Functional significance of point mutations in stress chaperone mortalin and their relevance to Parkinson disease

Therapeutic approaches in proteinopathies

A family of maladies known as amyloid disorders, proteinopathy, or amyloidosis, are characterized by the accumulation of abnormal protein aggregates containing cross-β-sheet amyloid fibrils in many organs and tissues. Often, proteins that have been improperly formed or folded make up these fibrils. Nowadays, most treatments for amyloid illness focus on managing symptoms rather than curing or preventing the underlying disease process. However, recent advances in our understanding of the biology of amyloid diseases have led to the development of innovative therapies that target the emergence and accumulation of amyloid fibrils. Examples of these treatments include the use of small compounds, monoclonal antibodies, gene therapy, and others. In the end, even if the majority of therapies for amyloid diseases are symptomatic, greater research into the biology behind these disorders is identifying new targets for potential therapy and paving the way for the development of more effective treatments in the future.

Gene Signals and SNPs Associated with Parkinson's Disease: A Nutrigenomics and Computational Prospective Insights

Parkinson's disease is the most prevalent chronic neurodegenerative disease. Neurological conditions for PD were influenced by a variety of epigenetic factors and SNPs in some of the coexisting genes that were expressed. This article focused on nutrigenomics of PD and the prospective highlighting of how these genes are regulated in terms of nutritive factors and the genetic basis of PD risk, onset, and progression. Multigenetic associations of the following genetic alterations in the genes of SNCA, LRRK2, UCHL1, PARK2,PINK1, DJ-1, and ATP13A2 have been reported with the familial and de novo genetic origins of PD. Over the past two decades, significant attempts have been made to understand the biological mechanisms that are potential causes for this disease, as well as to identify therapeutic substances for the prevention and management of PD. Nutrigenomics has sparked considerable interest due to its nutritional, safe, and therapeutic effects on a variety of chronic diseases. In this study, we summarise some of the nutritive supplements that have an impact on PD.

Is Disrupted Mitophagy a Central Player to Parkinson's Disease Pathology?

Whilst the pathophysiology at a cellular level has been defined, the cause of Parkinson's disease (PD) remains poorly understood. This neurodegenerative disorder is associated with impaired dopamine transmission in the substantia nigra, and protein accumulations known as Lewy bodies are visible in affected neurons. Cell culture models of PD have indicated impaired mitochondrial function, so the focus of this paper is on the quality control processes involved in and around mitochondria. Mitochondrial autophagy (mitophagy) is the process through which defective mitochondria are removed from the cell by internalisation into autophagosomes which fuse with a lysosome. This process involves many proteins, notably including PINK1 and parkin, both of which are known to be coded on genes associated with PD. Normally in healthy individuals, PINK1 associates with the outer mitochondrial membrane, which then recruits parkin, activating it to attach ubiquitin proteins to the mitochondrial membrane. PINK1, parkin, and ubiquitin cooperate to form a positive feedback system which accelerates the deposition of ubiquitin on dysfunctional mitochondria, resulting in mitophagy. However, in hereditary PD, the genes encoding PINK1 and parkin are mutated, resulting in proteins that are less efficient at removing poorly performing mitochondria, leaving cells more vulnerable to oxidative stress and ubiquitinated inclusion bodies, such as Lewy bodies. Current research that looks into the connection between mitophagy and PD is promising, already yielding potentially therapeutic compounds; until now, pharmacological support for the mitophagy process has not been part of the therapeutic arsenal. Continued research in this area is warranted.

Autophagy inhibition rescues structural and functional defects caused by the loss of mitochondrial chaperone Hsc70-5 in Drosophila

We investigated in larval and adult Drosophila models whether loss of the mitochondrial chaperone Hsc70-5 is sufficient to cause pathological alterations commonly observed in Parkinson disease. At affected larval neuromuscular junctions, no effects on terminal size, bouton size or number, synapse size, or number were observed, suggesting that we studied an early stage of pathogenesis. At this stage, we noted a loss of synaptic vesicle proteins and active zone components, delayed synapse maturation, reduced evoked and spontaneous excitatory junctional potentials, increased synaptic fatigue, and cytoskeleton rearrangements. The adult model displayed ATP depletion, altered body posture, and susceptibility to heat-induced paralysis. Adult phenotypes could be suppressed by knockdown of dj-1β, Lrrk, DCTN2-p50, DCTN1-p150, Atg1, Atg101, Atg5, Atg7, and Atg12. The knockdown of components of the macroautophagy/autophagy machinery or overexpression of human HSPA9 broadly rescued larval and adult phenotypes, while disease-associated HSPA9 variants did not. Overexpression of Pink1 or promotion of autophagy exacerbated defects.Abbreviations: AEL: after egg laying; AZ: active zone; brp: bruchpilot; Csp: cysteine string protein; dlg: discs large; eEJPs: evoked excitatory junctional potentials; GluR: glutamate receptor; H₂O₂: hydrogen peroxide; mEJP: miniature excitatory junctional potentials; MT: microtubule; NMJ: neuromuscular junction; PD: Parkinson disease; Pink1: PTEN-induced putative kinase 1; PSD: postsynaptic density; SSR: subsynaptic reticulum; SV: synaptic vesicle; VGlut: vesicular glutamate transporter.

RNA-seq profiling reveals PBMC RNA as a potential biomarker for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors and has extremely high morbidity and mortality. Although many existing studies have focused on the identification of biomarkers, little information has been uncovered regarding the PBMC RNA profile of HCC. We attempted to create a profile throughout using expression of peripheral blood mononuclear cell (PBMC) RNA using RNA-seq technology and compared the transcriptome between HCC patients and healthy controls. Seventeen patients and 17 matched healthy controls were included in this study, and PBMC RNA was sequenced from all samples. Sequencing data were analyzed using bioinformatics tools, and quantitative reverse transcription PCR (qRT-PCR) was used for selected validation of DEGs. A total of 1,578 dysregulated genes were found in the PBMC samples, including 1,334 upregulated genes and 244 downregulated genes. GO enrichment and KEGG studies revealed that HCC is closely linked to differentially expressed genes (DEGs) implicated in the immune response. Expression of 6 selected genes (SELENBP1, SLC4A1, SLC26A8, HSPA8P4, CALM1, and RPL7p24) was confirmed by qRT-PCR, and higher sensitivity and specificity were obtained by ROC analysis of the 6 genes. CALM1 was found to gradually decrease as tumors enlarged. Nearly the opposite expression modes were obtained when compared to tumor sequencing data. Immune cell populations exhibited significant differences between HCC and controls. These findings suggest a potential biomarker for the diagnosis of HCC. This study provides new perspectives for liver cancer development and possible future successful clinical diagnosis.

Induction of Senescence in Cancer Cells by a Novel Combination of Cucurbitacin B and Withanone: Molecular Mechanism and Therapeutic Potential

Cancer, an uncontrolled proliferation syndrome, is treated with synthetic chemotherapeutic drugs that are associated with severe adverse effects. Development and application of new natural compounds is warranted to deal with the exponentially increasing incidence of cancer worldwide. Keeping selective toxicity to cancer cells as a priority criterion, we developed a combination of Cucurbitacin B and Withanone, and analyzed its anticancer potential using non-small cell lung cancer cells. We demonstrate that the selective cytotoxicity of the combination, called CucWi-N, to cancer cells is mediated by induction of cellular senescence that was characterized by decrease in Lamin A/C, CDK2, CDK4, Cyclin D, Cyclin E, phosphorylated RB, mortalin and increase in p53 and CARF proteins. It compromised cancer cell migration that was mediated by decrease in mortalin, hnRNP-K, vascular endothelial growth factor, matrix metalloproteinase 2, and fibronectin. We provide in silico, molecular dynamics and experimental data to support that CucWi-N (i) possesses high capability to target mortalin-p53 interaction and hnRNP-K proteins, (ii) triggers replicative senescence and inhibits metastatic potential of the cancer cells, and (iii) inhibits tumor progression and metastasis in vivo. We propose that CucWi-N is a potential natural anticancer drug that warrants further mechanistic and clinical studies.

The mitochondrial PKCδ/retinol signal complex exerts real-time control on energy homeostasis

The review focuses on the role of vitamin A (retinol) in the control of energy homeostasis, and on the manner in which certain retinoids subvert this process, leading potentially to disease. In eukaryotic cells, the pyruvate dehydrogenase complex (PDHC) is negatively regulated by four pyruvate dehydrogenase kinases (PDKs) and two antagonistically acting pyruvate dehydrogenase phosphatases (PDPs). The second isoform, PDK2, is regulated by an autonomous mitochondrial signal cascade that is anchored on protein kinase Cδ (PKCδ), where retinoids play an indispensible co-factor role. Along with its companion proteins p66Shc, cytochrome c, and vitamin A, the PKCδ/retinol complex is located in the intermembrane space of mitochondria. At this site, and in contrast to cytosolic locations, PKCδ is activated by the site-specific oxidation of its cysteine-rich activation domain (CRD) that is configured into a complex RING-finger. Oxidation involves the transfer of electrons from cysteine moieties to oxidized cytochrome c, a step catalyzed by vitamin A. The PKCδ/retinol signalosome monitors the internal cytochrome c redox state that reflects the workload of the respiratory chain. Upon sensing demands for energy PKCδ signals the PDHC to increase glucose-derived fuel flux entering the KREBS cycle. Conversely, if excessive fuel flux surpasses the capacity of the respiratory chain, threatening the release of damaging reactive oxygen species (ROS), the polarity of the cytochrome c redox system is reversed, resulting in the chemical reduction of the PKCδ CRD, restoration of the RING-finger, refolding of PKCδ into the inactive, globular form, and curtailment of PDHC output, thereby constraining the respiratory capacity within safe margins. Several retinoids, notably anhydroretinol and fenretinide, capable of displacing retinol from binding sites on PKCδ, can co-activate PKCδ signaling but, owing to their extended system of conjugated double bonds, are unable to silence PKCδ in a timely manner. Left in the ON position, PKCδ causes chronic overload of the respiratory chain leading to mitochondrial dysfunction. This review explores how defects in the PKCδ signal machinery potentially contribute to metabolic and degenerative diseases.

Oxidative Stress in Parkinson's Disease: Potential Benefits of Antioxidant Supplementation

Parkinson's disease (PD) occurs in approximately 1% of the population over 65 years of age and has become increasingly more common with advances in age. The number of individuals older than 60 years has been increasing in modern societies, as well as life expectancy in developing countries; therefore, PD may pose an impact on the economic, social, and health structures of these countries. Oxidative stress is highlighted as an important factor in the genesis of PD, involving several enzymes and signaling molecules in the underlying mechanisms of the disease. This review presents updated data on the involvement of oxidative stress in the disease, as well as the use of antioxidant supplements in its therapy.

Novel Caffeic Acid Phenethyl Ester-Mortalin Antibody Nanoparticles Offer Enhanced Selective Cytotoxicity to Cancer Cells

Caffeic acid phenethyl ester (CAPE) is a key bioactive ingredient of honeybee propolis and is claimed to have anticancer activity. Since mortalin, a hsp70 chaperone, is enriched in a cancerous cell surface, we recruited a unique cell internalizing anti-mortalin antibody (MotAb) to generate mortalin-targeting CAPE nanoparticles (CAPE-MotAb). Biophysical and biomolecular analyses revealed enhanced anticancer activity of CAPE-MotAb both in in vitro and in vivo assays. We demonstrate that CAPE-MotAb cause a stronger dose-dependent growth arrest/apoptosis of cancer cells through the downregulation of Cyclin D1-CDK4, phospho-Rb, PARP-1, and anti-apoptotic protein Bcl2. Concomitantly, a significant increase in the expression of p53, p21^WAF1, and caspase cleavage was obtained only in CAPE-MotAb treated cells. We also demonstrate that CAPE-MotAb caused a remarkably enhanced downregulation of proteins critically involved in cell migration. In vivo tumor growth assays for subcutaneous xenografts in nude mice also revealed a significantly enhanced suppression of tumor growth in the treated group suggesting that these novel CAPE-MotAb nanoparticles may serve as a potent anticancer nanomedicine.

Overexpression of PGC-1α influences the mitochondrial unfolded protein response (mtUPR) induced by MPP+ in human SH-SY5Y neuroblastoma cells

Parkinson’s disease (PD) is a common dyskinesia disease, the mitochondrial unfolded protein response (mtUPR) may be directly or indirectly involved in the occurrence and development of PD, although the exact mechanism is unclear. We established a dopaminergic neuronal-like cell model of PD, by overexpression of PGC-1α to detect evaluate the expression of proteases and molecular chaperones of involved in the mtUPR, as well as the expression of PGC-1α and LRPPRC, illustrated the distribution of LRPPRC. Remarkably, the mtUPR activation reached maximal at 24 h after MPP⁺ treatment in SH-SY5Y cells, which the protein and transcription levels of the proteases and molecular chaperones reached maximal. The proteases and molecular chaperones were significantly increased when overexpressed PGC-1α, which indicated that PGC-1α overexpression activated the mtUPR, and PGC-1α had a protective effect on SH-SY5Y cells. The expression levels of PGC-1α and LRPPRC were significantly improved in the PGC-1α overexpression groups. LRPPRC was markedly reduced in the nucleus, suggesting that PGC-1α overexpression may play a protective role to the mitochondria through LRPPRC. Our finding indicates that overexpression of PGC-1α may activate mtUPR, reducing the oxidative stress injury induced by MPP⁺ through LRPPRC signaling, thus maintain mitochondrial homeostasis.

Protein Misfolding Diseases and Therapeutic Approaches

Protein folding is the process by which a polypeptide chain acquires its functional, native 3D structure. Protein misfolding, on the other hand, is a process in which protein fails to fold into its native functional conformation. This misfolding of proteins may lead to precipitation of a number of serious diseases such as Cystic Fibrosis (CF), Alzheimer's Disease (AD), Parkinson's Disease (PD), and Amyotrophic Lateral Sclerosis (ALS) etc. Protein Quality-control (PQC) systems, consisting of molecular chaperones, proteases and regulatory factors, help in protein folding and prevent its aggregation. At the same time, PQC systems also do sorting and removal of improperly folded polypeptides. Among the major types of PQC systems involved in protein homeostasis are cytosolic, Endoplasmic Reticulum (ER) and mitochondrial ones. The cytosol PQC system includes a large number of component chaperones, such as Nascent-polypeptide-associated Complex (NAC), Hsp40, Hsp70, prefoldin and T Complex Protein-1 (TCP-1) Ring Complex (TRiC). Protein misfolding diseases caused due to defective cytosolic PQC system include diseases involving keratin/collagen proteins, cardiomyopathies, phenylketonuria, PD and ALS. The components of PQC system of Endoplasmic Reticulum (ER) include Binding immunoglobulin Protein (BiP), Calnexin (CNX), Calreticulin (CRT), Glucose-regulated Protein GRP94, the thiol-disulphide oxidoreductases, Protein Disulphide Isomerase (PDI) and ERp57. ER-linked misfolding diseases include CF and Familial Neurohypophyseal Diabetes Insipidus (FNDI). The components of mitochondrial PQC system include mitochondrial chaperones such as the Hsp70, the Hsp60/Hsp10 and a set of proteases having AAA+ domains similar to the proteasome that are situated in the matrix or the inner membrane. Protein misfolding diseases caused due to defective mitochondrial PQC system include medium-chain acyl-CoA dehydrogenase (MCAD)/Short-chain Acyl-CoA Dehydrogenase (SCAD) deficiency diseases, hereditary spastic paraplegia. Among therapeutic approaches towards the treatment of various protein misfolding diseases, chaperones have been suggested as potential therapeutic molecules for target based treatment. Chaperones have been advantageous because of their efficient entry and distribution inside the cells, including specific cellular compartments, in therapeutic concentrations. Based on the chemical nature of the chaperones used for therapeutic purposes, molecular, chemical and pharmacological classes of chaperones have been discussed.

TGR5 promotes cholangiocarcinoma by interacting with mortalin

Takeda-G-protein-receptor-5 (TGR5) is a G-protein-coupled receptor (GPCR) activated by bile acids, and mortalin is a multipotent chaperone of the HSP70 family. In the present study, TGR5 was detected by immunohistochemistry (IHC) in extrahepatic cholangiocarcinoma (ECC) specimens, and TGR5 expression in ECC tissues and adjacent tissues was compared. In vitro TGR5 was overexpressed and knocked down in human intrahepatic cholangiocarcinoma (ICC) cell line RBE and human extrahepatic cholangiocarcinoma (ECC) cell line QBC-939 to observe its effects on the biological behavior of cholangiocarcinoma (CC) cells, including proliferation, apoptosis and migration. In vivo xenograft model was constructed to explore the role of TGR5 in CC growth. Proteins that interacted with TGR5 were screened using an immunoprecipitation spectrometry approach, and the identified protein was down-regulated to investigate its contribution to CC growth. The present study demonstrated that TGR5 is highly expressed in CC tissues, and strong TGR5 expression may indicate high malignancy in CC. Furthermore, TGR5 promotes CC cell proliferation, migration, and apoptosis resistance. TGR5 boosts CC growth in vivo. In addition, TGR5 combines with mortalin and regulates mortalin expression in the CC cell line. Mortalin participates in the TGR5-induced increase in CC cell proliferation. In conclusion, TGR5 is of clinical significance based on its implications for the degree of malignancy in patients with CC. Mortalin may be a downstream component regulated by TGR5, and TGR5 promotes cholangiocarcinoma at least partially by interacting with mortalin and upregulating its expression. Both TGR5 and mortalin are positive regulators, and may serve as potential therapeutic targets for CC.

Effect of fosinopril on the renal cortex protein expression profile of Otsuka Long-Evans Tokushima Fatty rats

Angiotensin-converting enzyme inhibitors (ACEIs) can reduce urinary protein excretion and postpone the deterioration of renal function. However, the mechanisms of renal protection are not yet fully understood. To investigate the mechanisms of ACEIs in the treatment of diabetic nephropathy (DN), the present study determined the effects of the ACEI fosinopril (FP) on the profiling of renal cortex protein expression in Otsuka Long-Evans Tokushima Fatty (OLETF) rats using Long-Evans Tokushima Otsuka (LETO) rats as controls. Urinary protein levels at 24 h were examined using the Broadford method. PAS staining was performed to observe renal histopathological changes. The kidney cortices of OLETF, FP-treated OLETF and LETO rats were examined using soluble and insoluble high-resolution subproteomic analysis methodology at age of 36 and 56 weeks. Differentiated proteins were further confirmed using western blotting analysis. The results demonstrated that FP significantly decreased the glomerulosclerosis index and reduced the 24 h urinary protein excretion of OLETF rats. Additionally, 17 proteins significantly changed following FP-treatment. Amongst these proteins, the abundances of the stress-response protein heat shock protein family A member 9 and the antioxidant glutathione peroxidase 3 were particularly increased. These results indicated that FP ameliorated diabetic renal injuries by inhibiting oxidative stress. In conclusion, the differentially expressed proteins may improve our understanding of the mechanism of ACEIs in the OLETF rats.

Mortalin stabilizes CD151-depedent tetraspanin-enriched microdomains and implicates in the progression of hepatocellular carcinoma

Background: Our previous studies showed that tetraspanin CD151 was implicated in the progression of hepatocellular carcinoma (HCC), mainly depending on the formation of functional complexes with molecular partners, including Mortalin. In this study, we investigate the role of mortalin in CD151-depedent progression of HCCs. Methods: Immunofluorescent staining, western blot and quantitative real-time polymerase chain reaction (qRT-PCR) were used to investigate the expression and location of CD151 and Mortalin in four HCC cell lines with different metastatic ability. The relationship between Mortalin and CD151 was investigated in HCCLM3 cells using co-immunoprecipitation. CD151 or Mortalin expression in HCC cells were modified by transfection technology. Wound-healing assay and Transwell assay were used to assay the role of CD151 and Mortalin in cell migration and invasion. The expression and prognostic implication of CD151 and Mortalin in 187 cases of HCCs were analyzed. Results: Expression of Mortalin in HCC cells was positive related to their metastatic ability and its tendency was in line with the expression of CD151. Immunofluorescent staining showed that Mortalin was located in cytoplasm, while positive staining for CD151 was observed in cytoplasm and membrane of HCC cells. co-IP revealed that Mortalin formed a complex with CD151. Down-regulation of Mortalin induced a moderate decreased CD151 protein, but not CD151 mRNA, while inhibition of CD151 did not influence the expression of Mortalin at the level of both protein and mRNA. Interference of Mortalin significantly inhibited the invasion and migration of HCC cells with high CD151 expression and partially restored the invasion and migration of HCC cells induced by CD151 over-expression. Clinically, high Mortalin expression correlated with malignant phenotype of HCC, such as microvascular invasion (p=0.017) and tumor diameter (p=0.001). HCC patients expressing high Mortalin were tend to have higher expression of CD151. HCC patients expressing high level of CD151 showed the poorer prognosis in a Mortalin-dependent manner. Conclusions: Mortalin maybe stabilize of the structure of CD151-dependent tetraspanin-enriched microdomains and implicate in the progression of HCC.

Molecular mechanisms of proteinopathies across neurodegenerative disease: a review

Background

Although there is a range of different symptoms across neurodegenerative diseases, they have been noted to have common pathogenic features. An archetypal feature shared between these diseases is protein misfolding; however, the mechanism behind the proteins abnormalities is still under investigation. There is an emerging hypothesis in the literature that the mechanisms that lead to protein misfolding may be shared across neurodegenerative processes, suggesting a common underlying pathology.

Main body

This review discusses the literature to date of the shared features of protein misfolding, failures in proteostasis, and potential propagation pathways across the main neurodegenerative disorders.

Conclusion

The current data suggests, despite overarching processes being shared, that the molecular events implicated in protein pathology are distinct across common neurodegenerative disorders.

Express ELISA for detection of mortalin

Mortalin is a widely studied stress chaperone that plays a significant role in diseases such as cancer, diabetes mellitus, liver cirrhosis, neurodegeneration and generalized aging. Based on these, the level of mortalin expression has been predicted to be an important and valuable diagnostic and prognostic marker. Conventional methods of protein analyses, such as Western blotting, immunohistochemistry or ELISA with antibodies provide specific, sensitive and useful outcomes. However, they are limited by lengthy and time-consuming protocols. Here, we present an upgrade to the existing ELISA techniques. We have prepared a conjugate of anti-mortalin antibody and luciferase enzyme that can be recruited for rapid (∼3 h) and quantitative detection of mortalin expression in a given biological sample.

Marine Carotenoid Fucoxanthin Possesses Anti-Metastasis Activity: Molecular Evidence

Fucoxanthin is commonly found in marine organisms; however, to date, it has been one of the scarcely explored natural compounds. We investigated its activities in human cancer cell culture-based viability, migration, and molecular assays, and found that it possesses strong anticancer and anti-metastatic activities that work irrespective of the p53 status of cancer cells. In our experiments, fucoxanthin caused the transcriptional suppression of mortalin. Cell phenotype-driven molecular analyses on control and treated cells demonstrated that fucoxanthin caused a decrease in hallmark proteins associated with cell proliferation, survival, and the metastatic spread of cancer cells at doses that were relatively safe to the normal cells. The data suggested that the cancer therapy regimen may benefit from the recruitment of fucoxanthin; hence, it warrants further attention for basic mechanistic studies as well as drug development.

Biophysical Consequences of EVEN-PLUS Syndrome Mutations for the Function of Mortalin

HSPA9, the gene coding for the mitochondrial chaperone mortalin, is involved in various cellular roles such as mitochondrial protein import, folding, degradation, Fe-S cluster biogenesis, mitochondrial homeostasis, and regulation of the antiapoptotic protein p53. Mutations in the HSPA9 gene, particularly within the region coding for the nucleotide-binding domain (NBD), cause the autosomal disorder known as EVEN-PLUS syndrome. The resulting mutants R126W and Y128C are located on the surface of the mortalin-NBD near the binding interface with the interdomain linker (IDL). We used differential scanning fluorimetry (DSF), biolayer interferometry, X-ray crystallography, ATP hydrolysis assays, and Rosetta docking simulations to study the structural and functional consequences of the EVEN-PLUS syndrome-associated R126W and Y128C mutations within the mortalin-NBD. These results indicate that the surface mutations R126W and Y128C have far-reaching effects that disrupt ATP hydrolysis, interdomain linker binding, and thermostability and increase the propensity for aggregation. The structural differences observed provide insight into how the conformations of mortalin differ from other heat shock protein 70 (Hsp70) homologues. Combined, our biophysical and structural studies contribute to the understanding of the molecular basis for how disease-associated mortalin mutations affect mortalin functionality and the pathogenesis of EVEN-PLUS syndrome.

Lifelong Football Training: Effects on Autophagy and Healthy Longevity Promotion

Aging is a physiological process characterized by a progressive decline of biological functions and an increase in destructive processes in cells and organs. Physical activity and exercise positively affects the expression of skeletal muscle markers involved in longevity pathways. Recently, a new mechanism, autophagy, was introduced to the adaptations induced by acute and chronic exercise as responsible of positive metabolic modification and health-longevity promotion. However, the molecular mechanisms regulating autophagy in response to physical activity and exercise are sparsely described. We investigated the long-term adaptations resulting from lifelong recreational football training on the expression of skeletal muscle markers involved in autophagy signaling. We demonstrated that lifelong football training increased the expression of messengers: RAD23A, HSPB6, RAB1B, TRAP1, SIRT2, and HSBPB1, involved in the auto-lysosomal and proteasome-mediated protein degradation machinery; of RPL1, RPL4, RPL36, MRLP37, involved in cellular growth and differentiation processes; of the Bcl-2, HSP70, HSP90, PSMD13, and of the ATG5-ATG12 protein complex, involved in proteasome promotion and autophagy processes in muscle samples from lifelong trained subjects compared to age-matched untrained controls. In conclusion, our results indicated that lifelong football training positively influence exercise-induced autophagy processes and protein quality control in skeletal muscle, thus promoting healthy aging.

Oxidation resistance 1 regulates post-translational modifications of peroxiredoxin 2 in the cerebellum

Protein aggregation, oxidative and nitrosative stress are etiological factors common to all major neurodegenerative disorders. Therefore, identifying proteins that function at the crossroads of these essential pathways may provide novel targets for therapy. Oxidation resistance 1 (Oxr1) is a protein proven to be neuroprotective against oxidative stress, although the molecular mechanisms involved remain unclear. Here, we demonstrate that Oxr1 interacts with the multifunctional protein, peroxiredoxin 2 (Prdx2), a potent antioxidant enzyme highly expressed in the brain that can also act as a molecular chaperone. Using a combination of in vitro assays and two animal models, we discovered that expression levels of Oxr1 regulate the degree of oligomerization of Prdx2 and also its post-translational modifications (PTMs), specifically suggesting that Oxr1 acts as a functional switch between the antioxidant and chaperone functions of Prdx2. Furthermore, we showed in the Oxr1 knockout mouse that Prdx2 is aberrantly modified by overoxidation and S-nitrosylation in the cerebellum at the presymptomatic stage; this in-turn affected the oligomerization of Prdx2, potentially impeding its normal functions and contributing to the specific cerebellar neurodegeneration in this mouse model.

Intracellular calcium dysregulation in autism spectrum disorder: An analysis of converging organelle signaling pathways

Autism spectrum disorder (ASD) is a group of complex, neurological disorders that affect early cognitive, social, and verbal development. Our understanding of ASD has vastly improved with advances in genomic sequencing technology and genetic models that have identified >800 loci with variants that increase susceptibility to ASD. Although these findings have confirmed its high heritability, the underlying mechanisms by which these genes produce the ASD phenotypes have not been defined. Current efforts have begun to "functionalize" many of these variants and envisage how these susceptibility factors converge at key biochemical and biophysical pathways. In this review, we discuss recent work on intracellular calcium signaling in ASD, including our own work, which begins to suggest it as a compelling candidate mechanism in the pathophysiology of autism and a potential therapeutic target. We consider how known variants in the calcium signaling genomic architecture of ASD may exert their deleterious effects along pathways particularly involving organelle dysfunction including the endoplasmic reticulum (ER), a major calcium store, and the mitochondria, a major calcium ion buffer, and theorize how many of these pathways intersect.

The genetic architecture of mitochondrial dysfunction in Parkinson's disease

Mitochondrial impairment is a well-established pathological pathway implicated in Parkinson's disease (PD). Defects of the complex I of the mitochondrial respiratory chain have been found in post-mortem brains from sporadic PD patients. Furthermore, several disease-related genes are linked to mitochondrial pathways, such as PRKN, PINK1, DJ-1 and HTRA2 and are associated with mitochondrial impairment. This phenotype can be caused by the dysfunction of mitochondrial quality control machinery at different levels: molecular, organellar or cellular. Mitochondrial unfolded protein response represents the molecular level and implicates various chaperones and proteases. If the molecular level of quality control is not sufficient, the organellar level is required and involves mitophagy and mitochondrial-derived vesicles to sequester whole dysfunctional organelle or parts of it. Only when the impairment is too severe, does it lead to cell death via apoptosis, which defines the cellular level of quality control. Here, we review how currently known PD-linked genetic variants interfere with different levels of mitochondrial quality control. We discuss the graded risk concept of the most recently identified PARK loci (PARK 17-23) and some susceptibility variants in GBA, LRRK2 and SNCA. Finally, the emerging concept of rare genetic variants in candidates genes for PD, such as HSPA9, TRAP1 and RHOT1, complete the picture of the complex genetic architecture of PD that will direct future precision medicine approaches.

Salidroside influences the cellular cross-talk of human fetal lung diploid fibroblasts: A proteomic approach

Senescence is a complex multiple factor proces, which is still poorly understood. The purpose of this study was to find the proteome of cultured human fetal lung diploid fibroblasts (2BS) of different population doubling (PD), as well as the altered proteome induced by salidroside (SAL) in 2BS cells. Proteins were identified by two-dimensional electrophoresis (2-DE) combining matrix-assisted laser desorption/ionization-time and flight mass spectrometry (MAL DI-TOF/MS). As a result, we found 16 proteins with two-fold variations in senescent cells or after SAL treatment, some being reduced such as reticulocalbin-1, heat shock protein beta-6, elongation factor 1-delta, F-actin-capping protein subunit alpha-1, and chloride intracellular channel 1. In contrast, 40S ribosomal protein SA, proteasome subunit alpha type-5, and zinc finger BED domain-containing protein 5 increased with cell age. Furthermore, heat shock protein beta-6, Zinc finger BED domain-containing protein 5 was increased in PD30 cells after 10 μM SAL treatment, whereas, elongation factor 1-delta, 6-phosphogluconolactonase, Nucleoside diphosphate kinase A, F-actin-capping protein subunit alpha-1, Probable ATP-dependent RNA helicase DDX41, Chloride intracellular channel 1, and Peroxiredoxin-6 were increased in PD50 cells after 10 μM SAL treatment. Some of these proteins were involved in the protein synthetic and degradative pathways, which emphasizes the metabolic disorder or functional impairment of cell senescence. Moreover, these proteins could be candidate biomarkers for evaluating the SAL anti-senescence effect.

Multi-chaperone function modulation and association with cytoskeletal proteins are key features of the function of AIP in the pituitary gland

Despite the well-recognized role of loss-of-function mutations of the aryl hydrocarbon receptor interacting protein gene (AIP) predisposing to pituitary adenomas, the pituitary-specific function of this tumor suppressor remains an enigma. To determine the repertoire of interacting partners for the AIP protein in somatotroph cells, wild-type and variant AIP proteins were used for pull-down/quantitative mass spectrometry experiments against lysates of rat somatotropinoma-derived cells; relevant findings were validated by co-immunoprecipitation and co-localization. Global gene expression was studied in AIP mutation positive and negative pituitary adenomas via RNA microarrays. Direct interaction with AIP was confirmed for three known and six novel partner proteins. Novel interactions with HSPA5 and HSPA9, together with known interactions with HSP90AA1, HSP90AB1 and HSPA8, indicate that the function/stability of multiple chaperone client proteins could be perturbed by a deficient AIP co-chaperone function. Interactions with TUBB, TUBB2A, NME1 and SOD1 were also identified. The AIP variants p.R304* and p.R304Q showed impaired interactions with HSPA8, HSP90AB1, NME1 and SOD1; p.R304* also displayed reduced binding to TUBB and TUBB2A, and AIP-mutated tumors showed reduced TUBB2A expression. Our findings suggest that cytoskeletal organization, cell motility/adhesion, as well as oxidative stress responses, are functions that are likely to be involved in the tumor suppressor activity of AIP.

Chaperone-Based Therapies for Disease Modification in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder and is characterized by the presence of pathological intracellular aggregates primarily composed of misfolded α-synuclein. This pathology implicates the molecular machinery responsible for maintaining protein homeostasis (proteostasis), including molecular chaperones, in the pathobiology of the disease. There is mounting evidence from preclinical and clinical studies that various molecular chaperones are downregulated, sequestered, depleted, or dysfunctional in PD. Current therapeutic interventions for PD are inadequate as they fail to modify disease progression by ameliorating the underlying pathology. Modulating the activity of molecular chaperones, cochaperones, and their associated pathways offers a new approach for disease modifying intervention. This review will summarize the potential of chaperone-based therapies that aim to enhance the neuroprotective activity of molecular chaperones or utilize small molecule chaperones to promote proteostasis.

Disruption of Protein Processing in the Endoplasmic Reticulum of DYT1 Knock-in Mice Implicates Novel Pathways in Dystonia Pathogenesis

Dystonia type 1 (DYT1) is a dominantly inherited neurological disease caused by mutations in TOR1A, the gene encoding the endoplasmic reticulum (ER)-resident protein torsinA. Previous work mostly completed in cell-based systems suggests that mutant torsinA alters protein processing in the secretory pathway. We hypothesized that inducing ER stress in the mammalian brain in vivo would trigger or exacerbate mutant torsinA-induced dysfunction. To test this hypothesis, we crossed DYT1 knock-in with p58(IPK)-null mice. The ER co-chaperone p58(IPK) interacts with BiP and assists in protein maturation by helping to fold ER cargo. Its deletion increases the cellular sensitivity to ER stress. We found a lower generation of DYT1 knock-in/p58 knock-out mice than expected from this cross, suggesting a developmental interaction that influences viability. However, surviving animals did not exhibit abnormal motor function. Analysis of brain tissue uncovered dysregulation of eiF2α and Akt/mTOR translational control pathways in the DYT1 brain, a finding confirmed in a second rodent model and in human brain. Finally, an unbiased proteomic analysis identified relevant changes in the neuronal protein landscape suggesting abnormal ER protein metabolism and calcium dysregulation. Functional studies confirmed the interaction between the DYT1 genotype and neuronal calcium dynamics. Overall, these findings advance our knowledge on dystonia, linking translational control pathways and calcium physiology to dystonia pathogenesis and identifying potential new pharmacological targets.

SIGNIFICANCE STATEMENT

Dystonia type 1 (DYT1) is one of the different forms of inherited dystonia, a neurological disorder characterized by involuntary, disabling movements. DYT1 is caused by mutations in the gene that encodes the endoplasmic reticulum (ER)-resident protein torsinA. How mutant torsinA causes neuronal dysfunction remains unknown. Here, we show the behavioral and molecular consequences of stressing the ER in DYT1 mice by increasing the amount of misfolded proteins. This resulted in the generation of a reduced number of animals, evidence of abnormal ER protein processing and dysregulation of translational control pathways. The work described here proposes a shared mechanism for different forms of dystonia, links for the first time known biological pathways to dystonia pathogenesis, and uncovers potential pharmacological targets for its treatment.

Protein misfolding in neurodegenerative diseases: implications and strategies

A hallmark of neurodegenerative proteinopathies is the formation of misfolded protein aggregates that cause cellular toxicity and contribute to cellular proteostatic collapse. Therapeutic options are currently being explored that target different steps in the production and processing of proteins implicated in neurodegenerative disease, including synthesis, chaperone-assisted folding and trafficking, and degradation via the proteasome and autophagy pathways. Other therapies, like mTOR inhibitors and activators of the heat shock response, can rebalance the entire proteostatic network. However, there are major challenges that impact the development of novel therapies, including incomplete knowledge of druggable disease targets and their mechanism of action as well as a lack of biomarkers to monitor disease progression and therapeutic response. A notable development is the creation of collaborative ecosystems that include patients, clinicians, basic and translational researchers, foundations and regulatory agencies to promote scientific rigor and clinical data to accelerate the development of therapies that prevent, reverse or delay the progression of neurodegenerative proteinopathies.

Essential Roles of E3 Ubiquitin Ligases in p53 Regulation

The ubiquitination pathway and proteasomal degradation machinery dominantly regulate p53 tumor suppressor protein stability, localization, and functions in both normal and cancerous cells. Selective E3 ubiquitin ligases dominantly regulate protein levels and activities of p53 in a large range of physiological conditions and in response to cellular changes induced by exogenous and endogenous stresses. The regulation of p53’s functions by E3 ubiquitin ligases is a complex process that can lead to positive or negative regulation of p53 protein in a context- and cell type-dependent manner. Accessory proteins bind and modulate E3 ubiquitin ligases, adding yet another layer of regulatory control for p53 and its downstream functions. This review provides a comprehensive understanding of p53 regulation by selective E3 ubiquitin ligases and their potential to be considered as a new class of biomarkers and therapeutic targets in diverse types of cancers.

Relevance of mortalin to cancer cell stemness and cancer therapy

Mortalin/mtHsp70 is a member of Hsp70 family of proteins. Enriched in a large variety of cancers, it has been shown to contribute to the process of carcinogenesis by multiple ways including inactivation of tumor suppressor p53 protein, deregulation of apoptosis and activation of EMT signaling. In this study, we report that upregulation of mortalin contributes to cancer cell stemness. Several cancer cell stemness markers, such as ABCG2, OCT-4, CD133, ALDH1, CD9, MRP1 and connexin were upregulated in mortalin-overexpressing cells that showed higher ability to form spheroids. These cells also showed higher migration, and were less responsive to a variety of cancer chemotherapeutic drugs. Of note, knockdown of mortalin by specific shRNA sensitized these cells to all the drugs used in this study. We report that low doses of anti-mortalin molecules, MKT-077 and CAPE, also caused similar sensitization of cancer cells to chemotherapeutic drugs and hence are potential candidates for effective cancer chemotherapy.

Proteins that mediate protein aggregation and cytotoxicity distinguish Alzheimer's hippocampus from normal controls

Neurodegenerative diseases are distinguished by characteristic protein aggregates initiated by disease‐specific ‘seed’ proteins; however, roles of other co‐aggregated proteins remain largely unexplored. Compact hippocampal aggregates were purified from Alzheimer's and control‐subject pools using magnetic‐bead immunoaffinity pulldowns. Their components were fractionated by electrophoretic mobility and analyzed by high‐resolution proteomics. Although total detergent‐insoluble aggregates from Alzheimer's and controls had similar protein content, within the fractions isolated by tau or Aβ_1–42 pulldown, the protein constituents of Alzheimer‐derived aggregates were more abundant, diverse, and post‐translationally modified than those from controls. Tau‐ and Aβ‐containing aggregates were distinguished by multiple components, and yet shared >90% of their protein constituents, implying similar accretion mechanisms. Alzheimer‐specific protein enrichment in tau‐containing aggregates was corroborated for individuals by three analyses. Five proteins inferred to co‐aggregate with tau were confirmed by precise in situ methods, including proximity ligation amplification that requires co‐localization within 40 nm. Nematode orthologs of 21 proteins, which showed Alzheimer‐specific enrichment in tau‐containing aggregates, were assessed for aggregation‐promoting roles in C. elegans by RNA‐interference ‘knockdown’. Fifteen knockdowns (71%) rescued paralysis of worms expressing muscle Aβ, and 12 (57%) rescued chemotaxis disrupted by neuronal Aβ expression. Proteins identified in compact human aggregates, bound by antibody to total tau, were thus shown to play causal roles in aggregation based on nematode models triggered by Aβ_1–42. These observations imply shared mechanisms driving both types of aggregation, and/or aggregate‐mediated cross‐talk between tau and Aβ. Knowledge of protein components that promote protein accrual in diverse aggregate types implicates common mechanisms and identifies novel targets for drug intervention.

Structural studies of UBXN2A and mortalin interaction and the putative role of silenced UBXN2A in preventing response to chemotherapy

Overexpression of the oncoprotein mortalin in cancer cells and its protein partners enables mortalin to promote multiple oncogenic signaling pathways and effectively antagonize chemotherapy-induced cell death. A UBX-domain-containing protein, UBXN2A, acts as a potential mortalin inhibitor. This current study determines whether UBXN2A effectively binds to and occupies mortalin's binding pocket, resulting in a direct improvement in the tumor's sensitivity to chemotherapy. Molecular modeling of human mortalin's binding pocket and its binding to the SEP domain of UBXN2A followed by yeast two-hybrid and His-tag pull-down assays revealed that three amino acids (PRO442, ILE558, and LYS555) within the substrate-binding domain of mortalin are crucial for UBXN2A binding to mortalin. As revealed by chase experiments in the presence of cycloheximide, overexpression of UBXN2A seems to interfere with the mortalin-CHIP E3 ubiquitin ligase and consequently suppresses the C-terminus of the HSC70-interacting protein (CHIP)-mediated destabilization of p53, resulting in its stabilization in the cytoplasm and upregulation in the nucleus. Overexpression of UBXN2A causes a significant inhibition of cell proliferation and the migration of colon cancer cells. We silenced UBXN2A in the human osteosarcoma U2OS cell line, an enriched mortalin cancer cell, followed by a clinical dosage of the chemotherapeutic agent 5-fluorouracil (5-FU). The UBXN2A knockout U2OS cells revealed that UBXNA is essential for the cytotoxic effect achieved by 5-FU. UBXN2A overexpression markedly increased the apoptotic response of U2OS cells to the 5-FU. In addition, silencing of UBXN2A protein suppresses apoptosis enhanced by UBXN2A overexpression in U2OS. The knowledge gained from this study provides insights into the mechanistic role of UBXN2A as a potent mortalin inhibitor and as a potential chemotherapy sensitizer for clinical application.

Mutations in the heat-shock protein A9 (HSPA9) gene cause the EVEN-PLUS syndrome of congenital malformations and skeletal dysplasia

We and others have reported mutations in LONP1, a gene coding for a mitochondrial chaperone and protease, as the cause of the human CODAS (cerebral, ocular, dental, auricular and skeletal) syndrome (MIM 600373). Here, we delineate a similar but distinct condition that shares the epiphyseal, vertebral and ocular changes of CODAS but also included severe microtia, nasal hypoplasia, and other malformations, and for which we propose the name of EVEN-PLUS syndrome for epiphyseal, vertebral, ear, nose, plus associated findings. In three individuals from two families, no mutation in LONP1 was found; instead, we found biallelic mutations in HSPA9, the gene that codes for mHSP70/mortalin, another highly conserved mitochondrial chaperone protein essential in mitochondrial protein import, folding, and degradation. The functional relationship between LONP1 and HSPA9 in mitochondrial protein chaperoning and the overlapping phenotypes of CODAS and EVEN-PLUS delineate a family of “mitochondrial chaperonopathies” and point to an unexplored role of mitochondrial chaperones in human embryonic morphogenesis.