increasing awareness of the variability of VCP-related diseases across different ethnicities, enabling early diagnosis, and understanding the mechanism for these genotype-phenotype variations.

Genotype–phenotype correlations in valosin-containing protein disease: a retrospective muticentre study

BackgroundValosin-containing protein (VCP) disease, caused by mutations in the VCP gene, results in myopathy, Paget’s disease of bone (PBD) and frontotemporal dementia (FTD). Natural history and genotype–phenotype correlation data are...

VCP suppresses proteopathic seeding in neurons

BackgroundNeuronal uptake and subsequent spread of proteopathic seeds, such as αS (alpha-synuclein), Tau, and TDP-43, contribute to neurodegeneration. The cellular machinery participating in this process is poorly understood. One proteinopathy called multisystem proteinopathy (MSP) is associated with dominant mutations in Valosin Containing Protein (VCP). MSP patients have muscle and neuronal degeneration characterized by aggregate pathology that can include αS, Tau and TDP-43.MethodsWe performed a fluorescent cell sorting based genome-wide CRISPR-Cas9 screen in αS biosensors. αS and TDP-43 seeding activity under varied conditions was assessed using FRET/Flow biosensor cells or immunofluorescence for phosphorylated αS or TDP-43 in primary cultured neurons. We analyzed in vivo seeding activity by immunostaining for phosphorylated αS following intrastriatal injection of αS seeds in control or VCP disease mutation carrying mice.ResultsOne hundred fifty-four genes were identified as suppressors of αS seeding. One suppressor, VCP when chemically or genetically inhibited increased αS seeding in cells and neurons. This was not due to an increase in αS uptake or αS protein levels. MSP-VCP mutation expression increased αS seeding in cells and neurons. Intrastriatal injection of αS preformed fibrils (PFF) into VCP-MSP mutation carrying mice increased phospho αS expression as compared to control mice. Cells stably expressing fluorescently tagged TDP-43 C-terminal fragment FRET pairs (TDP-43 biosensors) generate FRET when seeded with TDP-43 PFF but not monomeric TDP-43. VCP inhibition or MSP-VCP mutant expression increases TDP-43 seeding in TDP-43 biosensors. Similarly, treatment of neurons with TDP-43 PFFs generates high molecular weight insoluble phosphorylated TDP-43 after 5 days. This TDP-43 seed dependent increase in phosphorlyated TDP-43 is further augmented in MSP-VCP mutant expressing neurons.ConclusionUsing an unbiased screen, we identified the multifunctional AAA ATPase VCP as a suppressor of αS and TDP-43 aggregate seeding in cells and neurons. VCP facilitates the clearance of damaged lysosomes via lysophagy. We propose that VCP’s surveillance of permeabilized endosomes may protect against the proteopathic spread of pathogenic protein aggregates. The spread of distinct aggregate species may dictate the pleiotropic phenotypes and pathologies in VCP associated MSP.

VCP/p97 inhibitor CB-5083 modulates muscle pathology in a mouse model of VCP inclusion body myopathy

BackgroundPathogenic gain of function variants in Valosin-containing protein (VCP) cause a unique disease characterized by inclusion body myopathy with early-onset Paget disease of bone and frontotemporal dementia (also known as Multisystem proteinopathy (MSP)). Previous studies in drosophila models of VCP disease indicate treatment with VCP inhibitors mitigates disease pathology. Earlier-generation VCP inhibitors display off-target effects and relatively low therapeutic potency. New generation of VCP inhibitors needs to be evaluated in a mouse model of VCP disease. In this study, we tested the safety and efficacy of a novel and potent VCP inhibitor, CB-5083 using VCP patient-derived myoblast cells and an animal model of VCP disease.MethodsFirst, we analyzed the effect of CB-5083 in patient-derived myoblasts on the typical disease autophagy and TDP-43 profile by Western blot. Next, we determined the maximum tolerated dosage of CB-5083 in mice and treated the 2-month-old VCPR155H/R155H mice for 5 months with 15 mg/kg CB-5083. We analyzed motor function monthly by Rotarod; and we assessed the end-point blood toxicology, and the muscle and brain pathology, including autophagy and TDP-43 profile, using Western blot and immunohistochemistry. We also treated 12-month-old VCPR155H/+ mice for 6 months and performed similar analysis. Finally, we assessed the potential side effects of CB-5083 on retinal function, using electroretinography in chronically treated VCPR155H/155H mice.ResultsIn vitro analyses using patient-derived myoblasts confirmed that CB-5083 can modulate expression of the proteins in the autophagy pathways. We found that chronic CB-5083 treatment is well tolerated in the homozygous mice harboring patient-specific VCP variant, R155H, and can ameliorate the muscle pathology characteristic of the disease. VCP-associated pathology biomarkers, such as elevated TDP-43 and p62 levels, were significantly reduced. Finally, to address the potential adverse effect of CB-5083 on visual function observed in a previous oncology clinical trial, we analyzed retinal function in mice treated with moderate doses of CB-5083 for 5 months and documented the absence of permanent ocular toxicity.ConclusionsAltogether, these findings suggest that long-term use of CB-5083 by moderate doses is safe and can improve VCP disease-associated muscle pathology. Our results provide translationally relevant evidence that VCP inhibitors could be beneficial in the treatment of VCP disease.

REGISTRIES AND CARE OF NMD: EP.347 Development of a standard of care for patients with valosin-containing protein associated multisystem proteinopathy

Valosin-containing protein (VCP) associated multisystem proteinopathy (MSP) is a rare inherited disorder with a reported incidence of 0.66/100,000 based on population data from the UK. VCP-associated MSP may result in multisystem involvement of varying presentations and phenotypes including inclusion body myopathy, Paget's disease of bone, frontotemporal dementia, parkinsonism, and amyotrophic lateral sclerosis, among others. An international multidisciplinary consortium of 50+ experts in neuromuscular disease, dementia, psychology, cardiology, pulmonology, physical therapy, occupational therapy, speech and language pathology, nutrition, genetics, and endocrinology were convened by the patient advocacy organization, Cure VCP Disease, in 2021 to elicit collaboration and development of a standard of care for this rare and under-diagnosed disease. To achieve this goal, working groups were established to generate best evidence recommendations in 10 key areas: genetics and diagnosis, myopathy, frontotemporal dementia, Paget's disease of bone, ALS and CMT, parkinsonism, cardiomyopathy, supportive therapies, pulmonology, nutrition and supplements, and mental health. In April 2021, facilitated discussion of each working group's conclusion with consensus building techniques enabled final agreement on the recommended standard of care for patients with VCP-associated MSP. Timely referral to a specialty neuromuscular center is recommended to aid in efficient diagnosis of VCP-associated MSP via single-gene testing in the case of a known familial VCP variant, or multi-gene panel sequencing in undifferentiated cases. Additionally, regular and ongoing multidisciplinary team follow up is essential for proactive screening and management of the secondary complications. The goal of our consortium is to raise awareness of VCP-associated MSP, to expedite the time to accurate diagnosis and elevate the recommended best practices guidelines for multidisciplinary care internationally.

Neuronal VCP loss of function recapitulates FTLD-TDP pathology.

SUMMARYThe pathogenic mechanism by which dominant mutations in VCP cause multisystem proteinopathy (MSP), a rare neurodegenerative disease that presents as fronto-temporal lobar degeneration with TDP-43 inclusions (FTLD-TDP), remains unclear. To explore this, we inactivate VCP in murine postnatal forebrain neurons (VCP conditional knockout [cKO]). VCP cKO mice have cortical brain atrophy, neuronal loss, autophago-lysosomal dysfunction, and TDP-43 inclusions resembling FTLD-TDP pathology. Conditional expression of a single disease-associated mutation, VCP-R155C, in a VCP null background similarly recapitulates features of VCP inactivation and FTLD-TDP, suggesting that this MSP mutation is hypomorphic. Comparison of transcriptomic and proteomic datasets from genetically defined patients with FTLD-TDP reveal that progranulin deficiency and VCP insufficiency result in similar profiles. These data identify a loss of VCP-dependent functions as a mediator of FTLD-TDP and reveal an unexpected biochemical similarity with progranulin deficiency.

CRISPR/Cas9-engineered Drosophila knock-in models to study VCP diseases.

ABSTRACTMutations in Valosin Containing Protein (VCP) are associated with several degenerative diseases, including multisystem proteinopathy (MSP-1) and amyotrophic lateral sclerosis. However, patients with VCP mutations vary widely in their pathology and clinical penetrance, making it difficult to devise effective treatment strategies. A deeper understanding of how each mutation affects VCP function could enhance the prediction of clinical outcomes and design of personalized treatment options. The power of a genetically tractable model organism coupled with well-established in vivo assays and a relatively short life cycle make Drosophila an attractive system to study VCP disease pathogenesis. Using CRISPR/Cas9, we have generated individual Drosophila knock-in mutants that include nine hereditary VCP disease mutations. Our models display many hallmarks of VCP-mediated degeneration, including progressive decline in mobility, protein aggregate accumulation and defects in lysosomal and mitochondrial function. We also made some novel and unexpected findings, including nuclear morphology defects and sex-specific phenotypic differences in several mutants. Taken together, the Drosophila VCP disease models generated in this study will be useful for studying the etiology of individual VCP patient mutations and testing potential genetic and/or pharmacological therapies.

A p97/Valosin-Containing Protein Inhibitor Drug CB-5083 Has a Potent but Reversible Off-Target Effect on Phosphodiesterase-6.

CB-5083 is an inhibitor of p97/valosin-containing protein (VCP), for which phase I trials for cancer were terminated because of adverse effects on vision, such as photophobia and dyschromatopsia. Lower dose CB-5083 could combat inclusion body myopathy with early-onset Paget disease and frontotemporal dementia or multisystem proteinopathy caused by gain-of-function mutations in VCP. We hypothesized that the visual impairment in the cancer trial was due to CB-5083's inhibition of phosphodiesterase (PDE)-6, which mediates signal transduction in photoreceptors. To test our hypothesis, we used in vivo and ex vivo electroretinography (ERG) in mice and a PDE6 activity assay of bovine rod outer segment (ROS) extracts. Additionally, histology and optical coherence tomography were used to assess CB-5083's long-term ocular toxicity. A single administration of CB-5083 led to robust ERG signal deterioration, specifically in photoresponse kinetics. Similar recordings with known PDE inhibitors sildenafil, tadalafil, vardenafil, and zaprinast showed that only vardenafil had as strong an effect on the ERG signal in vivo as did CB-5083. In the biochemical assay, CB-5083 inhibited PDE6 activity with a potency higher than sildenafil but lower than that of vardenafil. Ex vivo ERG revealed a PDE6 inhibition constant of 80 nM for CB-5083, which is 7-fold smaller than that for sildenafil. Finally, we showed that the inhibitory effect of CB-5083 on visual function is reversible, and its chronic administration does not cause permanent retinal anomalies in aged VCP-disease model mice. Our results warrant re-evaluation of CB-5083 as a clinical therapeutic agent. We recommend preclinical ERG recordings as a routine drug safety screen. SIGNIFICANCE STATEMENT: This report supports the use of a valosin-containing protein (VCP) inhibitor drug, CB-5083, for the treatment of neuromuscular VCP disease despite CB-5083's initial clinical failure for cancer treatment due to side effects on vision. The data show that CB-5083 displays a dose-dependent but reversible inhibitory action on phosphodiesterase-6, an essential enzyme in retinal photoreceptor function, but no long-term consequences on retinal function or structure.

SVIP is a molecular determinant of lysosomal dynamic stability, neurodegeneration and lifespan

Missense mutations in Valosin-Containing Protein (VCP) are linked to diverse degenerative diseases including IBMPFD, amyotrophic lateral sclerosis (ALS), muscular dystrophy and Parkinson’s disease. Here, we characterize a VCP-binding co-factor (SVIP) that specifically recruits VCP to lysosomes. SVIP is essential for lysosomal dynamic stability and autophagosomal–lysosomal fusion. SVIP mutations cause muscle wasting and neuromuscular degeneration while muscle-specific SVIP over-expression increases lysosomal abundance and is sufficient to extend lifespan in a context, stress-dependent manner. We also establish multiple links between SVIP and VCP-dependent disease in our Drosophila model system. A biochemical screen identifies a disease-causing VCP mutation that prevents SVIP binding. Conversely, over-expression of an SVIP mutation that prevents VCP binding is deleterious. Finally, we identify a human SVIP mutation and confirm the pathogenicity of this mutation in our Drosophila model. We propose a model for VCP disease based on the differential, co-factor-dependent recruitment of VCP to intracellular organelles.

Ceramide contributes to pathogenesis and may be targeted for therapy in VCP inclusion body myopathy.

Knock-in homozygote VCPR155H/R155H mutant mice are a lethal model of valosin-containing protein (VCP)-associated inclusion body myopathy associated with Paget disease of bone, frontotemporal dementia and amyotrophic lateral sclerosis. Ceramide (d18:1/16:0) levels are elevated in skeletal muscle of the mutant mice, compared to wild-type controls. Moreover, exposure to a lipid-enriched diet reverses lethality, improves myopathy and normalizes ceramide levels in these mutant mice, suggesting that dysfunctions in lipid-derived signaling are critical to disease pathogenesis. Here, we investigated the potential role of ceramide in VCP disease using pharmacological agents that manipulate the ceramide levels in myoblast cultures from VCP mutant mice and VCP patients. Myoblasts from wild-type, VCPR155H/+ and VCPR155H/R155H mice, as well as patient-induced pluripotent stem cells (iPSCs), were treated with an inhibitor of ceramide degradation to increase ceramide via acid ceramidase (ARN082) for proof of principle. Three chemically distinct inhibitors of ceramide biosynthesis via serine palmitoyl-CoA transferase (L-cycloserine, myriocin or ARN14494) were used as a therapeutic strategy to reduce ceramide in myoblasts. Acid ceramidase inhibitor, ARN082, elevated cellular ceramide levels and concomitantly enhanced pathology. Conversely, inhibitors of ceramide biosynthesis L-cycloserine, myriocin and ARN14494 reduced ceramide production. The results point to ceramide-mediated signaling as a key contributor to pathogenesis in VCP disease and suggest that manipulating this pathway by blocking ceramide biosynthesis might exert beneficial effects in patients with this condition. The ceramide pathway appears to be critical in VCP pathogenesis, and small-molecule inhibitors of ceramide biosynthesis might provide therapeutic benefits in VCP and related neurodegenerative diseases.

Phenotypic diversity in an international Cure VCP Disease registry

BackgroundDominant mutations in valosin-containing protein (VCP) gene cause an adult onset inclusion body myopathy, Paget’s disease of bone, and frontotemporal dementia also termed multisystem proteinopathy (MSP). The genotype-phenotype relationships in VCP-related MSP are still being defined; in order to understand this better, we investigated the phenotypic diversity and patterns of weakness in the Cure VCP Disease Patient Registry.MethodsCure VCP Disease, Inc. was founded in 2018 for the purpose of connecting patients with VCP gene mutations and researchers to help advance treatments and cures. Cure VCP Disease Patient Registry is maintained by Coordination of Rare Diseases at Sanford. The results of two questionnaires with a 5-point Likert scale questions regarding to patients’ disease onset, symptoms, and daily life were obtained from 59 participants (28 males and 31 females) between June 2018 and May 2020. Independent of the registry, 22 patients were examined at the Cure VCP Disease annual patient conference in 2019.ResultsIn the questionnaires of the registry, fifty-three patients (90%) reported that they were with inclusion body myopathy, 17 patients (29%) with Paget’s disease of bone, eight patients (14%) with dementia, two patients (3%) with amyotrophic lateral sclerosis, and a patient with parkinsonism. Thirteen patients (22%) reported dysphagia and 25 patients (42%) reported dyspnea on exertion. A self-reported functional rating scale for motor function identified challenges with sit to stand (72%), walking (67%), and climbing stairs (85%). Thirty-five (59%) patients in the registry answered that their quality of life is more than good. As for the weakness pattern of the 22 patients who were evaluated at the Cure VCP Disease annual conference, 50% of patients had facial weakness, 55% had scapular winging, 68% had upper proximal weakness, 41% had upper distal weakness, 77% had lower proximal, and 64% had lower distal weakness.ConclusionsThe Cure VCP Disease Patient Registry is useful for deepening the understanding of patient daily life, which would be a basis to develop appropriate clinical outcome measures. The registry data is consistent with previous studies evaluating VCP patients in the clinical setting. Patient advocacy groups are essential in developing and maintaining disease registries.

A cross-sectional analysis of clinical evaluation in 35 individuals with mutations of the valosin-containing protein gene

Inclusion body myopathy (IBM) associated with Paget disease of the bone and frontotemporal dementia or IBMPFD is an autosomal dominant degenerative disorder caused by mutations in the valosin-containing protein (VCP) gene. We aim to establish a detailed clinical phenotype of VCP disease amongst 35 (28 affected individuals, 7 presymptomatic gene carriers) individuals versus 14 unaffected first-degree relatives in 14 families to establish useful biomarkers for IBMPFD and identify the most meaningful tests for monitoring disease progression in future clinical trials. Comprehensive studies included the Inclusion Body Myositis Functional Rating Scale (IBMFRS) and fatigue severity scale questionairres, strength measurements using the Manual Muscle Test with Medical Research Council (MRC) scales, hand-held dynamometry using the microFET and Biodex dynamometers, 6 minute walk test (6MWT), and pulmonary function studies. Strong correlation was observed between the IBMFRS and measurements of muscle strength with dynamometry and the other functional tests, indicating that it may be utilized in long-term follow-up assessments due to its relative simplicity. This cross-section study represents the most comprehensive evaluation of individuals with VCP disease to date and provides a useful guide for evaluating and possible monitoring of muscle weakness and pulmonary function progression in this unique cohort of individuals.

Genotype‐phenotype study in patients with valosin‐containing protein mutations associated with multisystem proteinopathy

Mutations in valosin-containing protein (VCP), an ATPase involved in protein degradation and autophagy, cause VCP disease, a progressive autosomal dominant adult onset multisystem proteinopathy. The goal of this study is to examine if phenotypic differences in this disorder could be explained by the specific gene mutations. We therefore studied 231 individuals (118 males and 113 females) from 36 families carrying 15 different VCP mutations. We analyzed the correlation between the different mutations and prevalence, age of onset and severity of myopathy, Paget's disease of bone (PDB), and frontotemporal dementia (FTD), and other comorbidities. Myopathy, PDB and FTD was present in 90%, 42% and 30% of the patients, respectively, beginning at an average age of 43, 41, and 56 years, respectively. Approximately 9% of patients with VCP mutations had an amyotrophic lateral sclerosis (ALS) phenotype, 4% had been diagnosed with Parkinson's disease (PD), and 2% had been diagnosed with Alzheimer's disease (AD). Large interfamilial and intrafamilial variation made establishing correlations difficult. We did not find a correlation between the mutation type and the incidence of any of the clinical features associated with VCP disease, except for the absence of PDB with the R159C mutation in our cohort and R159C having a later age of onset of myopathy compared with other molecular subtypes.

Myogenic differentiation of VCP disease-induced pluripotent stem cells: A novel platform for drug discovery.

Valosin Containing Protein (VCP) disease is an autosomal dominant multisystem proteinopathy caused by mutations in the VCP gene, and is primarily associated with progressive muscle weakness, including atrophy of the pelvic and shoulder girdle muscles. Currently, no treatments are available and cardiac and respiratory failures can lead to mortality at an early age. VCP is an AAA ATPase multifunction complex protein and mutations in the VCP gene resulting in disrupted autophagic clearance. Due to the rarity of the disease, the myopathic nature of the disorder, ethical and practical considerations, VCP disease muscle biopsies are difficult to obtain. Thus, disease-specific human induced pluripotent stem cells (hiPSCs) now provide a valuable resource for the research owing to their renewable and pluripotent nature. In the present study, we report the differentiation and characterization of a VCP disease-specific hiPSCs into precursors expressing myogenic markers including desmin, myogenic factor 5 (MYF5), myosin and heavy chain 2 (MYH2). VCP disease phenotype is characterized by high expression of TAR DNA Binding Protein-43 (TDP-43), ubiquitin (Ub), Light Chain 3-I/II protein (LC3-I/II), and p62/SQSTM1 (p62) protein indicating disruption of the autophagy cascade. Treatment of hiPSC precursors with autophagy stimulators Rapamycin, Perifosine, or AT101 showed reduction in VCP pathology markers TDP-43, LC3-I/II and p62/SQSTM1. Conversely, autophagy inhibitors chloroquine had no beneficial effect, and Spautin-1 or MHY1485 had modest effects. Our results illustrate that hiPSC technology provide a useful platform for a rapid drug discovery and hence constitutes a bridge between clinical and bench research in VCP and related diseases.

Valosin-containing protein (VCP/p97) inhibitors relieve Mitofusin-dependent mitochondrial defects due to VCP disease mutants.

Missense mutations of valosin-containing protein (VCP) cause an autosomal dominant disease known as inclusion body myopathy, Paget disease with frontotemporal dementia (IBMPFD) and other neurodegenerative disorders. The pathological mechanism of IBMPFD is not clear and there is no treatment. We show that endogenous VCP negatively regulates Mitofusin, which is required for outer mitochondrial membrane fusion. Because 90% of IBMPFD patients have myopathy, we generated an in vivo IBMPFD model in adult Drosophila muscle, which recapitulates disease pathologies. We show that common VCP disease mutants act as hyperactive alleles with respect to regulation of Mitofusin. Importantly, VCP inhibitors suppress mitochondrial defects, muscle tissue damage and cell death associated with IBMPFD models in Drosophila. These inhibitors also suppress mitochondrial fusion and respiratory defects in IBMPFD patient fibroblasts. These results suggest that VCP disease mutants cause IBMPFD through a gain-of-function mechanism, and that VCP inhibitors have therapeutic value.

A Fine Balance of Dietary Lipids Improves Pathology of a Murine Model of VCP-Associated Multisystem Proteinopathy.

The discovery of effective therapies and of disease mechanisms underlying valosin containing protein (VCP)-associated myopathies and neurodegenerative disorders remains elusive. VCP disease, caused by mutations in the VCP gene, are a clinically and genetically heterogeneous group of disorders with manifestations varying from hereditary inclusion body myopathy, Paget’s disease of bone, frontotemporal dementia (IBMPFD), and amyotrophic lateral sclerosis (ALS). In the present study, we examined the effects of higher dietary lipid percentages on VCPR155H/R155H, VCPR155H/+ and Wild Type (WT) mice from birth until 15 months of age by immunohistochemical and biochemical assays. Findings illustrated improvement in the muscle strength, histology, and autophagy signaling pathway in the heterozygote mice when fed 9% lipid-enriched diets (LED). However, increasing the LED by 12%, 30%, and 48% showed no improvement in homozygote and heterozygote survival, muscle pathology, lipid accumulation or the autophagy cascade. These findings suggest that a balanced lipid supplementation may have a therapeutic strategy for patients with VCP-associated multisystem proteinopathies.

Rapamycin and Chloroquine: The In Vitro and In Vivo Effects of Autophagy-Modifying Drugs Show Promising Results in Valosin Containing Protein Multisystem Proteinopathy

Mutations in the valosin containing protein (VCP) gene cause hereditary Inclusion body myopathy (hIBM) associated with Paget disease of bone (PDB), frontotemporal dementia (FTD), more recently termed multisystem proteinopathy (MSP). Affected individuals exhibit scapular winging and die from progressive muscle weakness, and cardiac and respiratory failure, typically in their 40s to 50s. Histologically, patients show the presence of rimmed vacuoles and TAR DNA-binding protein 43 (TDP-43)-positive large ubiquitinated inclusion bodies in the muscles. We have generated a VCPR155H/+ mouse model which recapitulates the disease phenotype and impaired autophagy typically observed in patients with VCP disease. Autophagy-modifying agents, such as rapamycin and chloroquine, at pharmacological doses have previously shown to alter the autophagic flux. Herein, we report results of administration of rapamycin, a specific inhibitor of the mechanistic target of rapamycin (mTOR) signaling pathway, and chloroquine, a lysosomal inhibitor which reverses autophagy by accumulating in lysosomes, responsible for blocking autophagy in 20-month old VCPR155H/+ mice. Rapamycin-treated mice demonstrated significant improvement in muscle performance, quadriceps histological analysis, and rescue of ubiquitin, and TDP-43 pathology and defective autophagy as indicated by decreased protein expression levels of LC3-I/II, p62/SQSTM1, optineurin and inhibiting the mTORC1 substrates. Conversely, chloroquine-treated VCPR155H/+ mice revealed progressive muscle weakness, cytoplasmic accumulation of TDP-43, ubiquitin-positive inclusion bodies and increased LC3-I/II, p62/SQSTM1, and optineurin expression levels. Our in vitro patient myoblasts studies treated with rapamycin demonstrated an overall improvement in the autophagy markers. Targeting the mTOR pathway ameliorates an increasing list of disorders, and these findings suggest that VCP disease and related neurodegenerative multisystem proteinopathies can now be included as disorders that can potentially be ameliorated by rapalogs.