ATP-binding Cassette Subfamily A Member 3 Research Articles

Cyclosporine A in children with ABCA3 deficiency.

Biallelic ATP-binding cassette subfamily A member 3 (ABCA3) variants can cause interstitial lung disease in children and adults, for which no proven treatments exist. Recent in vitro evidence suggested that cyclosporine A (CsA) could correct some ABCA3 variants, however for other variants this is unknown and no data in patients exist. We retrieved the clinical data of two children aged 2 and 4 years carrying homozygous ABCA3 variants (G210C and Q1045R, respectively) and empiric CsA treatment from the Kids Lung Register database. In vitro experiments functionally characterized the two variants and explored the effects of CsA alone or combined with hydroxychloroquine (HCQ) in a human alveolar epithelial cell line (A549) derived from adenocarcinoma cells. Six weeks following the introduction of CsA, both children required a reduced O2 flow supply, which then remained stable on CsA. Later, when CsA was discontinued, the clinical status of the children remained unchanged. Of note, the children simultaneously received prednisolone, azithromycin, and HCQ. In vitro, both ABCA3 variants demonstrated defective lysosomal colocalization and impaired ABCA3+ vesicle size, with proteolytic cleavage impairment only in Q1045R. CsA alone corrected the trafficking impairment and ABCA3+ vesicle size of both variants with a variant-specific effect on phosphatidylcholine recycling in G210C. CsA combined with HCQ were additive for improving trafficking of ABCA3 in G210C, but not in Q1045R. CsA treatment might be helpful for certain patients with ABCA3 deficiency, however, currently strong clinical supporting evidence is lacking. Appropriate trials are necessary to overcome this unmet need.

ABCA3, a tumor suppressor gene, inhibits the proliferation, migration and invasion of lung adenocarcinoma by regulating the epithelial‑mesenchymal transition process.

Lung adenocarcinoma (LUAD) is one of the most common types of lung cancer, which affects the life and health of patients. The role of ATP-binding cassette subfamily A member 3 (ABCA3) in the occurrence and development of LUAD is unclear; therefore, ABCA3 expression in LUAD and other tumors was analyzed in the present study. In addition, ABCA3 expression in patients with LUAD and their survival were analyzed using a public database. ABCA3 co-expressed genes were identified and their enriched pathways were analyzed. Furthermore, ABCA3 expression was knocked down in LUAD cell lines. The proliferation, invasion and migration of cells, and the process of epithelial-mesenchymal transition (EMT), were studied through cytological and molecular biology experiments. Compared with that in normal lung tissues, ABCA3 expression was significantly reduced in tumor tissues. Patients with low ABCA3 expression had a markedly worse overall survival compared with those with high ABCA3 expression. Notably, abnormal ABCA3 expression has been observed in a variety of tumors. Subsequently, multiple pathophysiological pathways enriched by ABCA3 and its co-expressed genes were explored. Furthermore, the malignant behavior of tumor cells was enhanced when ABCA3 expression was knocked down, and the EMT process was activated after ABCA3 expression was knocked down. In conclusion, as a tumor suppressor gene, ABCA3 serves a protective role in the development of tumors, and may have a potential role in clinical applications, and thus, is worthy of further study.

ABCA3 Deficiency-Variant-Specific Response to Hydroxychloroquine.

Biallelic variants in ABCA3, the gene encoding the lipid transporter ATP-binding cassette subfamily A member 3 (ABCA3) that is predominantly expressed in alveolar type II cells, may cause interstitial lung diseases in children (chILD) and adults. Currently, there is no proven therapy, but, frequently, hydroxychloroquine (HCQ) is used empirically. We hypothesized that the in vitro responsiveness to HCQ might correlate to patients' clinical outcomes from receiving HCQ therapy. The clinical data of the subjects with chILD due to ABCA3 deficiency and treated with HCQ were retrieved from the literature and the Kids Lung Register data base. The in vitro experiments were conducted on wild type (WT) and 16 mutant ABCA3-HA-transfected A549 cells. The responses of the functional read out were assessed as the extent of deviation from the untreated WT. With HCQ treatment, 19 patients had improved or unchanged respiratory conditions, and 20 had respiratory deteriorations, 5 of whom transiently improved then deteriorated. The in vitro ABCA3 functional assays identified two variants with complete response, five with partial response, and nine with no response to HCQ. The variant-specific HCQ effects in vivo closely correlated to the in vitro data. An ABCA3+ vesicle volume above 60% of the WT volume was linked to responsiveness to HCQ; the HCQ treatment response was concentration dependent and differed for variants in vitro. We generated evidence for an ABCA3 variant-dependent impact of the HCQ in vitro. This may also apply for HCQ treatment in vivo, as supported by the retrospective and uncontrolled data from the treatment of chILD due to ABCA3 deficiency.

Quantifying Functional Impairment of ABCA3 Variants Associated with Interstitial Lung Disease.

ATP-binding cassette subfamily A member 3 (ABCA3) is a lipid transporter within alveolar type II cells. Patients with bi-allelic variants in ABCA3 may suffer from a variable severity of interstitial lung disease. We characterized and quantified ABCA3 variants' overall lipid transport function by assessing the in vitro impairment of its intracellular trafficking and pumping activity. We expressed the results relative to the wild type, integrated the quantitative readouts from eight different assays and used newly generated data combined with previous results to correlate the variants' function and clinical phenotype. We differentiated normal (within 1 normalized standard deviation (nSD) of the wild-type mean), impaired (within 1 to 3 nSD) and defective (beyond 3 nSD) variants. The transport of phosphatidylcholine from the recycling pathway into ABCA3+ vesicles proved sensitive to the variants' dysfunction. The sum of the quantitated trafficking and pumping predicted a clinical outcome. More than an approximately 50% loss of function was associated with considerable morbidity and mortality. The in vitro quantification of ABCA3 function enables detailed variant characterization, substantially improves the phenotype prediction of genetic variants and possibly supports future treatment decisions.

ABCA3-related interstitial lung disease beyond infancy

BackgroundThe majority of patients with childhood interstitial lung disease (chILD) caused by pathogenic variants in ATP binding cassette subfamily A member 3 (ABCA3) develop severe respiratory insufficiency within their first...

Childhood interstitial lung disease: The end of a diagnostic odyssey

Dear Editor, Childhood interstitial lung disease is a heterogeneous group of rare disorders featuring pulmonary interstitial remodelling and diffuse parenchymal infiltrates on imaging.1 Incidence is estimated at 0.13–16.2 cases/100,000 children per year.1 ABCA3 (ATP-Binding Cassette, Subfamily A, Member 3) (OMIM #601615) is expressed in alveolar type II cells involved in pulmonary surfactant production,2 thus attributed

Primary Nasal Epithelial Cells as a Surrogate Cell Culture Model for Type-II Alveolar Cells to Study ABCA-3 Deficiency.

ATP Binding Cassette Subfamily A Member 3 (ABCA-3) is a lipid transporter protein highly expressed in type-II alveolar (AT-II) cells. Mutations in ABCA3 can result in severe respiratory disease in infants and children. To study ABCA-3 deficiency in vitro, primary AT-II cells would be the cell culture of choice although sample accessibility is limited. Our aim was to investigate the suitability of primary nasal epithelial cells, as a surrogate culture model for AT-II cells, to study ABCA-3 deficiency. Expression of ABCA3, and surfactant protein genes, SFTPB and SFTPC, was detected in primary nasal epithelial cells but at a significantly lower level than in AT-II cells. ABCA-3, SP-B, and SP-C were detected by immunofluorescence microscopy in primary nasal epithelial cells. However, SP-B and SP-C were undetectable in primary nasal epithelial cells using western blotting. Structurally imperfect lamellar bodies were observed in primary nasal epithelial cells using transmission electron microscopy. Functional assessment of the ABCA-3 protein demonstrated that higher concentrations of doxorubicin reduced cell viability in ABCA-3 deficient nasal epithelial cells compared to controls in an assay-dependent manner. Our results indicate that there may be a role for primary nasal epithelial cell cultures to model ABCA-3 deficiency in vitro, although additional cell culture models that more effectively recapitulate the AT-II phenotype may be required.

High-Content Screening Identifies Cyclosporin A as a Novel ABCA3-Specific Molecular Corrector.

ABCA3 (ATP-binding cassette subfamily A member 3) is a lipid transporter expressed in alveolar type II cells and localized in the limiting membrane of lamellar bodies. It is crucial for pulmonary surfactant storage and homeostasis. Mutations in the ABCA3 gene are the most common genetic cause of respiratory distress syndrome in mature newborns and of interstitial lung disease in children. Apart from lung transplant, there is no cure available. To address the lack of causal therapeutic options for ABCA3 deficiency, a rapid and reliable approach is needed to investigate variant-specific molecular mechanisms and to identify pharmacologic modulators for monotherapies or combination therapies. To this end, we developed a phenotypic cell-based assay to autonomously identify ABCA3 wild-type-like or mutant-like cells by using machine learning algorithms aimed at identifying morphologic differences in wild-type and mutant cells. The assay was subsequently used to identify new drug candidates for ABCA3-specific molecular correction by using high-content screening of 1,280 Food and Drug Administration-approved small molecules. Cyclosporin A was identified as a potent corrector, specific for some but not all ABCA3 variants. Results were validated by using our previously established functional small-format assays. Hence, cyclosporin A may be selected for orphan drug evaluation in controlled repurposing trials in patients.

Epitope mimicry analysis of SARS-COV-2 surface proteins and human lung proteins

BackgroundAutoimmune response after the infection of SARS-COV-2 is evident as more cases of Guillain Barre syndrome and Kawasaki disease are diagnosed. In this study, we aim to investigate a possible mechanism of autoimmune lung injury. MethodsWe extracted the peptide sequences of surface proteins of the SARS-COV-2 from the NCBI data protein. We used Blastp to assess the homologous sequences between the human proteins in the UNIPROT database that are associated with respiratory distress. Then, we filtered the homologous sequences to those selectively expressed in the lung and homologous to surface viral proteins. We then assessed the epitope sequences for MHC-I and MHC-II using recommended settings and reference MHC in the IEDB database. ResultsHomeobox protein 2.1 (NKX2-1) and ATP-binding cassette sub-family A member 3 (ABCA3) showed homologous sequence to both surface glycoproteins and envelope proteins. The HLA-DR and HLA-DQ had a similar binding pattern to ABCA3 as surface glycoproteins and envelope proteins, respectively. Other HLA molecules that had a similar binding pattern to SARS-COV-2 as human proteins were HLA-A and HLA-DP. ConclusionOur study indicates that there is a possible autoimmune mechanism underlying the acute respiratory distress syndrome in SARS-COV-2.

Metabolic labelling of choline phospholipids probes ABCA3 transport in lamellar bodies

In the metabolism of pulmonary surfactant, the ATP-binding cassette sub-family A member 3 (ABCA3) is a crucial protein in the formation of the storage compartment for surfactant, the lamellar body (LB), and the transport of phospholipids in it. Mutations in ABCA3 not only disturb surfactant metabolism but also cause chronic interstitial lung diseases. Assays for ABCA3 transport function are needed to investigate pathophysiology of the mutations and treatment options for the patients.We metabolically labeled choline (Cho) head phospholipids with the Cho analogue, propargyl-Cho. The universal incorporation of propargyl-Cho was confirmed by mass spectrometry and labeled lipids were visualized in confocal microscopy by click reaction with an azide fluorophore. After pulse-labeling propargyl-Cho labeled lipids accumulated in ABCA3+ vesicles in a time and concentration dependent manner. When treated with the choline kinase inhibitor MN58b during the first 12 h, the lipids intensity inside ABCA3+ vesicles decreased, whereas intensity was unchanged when treated after 12 h. Miltefosine, a substrate of ABCA3, decreased the incorporation of labeled lipids in ABCA3+ vesicles at all time points. The lipids intensity inside the mutated (p.N568D or p.L1580P) ABCA3+ vesicles was decreased compared to wild type, while the intensity outside of vesicles showed no difference.Propargyl-Cho can metabolically pulse-label Cho phospholipids. Visualization and quantification of fluorescence intensity of the labeled lipids inside ABCA3+ vesicles at equilibrium can specifically assess the transport function of ABCA3.

Lung disease in STAT3 hyper-IgE syndrome requires intense therapy.

Pulmonary complications are responsible for high morbidity and mortality rates in patients with the rare immunodeficiency disorder STAT3 hyper-IgE syndrome (STAT3-HIES). The aim of this study was to expand knowledge about lung disease in STAT3-HIES. The course of pulmonary disease, radiological and histopathological interrelations, therapeutic management, and the outcome of 14 STAT3-HIES patients were assessed. The patients' quality of life was compromised most by pulmonary disease. All 14 patients showed first signs of lung disease at a median onset of 1.5years of age. Lung function revealed a mixed obstructive-restrictive impairment with reduced FEV1 and FVC in 75% of the patients. The severity of lung function impairment was associated with Aspergillus fumigatus infection and prior lung surgery. Severe lung tissue damage, with reduced numbers of ATP-binding cassette sub-family A member 3 (ABCA3) positive type II pneumocytes, was observed in the histological assessment of two deceased patients. Imaging studies of all patients above 6years of age showed severe airway and parenchyma destruction. Lung surgeries frequently led to complications, including fistula formation. Long-term antifungal and antibacterial treatment proved to be beneficial, as were inhalation therapy, chest physiotherapy, and exercise. Regular immunoglobulin replacement therapy tended to stabilize lung function. Due to its severity, pulmonary disease in STAT3-HIES patients requires strict monitoring and intensive therapy.

ABCA3 missense mutations causing surfactant dysfunction disorders have distinct cellular phenotypes.

Mutations in the ATP-binding cassette subfamily A member 3 (ABCA3) gene are the most common monogenetic cause of surfactant dysfunction disorders in newborns and interstitial lung diseases in children and young adults. Although the effect of mutations resulting in truncated or incomplete proteins can be predicted, the consequences of missense variants cannot be as easily. Our aim was to investigate the intracellular handling and disturbance of the cellular surfactant system in a stable cell model with several different clinically relevant ABCA3 missense mutations. We found that the investigated missense mutations within the ABCA3 gene affect surfactant homeostasis in different ways: first by disrupting intracellular ABCA3 protein localization (c.643C>A, p.Q215K; c.2279T>G, p.M760R), second by impairing the lipid transport of ABCA3 protein (c.875A>T, p.E292V; c.4164G>C, p.K1388N), and third by yet undetermined mechanisms predisposing for the development of interstitial lung diseases despite correct localization and normal lipid transport of the variant ABCA3 protein (c.622C>T, p.R208W; c.863G>A, p.R288K; c.2891G>A, p.G964D). In conclusion, we classified cellular consequences of missense ABCA3 sequence variations leading to pulmonary disease of variable severity. The corresponding molecular pathomechanisms of such ABCA3 variants may specifically be addressed by targeted treatments.

The classification of ATP-binding cassette subfamily A member 3 mutations using the cystic fibrosis transmembrane conductance regulator classification system.

ImportanceThe ATP‐binding cassette subfamily A member 3 (ABCA3) protein plays a vital role in surfactant homeostasis. Mutations in the ABCA3 gene lead to the development of interstitial lung disease. In the most severe manifestation, mutations can lead to a fatal respiratory distress syndrome in neonates. ABCA3 belongs to the same ATP‐binding cassette transporter superfamily as the cystic fibrosis transmembrane conductance regulator (CFTR), the gene that causes cystic fibrosis.ObjectiveTo classify ABCA3 mutations in a manner similar to CFTR mutations in order to take advantage of recent advances in therapeutics.MethodsSequence homology between the CFTR protein and the ABCA3 protein was established. The region of CFTR that is a target for the new potentiator class of drugs was of particular interest. We performed a literature search to obtain all published mutations that were thought to be disease causing. We classified these mutations using the established CFTR classification system. When possible, we drew on previous experimental classification of ABCA3 mutations.ResultsAlthough the proteins share the same overall structure, only a 19% identity was established between CFTR and ABCA3. The CFTR therapeutic target region has a 22% homology with the corresponding ABCA3 region. Totally 233 unique protein mutations were identified. All protein mutations were classified and mapped to a schematic diagram of the ABCA3 protein.InterpretationThis new classification system for ABCA3, based on CFTR classification, will likely aid further research of clinical outcomes and identification of mutation‐tailored therapeutics, with the aim for improving clinical care for patients with ABCA3 mutations.

Lung disease caused by ABCA3 mutations

BackgroundKnowledge about the clinical spectrum of lung disease caused by variations in the ATP binding cassette subfamily A member 3 (ABCA3) gene is limited. Here we describe genotype-phenotype correlations in...

Abca3 haploinsufficiency is a risk factor for lung injury induced by hyperoxia or mechanical ventilation in a murine model

Heterozygous ATP-binding-cassette subfamily A member 3 (ABCA3) mutations are associated with neonatal respiratory complications. In an adult murine model, we investigated whether Abca3 haploinsufficiency is a predisposing factor for lung injury induced by hyperoxia or mechanical ventilation. Abca3 haploinsufficient (Abca3(+/-)) and wild-type (WT) mice were prospectively randomized to 25 min of ventilation or 72 h of hyperoxia or left unchallenged in air. As compared with WT mice, unchallenged Abca3(+/-) mice had significantly decreased lung phosphatidylcholine (PC) and phosphatidylglycerol (PG) levels (P < 0.02) and decreased lung compliance (P < 0.05). When ventilated for 25 min, Abca3(+/-) mice demonstrated a significantly greater increase in bronchoalveolar lavage (BAL) interleukins (P ≤ 0.01) and lung wet to dry ratio (P < 0.005). Hyperoxia resulted in increased compliance (P < 0.05) and total lung capacity (TLC) (P = 0.01) only in the Abca3(+/-) mice, consistent with enlarged alveolar spaces. The ratio of PC to PG in BAL-relevant for surfactant dysfunction-was significantly elevated by oxygen exposure, with the greatest increase in Abca3(+/-) mice. In a murine model, Abca3 haploinsufficiency results in an altered biochemical and lung mechanical phenotype, as well as a greater lung injury induced by hyperoxia or mechanical ventilation. The inability to maintain a normal PC/PG ratio appears to play a key role.

Genetic testing in children with surfactant dysfunction

ObjectivesTo present the UK experience in genetic diagnoses of surfactant protein dysfunction disorders and develop a referral algorithm for neonates and children with persistent respiratory problems.Materials and methodsBetween 2006 and...

Acute megakaryoblastic leukemia and severe pulmonary fibrosis in a child with down syndrome: Successful treatment with ultra low-dose cytarabine using GATA1 mutation to monitor minimal residual disease

Acute megakaryoblastic leukemia and severe pulmonary fibrosis in a child with down syndrome: Successful treatment with ultra low-dose cytarabine using GATA1 mutation to monitor minimal residual disease

Loss of Shp2 in alveoli epithelia induces deregulated surfactant homeostasis, resulting in spontaneous pulmonary fibrosis

Type II alveolar epithelial (AT-II) cells produce pulmonary surfactant proteins that are essential for alveolar function. AT-II is a major target in lung injury, and ineffective repair of damaged alveolar epithelia has been postulated to cause pulmonary fibrosis. Previous studies have shown that tyrosine phosphatase Shp2 is expressed highly in the embryonic lung epithelial buds, and Shp2 activity is required for FGF-induced lung branching morphogenesis. To investigate in vivo function of pulmonary Shp2, we generated alveoli epithelia-specific Shp2-knockout (Shp2(Δ/Δ)) mice. Shp2(Δ/Δ) mice exhibit marked reduction in surfactant proteins, disorganized lamellar bodies, increased alveolar epithelial apoptosis, and interstitial pulmonary fibrosis without preceding inflammation. Mechanistically, Shp2 acts to mediate expression of thyroid transcription factor 1 (TTF1) and ATP-binding cassette subfamily A member 3 (ABCA3). Shp2 also plays a central role in mediating FGF/GAB/ERK activity, required for epithelial repair program. Together, our results identify a novel role of tyrosine phosphatase Shp2 in surfactant homeostasis, and deregulation of Shp2 triggers spontaneous pulmonary fibrosis with minimal inflammation.

Molecular and cellular characteristics of ABCA3 mutations associated with diffuse parenchymal lung diseases in children

ABCA3 (ATP-binding cassette subfamily A, member 3) is expressed in the lamellar bodies of alveolar type II cells and is crucial to pulmonary surfactant storage and homeostasis. ABCA3 gene mutations have been associated with neonatal respiratory distress (NRD) and pediatric interstitial lung disease (ILD). The objective of this study was to look for ABCA3 gene mutations in patients with severe NRD and/or ILD. The 30 ABCA3 coding exons were screened in 47 patients with severe NRD and/or ILD. ABCA3 mutations were identified in 10 out of 47 patients, including 2 homozygous, 5 compound heterozygous and 3 heterozygous patients. SP-B and SP-C expression patterns varied across patients. Among patients with ABCA3 mutations, five died shortly after birth and five developed ILD (including one without NRD). Functional studies of p.D253H and p.T1173R mutations revealed that p.D253H and p.T1173R induced abnormal lamellar bodies. Additionally, p.T1173R increased IL-8 secretion in vitro. In conclusion, we identified new ABCA3 mutations in patients with life-threatening NRD and/or ILD. Two mutations associated with ILD acted via different pathophysiological mechanisms despite similar clinical phenotypes.

ATP-binding cassette sub-family A member 3 (ABCA3)

ATP-binding cassette sub-family A member 3 (ABCA3)