Human Α1-antitrypsin Research Articles

Functional characterization of the mouse Serpina1 paralog DOM-7.

The generation of authentic mouse-models for human α1-antitrypsin (A1AT)-deficiency is difficult due to the high complexity of the mouse Serpina1 gene locus. Depending on the exact mouse strain, three to five paralogs are expressed, with different proteinase inhibitory properties. Nowadays with CRISPR-technology, genome editing of complex genomic loci is feasible and could be employed for the generation of A1AT-deficiency mouse models. In preparation of a CRISPR/Cas9-based genome-engineering approach we identified cDNA clones with a functional CDS for the Serpina1-paralog DOM-7. Here, we show that DOM-7 functionally inhibits neutrophil elastase (ELANE) and chymotrypsin, and therefore needs to be considered when aiming at the generation of A1AT-deficient models.

Sex-specific lung functional changes in adult mice exposed only to second-hand smoke in utero

BackgroundAn increasing number of epidemiological and experimental studies have associated exposure to second-hand smoke (SHS) during pregnancy with adverse outcomes in newborns. As we have previously shown in mice, in utero exposure to SHS at critical stages of fetal development, results in altered lung responses and increased disease susceptibility upon re-exposure to irritants (SHS or ovalbumin) in adulthood. In this study, we asked whether the in utero SHS exposure alone is sufficient to alter lung structure and function in adult mice.MethodsPregnant BALB/c mice were exposed from days 6 to 19 of pregnancy to 10 mg/m3 of SHS or HEPA-filtered air. Male and female offspring (n = 13–15/group) were sacrificed at 15 weeks of age. We measured lung function with non-invasive and invasive methods, performed lung morphometric analysis on trichrome-stained lung tissue samples, and assessed lung gene expression via RNA sequencing and protein assays.ResultsIn utero SHS exposure significantly increased mean linear intercept and decreased the surface area per unit volume of the lungs in both males and females, indicating perturbation in alveolar developmental processes. Tidal volume, minute volume and inspiratory capacity were significantly decreased compared with the controls only in male mice exposed in utero to SHS, suggesting that males are more sensitive than females to an SHS insult during lung development. This also suggests that in our model, lung structure changes may be necessary but are not sufficient to impair lung function. SERPINA1A, the mouse ortholog of human α1-antitrypsin, deficiency of which is a known genetic risk factor for emphysema, was down-regulated at the protein level in the in utero SHS-exposed mice. Additionally, DNMT3A protein expression was dysregulated, indicating that DNA methylation occurred in the lungs.ConclusionsOur results indicate that in utero SHS exposure alone alters both lung function and structure well into adulthood (15 weeks) in male mice. Furthermore, lung function alterations in this model are sex-specific, with males being more susceptible to in utero SHS effects. Overall, our data suggest that in utero SHS exposure alone can predispose to adult lung diseases.

Human α1-antitrypsin attenuates injury-induced Inflammation through interacting with high mobility group box-1 (HMGB1)

Abstract HMGB1 is involved in pathologies such as cellular injury and autoimmunity. Indeed, upon binding to immune-related receptors, HMGB1 promotes an inflammatory response, such as that might take part in pancreatic islet destruction during both autoimmune diabetes and islet transplant rejection. Specifically, elevated circulating HMGB1 levels were reported in patients with type 1 diabetes, and increased release of HMGB1 was found to correlate with injury degree and islet allograft survival. The anti-inflammatory and immune-modulatory acute-phase protein human α1-antitrypsin (hAAT) promotes islet survival in both transplantation and autoimmune diabetes models. While AAT binds to damage-released proteins, such as gp96 and HSP70, its tissue protective mechanism remains poorly understood. We now extend this observation that AAT protective activity is related to its interaction with HMGB1. Clinical-grade AAT (Glassia, Kamada Ltd., Israel), diminished recombinant HMGB1-induced inflammatory responses in mouse pancreatic islets (while restoring disrupted insulin inflammation-mediated release). Similar behavior was depicted in HMGB1-stimulated peritoneal macrophages introduced to hAAT. In addition, hAAT modulated HMGB1-inducible surface expression by altering its distribution. Lastly, we show by immunoprecipitation that HMGB1 associated proteins was positive for the presence of AAT, this is also supported by a direct ELISA. Our findings suggest that hAAT is a naturally-occurring regulator of inflammatory responses mediated by extracellular HMGB1, such that preclude outcomes of islet transplantation. hAAT may therefore be considered for therapy of cell damage-mediated pathologies in a clinically-safe manner.

Expression of α-1,6-fucosyltransferase (FUT8) in rice grain and immunogenicity evaluation of plant-specific glycans

Rice seed is a cost-effective bioreactor for the large-scale production of pharmaceuticals. However, convincing evidence of the immunogenicity of plant-specific glycans is still limited although plant-specific glycans are considered potential allergic antigens. In the present study, we found that the α-1,3-fucose content of the glycoprotein produced from rice seed was much lower than that in leaf, and conversely, a higher β-1,2-xylose content was detected in seed than that in leaf. We detected the α-1,6-fucose content in the glutelin and recombinant human α1-antitrypsin (OsrAAT). The further results in a line containing AAT and FUT8 genes indicated that the α-1,6-fucose content of modified glycosylated recombinant α1-antitrypsin (mgOsrAAT) was 38.4%, while glutelin was only 6.8%. Interestingly, the α-1,3-fucose content of mgOsrAAT was significantly reduced by 59.8% compared with that of OsrAAT. Furthermore, we assessed the immunogenicity of OsrAAT, mgOsrAAT and human α1-antitrypsin (hAAT) using an animal system. The PCA results indicated no significant differences in the IgG, IgM and IgE titers among OsrAAT, mgOsrAAT and hAAT. Further studies revealed that those antibodies were mainly from α-1,3-fucose, but not from β-1,2-xylose, indicating that α-1,3-fucose was the major immunogenic resource. Our results demonstrated that α-1,3-fucose contents in seed proteins was much less than that of leaf, and could not be a plant-specific glycan because it also exists in human proteins.

Understanding Lung Deposition of Alpha-1 Antitrypsin in Acute Experimental Mouse Lung Injury Model Using Fluorescence Microscopy.

Human plasma-derived α1-antitrypsin (AAT) delivered by intravenous infusion is used as augmentation therapy in patients with emphysema who have a genetic mutation resulting in deficiency of AAT. Inhalation is an alternative route of administration that can potentially increase the efficacy and convenience of treatment. This study was conducted to determine whether delivery to the lungs, initially via the intratracheal (IT) route of administration, would deliver efficacious levels of a recombinant AAT (rAAT) to the site of action in the lungs in mice. 125I-radiolabeled rAAT, fluorophore-conjugated rAAT (rAAT-Alexa488), and NE680 (neutrophil elastase 680, a silent fluorescent substrate of neutrophil elastase which fluoresces in the near-infrared range upon activation by neutrophil elastase) were used to characterize the pharmacokinetics and tissue distribution profile, distribution of rAAT within the lung, and efficacy of rAAT to inhibit neutrophil elastase at the site of action, respectively. The study has demonstrated that rAAT was able to gain access to locations where neutrophil elastase was localized. The histochemical quantification of rAAT activity relative to dose at the site of action provided here will improve confidence in predicting the human dose via the inhalation route.

Exploration of α1-antitrypsin treatment protocol for islet transplantation: dosing plan and route of administration.

Lifelong weekly infusions of human α1-antitrypsin (hAAT) are currently administered as augmentation therapy for patients with genetic AAT deficiency (AATD). Several recent clinical trials attempt to extend hAAT therapy to conditions outside AATD, including type 1 diabetes. Because the endpoint for AATD is primarily the reduction of risk for pulmonary emphysema, the present study explores hAAT dose protocols and routes of administration in attempt to optimize hAAT therapy for islet-related injury. Islet-grafted mice were treated with hAAT (Glassia; intraperitoneally or subcutaneously) under an array of clinically relevant dosing plans. Serum hAAT and immunocyte cell membrane association were examined, as well as parameters of islet survival. Results indicate that dividing the commonly prescribed 60 mg/kg i.p. dose to three 20 mg/kg injections is superior in affording islet graft survival; in addition, a short dynamic descending dose protocol (240→120→60→60 mg/kg i.p.) is comparable in outcomes to indefinite 60 mg/kg injections. Although pharmacokinetics after intraperitoneal administration in mice resembles exogenous hAAT treatment in humans, subcutaneous administration better imitated the physiologic progressive rise of hAAT during acute phase responses; nonetheless, only the 60 mg/kg dose depicted an advantage using the subcutaneous route. Taken together, this study provides a platform for extrapolating an islet-relevant clinical protocol from animal models that use hAAT to protect islets. In addition, the study places emphasis on outcome-oriented analyses of drug efficacy, particularly important when considering that hAAT is presently at an era of drug-repurposing toward an extended list of clinical indications outside genetic AATD.

474. Consequences of Infusion Time on Efficiency of Intravenous Delivery of Vector Genomes to the Liver

Based on the knowledge that, when administered intravenously (IV), 90% of adeno-associated virus (AAV) gene transfer vectors are transferred to the liver, the IV route has become the standard for gene therapy applications directed toward genetic modification of liver cells. To achieve maximum transfer of vector genomes to the liver, most attention has been focused on AAV serotype and dose, but little focus has been directed toward whether differences could be achieved by varying the timing of IV vector administration. To assess this variable, we administered rh. 10 serotype AAV vectors intravenously to rodents using 2 variables: (1) single vs multiple administrations; and (2) length of time of infusion. To assess single vs multiple administration, mouse cohorts (C57Bl/6 males, n=5/group) were administered AAVrh.10hα1AT, encoding for human α1-antitrypsin (α1AT), IV at 1012 genome copies (gc)/kg, 4×1012 gc/kg and a 3rd cohort receiving the 1012 gc/kg dose on 4 consecutive days. Mice were bled at 4, 14, 28, and 112 days post-administration. Serum human αlAT levels showed the expected dose response. Mice administered 1012 gc/kg daily for 4 days had αlAT serum levels below those achieved by the single dose 4×1012 gc/kg group (day 112, p 0.1, for all time comparisons in each dosage group). We conclude that, at least in rodents, the use of multiple daily injections influences the expression patterns of the targeted gene; however, the rate of infusion does not appear to be a critical parameter for the design of intravenous infusion for targeting AAV vectors to liver.

SiRNA Therapeutics for Primary Hyperoxaluria: A Beginning

Realization of the early promise of gene therapy has been elusive. Long and eagerly anticipated, particularly for orphan diseases with few available therapeutic alternatives, only within recent years have such treatments begun to reach phase III clinical trials.1 Two articles in this issue of Molecular Therapy identify inhibition of glycolate oxidase as a potential treatment for type 1 primary hyperoxaluria (PH1), an autosomal recessive condition in which excess oxalate produced by the liver causes kidney damage and severe systemic disease. Both teams of investigators demonstrated reduction in oxalate production in a mouse knockout model of the disease through absence or inhibition of glycolate oxidase (GO). Hepatic GO converts glycolate to glyoxylate, which is the primary substrate for production of oxalate. Thus, substrate reduction was achieved. Martin-Higueras and colleagues2 demonstrated that the hyperoxaluria of the AGXT knockout mouse was substantially reduced following double knockout of AGXT and GO. Dutta and colleagues3 approached the problem differently, using Dicer-short interfering RNA (Dicer-siRNA) for inhibition targeting hydroxyacid oxidase 1 (HAO-1) messenger RNA, which encodes GO.3 Using this approach, they were able to demonstrate normalization of oxalate production in hepatocytes of AGXT knockout mice. These observations suggest an innovative approach to treatment for patients with PH1 and impart new hope for patients with PH, their families, and the physicians who care for them. This is especially true in that early experience with other applications of siRNA for treatment of human diseases, including amyloidosis, hypercholesterolemia, and α1-antitrypsin deficiency, has been encouraging.1,4

Human α1-antitrypsin improves early post-transplant lung function: Pre-clinical studies in a pig lung transplant model

The translation of novel drugs in lung transplantation is challenged by different physiologic conditions between small animals and humans. Large-animal models provide important pre-clinical evidence and the next step that best informs clinical trials. In the present study, we used a pig lung transplant model to determine whether human α1-antitrypsin (A1AT), a medication shown to prevent pulmonary ischemia-reperfusion injury in rats, could attenuate reperfusion injury after prolonged hypothermic preservation in a large-animal lung transplant model. Donor lungs were preserved for 24 hours at 4°C, followed by lung transplantation. In a randomized and blinded fashion, intravenous A1AT (240 mg/kg; n = 5) or human albumin (n = 5) was administered to the recipient before reperfusion. Allograft gas exchange function and lung mechanics were monitored during a 4-hour reperfusion period. Microscopic lung injury, inflammatory response, coagulation activity, and cell death were assessed. Pulmonary gas exchange was significantly better during the 4-hour reperfusion period in the A1AT group. Treatment with A1AT improved static pulmonary compliance and significantly reduced pulmonary edema and lung permeability. A1AT treatment inhibited inflammatory mediators in the circulation, with reduced activation of nuclear factor-κB and inflammasome, reduced formation of thrombin-antithrombin complex in plasma, and reduced apoptosis in the allografts. Administration of human A1AT before reperfusion in recipients improved immediate post-transplant lung function in pigs. A large-animal survival model should be considered to support further advancement toward a clinical trial of A1AT to prevent primary graft dysfunction in lung transplantation.

A Chimeric Affinity Tag for Efficient Expression and Chromatographic Purification of Heterologous Proteins from Plants

The use of plants as expression hosts for recombinant proteins is an increasingly attractive option for the production of complex and challenging biopharmaceuticals. Tools are needed at present to marry recent developments in high-yielding gene vectors for heterologous expression with routine protein purification techniques. In this study, we designed the Cysta-tag, a new purification tag for immobilized metal affinity chromatography (IMAC) of plant-made proteins based on the protein-stabilizing fusion partner SlCYS8. We show that the Cysta-tag may be used to readily purify proteins under native conditions, and then be removed enzymatically to isolate the protein of interest. We also show that commonly used protease recognition sites for linking purification tags are differentially stable in leaves of the commonly used expression host Nicotiana benthamiana, with those linkers susceptible to cysteine proteases being less stable then serine protease-cleavable linkers. As an example, we describe a Cysta-tag experimental scheme for the one-step purification of a clinically useful protein, human α1-antitrypsin, transiently expressed in N. benthamiana. With potential applicability to the variety of chromatography formats commercially available for IMAC-based protein purification, the Cysta-tag provides a convenient means for the efficient and cost-effective purification of recombinant proteins from plant tissues.

Factors related to outcomes in lupus-related protein-losing enteropathy

Background/Aims:Protein-losing enteropathy (PLE), characterized by severe hypoalbuminemia and peripheral edema, is a rare manifestation of systemic lupus erythematosus. This present study aimed to identify the distinctive features of lupus-related PLE and evaluate the factors related to the treatment response.Methods:From March 1998 to March 2014, the clinical data of 14 patients with lupus PLE and seven patients with idiopathic PLE from a tertiary center were reviewed. PLE was defined as a demonstration of protein leakage from the gastrointestinal tract by either technetium 99m-labelled human albumin scanning or fecal α1-antitrypsin clearance. A positive steroid response was defined as a return of serum albumin to ≥ 3.0 g/dL within 4 weeks after initial steroid monotherapy, and remission as maintenance of serum albumin ≥ 3.0 g/dL for at least 3 months. A high serum total cholesterol level was defined as a level of ≥ 240 mg/dL.Results:The mean age of the lupus-related PLE patients was 37.0 years, and the mean follow-up duration was 55.8 months. Significantly higher erythrocyte sedimentation rate and serum total cholesterol levels were found for lupus PLE than for idiopathic PLE. Among the 14 patients with lupus PLE, eight experienced a positive steroid response, and the serum total cholesterol level was significantly higher in the positive steroid response group. A positive steroid response was associated with an initial high serum total cholesterol level and achievement of remission within 6 months.Conclusions:In lupus-related PLE, a high serum total cholesterol level could be a predictive factor for the initial steroid response, indicating a good response to steroid therapy alone.

Acute phase protein α1-antitrypsin reduces the bacterial burden in mice by selective modulation of innate cell responses.

Severe bacterial infection can cause sepsis, multiple organ dysfunction syndrome (MODS), and death. Human α1-antitrypsin (hAAT) is an antiinflammatory, immune-modulating, and tissue-protective circulating serine-protease inhibitor, with levels that increase during acute-phase responses. It is currently being evaluated as a therapeutic agent for individuals with diabetes and graft-versus-host disease. However, the concern of opportunistic bacterial infections has yet to be addressed. Therefore, we investigated host immune cell responses during acute bacterial infections under conditions of elevated hAAT levels. Peritonitis and sepsis models were created using wild-type mice and hAAT-transgenic mice. Bacterial loads, MODS, leukopenia, neutrophil infiltration, immune cell activation, circulating cytokine levels, and survival rates were then assessed. hAAT significantly reduced infection-induced leukopenia and liver, pancreas, and lung injury, and it significantly improved 24-hour survival rates. Unexpectedly, bacterial load was reduced. Levels of early proinflammatory mediators and neutrophil influx were increased by hAAT soon after infection but not during sterile peritonitis. hAAT reduces the bacterial burden after infection. Since hAAT does not block bacterial growth in culture, its effects might rely on host immune cell modulation. These outcomes suggest that prolonged hAAT treatment in patients without hAAT deficiency is safe. Additionally, hAAT treatment may be considered a preemptive therapeutic measure for individuals who are at risk for bacterial infections.

Proteolytic and N-glycan processing of human α1-antitrypsin expressed in Nicotiana benthamiana.

Plants are increasingly being used as an expression system for complex recombinant proteins. However, our limited knowledge of the intrinsic factors that act along the secretory pathway, which may compromise product integrity, renders process design difficult in some cases. Here, we pursued the recombinant expression of the human protease inhibitor α1-antitrypsin (A1AT) in Nicotiana benthamiana. This serum protein undergoes intensive posttranslational modifications. Unusually high levels of recombinant A1AT were expressed in leaves (up to 6 mg g(-1) of leaf material) in two forms: full-length A1AT located in the endoplasmic reticulum displaying inhibitory activity, and secreted A1AT processed in the reactive center loop, thus rendering it unable to interact with target proteinases. We found that the terminal protein processing is most likely a consequence of the intrinsic function of A1AT (i.e. its interaction with proteases [most likely serine proteases] along the secretory pathway). Secreted A1AT carried vacuolar-type paucimannosidic N-glycans generated by the activity of hexosaminidases located in the apoplast/plasma membrane. Notwithstanding, an intensive glycoengineering approach led to secreted A1AT carrying sialylated N-glycan structures largely resembling its serum-derived counterpart. In summary, we elucidate unique insights in plant glycosylation processes and show important aspects of postendoplasmic reticulum protein processing in plants.

An Endoplasmic Reticulum Cyclophilin Cpr5p Rescues Z-type α1-Antitrypsin from Retarded Folding

Human α1-antitrypsin (α1-AT) is a natural inhibitor of neutrophil elastases and has several dozens of genetic variants. Most of the deficient genetic variants of human α1-AT are unstable and cause pulmonary emphysema. However, the most clinically significant variant, Z-type α1-AT, exhibits retarded protein folding that leads to accumulation of folding intermediates. These aggregate within the endoplasmic reticulum (ER) of hepatocytes, subsequently causing liver cirrhosis as well as emphysema. Here, we studied the role of an ER folding assistant protein Cpr5p on Z-type α1-AT folding. Cpr5p was induced > 2-fold in Z-type α1-AT-expressing yeast cells compared with the wild type. Knockout of CPR5 exacerbated cytotoxicity of Z-type α1-AT, and re-introduction of CPR5 rescued the knockout cells from aggravated cytotoxicity caused by the α1-AT variant. Furthermore, Cpr5p co-immunoprecipitated with Z-type α1-AT and facilitated its protein folding. Our results suggest that protein-folding diseases may be suppressed by folding assistant proteins at the site of causal protein biosynthesis.

Acute-phase protein α1-antitrypsin--a novel regulator of angiopoietin-like protein 4 transcription and secretion.

The angiopoietin-like protein 4 (angptl4, also known as peroxisome proliferator-activated receptor [PPAR]γ-induced angiopoietin-related protein) is a multifunctional protein associated with acute-phase response. The mechanisms accounting for the increase in angptl4 expression are largely unknown. This study shows that human α1-antitrypsin (A1AT) upregulates expression and release of angplt4 in human blood adherent mononuclear cells and in primary human lung microvascular endothelial cells in a concentration- and time-dependent manner. Mononuclear cells treated for 1 h with A1AT (from 0.1 to 4 mg/ml) increased mRNA of angptl4 from 2- to 174-fold, respectively, relative to controls. In endothelial cells, the maximal effect on angptl4 expression was achieved at 8 h with 2 mg/ml A1AT (11-fold induction versus controls). In 10 emphysema patients receiving A1AT therapy (Prolastin), plasma angptl4 levels were higher relative to patients without therapy (nanograms per milliliter, mean [95% confidence interval] 127.1 [99.5-154.6] versus 76.8 [54.8-98.8], respectively, p = 0.045) and correlated with A1AT levels. The effect of A1AT on angptl4 expression was significantly diminished in cells pretreated with a specific inhibitor of ERK1/2 activation (UO126), irreversible and selective PPARγ antagonist (GW9662), or genistein, a ligand for PPARγ. GW9662 did not alter the ability of A1AT to induce ERK1/2 phosphorylation, suggesting that PPARγ is a critical mediator in the A1AT-driven angptl4 expression. In contrast, the forced accumulation of HIF-1α, an upregulator of angptl4 expression, enhanced the effect of A1AT. Thus, acute-phase protein A1AT is a physiological regulator of angptl4, another acute-phase protein.

Identification and Characterization of a Novel Secreted Glycosidase with Multiple Glycosidase Activities in Streptococcus intermedius

Streptococcus intermedius is a known human pathogen and belongs to the anginosus group (S. anginosus, S. intermedius, and S. constellatus) of streptococci (AGS). We found a large open reading frame (6,708 bp) in the lac operon, and bioinformatic analysis suggested that this gene encodes a novel glycosidase that can exhibit β-d-galactosidase and N-acetyl-β-d-hexosaminidase activities. We, therefore, named this protein "multisubstrate glycosidase A" (MsgA). To test whether MsgA has these glycosidase activities, the msgA gene was disrupted in S. intermedius. The msgA-deficient mutant no longer showed cell- and supernatant-associated β-d-galactosidase, β-d-fucosidase, N-acetyl-β-d-glucosaminidase, and N-acetyl-β-d-galactosaminidase activities, and all phenotypes were complemented in trans with a recombinant plasmid carrying msgA. Purified MsgA had all four of these glycosidase activities and exhibited the lowest Km with 4-methylumbelliferyl-linked N-acetyl-β-d-glucosaminide and the highest kcat with 4-methylumbelliferyl-linked β-d-galactopyranoside. In addition, the purified LacZ domain of MsgA had β-d-galactosidase and β-d-fucosidase activities, and the GH20 domain exhibited both N-acetyl-β-d-glucosaminidase and N-acetyl-β-d-galactosaminidase activities. The β-d-galactosidase and β-d-fucosidase activities of MsgA are thermolabile, and the optimal temperature of the reaction was 40°C, whereas almost all enzymatic activities disappeared at 49°C. The optimal temperatures for the N-acetyl-β-d-glucosaminidase and N-acetyl-β-d-galactosaminidase activities were 58 and 55°C, respectively. The requirement of sialidase treatment to remove sialic acid residues of the glycan branch end for glycan degradation by MsgA on human α1-antitrypsin indicates that MsgA has exoglycosidase activities. MsgA and sialidase might have an important function in the production and utilization of monosaccharides from oligosaccharides, such as glycans for survival in a normal habitat and for pathogenicity of S. intermedius.

A C. elegans model of human α1-antitrypsin deficiency links components of the RNAi pathway to misfolded protein turnover.

The accumulation of serpin oligomers and polymers within the endoplasmic reticulum (ER) causes cellular injury in patients with the classical form α1-antitrypsin deficiency (ATD). To better understand the cellular and molecular genetic aspects of this disorder, we generated transgenic C. elegans strains expressing either the wild-type (ATM) or Z mutant form (ATZ) of the human serpin fused to GFP. Animals secreted ATM, but retained polymerized ATZ within dilated ER cisternae. These latter animals also showed slow growth, smaller brood sizes and decreased longevity; phenotypes observed in ATD patients or transgenic mouse lines expressing ATZ. Similar to mammalian models, ATZ was disposed of by autophagy and ER-associated degradation pathways. Mutant strains defective in insulin signaling (daf-2) also showed a marked decrease in ATZ accumulation. Enhanced ATZ turnover was associated with the activity of two proteins central to systemic/exogenous (exo)-RNAi pathway: the dsRNA importer, SID-1 and the argonaute, RDE-1. Animals with enhanced exo-RNAi activity (rrf-3 mutant) phenocopied the insulin signaling mutants and also showed increased ATZ turnover. Taken together, these studies allude to the existence of a novel proteostasis pathway that mechanistically links misfolded protein turnover to components of the systemic RNAi machinery.

Retarded protein folding of the human Z-type α1-antitrypsin variant is suppressed by Cpr2p

The human Z-type α1-antitrypsin variant has a strong tendency to accumulate folding intermediates due to extremely slow protein folding within the endoplasmic reticulum (ER) of hepatocytes. Human α1-antitrypsin has 17 peptidyl-prolyl bonds per molecule; thus, the effect of peptidyl-prolyl isomerases on Z-type α1-antitrypsin protein folding was analyzed in this study. The protein level of Cpr2p, a yeast ER peptidyl-prolyl isomerase, increased more than two-fold in Z-type α1-antitrypsin-expressing yeast cells compared to that in wild-type α1-antitrypsin-expressing cells. When CPR2 was deleted from the yeast genome, the cytotoxicity of Z-type α1-antitrypsin increased significantly. The interaction between Z-type α1-antitrypsin and Cpr2p was confirmed by co-immunoprecipitation. In vitro folding assays showed that Cpr2p facilitated Z-type α1-antitrypsin folding into the native state. Furthermore, Cpr2p overexpression significantly increased the extracellular secretion of Z-type α1-antitrypsin. Our results indicate that ER peptidyl-prolyl isomerases may rescue Z-type α1-antitrypsin molecules from retarded folding and eventually relieve clinical symptoms caused by this pathological α1-antitrypsin.

Empty virions in AAV8 vector preparations reduce transduction efficiency and may cause total viral particle dose-limiting side effects

Empty virions are inadvertent by-products of recombinant adeno-associated virus (rAAV) packaging process, resulting in vector lots with mixtures of full and empty virions at variable ratios. Impact of empty virions on the efficiency and side effects of rAAV transduction has not been well characterized. Here, we generated partially and completely empty AAV8 virions, fully packaged rAAV8 lots, and mixtures of empty and fully packaged virions with variable ratios of empty virions. The aforementioned dosing formulations of rAAV8 expressing either cellular (EGFP (enhanced green fluorescent protein) or nuclear-targeted (n) LacZ) or secreted (human α1-antitrypsin (hA1AT)) reporter genes were intravenously injected into two different mouse strains, followed by analyses of transgene expressions and serum alanine aminotransferase (ALT) levels at different time points. We found that addition of empty particles to the fixed doses of rAAV8 preparations repressed liver transduction up to 64% (serum hA1AT) and 44% (nLacZ) in C57BL/6 mice, respectively. The similar trend in inhibiting EGFP expression together with concurrent elevations of serum ALT levels were observed in the BALB/c mice, indicating that empty particles may also exacerbate side effects of rAAV8 EGFP transduction. Our results suggest that removal of empty particles from rAAV preparations may improve efficacy and safety of AAV in clinical applications.

Urochordate serpins are Classified into Six Groups Encoded by Exon-Intron Structures, Microsynteny and Bayesian Phylogenetic Analyses.

Members of serpin superfamily are involved in wide array of cellular processes to control proteolytic activities of eukaryotic organisms. Vertebrate serpins are extensively studied and reported to be classified into six groups (V1-V6) based on gene structures. However, there is no study conducted for serpins in urochordates (the closest living invertebrates related to vertebrates) to date. To unravel further the phylogenetic history of serpin genes, we characterized serpin genes from two urochordates (Ciona intestinalis and Ciona savignyi). There are 11 and 5 serpins in the C. intestinalis and C. savignyi, respectively. The exon/intron structures and genomic locus comparisons together with sequence phylogenetic analysis, suggested that urochordate serpins are classified into six groups (U1-U6), different from six groups (V1-V6) of vertebrate serpins. Human α1-antitrypsin shared lower sequence identities and similarities with urochordates serpins ranged from 14-29% and 30-49%, respectively. Based on protein sequences, genes and genomic architectures, we conclude that these two urochordates do not contain a single copy of genuine ortholog of the vertebrate serpins.