Comparative analyses of long non-coding RNA profiles in vivo in cystic fibrosis lung airway and parenchyma tissues.

BACKGROUND: Recent advances in the functional analyses of endogenous non-coding RNA (ncRNA) molecules, including long non-coding RNAs (LncRNAs), have provided a new perspective on the crucial roles of RNA in gene regulation. Consequently, LncRNA deregulation is a key factor in various diseases, including pulmonary disorders like Cystic Fibrosis (CF). CF is the most common life limiting recessive disease in the U.S., and is due to mutations in the CFTR gene. CF mutations, of which the most common is F508del-CFTR, prevents correct folding, trafficking and function of the mutant CFTR protein and is further manifested by the hyper-expression of pro-inflammatory cytokines and chemokines into the airway lumen leading to bronchiectasis and culminating in lung destruction. METHODS: Here we report a distinct LncRNA signature and corresponding mRNAs that distinguishes CF lung (airway and parenchyma) tissues from matched non-CF controls (n = 4 each group), generated by microarray specific for LncRNAs which includes corresponding mRNA expressions. In silico analyses of the cellular processes that are impacted by these LncRNAs was performed using Gene Ontology (GO). A selected subset of LncRNAs were validated by quantitative real-time PCR. RESULTS: We have identified 636 LncRNAs differentially expressed in CF airway epithelium and 1974 in CF lung parenchyma compared to matched non-CF controls (fold change ≥2, p < 0.05), majority of which (> 50%) are intergenic. Interestingly, 15 of these differentially expressed LncRNAs and 9 coding mRNAs are common to airway and parenchyma tissues. GO analyses indicates that signaling pathways and cell membrane functions are significantly affected by the alteration in LncRNA expressions in CF lung tissues. Seven of the differentially expressed LncRNAs, exhibit similar expression trends in CFBE41o- compared to control cells. CONCLUSION: Understanding the mechanisms by which these LncRNAs regulate CF disease phenotype will help develop novel therapeutic targets for CF and related pulmonary diseases, such as COPD and Asthma.

The Influence of Neonatal Nursery Design on Mothers' Interactions in the Nursery.

UNLABELLED: This study examined the influence of neonatal nursery design on interactions between nurses and mothers of infants in the nursery. DESIGN AND METHODS: We used a natural quasi-experimental design, using semi-structured interviews and a structured measure of mothers' and nurses' perceptions of nursing care, to compare mothers (n=26 and n=40) and nurses (n=22 and n=29) in an open-bay (OB) nursery and a single family room (SFR) nursery. Thematic analysis was used to generate key themes from the interviews. RESULTS: Mothers and nurses in both nursery designs talked about Valuing interactions; the importance of interactions between mothers and nurses. Mothers and nurses described SFRs as providing a space, My/their room, which enhanced mothers' sense of control and connection with the infant. SFRs were also associated with Changing the norms of interactions with nurses and other mothers, which created challenges in the desired quantity and quality of interactions for mothers and nurses. Nurses in the SFR nursery also reported Enhanced interactions, including improved confidentiality and personalized communication. Mothers in the OB nursery reported more supportive mothering actions from nurses than mothers in the SFR nursery. Both mothers and nurses in the OB nursery also talked about Our nursery community, which captured the value of having other nurses and mothers in the rooms. CONCLUSION: Mothers and nurses perceived that the SFR nursery enhanced privacy and maternal closeness for mothers compared to the OB nursery. However, the SFR nursery design presented challenges to some interactions of value to nurses and mothers.

A mosaic activating mutation in AKT1 associated with the Proteus syndrome.

BACKGROUND: The Proteus syndrome is characterized by the overgrowth of skin, connective tissue, brain, and other tissues. It has been hypothesized that the syndrome is caused by somatic mosaicism for a mutation that is lethal in the nonmosaic state. METHODS: We performed exome sequencing of DNA from biopsy samples obtained from patients with the Proteus syndrome and compared the resultant DNA sequences with those of unaffected tissues obtained from the same patients. We confirmed and extended an observed association, using a custom restriction-enzyme assay to analyze the DNA in 158 samples from 29 patients with the Proteus syndrome. We then assayed activation of the AKT protein in affected tissues, using phosphorylation-specific antibodies on Western blots. RESULTS: Of 29 patients with the Proteus syndrome, 26 had a somatic activating mutation (c.49G→A, p.Glu17Lys) in the oncogene AKT1, encoding the AKT1 kinase, an enzyme known to mediate processes such as cell proliferation and apoptosis. Tissues and cell lines from patients with the Proteus syndrome harbored admixtures of mutant alleles that ranged from 1% to approximately 50%. Mutant cell lines showed greater AKT phosphorylation than did control cell lines. A pair of single-cell clones that were established from the same starting culture and differed with respect to their mutation status had different levels of AKT phosphorylation. CONCLUSIONS: The Proteus syndrome is caused by a somatic activating mutation in AKT1, proving the hypothesis of somatic mosaicism and implicating activation of the PI3K-AKT pathway in the characteristic clinical findings of overgrowth and tumor susceptibility in this disorder. (Funded by the Intramural Research Program of the National Human Genome Research Institute.).

Pharmacological rescue of the mutant cystic fibrosis transmembrane conductance regulator (CFTR) detected by use of a novel fluorescence platform.

Numerous human diseases arise because of defects in protein folding, leading to their degradation in the endoplasmic reticulum. Among them is cystic fibrosis (CF), caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR ), an epithelial anion channel. The most common mutation, F508del, disrupts CFTR folding, which blocks its trafficking to the plasma membrane. We developed a fluorescence detection platform using fluorogen-activating proteins (FAPs) to directly detect FAP-CFTR trafficking to the cell surface using a cell-impermeant probe. By using this approach, we determined the efficacy of new corrector compounds, both alone and in combination, to rescue F508del-CFTR to the plasma membrane. Combinations of correctors produced additive or synergistic effects, improving the density of mutant CFTR at the cell surface up to ninefold over a single-compound treatment. The results correlated closely with assays of stimulated anion transport performed in polarized human bronchial epithelia that endogenously express F508del-CFTR. These findings indicate that the FAP-tagged constructs faithfully report mutant CFTR correction activity and that this approach should be useful as a screening assay in diseases that impair protein trafficking to the cell surface.

Baclofen reduces binge eating in a double-blind, placebo-controlled, crossover study.

Baclofen has shown promise in treating substance use disorders and also reduced binge frequency in an open-label trial. This placebo-controlled, double-blind, crossover study further assessed the effects of baclofen on binge eating. Twelve individuals who self-reported binge eating completed the study. Data were collected during a run-in period (no drug or placebo), placebo phase (48 days), and baclofen phase (titrated up to 60 mg daily or the maximum tolerated dose, 48 days). All the participants were exposed to all conditions. Participants completed a binge diary daily, and the Binge Eating Scale (BES), Food Craving Inventory-II (FCI-II), and Hospital Anxiety and Depression Scale (HADS) at regular intervals throughout the study. Baclofen significantly reduced binge frequency relative to placebo and run-in (P<0.05). This confirms results from the previous open-label trial. Baclofen also produced slight, but significant, increases in depression symptomatology as assessed by the HADS. Binge severity (BES scores) and craving (FCI-II scores) were significantly reduced during placebo and baclofen phases, that is both measures exhibited significant placebo effects. Tiredness, fatigue, and upset stomach were the most commonly reported side-effects. These results indicate that baclofen may be a useful treatment for binge eating in some patients.

Uncertainty management and communication preferences related to genetic relativism among families affected by down syndrome, Marfan syndrome, and neurofibromatosis.

Genes hold opportunities for us to look backward and forward in family health and disease incidence. Our beliefs about genes' roles in health form around frameworks relating to personal control, and the influence of social networks and/or religious faith on genetic expression in health. These genetic relativistic frameworks were found to predict levels of illness uncertainty among 541 diagnosed adults and family members affected by neurofibromatosis, Down syndrome, and Marfan syndrome. Participants were recruited and surveyed about their expectations and preferences for communicating about their respective disorder, with illness uncertainty found to predict the desire to communicate about the condition and to manage related uncertainty. The desire to manage uncertainty in ways that foster control and hope partially mediated the relationship between illness uncertainty and communication preferences. Negative feelings about the condition, which were stronger for affected participants than for family members, related to illness uncertainty, the desire to manage uncertainty, and communication preferences, mediating the relationship between illness uncertainty and uncertainty management. Findings contribute to research in illness uncertainty management and have pragmatic implications for the design of counseling and educational materials associated with the genetic conditions considered in this research.

A comparison of the background, needs, and expectations of patients seeking genetic counseling services.

Patient background, needs, and expectations (BNE) can be important predictors and modifiers of the process and outcomes of genetic counseling. We describe the assessment of BNE of 216 genetic counseling clients using the BNE Scale. Twenty-five percent sought reproductive genetic counseling (RGC), 57% sought adult-pediatric genetic counseling (APGC), and 18% sought cancer genetic counseling (CaGC). Analyses of the BNE of these patient groups identified significant differences in general unsureness/uncertainty about their condition (df = 2, F = 3.96, Significance =0.02), beliefs about treatment for the condition (d f= 2, F = 3.352, Significance = 0.04), and interest in support group involvement (df = 2, F =4.6, Significance = 0.01). Respondents who had not had genetic counseling more readily endorsed the desire to address educational issues than those who had previously had genetic counseling (Previous GC: Mean = 4.03, SD = 0.67; No Previous GC: Mean = 4.29, SD = 0.61; t-value; -2.86; P < 0.01). These results suggest that there are significant differences in the BNE of groups of patients seeking genetic counseling. These data support differential genetic counseling goal setting based on practice subspecialty, as well as sustain the requirement of broad based clinical training in genetic counseling. Further, these data provide additional evidence of the reliability and validity of the BNE Scale to characterize groups of individuals eligible for genetic counseling.

Comparison of the background, needs, and expectations for genetic counseling of adults with experience with Down syndrome, Marfan syndrome, and neurofibromatosis.

We describe an analysis of the responses of 605 adults with experience with Down syndrome, Marfan syndrome, or neurofibromatosis (NF) to the BNE Scale, a scale specifically designed to assess the background, needs, and expectations (BNE) of genetic counseling patients. Significant group differences were found. Specifically, the respondents in the Down syndrome group reported more favorable beliefs about the condition and the availability of social support than the respondents in the other groups. Respondents in the NF group reported more unsureness about their condition and a greater need for genetic information than members of the other groups. Notably, having positive feelings about the condition was negatively correlated with support group interest for respondents of the Marfan syndrome group (r = -0.159, P < 0.01). Having an affected child was associated with interest in health provider input (t = -3.4; P = 0.001) and the desire to talk about psychosocial issues (t = -2.9; P = 0.004). However, previous experience with genetic counseling was not found to affect BNE. These results support the usefulness of the BNE Scale to compare the BNE of patient groups, as well as provide important insight into the BNE of individuals seeking counseling about Down syndrome, Marfan syndrome, and NF.

Development of a scale to assess the background, needs, and expectations of genetic counseling clients.

Genetic professionals seek to tailor their counseling to meet the background, needs, and expectations (BNE) of their clients. We present the development of a new instrument, the BNE Scale, designed to assess BNE in genetic counseling clients. The initial items for the scale were created based on a review of the literature and clinical experience. The draft scale was piloted tested with 10 subjects, using cognitive interviewing techniques. Based on those results, a revised 82-item-scale was created and posted online. It was completed by 608 adult subjects who have experience with Down syndrome, Marfan syndrome, or neurofibromatosis. Responses were analyzed in aggregate based on clinically relevant item groupings. Exploratory factor analysis was used to refine the item groupings, and these groups were evaluated for reliability and cross-correlations. As a result, 61 items across 16 subscales were retained for the final BNE Scale. Further, the subscales were segregated thematically into four groups: (1) Beliefs which includes the Consequences, Unsureness, Feelings, and Treatment subscales, (2) Social Support which includes the Spousal (or Partner) Support, Family Support, Friend Support, Healthcare Provider Support, Faith/God Support, and Support Group Interest subscales, (3) Needs which includes the Need for Information, Need for Context, and Need for Provider Input subscales, and (4) Expectations which includes the Education, Counseling, and Desired Feelings subscales. These data provide initial support for the BNE Scale as a psychometrically acceptable means to assess the clients' background, needs and expectations of genetic counseling.

The relationship between the genetic counseling profession and the disability community: a commentary.

Since the inception of the field of genetic counseling, the profession has had a tenuous relationship with the disability community. Genetic counselors both offer prenatal diagnostic testing that allows individuals the opportunity to avoid the birth of a child with a disability and they advocate for the rights of individuals who have a disability. Some in the disability rights community have argued that they feel their lives and the lives of the disabled individuals in their families judged by the offer of prenatal genetic diagnosis and by the attitudes of genetic service providers they encounter in clinical settings. Select voices from the disability community fear that the result of developing technologies may contribute to a world less tolerant of disabilities. The available empirical data suggest that genetic counselors do little to counteract these perspectives. Although limited, investigations into the attitudes and practices of genetic counselors suggest that they have a more negative perspective on disabilities than individuals whose lives are directly affected by them and these attitudes may affect their description of disabling conditions in a prenatal setting. The National Society of Genetic Counselors, the organization that represents the profession in the US has more publicly aligned itself with abortion service providers over disease advocacy organizations, thus subjecting itself to the perception of bias. We suggest possible solutions to these criticisms and argue that individually and collectively, genetic counseling professionals should develop and identify opportunities to more fully support and advocate for the needs of a broader spectrum of clients.

Cystic Fibrosis Transmembrane Conductance Regulator Folding Mutations Reveal Differences in Corrector Efficacy Linked to Increases in Immature Cystic Fibrosis Transmembrane Conductance Regulator Expression.

Background: Most cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that lead to protein misfolding and degradation by the ubiquitin-proteasome system. Previous studies demonstrated that PIAS4 facilitates the modification of wild-type (WT) and F508del CFTR by small ubiquitin-like modifier (SUMO)-1, enhancing CFTR biogenesis by slowing immature CFTR degradation and producing increased immature CFTR band B. Methods: We evaluated two correction strategies using misfolding mutants, including the common variant, F508del. We examined the effects on mutant expression of co-expression with PIAS4 (E3 SUMO ligase), and/or the corrector, C18. To study the impact of these correction conditions, we transfected CFBE410- cells, a bronchial epithelial cell line, with a CFTR mutant plus: (1) empty vector, (2) empty vector plus overnight 5 µM C18, (3) PIAS4, and (4) PIAS4 plus C18. We assessed expression at steady state by immunoblot of CFTR band B, and if present, band C, and the corresponding C:B band ratio. The large PIAS4-induced increase in band B expression allowed us to ask whether C18 could act on the now abundant immature protein to enhance correction above the control level, as reported by the C:B ratio. Results: The data fell into three mutant CFTR categories as follows: (1) intransigent: no observable band C under any condition (i.e., C:B = 0); (2) throughput responsive: a C:B ratio less than control, but suggesting that the increased band C resulted from PIAS4-induced increases in band B production; and (3) folding responsive: a C:B ratio greater than control, reflecting C18-induced folding greater than that expected from increased throughput due to the PIAS4-induced band B level. Conclusion: These results suggest that the immature forms of CFTR folding intermediates occupy different loci within the energetic/kinetic folding landscape of CFTR. The evaluation of their properties could assist in the development of correctors that can target the more difficult-to-fold mutant conformations that occupy different sites within the CFTR folding pathway.

Co-Translational Folding of the First Transmembrane Domain of ABC-Transporter CFTR is Supported by Assembly with the First Cytosolic Domain.

ABC transporters transport a wealth of molecules across membranes and consist of transmembrane and cytosolic domains. Their activity cycle involves a tightly regulated and concerted domain choreography. Regulation is driven by the cytosolic domains and function by the transmembrane domains. Folding of these polytopic multidomain proteins to their functional state is a challenge for cells, which is mitigated by co-translational and sequential events. We here reveal the first stages of co-translational domain folding and assembly of CFTR, the ABC transporter defective in the most abundant rare inherited disease cystic fibrosis. We have combined biosynthetic radiolabeling with protease-susceptibility assays and domain-specific antibodies. The most N-terminal domain, TMD1 (transmembrane domain 1), folds both its hydrophobic and soluble helices during translation: the transmembrane helices pack tightly and the cytosolic N- and C-termini assemble with the first cytosolic helical loop ICL1, leaving only ICL2 exposed. This N-C-ICL1 assembly is strengthened by two independent events: (i) assembly of ICL1 with the N-terminal subdomain of the next domain, cytosolic NBD1 (nucleotide-binding domain 1); and (ii) in the presence of corrector drug VX-809, which rescues cell-surface expression of a range of disease-causing CFTR mutants. Both lead to increased shielding of the CFTR N-terminus, and their additivity implies different modes of action. Early assembly of NBD1 and TMD1 is essential for CFTR folding and positions both domains for the required assembly with TMD2. Altogether, we have gained insights into this first, nucleating, VX-809-enhanced domain-assembly event during and immediately after CFTR translation, involving structures conserved in type-I ABC exporters.

Identification and membrane localization of electrogenic sodium bicarbonate cotransporters in Calu-3 cells.

Cystic fibrosis (CF) is a severely life-shortening genetic disease resulting from mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR). Impaired bicarbonate secretion is a key component of CF-related pancreatic disease, but the role of impaired bicarbonate secretion in CF lung disease is less well understood. The submucosal glands of the conducting airways produce and secrete a complex airway surface liquid that lines the airway epithelium and plays a significant role in mucociliary clearance. The serous cell is the predominant cell type of the submucosal gland and a predominant site of CFTR expression. Calu-3 cells are a model of airway submucosal gland serous cells that demonstrates vectorial bicarbonate secretion in response to elevations in cAMP. Based on previously published measurements of unidirectional ion flux, pharmacological inhibition of short-circuit current and ion substitution studies, one can hypothesize the existence of an electrogenic sodium bicarbonate cotransporter (NBC) in the basolateral membrane of Calu-3 cells that mediates bicarbonate entry from the interstitium. To test this hypothesis, we performed reverse-transcriptase PCR, western blotting, and surface biotinylation to identify and localize electrogenic NBCs in Calu-3 cells. Our data demonstrate that both pNBC1 and NBC4 mRNAs can be identified and that their protein products are expressed at the basolateral membrane of polarized Calu-3 cells. These data suggest that these transporters contribute to regulated bicarbonate secretion across Calu-3 cells and perhaps human airway submucosal glands.

From CFTR biology toward combinatorial pharmacotherapy: expanded classification of cystic fibrosis mutations.

More than 2000 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) have been described that confer a range of molecular cell biological and functional phenotypes. Most of these mutations lead to compromised anion conductance at the apical plasma membrane of secretory epithelia and cause cystic fibrosis (CF) with variable disease severity. Based on the molecular phenotypic complexity of CFTR mutants and their susceptibility to pharmacotherapy, it has been recognized that mutations may impose combinatorial defects in CFTR channel biology. This notion led to the conclusion that the combination of pharmacotherapies addressing single defects (e.g., transcription, translation, folding, and/or gating) may show improved clinical benefit over available low-efficacy monotherapies. Indeed, recent phase 3 clinical trials combining ivacaftor (a gating potentiator) and lumacaftor (a folding corrector) have proven efficacious in CF patients harboring the most common mutation (deletion of residue F508, ΔF508, or Phe508del). This drug combination was recently approved by the U.S. Food and Drug Administration for patients homozygous for ΔF508. Emerging studies of the structural, cell biological, and functional defects caused by rare mutations provide a new framework that reveals a mixture of deficiencies in different CFTR alleles. Establishment of a set of combinatorial categories of the previously defined basic defects in CF alleles will aid the design of even more efficacious therapeutic interventions for CF patients.

A simplified education program improves knowledge, self-care behavior, and disease severity in heart failure patients in rural settings.

BACKGROUND: Self-monitoring by heart failure (HF) patients of worsening symptoms caused by fluid overload is a cornerstone of HF care. Disease management has improved outcomes in HF; however, these resource-intensive programs are limited to urban centers and are generally unavailable in rural or limited health care access areas. This pilot study sought to determine whether a simplified education program focused on a single component of disease management (symptom recognition and management of fluid weight) could improve knowledge, patient-reported self-care behavior, and HF severity in a rural setting. METHODS: This randomized clinical trial enrolled 36 rural HF patients into an intervention or control group. The intervention group received a simplified education program with a follow-up phone call focusing on symptom management delivered by a non-cardiac-trained nurse. Patient knowledge, self-care behaviors, and HF severity (B-natriuretic peptide [BNP]) were measured at enrollment and at 3 months. RESULTS: The sample was primarily white men and married with a mean age of 71 years and ejection fraction of 47%. There were no differences between groups in knowledge, self-care behaviors and BNP at baseline; however, knowledge and self-care behavior related to daily weights improved significantly at 3 months in the intervention group (P = .01 and .03, respectively). Although the changes in mean BNP at 3 months were in the hypothesized direction, the difference between the 2 groups was not significant. CONCLUSIONS: A simplified education program designed for use in resource scarce settings improves knowledge and patient-reported self-care behaviors. These findings are important in providing care to patients with HF in limited access settings but should be studied for longer periods in more heterogeneous populations.

Small heat shock proteins target mutant cystic fibrosis transmembrane conductance regulator for degradation via a small ubiquitin-like modifier-dependent pathway.

Small heat shock proteins (sHsps) bind destabilized proteins during cell stress and disease, but their physiological functions are less clear. We evaluated the impact of Hsp27, an sHsp expressed in airway epithelial cells, on the common protein misfolding mutant that is responsible for most cystic fibrosis. F508del cystic fibrosis transmembrane conductance regulator (CFTR), a well-studied protein that is subject to cytosolic quality control, selectively associated with Hsp27, whose overexpression preferentially targeted mutant CFTR to proteasomal degradation. Hsp27 interacted physically with Ubc9, the small ubiquitin-like modifier (SUMO) E2 conjugating enzyme, implying that F508del SUMOylation leads to its sHsp-mediated degradation. Enhancing or disabling the SUMO pathway increased or blocked Hsp27's ability to degrade mutant CFTR. Hsp27 promoted selective SUMOylation of F508del NBD1 in vitro and of full-length F508del CFTR in vivo, which preferred endogenous SUMO-2/3 paralogues that form poly-chains. The SUMO-targeted ubiquitin ligase (STUbL) RNF4 recognizes poly-SUMO chains to facilitate nuclear protein degradation. RNF4 overexpression elicited F508del degradation, whereas Hsp27 knockdown blocked RNF4's impact on mutant CFTR. Similarly, the ability of Hsp27 to degrade F508del CFTR was lost during overexpression of dominant-negative RNF4. These findings link sHsp-mediated F508del CFTR degradation to its SUMOylation and to STUbL-mediated targeting to the ubiquitin-proteasome system and thereby implicate this pathway in the disposal of an integral membrane protein.

Phosphorylation-dependent 14-3-3 protein interactions regulate CFTR biogenesis.

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP/protein kinase A (PKA)-regulated chloride channel whose phosphorylation controls anion secretion across epithelial cell apical membranes. We examined the hypothesis that cAMP/PKA stimulation regulates CFTR biogenesis posttranslationally, based on predicted 14-3-3 binding motifs within CFTR and forskolin-induced CFTR expression. The 14-3-3ß, γ, and ε isoforms were expressed in airway cells and interacted with CFTR in coimmunoprecipitation assays. Forskolin stimulation (15 min) increased 14-3-3ß and ε binding to immature and mature CFTR (bands B and C), and 14-3-3 overexpression increased CFTR bands B and C and cell surface band C. In pulse-chase experiments, 14-3-3ß increased the synthesis of immature CFTR, reduced its degradation rate, and increased conversion of immature to mature CFTR. Conversely, 14-3-3ß knockdown decreased CFTR B and C bands (70 and 55%) and elicited parallel reductions in cell surface CFTR and forskolin-stimulated anion efflux. In vitro, 14-3-3ß interacted with the CFTR regulatory region, and by nuclear magnetic resonance analysis, this interaction occurred at known PKA phosphorylated sites. In coimmunoprecipitation assays, forskolin stimulated the CFTR/14-3-3ß interaction while reducing CFTR's interaction with coat protein complex 1 (COP1). Thus 14-3-3 binding to phosphorylated CFTR augments its biogenesis by reducing retrograde retrieval of CFTR to the endoplasmic reticulum. This mechanism permits cAMP/PKA stimulation to make more CFTR available for anion secretion.

CFTR Folding Consortium: methods available for studies of CFTR folding and correction.

The CFTR Folding Consortium (CFC) was formed in 2004 under the auspices of the Cystic Fibrosis Foundation and its drug discovery and development affiliate, CFF Therapeutics. A primary goal of the CFC is the development and distribution of reagents and assay methods designed to better understand the mechanistic basis of mutant CFTR misfolding and to identify targets whose manipulation may correct CFTR folding defects. As such, reagents available from the CFC primarily target wild-type CFTR NBD1 and its common variant, F508del, and they include antibodies, cell lines, constructs, and proteins. These reagents are summarized here, and two protocols are described for the detection of cell surface CFTR: (a) an assay of the density of expressed HA-tagged CFTR by ELISA and (b) the generation and use of an antibody to CFTR's first extracellular loop for the detection of endogenous CFTR. Finally, we highlight a systematic collection of assays, the CFC Roadmap, which is being used to assess the cellular locus and mechanism of mutant CFTR correction. The Roadmap queries CFTR structure-function relations at levels ranging from purified protein to well-differentiated human airway primary cultures.

AS160 modulates aldosterone-stimulated epithelial sodium channel forward trafficking.

Aldosterone-induced increases in apical membrane epithelial sodium channel (ENaC) density and Na transport involve the induction of 14-3-3 protein expression and their association with Nedd4-2, a substrate of serum- and glucocorticoid-induced kinase (SGK1)-mediated phosphorylation. A search for other 14-3-3 binding proteins in aldosterone-treated cortical collecting duct (CCD) cells identified the Rab-GAP, AS160, an Akt/PKB substrate whose phosphorylation contributes to the recruitment of GLUT4 transporters to adipocyte plasma membranes in response to insulin. In CCD epithelia, aldosterone (10 nM, 24 h) increased AS160 protein expression threefold, with a time-course similar to increases in SGK1 expression. In the absence of aldosterone, AS160 overexpression increased total ENaC expression 2.5-fold but did not increase apical membrane ENaC or amiloride-sensitive Na current (I(sc)). In AS160 overexpressing epithelia, however, aldosterone increased apical ENaC and I(sc) 2.5-fold relative to aldosterone alone, thus recruiting the accumulated ENaC to the apical membrane. Conversely, AS160 knockdown increased apical membrane ENaC and I(sc) under basal conditions to approximately 80% of aldosterone-stimulated values, attenuating further steroid effects. Aldosterone induced AS160 phosphorylation at five sites, predominantly at the SGK1 sites T568 and S751, and evoked AS160 binding to the steroid-induced 14-3-3 isoforms, beta and epsilon. AS160 mutations at SGK1 phospho-sites blocked its selective interaction with 14-3-3beta and epsilon and suppressed the ability of expressed AS160 to augment aldosterone action. These findings indicate that the Rab protein regulator, AS160, stabilizes ENaC in a regulated intracellular compartment under basal conditions, and that aldosterone/SGK1-dependent AS160 phosphorylation permits ENaC forward trafficking to the apical membrane to augment Na absorption.

Regulation of CFTR trafficking by its R domain.

Phosphorylation of the R domain is required for cystic fibrosis transmembrane conductance regulator (CFTR) channel gating, and cAMP/protein kinase A (PKA) simulation can also elicit insertion of CFTR into the plasma membrane from intracellular compartments (Bertrand, C. A., and Frizzell, R. A. (2003) Am. J. Physiol. 285, C1-C18). We evaluated the structural basis of regulated CFTR trafficking by determining agonist-evoked increases in plasma membrane capacitance (Cm) of Xenopus oocytes expressing CFTR deletion mutants. Expression of CFTR as a split construct that omitted the R domain (Deltaamino acids 635-834) produced a channel with elevated basal current (Im) and no DeltaIm or trafficking response (DeltaCm) upon cAMP/PKA stimulation, indicating that the structure(s) required for regulated CFTR trafficking are contained within the R domain. Additional deletions showed that removal of amino acids 817-838, a 22-amino acid conserved helical region having a net charge of -9, termed NEG2 (Xie, J., Adams, L. M., Zhao, J., Gerken, T. A., Davis, P. B., and Ma, J. (2002) J. Biol. Chem. 277, 23019-23027), produced a channel with regulated gating that lacked the agonist-induced increase in CFTR trafficking. Injection of NEG2 peptides into oocytes expressing split DeltaNEG2 CFTR prior to stimulation restored the agonist-evoked DeltaCm, consistent with the concept that this sequence mediates the regulated trafficking event. In support of this idea, DeltaNEG2 CFTR escaped from the inhibition of wild type CFTR trafficking produced by overexpression of syntaxin 1A. These observations suggest that the NEG2 region at the C terminus of the R domain allows stabilization of CFTR in a regulated intracellular compartment from which it traffics to the plasma membrane in response to cAMP/PKA stimulation.