CFTR Channel Research Articles

Discovering the chloride pathway in the CFTR channel

Cystic fibrosis (CF), a lethal monogenic disease, is caused by pathogenic variants of the CFTR chloride channel. The majority of CF mutations affect protein folding and stability leading overall to diminished apical anion conductance of epithelial cells. The recently published cryo-EM structures of full-length human and zebrafish CFTR provide a good model to gain insight into structure–function relationships of CFTR variants. Although, some of the structures were determined in the phosphorylated and ATP-bound active state, none of the static structures showed an open pathway for chloride permeation. Therefore, we performed molecular dynamics simulations to generate a conformational ensemble of the protein and used channel detecting algorithms to identify conformations with an opened channel. Our simulations indicate a main intracellular entry at TM4/6, a secondary pore at TM10/12, and a bottleneck region involving numerous amino acids from TM1, TM6, and TM12 in accordance with experiments. Since chloride ions entered the pathway in our equilibrium simulations, but did not traverse the bottleneck region, we performed metadynamics simulations, which revealed two possible exits. One of the chloride ions exits includes hydrophobic lipid tails that may explain the lipid-dependency of CFTR function. In summary, our in silico study provides a detailed description of a potential chloride channel pathway based on a recent cryo-EM structure and may help to understand the gating of the CFTR chloride channel, thus contributing to novel strategies to rescue dysfunctional mutants.

Тargeted therapy for CF patients with F508del/F508del genotype

Targeted therapy for cystic fibrosis (CF) is a novel approach to CF treatment that can restore and potentiate CFTR channel activity. Lumacaftor/ivacaftor combination therapy is related to significant clinical and functional benefits in CF patients who are homozygous for F508del CFTR mutation. The authors described a case of effective treatment with lumacaftor/ivacaftor combination in a homozygous F508del CF patient with severe lung disease. This experience demonstrates an urgent need to make this pathogenic treatment available for patients with this genotype in Russia.

Identifying the molecular target sites for CFTR potentiators GLPG1837 and VX-770.

The past two decades have witnessed major breakthroughs in developing compounds that target the chloride channel CFTR for the treatment of patients with cystic fibrosis. However, further improvement in affinity and efficacy for these CFTR modulators will require insights into the molecular interactions between CFTR modulators and their binding targets. In this study, we use in silico molecular docking to identify potential binding sites for GLPG1837, a CFTR potentiator that may share a common mechanism and binding site with VX-770, the FDA-approved drug for patients carrying mutations with gating defects. Among the five binding sites predicted by docking, the two top-scoring sites are located at the interface between CFTR's two transmembrane domains: site I consists of D924, N1138, and S1141, and site IIN includes F229, F236, Y304, F312, and F931. Using mutagenesis to probe the importance of these sites for GLPG187 binding, we find that disruption of predicted hydrogen-bonding interactions by mutation of D924 decreases apparent affinity, while hydrophobic amino acids substitutions at N1138 and introduction of positively charged amino acids at S1141 improve the apparent affinity for GLPG1837. Alanine substitutions at Y304, F312, and F931 (site IIN) decrease the affinity for GLPG1837, whereas alanine substitutions at F229 and F236 (also site IIN), or at residues in the other three lower-scoring sites, have little effect. In addition, current relaxation analysis to assess the apparent dissociation rate of VX-770 yields results consistent with the dose-response experiments for GLPG8137, with the dissociation rate of VX-770 accelerated by D924N, F236A, Y304A, and F312A, but decelerated by N1138L and S1141K mutations. Collectively, these data identify two potential binding sites for GLPG1837 and VX-770 in CFTR. We discuss the pros and cons of evidence for these two loci and the implications for future drug design.

Staphylococcus aureus in chronic rhinosinusitis: the effect on the epithelial chloride channel (cystic fibrosis transmembrane conductance regulator, CFTR) and the epithelial sodium channel (ENaC) physiology

Background: Chronic rhinosinusitis (CRS) is an inflammatory disease of the nose and the paranasal sinuses, often associated with an infection by Staphylococcus aureus (S. aureus). Disturbance in the function of ion channels is regarded as an etiological factor for pathogenesis of CRS.Aims: The study aims to measure the mRNA expression of the ENaC and CFTR ion channels in nasal epithelial cells (NECs) and to investigate the effect of both the budesonide and S. aureus on these ion channels.Materials and method: NECs biopsies obtained from healthy volunteers and patients with CRS. NECs were infected with S. aureus strains and/or budesonide to study the mRNA expression levels of the ENaC and CFTR ion channels.Results: The mRNA expression level of CFTR was increased while that of ENaC was decreased. S. aureus infection and budesonide treatment induced a significant modulation of ENaC and CFTR ion channels expression.Conclusion: The CFTR and ENaC ion channel physiology are of importance in the pathogenesis of CRS. Exposure to S. aureus infection and treatment with budesonide modulated the mRNA expression of CFTR and ENaC ion channels.Significance: Better understanding of the pathophysiology of CRS.

ОПЫТ ПРИМЕНЕНИЯ МЕТОДОВ ОЦЕНКИ ФУНКЦИОНАЛЬНОСТИ АНИОННОГО КАНАЛА CFTR У ПАЦИЕНТОВ С УСТАНОВЛЕННЫМ И ПРЕДПОЛАГАЕМЫМ ДИАГНОЗОМ МУКОВИСЦИДОЗА

ОПЫТ ПРИМЕНЕНИЯ МЕТОДОВ ОЦЕНКИ ФУНКЦИОНАЛЬНОСТИ АНИОННОГО КАНАЛА CFTR У ПАЦИЕНТОВ С УСТАНОВЛЕННЫМ И ПРЕДПОЛАГАЕМЫМ ДИАГНОЗОМ МУКОВИСЦИДОЗА

Impact of CFTR-modulating drugs on GH-IGF-1 axis impairment in adult patients with cystic fibrosis.

A new class of drugs in the treatment of cystic fibrosis (CF) includes two agents: lumacaftor, which corrects CFTR channel protein, and ivacaftor, which increases CFTR channel activity. In our previous study we recruited 50 stable adults with CF and 16 of them showed growth hormone deficit (GHD): 7 patients severe and 9 patients partial GHD. We decided to re-evaluate ten patients with the GHRH + arginine test of whom only five were treated with lumacaftor/ivacaftor. All CF patients in therapy with lumacaftor/ivacaftor showed a marked improvement in GHD. Two patients moved from a severe GHD to a normal response to the GH/IGF-1 axis test, and three patients who had partial GHD moved to normal response. The pituitary gland may be damaged by CF disease and could benefit of the action of correcting drugs.

Slc26 Family of Anion Transporters in the Gastrointestinal Tract: Expression, Function, Regulation, and Role in Disease.

SLC26 family members are multifunctional transporters of small anions, including Cl- , HCO3 - , sulfate, oxalate, and formate. Most SLC26 isoforms act as secondary (coupled) anion transporters, while others mediate uncoupled electrogenic transport resembling Cl- channels. Of the 11 described SLC26 isoforms, the SLC26A1,2,3,6,7,9,11 are expressed in the gastrointestinal tract, where they participate in salt and water transport, surface pH-microclimate regulation, affect the microbiome composition, the absorption, and secretion of oxalate and sulfate, and other functions that require further study. Several intestinal or extra-intestinal diseases are related to SLC26A mutations. Patients with congenital chloride diarrhea (CLD) suffer from Cl- -rich acidic diarrhea and systemic alkalosis due to SLC26A3 mutations. Patients with osteochondrodysplastic syndromes experience skeletal defects due to SLC26A2 mutations, resulting in defective sulfate absorption in enterocytes and sulfate uptake in chondrocytes. Because of functional interactions between SLC26 and other proteins, such as the Cl- channel CFTR, some of the intestinal cystic fibrosis manifestations may be attributed to impaired SLC26 isoform localization and function. The altered expression of SLC26 members due to inflammation or operative procedures have important consequences on intestinal transport and barrier function in common diseases as inflammatory bowel disease or bariatric surgery. The present review gives an overview on the current state of knowledge of the intestinally expressed SLC26A isoforms (SLC26A1,2,3,6,7,9,11) from the history of their functional identification, cloning and expression, the insights into their function, interaction partners and regulation gained in heterologous expression systems and Slc26a-deficient mice, to information about their transcriptional regulation and roles in gastrointestinal disease manifestations. © 2019 American Physiological Society. Compr Physiol 9:839-872, 2019.

Functional Role of Basolateral ClC-2 Channels in the Regulation of Duodenal Anion Secretion in Mice.

Although ClC-2 channels are important in colonic Cl- secretion, it is unclear about their roles in small intestinal anion secretion. Therefore, we sought to examine whether ClC-2 channels play important roles in anion secretion, particularly duodenal bicarbonate secretion (DBS). Duodenal mucosae from mice were stripped of seromuscular layers and mounted in Ussing chambers. Both duodenal short-circuit current (Isc) and HCO3- secretion in vitro were simultaneously recorded. DBS in vivo was measured by a CO2-sensitive electrode. Lubiprostone, a selective ClC-2 activator, concentration-dependently increased both duodenal Isc and DBS only when applied basolaterally, but not when applied apically. Removal of extracellular Cl- abolished lubiprostone-induced duodenal Isc, but did not alter HCO3- secretion even in the presence of DIDS, a Cl-/HCO3- exchanger inhibitor. However, further addition of glibenclamide, a CFTR channel blocker, abolished lubiprostone-evoked HCO3- secretion. Moreover, lubiprostone-induced HCO3- secretion was impaired in CFTR-/- mice compared to wild-type littermates. Luminal perfusion of duodenal lumen with lubiprostone did not alter basal DBS in vivo, but lubiprostone (i.p.) was able to induce DBS, which was also significantly inhibited by Cd2+, a ClC-2 channel blocker. [Ca2+]cyt level, Ca2+-activated K+ channel- and cAMP-mediated duodenal Isc, and HCO3- secretion were unchanged by lubiprostone. We have provided the first evidence for the novel functional role of basolateral ClC-2 channels in the regulation of duodenal anion secretion.

Phage therapy against Pseudomonas aeruginosa infections in a cystic fibrosis zebrafish model

Cystic fibrosis (CF) is a hereditary disease due to mutations in the CFTR gene and causes mortality in humans mainly due to respiratory infections caused by Pseudomonas aeruginosa. In a previous work we used phage therapy, which is a treatment with a mix of phages, to actively counteract acute P. aeruginosa infections in mice and Galleria mellonella larvae. In this work we apply phage therapy to the treatment of P. aeruginosa PAO1 infections in a CF zebrafish model. The structure of the CFTR channel is evolutionary conserved between fish and mammals and cftr-loss-of-function zebrafish embryos show a phenotype that recapitulates the human disease, in particular with destruction of the pancreas. We show that phage therapy is able to decrease lethality, bacterial burden, and the pro-inflammatory response caused by PAO1 infection. In addition, phage administration relieves the constitutive inflammatory state of CF embryos. To our knowledge, this is the first time that phage therapy is used to cure P. aeruginosa infections in a CF animal model. We also find that the curative effect against PAO1 infections is improved by combining phages and antibiotic treatments, opening a useful therapeutic approach that could reduce antibiotic doses and time of administration.

Different functional roles for K+ channel subtypes in regulating small intestinal glucose and ion transport.

ABSTRACTAlthough K+ channels are important in mediating the driving force for colonic ion transport, their role in small intestinal transport is poorly understood. To investigate this, small intestinal short circuit currents (Isc) and HCO3− secretion were measured in mice, and intracellular pH (pHi) was measured in small intestinal epithelial SCBN cells. The expression and location of Kv subtypes were verified by RT-PCR, western blotting and immunohistochemistry. Diabetic mice were also used to investigate the role of Kv subtypes in regulating intestinal glucose absorption. We found that KV7.1 is not involved in duodenal ion transport, while KCa3.1 selectively regulates duodenal Isc and HCO3− secretion in a Ca2+-mediated but not cAMP-mediated manner. Blockade of KCa3.1 increased the rate of HCO3− fluxes via cystic fibrosis transmembrane conductance regulator (CFTR) channels in SCBN cells. Jejunal Isc was significantly stimulated by glucose, but markedly inhibited by 4-aminopyridine (4-AP) and tetraethylammonium (TEA). Moreover, both Kv1.1 and Kv1.3 were expressed in jejunal mucosae. Finally, 4-AP significantly attenuated weight gain of normal and diabetic mice, and both 4-AP and TEA significantly lowered blood glucose of diabetic mice. This study not only examines the contribution of various K+ channel subtypes to small intestinal epithelial ion transport and glucose absorption, but also proposes a novel concept for developing specific K+ channel blockers to reduce weight gain and lower blood glucose in diabetes mellitus.

СОСТАВ ДУКТАЛЬНОГО СЕКРЕТА ПОДЖЕЛУДОЧНОЙ ЖЕЛЕЗЫ ПРИ ХРОНИЧЕСКИХ ПАНКРЕАТИТАХ АЛКОГОЛЬНОЙ ЭТИОЛОГИИ

The purpose of the review is to provide an analysis of current scientific information on changes in the composition of the ductal secretion of the pancreas in chronic alcoholic pancreatitis. It has been shown that the toxic effect of alcohol at the cellular level is manifested primarily by the insufficient secretion of water and carbonates by the cells of small ducts. The crucial role of dysfunction of CFTR channels in these disorders is considered. Possible mechanisms of participation of trypsin, lactoferrin, lithostatine and calcium in precipitation and stone formation are discussed.

CFTR is not a gluten lover either.

Coeliac disease ( CD ) is an inflammatory autoimmune disease caused by ingestion of gluten proteins, mainly gliadin. Undigested gliadin proline‐rich peptides trigger the innate and adaptive immune response, resulting in intestinal cell stress and damage. A new study by Villella et al (2019) addressing the unclear primary cause of intestinal cell stress reports that gliadin peptides inhibit the function of the chloride and bicarbonate channel CFTR , causing intestinal cell stress, which is sufficient to trigger CD symptoms. Notably, CFTR potentiators used to treat cystic fibrosis effectively rescue CFTR function and markedly ameliorate the pathology of coeliac disease.

A new coupling of an acid-base transporter to PKD and cyst formation.

A new coupling of an acid-base transporter to PKD and cyst formation.

Carbocisteine stimulated an increase in ciliary bend angle via a decrease in [Cl-]i in mouse airway cilia.

Carbocisteine (CCis), a mucoactive agent, is widely used to improve respiratory diseases. This study demonstrated that CCis increases ciliary bend angle (CBA) by 30% and ciliary beat frequency (CBF) by 10% in mouse airway ciliary cells. These increases were induced by an elevation in intracellular pH (pHi; the pHi pathway) and a decrease in the intracellular Cl- concentration ([Cl-]i; the Cl- pathway) stimulated by CCis. The Cl- pathway, which is independent of CO2/HCO3-, increased CBA by 20%. This pathway activated Cl- release via activation of Cl- channels, leading to a decrease in [Cl-]i, and was inhibited by Cl- channel blockers (5-nitro-2-(3-phenylpropylamino) benzoic acid and CFTR(inh)-172). Under the CO2/HCO3--free condition, the CBA increase stimulated by CCis was mimicked by the Cl--free NO3- solution. The pHi pathway, which depends on CO2/HCO3-, increased CBF and CBA by 10%. This pathway activated HCO3- entry via Na+/HCO3- cotransport (NBC), leading to a pHi elevation, and was inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid. The effects of CCis were not affected by a protein kinase A inhibitor (1μM PKI-A) or Ca2+-free solution. Thus, CCis decreased [Cl-]i via activation of Cl- channels including CFTR, increasing CBA by 20%, and elevated pHi via NBC activation, increasing CBF and CBA by 10%.

Epidemiology of Non-Malignant Gastrointestinal Disorders in Individuals With Cystic Fibrosis in the U.S. From 2013 to 2018: A Population-Based National Study

Introduction: Gastrointestinal (GI) manifestations in patients with cystic fibrosis (CF) have been explored, both anecdotally and in previous small-scale studies. The stronger association of CF with GI malignancy is well established; however, other non-malignant GI conditions appear to occur more frequently in CF patients. We sought to describe the epidemiology of GERD, constipation, intestinal obstruction, inflammatory bowel disease, celiac disease, and eosinophilic esophagitis in patients with CF. Methods: We queried a commercial database (Explorys Inc, Cleveland, OH), an aggregate of Electronic Health Record data from 26 major integrated healthcare systems in the US from 1999 to 2018. We identified an aggregated patient cohort of eligible patients with “Cystic Fibrosis” (CF), and aforementioned GI disorders between June 2013 and 2018, based on Systemized Nomenclature Of Medicine - Clinical Terms. We calculated the prevalence of the aforementioned GI disorders in CF. Results: Of the 34,589,040 total patients in the database between 2013 and 2018, 17,610 were diagnosed with CF (51 per 100,000). Compared to the general population, patients with CF had a significantly higher rate of GERD (26% vs 12%, OR: 2.47,CI: 2.39-2.56, P<.0001), constipation (16% vs 6.0%, OR: 2.97, CI: 2.85-3.09, P<.0001), intestinal obstruction ( 5.5% vs 1.1%, OR: 5.23, CI:4.90-5.58, P<.0001), Crohn’s Disease (1.1% vs 0.4%, OR: 2.57, CI:2.23-2.96, P<.0001), Ulcerative Colitis (0.8% vs 0.3%, OR: 2.13,CI: 1.81-2.52, P<.0001), Celiac disease ( 0.9% vs 0.3%, OR: 3.22, CI: 2.74-3.78, P<.0001), and Eosinophilic Esophagitis (0.2% vs .07%, OR: 3.15, CI: 2.30-4.29, P<.0001). Conclusion: This large study concurs with established research that shows that CF patients have significantly higher comorbid rates of GI disease compared to the general population. CFTR channels found in the epithelium throughout the GI tract may contribute to obstructive, inflammatory, and autoimmune disease in these patients. Because of these findings, clinicians should have higher suspicion for these conditions when treating CF patients.126_A Figure 1. Demographics of populations126_B Figure 2. Incidence and odds ratio of different GI conditions in cystic fibrosis and non CF patients126_C Figure 3. Prevalence of GI disorders in patients with and without CF

Evolutionary trade-offs associated with loss of PmrB function in host-adapted Pseudomonas aeruginosa

Pseudomonas aeruginosa colonises the upper airway of cystic fibrosis (CF) patients, providing a reservoir of host-adapted genotypes that subsequently establish chronic lung infection. We previously experimentally-evolved P. aeruginosa in a murine model of respiratory tract infection and observed early-acquired mutations in pmrB, encoding the sensor kinase of a two-component system that promoted establishment and persistence of infection. Here, using proteomics, we show downregulation of proteins involved in LPS biosynthesis, antimicrobial resistance and phenazine production in pmrB mutants, and upregulation of proteins involved in adherence, lysozyme resistance and inhibition of the chloride ion channel CFTR, relative to wild-type strain LESB65. Accordingly, pmrB mutants are susceptible to antibiotic treatment but show enhanced adherence to airway epithelial cells, resistance to lysozyme treatment, and downregulate host CFTR expression. We propose that P. aeruginosa pmrB mutations in CF patients are subject to an evolutionary trade-off, leading to enhanced colonisation potential, CFTR inhibition, and resistance to host defences, but also to increased susceptibility to antibiotics.

The Importance of Connexin 43 in Enamel Development and Mineralization.

During enamel development, formation of hydroxyapatite crystals and regulation of pH in the enamel matrix require massive transport of ions. Both ameloblasts and adjacent dental epithelial cells in the stellate reticulum co-express several transmembrane cotransporters/ion-exchangers for transport of ions across plasma membranes. Gap junctions (GJs) enable intercellular exchanges of ions between neighboring cells. This suggests that the ameloblasts and other cell layers of the enamel organ, form a functional unit. During the bell stage of tooth formation, the non-ameloblast dental epithelium highly expresses the Na-K-Cl cotransporter (Nkcc1). Nkcc1-null mice are associated with enamel hypomineralization and increased expression of GJ protein connexin 43 (Cx43), suggesting that reduced ion transport in the Nkcc1-null mouse is in part compensated by increased intercellular ion transport through GJs. To understand the role of GJs in ion transport and its effect on pH regulation, we examined in a mouse strain in which Cx43 was ablated selectively in DMP1 expressing cells (Cx43flox/flox mice crossed with DMP1-8kb-Cre mice), including ameloblasts. Micro-CT analysis showed that the mineral density at late maturation stage incisal enamel of the Cx43-null mice was 10% less than in controls, whereas that in dentin was unchanged. Maturation stage ameloblasts of mice lacking the pH regulating sodium/bicarbonate transporter NBCe1 (Nbce1-null), or chloride channel Cftr (Cftr-null) were found to have increased Cx43-immunostaining. These results support the possibility that GJs in the ameloblast–papillary complex at the maturation stage contribute to ion transport by enabling passage of ions directly from cells of the papillary layer into ameloblast layer. Increasing the number of GJs may partly compensate the reduction of ion-cotransporters and ion exchangers in dental epithelium.

The psychoactive substance of cannabis Δ9-tetrahydrocannabinol (THC) negatively regulates CFTR in airway cells

BackgroundMarijuana consumption is on the rise in the US but the health benefits of cannabis smoking are controversial and the impact of cannabis components on lung homeostasis is not well-understood. Lung function requires a fine regulation of the ion channel CFTR, which is responsible for fluid homeostasis and mucocilliary clearance. The goal of this study was to assess the effect that exposure to Δ9-tetrahydrocannabinol (THC), the psychoactive substance present in marijuana, has on CFTR expression and function. MethodsCultures of human bronchial epithelial cell line 16HBE14o- and primary human airway epithelial cells were exposed to THC. The expression of CFTR protein was determined by immunoblotting and CFTR function was measured using Ussing chambers. We also used specific pharmacological inhibitors of EGFR and ERK to determine the role of this pathway in THC-induced regulation of CFTR. ResultsTHC decreased CFTR protein expression in primary human bronchial epithelial cells. This decrease was associated with reduced CFTR-mediated short-circuit currents. THC also induced activation of the ERK MAPK pathway via activation of EGFR. Inhibition of EGFR or MEK/ERK prevented THC-induced down regulation of CFTR protein expression. Conclusions and general significanceTHC negatively regulates CFTR and this is mediated through the EGFR/ERK axis. This study provides the first evidence that THC present in marijuana reduces the expression and function of CFTR in airway epithelial cells.

2058 miRNA manipulation to improve CFTR correction in cystic fibrosis

OBJECTIVES/SPECIFIC AIMS: CFTR is the mutant protein that causes cystic fibrosis (CF), a fatal respiratory diseases affecting 1 in 3500 children. CFTR modulators are small molecules that directly address mutant CFTR function. Improving correction of the F508del CFTR mutation (affecting 90% of CF patients) is one of the most pressing unmet needs in CF. Currently available F508del therapeutics only marginally improve CF, In vitro, we have identified a miRNA that impairs utility of CFTR directed therapies. miR-145 is upregulated by TGF-β (a genetic modifier of CF lung disease) with a direct binding site on the 3’-untranslated region of CFTR mRNA. Binding of miR-145 to CFTR destabilizes mRNA transcript and impedes protein translation. Overexpression of miR-145 abolishes benefit of F508del CFTR correction. Antagonists to miR-145 block TGF-β suppression of CFTR function and augment response to CFTR correction. This project evaluate in vivo impact of TGF-beta and miRNA manipulation on CFTR functional readouts including nasal potential difference (NPD) and short circuit current (Isc) across tracheal explants in addition to standard biochemical measures. METHODS/STUDY POPULATION: Wild-type Sprague-Dawley rats were inoculated with an adenoviral vector containing bioactive TGF-beta or sham at 1×109 pfu/animal placed in the left nares. Seven days post-inoculation, functional, and biochemical measures were conducted. NPD was measured with a microelectrode placed in the left nare and grounded the tail. The nare was sequentially perfused with standard Ringer’s solution, amiloride (to block the ENaC sodium channel), low chloride Ringer’s (to stimulate chloride efflux), forskolin (to open the CFTR channel) and CFTRinh-172 (to block the CFTR channel. Tracheal explants were harvested, microdissected, and placed on modified Ussing chambers. RESULTS/ANTICIPATED RESULTS: We have inoculated WT rats with bioactive TGF-β Versus sham delivered by intranasal inoculation of an adenoviral vector. Functional readout of CFTR function is by Isc across tracheal epithelia and NPD. Lung homogenates are analyzed for TGF-β signaling, miRNA expression, and CFTR transcripts. Both tracheal explants and NPD indicate TGF-β stimulation diminishes CFTR function in vivo. In tracheal explants, TGF-β exposure diminishes CFTR response to forskolin-stimulation by 75%. Loss of current after CFTR inhibition (CFTRinh-172) is halved. By nasal PD, TGF-β inoculation similarly halves the bioelectric response to low chloride and forskolin stimulation. Evaluation by qPCR reveals a strong increase in TGF-β signaling demarcated by PAI-1, prompting a reduction in CFTR mRNA. miR-145 is expressed highly in rat pulmonary tissue, but no change in overall miR-145 levels was detected between TGF-β and sham exposed rats. This finding reflects what we have observed in human lungs, with a localized increased miR-145 expression in CF epithelia, but similarly high levels of miR-145 in both CF and non-CF whole lung homogenates. Although expressed at lower levels than miR-145, we did find increased expression in TGF-β relevant miR-101, miR-494, and miR-144 that have a predicted binding site on rat 3’-UTR in TGF-β exposed Versus sham lungs. DISCUSSION/SIGNIFICANCE OF IMPACT: Our data indicate the relevance of TGF-β stimulation to suppress CFTR synthesis and function in vivo. Future work will evaluate whether these additional miRNA with CFTR binding sites may mediate TGF-β suppression of CFTR in the rat model, and the utility of miRNA manipulation to augment F508del CFTR correction.

P019 Advanced molecular dynamics simulations for understanding the functions and dysfunctions of the CFTR channel

P019 Advanced molecular dynamics simulations for understanding the functions and dysfunctions of the CFTR channel