Defective beta adrenergic response of cystic fibrosis sweat glands in vivo and in vitro

A new role for bicarbonate secretion in cervico-uterine mucus release

Cervical mucus thinning and release during the female reproductive cycle is thought to rely mainly on fluid secretion. However, we now find that mucus released from the murine reproductive tract critically depends upon concurrent bicarbonate (HCO(3)(-)) secretion. Prostaglandin E(2) (PGE(2))- and carbachol-stimulated mucus release was severely inhibited in the absence of serosal HCO(3)(-), HCO(3)(-) transport, or functional cystic fibrosis transmembrane conductance regulator (CFTR). In contrast to mucus release, PGE(2)- and carbachol-stimulated fluid secretion was not dependent on bicarbonate or on CFTR, but was completely blocked by niflumic acid. We found stimulated mucus release was severely impaired in the cystic fibrosis F508 reproductive tract, even though stimulated fluid secretion was preserved. Thus, CFTR mutations and/or poor bicarbonate secretion may be associated with reduced female fertility associated with abnormal mucus and specifically, may account for the increased viscosity and lack of cyclical changes in cervical mucus long noted in women with cystic fibrosis.

Loss of TMEM16A causes a defect in epithelial Ca2+-dependent chloride transport

Molecular identification of the Ca(2+)-dependent chloride channel TMEM16A (ANO1) provided a fundamental step in understanding Ca(2+)-dependent Cl(-) secretion in epithelia. TMEM16A is an intrinsic constituent of Ca(2+)-dependent Cl(-) channels in cultured epithelia and may control salivary output, but its physiological role in native epithelial tissues remains largely obscure. Here, we demonstrate that Cl(-) secretion in native epithelia activated by Ca(2+)-dependent agonists is missing in mice lacking expression of TMEM16A. Ca(2+)-dependent Cl(-) transport was missing or largely reduced in isolated tracheal and colonic epithelia, as well as hepatocytes and acinar cells from pancreatic and submandibular glands of TMEM16A(-/-) animals. Measurement of particle transport on the surface of tracheas ex vivo indicated largely reduced mucociliary clearance in TMEM16A(-/-) mice. These results clearly demonstrate the broad physiological role of TMEM16A(-/-) for Ca(2+)-dependent Cl(-) secretion and provide the basis for novel treatments in cystic fibrosis, infectious diarrhea, and Sjöegren syndrome.

Detection of cystic fibrosis transmembrane conductance regulator activity in early-phase clinical trials

Advances in our understanding of cystic fibrosis pathogenesis have led to strategies directed toward treatment of underlying causes of the disease rather than treatments of disease-related symptoms. To expedite evaluation of these emerging therapies, early-phase clinical trials require extension of in vivo cystic fibrosis transmembrane conductance regulator (CFTR)-detecting assays to multicenter trial formats, including nasal potential difference and sweat chloride measurements. Both of these techniques can be used to fulfill diagnostic criteria for the disease, and can discriminate various levels of CFTR function. Full realization of these assays in multicenter clinical trials requires identification of sources of nonbiological intra- and intersite variability, and careful attention to study design and statistical analysis of study-generated data. In this review, we discuss several issues important to the performance of these assays, including efforts to identify and address aspects that can contribute to inconsistent and/or potentially erroneous results. Adjunctive means of detecting CFTR including mRNA expression, immunocytochemical localization, and other methods are also discussed. Recommendations are presented to advance our understanding of these biomarkers and to improve their capacity to predict cystic fibrosis outcomes.

Effects of topiramate on mouse eccrine sweat gland responsiveness to heat exposure

Young mice (2 weeks old) were given topiramate daily for 1 month, and sudomotor function was evaluated utilizing impression mould techniques to determine the number of sweat glands reactive to heat exposure and sweat output per gland on the plantar surface of mice hind-paws. Immunohistochemical quantitation of protein gene product 9.5, choline acetyltransferase and tyrosine hydroxylase in footpads was determined after topiramate treatment. While a 25% decrease in the number of secreting sweat glands and a 42% decline in sweat output per gland were observed following topiramate treatment, no significant differences were noted in sudomotor innervation, expressed as length of choline acetyltransferase, tyrosine hydroxylase and protein gene product 9.5 immunoreactive nerve profiles in single secretory coils or in sweat gland sizes within the secretory coil area. Long-term topiramate stimulation resulted in a reduction in the number of reactive sweat glands, without changes in sweat gland innervation, suggesting that the diminished responsiveness of the glands to heat exposure induced by topiramate might have resulted from a decrease in the intrinsic regulatory activity of sweat glands, as opposed to the loss of periglandular neurotransmitters or the impairment of the structure of the glands.

Stimulation of salivary secretion in vivo by CFTR potentiators in Cftr+/+ and Cftr-/- mice

BACKGROUND

Physiologically, salivary secretion is controlled by cholinergic and adrenergic pathways but the role of ionic channels in this process is not yet clearly understood. In cystic fibrosis (CF), most exocrine glands failed to response to beta-adrenergic agonists.

METHODS

To determine the implication of CFTR in this process, we measured in vivo the salivary secretion of Cftr(+/+) and Cftr(-/-) mice in the presence of 2 water-soluble benzo[c]quinolizinium derivatives; MPB-07 a potentiator of CFTR Cl(-) channel and MPB-05 an inactive analogue. We also used genistein and its vehicle ethanol to confirm the implication of CFTR in salivary secretion.

RESULTS

We showed that subcutaneous injection of MPB-07 in the mice cheek enhanced in a dose dependent manner the isoprenaline-induced salivary secretion in Cftr(+/+) but not in Cftr(-/-) mice. By contrast, MPB-05 did not activate the salivary secretion in Cftr(+/+) mice. The CFTR activator genistein (50 microM) significantly potentiated the secretory response of Cftr(+/+) mice whereas its vehicle, ethanol, had no effect.

CONCLUSIONS

These results show for the first time in vivo pharmacological stimulation of salivary secretion by a water-soluble CFTR potentiator, MPB-07 and by the isoflavone, ethanol-soluble genistein and suggest that this chloride channel plays an important role in salivary gland physiology.

Cystic Fibrosis: Lessons from the Sweat Gland

Lessons from the sweat gland on cystic fibrosis (CF) began long before modern medicine became a science. In European folklore, the curse that “a child that taste salty when kissed will soon die” (Alonso y de los Ruyzes de Fonteca J. Diez Previlegios para Mugeres Prenadas. Henares, Spain, 1606) has been taken by many as a direct reference to cystic fibrosis [Busch R. Acta Univ Carol Med (Praha) 36: 13–15, 1990]. The high salt concentration in sweat from patients with CF is now accepted as almost pathognomonic with this fatal genetic disease, but the earliest descriptions of cystic fibrosis as a disease entity did not mention sweat or sweat glands (Andersen DH. Am J Dis Child 56: 344–399, 1938; Andersen DH, Hodges RG. Am J Dis Child 72: 62–80, 1946). Nonetheless, defective sweating soon became an inseparable, and major, component of the constellation of symptoms that diagnose “cystic fibrosis” (Davis PB. Am J Respir Crit Care Med 173: 475–482, 2006). The sweat gland has played a foremost role in diagnosing, defining pathophysiology, debunking misconceptions, and increasing our understanding of the effects of the disease on organs, tissues, cells, and molecules. The sweat gland has taught us much.

Acinar origin of CFTR-dependent airway submucosal gland fluid secretion

Cystic fibrosis (CF) airway disease arises from defective innate defenses, especially defective mucus clearance of microorganisms. Airway submucosal glands secrete most airway mucus, and CF airway glands do not secrete in response to VIP or forskolin. CFTR, the protein that is defective in CF, is expressed in glands, but immunocytochemistry finds the highest expression of CFTR in either the ciliated ducts or in the acini, depending on the antibodies used. CFTR is absolutely required for forskolin-mediated gland secretion; we used this finding to localize the origin of forskolin-stimulated, CFTR-dependent gland fluid secretion. We tested the hypothesis that secretion to forskolin might originate from the gland duct rather than or in addition to the acini. We ligated gland ducts at various points, stimulated the glands with forskolin, and monitored the regions of the glands that swelled. The results supported an acinar rather than ductal origin of secretion. We tracked particles in the mucus using Nomarski time-lapse imaging; particles originated in the acini and traveled toward the duct orifice. Estimated bulk flow accelerated in the acini and mucus tubules, consistent with fluid secretion in those regions, but was constant in the unbranched duct, consistent with a lack of fluid secretion or absorption by the ductal epithelium. We conclude that CFTR-dependent gland fluid secretion originates in the serous acini. The failure to observe either secretion or absorption from the CFTR and epithelial Na+ channel (ENaC)-rich ciliated ducts is unexplained, but may indicate that this epithelium alters the composition rather than the volume of gland mucus.

Cystic fibrosis and airway submucosal glands

The chronic pulmonary infections and inflammation associated with cystic fibrosis (CF) are responsible for almost all the morbidity and mortality of this disease. Our understanding of the mechanisms that underlie the very early stages of CF lung disease, that result directly from mutations in the CF gene, is relatively poor. However, the demonstration that the predominant sites of expression of the CF gene in normal lungs are the submucosal glands, together with the histological observations showing that hyperplasia of these glands and mucin occlusion of the gland ducts are the earliest signs of disease in the CF lung, suggest that malfunction of the submucosal glands may be an important factor contributing to the early pathophysiology of CF lung disease. This review describes the function of submucosal glands in normal lungs, and the way in which their function may be disrupted in CF and may thus contribute to the early stages of CF lung disease.

The impact of cystic fibrosis and PSTI/SPINK1 gene mutations on susceptibility to chronic pancreatitis

This article reviews current concepts regarding the pathobiology of cystic fibrosis pancreatic disease. It summarizes recent studies on the relationship between CFTR mutations and pancreatitis, and it reviews several unresolved issues in the field.

Reduced CFTR function and the pathobiology of idiopathic pancreatitis

Idiopathic chronic pancreatitis (ICP) is the leading cause of chronic pancreatitis in children and nonalcoholic adults. The risk of developing ICP is increased in individuals who have mutations of the cystic fibrosis gene (CFTR) and of a trypsin inhibitor gene (PSTI). In studies from the United States and France, the risk of ICP is increased about 40-fold by having two abnormal copies of the CFTR gene, about 14-fold by having the N34S PSTI mutation, and about 500-fold by having both. When ICP patients have two abnormal copies of the CFTR gene, there is also evidence of reduced residual CFTR protein function in extrapancreatic tissues based on clinical findings and nasal ion transport responses. Thus, pancreatitis risk is highest in individuals who have abnormalities in both the pancreatic ducts (CFTR) and acini (PSTI). These findings indicate that PSTI is a modifier gene for CFTR-related ICP and have implications for the diagnosis and pathogenesis of pancreatitis.

The role of cystic fibrosis gene mutations in determining susceptibility to chronic pancreatitis

This article reviews current concepts regarding the pathobiology of cystic fibrosis pancreatic disease. It summarizes recent studies on the relationship between CFTR mutations and pancreatitis, and it reviews several unresolved issues in the field.

Salivary secretion assay for drug efficacy for cystic fibrosis in mice

Computerized assays on cultured cells ex vivo have been used to screen thousands of compounds for their effectiveness in correcting the basic physiological defect in cystic fibrosis (CF). While a number of these compounds appear promising, their effectiveness will almost certainly need to be demonstrated in animals before therapeutic tests in humans will be possible. We show herein that the function of salivary secretion in the mouse model for CF could be used as a simple, easy and rapid in vivo assay for drug effects. We demonstrate that salivary secretory capacity stimulated with a beta-adrenergic agonist closely reflects the genotype of origin. Specifically, the mean maximal secretory rate of saliva in normal wild type (+/+) mice was about 1.5 times higher than that of the mean rate in heterozygote (+/-) mice and more than 50 times greater than in CF (-/-) mice. Total saliva secreted per stimulated period obeyed a similar phenotype-genotype segregation. The data indicate that salivary secretory rates in CF mice could be used to assay potential drugs for their effectiveness in correcting the secretory defect in cystic fibrosis.

Structure and function of human sweat glands studied with histochemistry and cytochemistry

The basic structure and the physiological function of human sweat glands were reviewed. Histochemical and cytochemical techniques greatly contributed the elucidation of the ionic mechanism of sweat secretion. X-ray microanalysis using freeze-dried cryosections clarified the level of Na, K, and Cl in each secretory cell of the human sweat gland. Enzyme cytochemistry, immunohistochemistry and autoradiography elucidated the localization of Na,K-ATPase. These data supported the idea that human eccrine sweat is produced by the model of N-K-2Cl cotransport. Cationic colloidal gold localizes anionic sites on histological sections. Human eccrine and apocrine sweat glands showed completely different localization and enzyme sensitivity of anionic sites studied with cationic gold. Human sweat glands have many immunohistochemical markers. Some of them are specific to apocrine sweat glands, although many of them stain both eccrine and apocrine sweat glands. Histochemical techniques, especially immunohistochemistry using a confocal laser scanning microscope and in situ hybridization, will further clarify the relationship of the structure and function in human sweat glands.

Cystic fibrosis transport regulator and its mRNA are expressed in human epidermis

Cystic fibrosis transport regulator is a cAMP-dependent chloride channel protein. Normal (non cystic fibrosis) human epidermis stained positive for cystic fibrosis transport regulator as densely as did the eccrine sweat gland when three monoclonal antibodies for R (regulatory) and C (C-terminus) domains of cystic fibrosis transport regulator were used. All the layers of the epidermis took up staining uniformly. A peptide for C-epitope completely blocked the staining with monoclonal antibodies for C. Nested reverse transcription polymerase chain reaction of freshly isolated human epidermal fragments and the eccrine sweat glands amplified the cystic fibrosis transport regulator mRNA sequence derived from exons 13 and 14 to comparable extents. The 526 base pair antisense, but not sense, RNA probe derived from exons 10-13 stained cystic fibrosis transport regulator mRNA in both the epidermis and the sweat gland to a similar extent. In the epidermis, the cytoplasm of basal cells, stratum spinosum cells, and granular layer cells were all stained uniformly, but not corneocytes in the stratum corneum. In the sweat secretory coils, both clear and dark cells were stained but not the myoepithelium, with the dark cells staining more densely than the clear cells as in a previous study. In the duct, both luminal and basal ductal cells took up cystic fibrosis transport regulator staining uniformly but luminal cytoplasm of luminal ductal cells was devoid of cystic fibrosis transport regulator mRNA. Although the function of cystic fibrosis transport regulator in the epidermis is totally unknown, its recently proposed role as a universal regulator of a variety of cellular and membrane functions necessitates further studies on its regulation and function in health and disease.

Lung infections associated with cystic fibrosis

While originally characterized as a collection of related syndromes, cystic fibrosis (CF) is now recognized as a single disease whose diverse symptoms stem from the wide tissue distribution of the gene product that is defective in CF, the ion channel and regulator, cystic fibrosis transmembrane conductance regulator (CFTR). Defective CFTR protein impacts the function of the pancreas and alters the consistency of mucosal secretions. The latter of these effects probably plays an important role in the defective resistance of CF patients to many pathogens. As the modalities of CF research have changed over the decades from empirical histological studies to include biophysical measurements of CFTR function, the clinical management of this disease has similarly evolved to effectively address the ever-changing spectrum of CF-related infectious diseases. These factors have led to the successful management of many CF-related infections with the notable exception of chronic lung infection with the gram-negative bacterium Pseudomonas aeruginosa. The virulence of P. aeruginosa stems from multiple bacterial attributes, including antibiotic resistance, the ability to utilize quorum-sensing signals to form biofilms, the destructive potential of a multitude of its microbial toxins, and the ability to acquire a mucoid phenotype, which renders this microbe resistant to both the innate and acquired immunologic defenses of the host.

Increased expression of G protein-coupled receptor kinases in cystic fibrosis lung

A reduction in airway beta-adrenoceptor density has been reported in cystic fibrosis lung but the mechanism underlying this defect remains unclear. In this study, we have investigated whether the decrease in beta2-adrenoceptor associates with altered G protein-coupled receptor kinase (GRK) levels. We assessed GRK activity by rhodopsin phosphorylation, and beta2-adrenoceptor and GRK at the mRNA and protein levels by Northern and Western blotting in peripheral lung samples from normal donors and patients with cystic fibrosis. GRK activity was significantly increased in peripheral cystic fibrosis lung with parallel increases in GRK2/5 mRNAs and protein expression. Functionally, isoproterenol-stimulated adenylyl cyclase activity was also diminished by 65% in cystic fibrosis lung homogenates. These data suggest that the increase in GRK activity may be one of the mechanisms underlying alterations in the coupling between beta2-adrenoceptor and adenylyl cyclase via G-protein and may thus contribute to the downregulation of beta2-adrenoceptor in cystic fibrosis lung.

Cystic fibrosis: the 'bicarbonate before chloride' hypothesis

The specific effects of some mutations that cause cystic fibrosis suggest that reduced HCO(3)(-) transport is the key to understanding cystic fibrosis pathology. But there is a puzzling discrepancy between measures of CFTR-mediated chloride conductance in expression systems and the sweat chloride values of patients.

cAMP-independent phosphorylation activation of CFTR by G proteins in native human sweat duct

It is generally believed that cAMP-dependent phosphorylation is the principle mechanism for activating cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channels. However, we showed that activating G proteins in the sweat duct stimulated CFTR Cl(-) conductance (G(Cl)) in the presence of ATP alone without cAMP. The objective of this study was to test whether the G protein stimulation of CFTR G(Cl) is independent of protein kinase A. We activated G proteins and monitored CFTR G(Cl) in basolaterally permeabilized sweat duct. Activating G proteins with guanosine 5'-O-(3-thiotriphosphate) (10-100 microM) stimulated CFTR G(Cl) in the presence of 5 mM ATP alone without cAMP. G protein activation of CFTR G(Cl) required Mg(2+) and ATP hydrolysis (5'-adenylylimidodiphosphate could not substitute for ATP). G protein activation of CFTR G(Cl) was 1) sensitive to inhibition by the kinase inhibitor staurosporine (1 microM), indicating that the activation process requires phosphorylation; 2) insensitive to the adenylate cyclase (AC) inhibitors 2',5'-dideoxyadenosine (1 mM) and SQ-22536 (100 microM); and 3) independent of Ca(2+), suggesting that Ca(2+)-dependent protein kinase C and Ca(2+)/calmodulin-dependent kinase(s) are not involved in the activation process. Activating AC with 10(-6) M forskolin plus 10(-6) M IBMX (in the presence of 5 mM ATP) did not activate CFTR, indicating that cAMP cannot accumulate sufficiently to activate CFTR in permeabilized cells. We concluded that heterotrimeric G proteins activate CFTR G(Cl) endogenously via a cAMP-independent pathway in this native absorptive epithelium.

A simplified cyclic adenosine monophosphate-mediated sweat rate test for quantitative measure of cystic fibrosis transmembrane regulator (CFTR) function

OBJECTIVE

Sweat production is stimulated by both cholinergic and beta-adrenergic pathways in the sweat gland secretory coil. beta-Adrenergic pathway-mediated sweating is absent in cystic fibrosis (CF) because cyclic adenosine monophosphate (cAMP)-mediated chloride transport through the cystic fibrosis transmembrane regulator (CFTR) is disrupted. We report the development of a rapid, reproducible, macroscopic, and quantitative methodology to test the hypothesis that beta-adrenergic sweat rate discriminates among 3 different CFTR phenotypes-CF, heterozygote CF carriers, and non-CF.

STUDY DESIGN

Intradermal injection of a mixture of 50 micromol/L isoproterenol, 5 mmol/L aminophylline (to potentiate the beta-adrenergic stimulation), and 140 micromol/L atropine (to block potential cholinergic stimulation) in lactated Ringer's solution was performed in duplicate on one forearm. A single injection of 0.5 mmol/L methacholine to stimulate sweat production by the cholinergic pathway was performed on the other forearm. Sweat rate was determined as the amount of sweat collected on filter paper over 20 minutes.

RESULTS AND CONCLUSIONS

Median cAMP-mediated sweat rates were 1.45 mg/20 min (CF, n = 29), 2.55 mg/20 min (CF heterozygote carriers, n = 30), and 3.65 mg/20 min (non-CF, n = 30) and were significantly different in all 3 groups (P =.0001, Kruskal-Wallis test). Methacholine-stimulated sweat rates were similar for all 3 groups. The cAMP-mediated sweat rate test may be a useful endpoint for studies of new agents to increase the function of CFTR.

Electrophysiological characteristics of the Ca2+-activated Cl- channel family of anion transport proteins

1. A protein isolated from the bovine tracheal epithelium behaves as a Ca2+-activated Cl- channel (CaCC) when incorporated into planar lipid bilayers. 2. An antibody raised against this protein was used to screen a cDNA expression library and resulted in the isolation of a cDNA clone that exhibited nearly identical electrophysiological characteristics to the isolated endogenous protein when expressed. 3. Recent cloning of several related proteins has revealed that the cloned bovine CaCC is one of a large and growing family. All new family members so far examined are associated with the appearance of a novel Ca2+-mediated Cl- conductance when heterologously expressed. 4. This new group of proteins may underlie the Ca2+-mediated Cl- conductance upregulated in the cystic fibrosis (CF) knockout mouse and thought to be responsible for the escape from the significant airway pathology associated with CF.

Lung disease associated with the IVS8 5T allele of the CFTR gene

Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene. The 5T allele in intron 8 (IVS8) causes abnormal splicing in the CFTR gene, and is associated with lung disease when it occurs in cis with a missense mutation in the CFTR gene, R117H. However, the 5T variant alone has not been reported to cause lung disease. We describe two adult female patients with CF-like lung disease associated with the 5T allele. One patient's genotype is 5T-TG12-M470V/5T-TG12-M470V, and the other is DeltaF508/5T-TG12-M470V; full sequencing of the CFTR gene revealed no other mutation on the same allele as the 5T variant. The levels of full-length CFTR mRNA in respiratory epithelia were very low in these patients (11 and 6%, respectively, of total CFTR mRNA expression). Both patients had defective CFTR-mediated chloride conductance in the sweat ductal and/or acinar epithelia (sweat chloride, mmol/L, mean +/- SEM: 40.0 +/- 5.0 [n = 8 samples] and 80. 0 +/- 3.5 [n = 6 samples]) and airway epithelia (mV, mean +/- SEM CFTR-mediated Cl(-) conductance of 1.2 +/- 2.2 [n = 5 studies] and -6.75 +/- 8.1 [n = 4 studies]). These data suggest that the 5T polythymidine tract sequence on specific haplotype backgrounds (TG12 and M470V) may cause a low level of full-length functional CFTR protein and CF-like lung disease.

Pitfalls in the immunohistochemical localization of the cystic fibrosis transmembrane conductance regulator in paraffin embedded sweat glands

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause the hereditary disease cystic fibrosis. The most frequent mutant deltaF508 has been shown in vitro to be retained in the endoplasmic reticulum. Ex vivo studies using immunohistochemical labelling in cryofixed skin biopsies have confirmed the mislocalization of deltaF508 CFTR in sweat glands. The purpose of this study was to test CFTR antibodies in paraffin-embedded skin biopsies to take advantage of the superior tissue preservation as compared to cryofixation. A panel of 7 CFTR antibodies was applied to skin sections of healthy controls and of cystic fibrosis patients homozygous for the deltaF508 mutation. Sweat gland labelling consistent with CFTR localization and different between control and cystic fibrosis tissue was obtained with 2 antibodies. Conventional staining controls confirmed the labelling specificity. The antibodies were subsequently tested in a series of 237 sections of 16 biopsy specimens. However, the sweat gland labelling pattern proved not to be dependent on CFTR genotype. This finding was the sole indicator of non-specificity of the staining which was revealed only by the size of our random sample. Our results emphasize that CFTR immunolabelling following formalin fixation has to be interpreted with the utmost caution.

Cloning a chloride conductance mediator from the apical membrane of porcine ileal enterocytes

Attempts to attribute ileal brush-border chloride conductance to specific proteins were pursued by screening a porcine intestinal cDNA library. A 0.94-kb clone was identified on expression screening with a monoclonal antibody that inhibited enterocyte brush-border chloride conductance. Further screening approaches led to the isolation of a 3.1-kb full-length sequence called pCLCA1, consistent with the identification of a 2.9-kb transcript through Northern analysis. This sequence had significant homology to the CLCA gene family of calcium-regulated chloride channels, especially to hCLCA1. However, a strong A-kinase consensus phosphorylation site in a predicted cytoplasmic loop of the protein was a notable difference from the hCLCA1 gene product. Several porcine exocrine epithelial tissues, including ileum, trachea, and the major salivary glands express pCLCA1 mRNA. In situ hybridization studies localized the expression of pCLCA1 mRNA to the crypt and villus epithelia of porcine ileum, whereas tracheal expression was observed in both surface epithelium and submucosal glands. In situ expression of pCLCA1 in mouse 3T3 cells induces an ionomycin-dependent chloride conductance activity in these cells.

cAMP-dependent Cl(-) channel protein (CFTR) and its mRNA are expressed in the secretory portion of human eccrine sweat gland

Immunoreactive cystic fibrosis transport regulator (CFTR) proteins in human sweat ducts has been documented but CFTR expression in the secretory coil has remained uncertain. Using monoclonal antibodies (MAbs) against epitopes in the R-domain and C-terminus, we observed the following: Formalin fixation masks the CFTR epitopes but the epitopes are exposed by treatment with urea and heat (antigen retrieval). Pen-Fix fixation preserves CFTR epitopes. The secretory coil also expresses CFTR epitopes for the R-domain and C-terminus. An MAb against C-terminus amino acids 1466-1480 coupled to keyhole limpet hemocyanin (MAb WC) stained dark cells predominantly. Staining by MAbs against the C-terminus was completely blocked by a C-terminus peptide. mRNA for CFTR was amplified by RT-PCR in both the duct and the secretory coil. In situ hybridization for CFTR mRNA after 3SR amplification indicates that mRNA is localized in the dark cells and perhaps also in the clear cell cytoplasm near the secretory coil. mRNA is present in both the luminal and basal duct cells. We conclude that CFTR is expressed equally well in both the duct and the secretory coil, suggesting that cAMP-dependent Cl(-) channels are involved in regulation of sweat secretion and duct absorption.

Activation of the epithelial Na+ channel (ENaC) requires CFTR Cl- channel function

It is increasingly being recognized that cells coordinate the activity of separate ion channels that allow electrolytes into the cell. However, a perplexing problem in channel regulation has arisen in the fatal genetic disease cystic fibrosis, which results from the loss of a specific Cl- channel (the CFTR channel) in epithelial cell membranes. Although this defect clearly inhibits the absorption of Na+ in sweat glands, it is widely accepted that Na+ absorption is abnormally elevated in defective airways in cystic fibrosis. The only frequently cited explanation for this hypertransport is that the activity of an epithelial Na+ channel (ENaC) is inversely related to the activity of the CFTR Cl- channel. However, we report here that, in freshly isolated normal sweat ducts, ENaC activity is dependent on, and increases with, CFTR activity. Surprisingly, we also find that the primary defect in Cl- permeability in cystic fibrosis is accompanied secondarily by a Na+ conductance in this tissue that cannot be activated. Thus, reduced salt absorption in cystic fibrosis is due not only to poor Cl- conductance but also to poor Na+ conductance.

Control of CFTR channel gating by phosphorylation and nucleotide hydrolysis

Control of CTFR Channel Gating by Phosphorylation and Nucleotide Hydrolysis. Physiol. Rev. 79, Suppl.: S77-S107, 1999. - The cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel is the protein product of the gene defective in cystic fibrosis, the most common lethal genetic disease among Caucasians. Unlike any other known ion channel, CFTR belongs to the ATP-binding cassette superfamily of transporters and, like all other family members, CFTR includes two cytoplasmic nucleotide-binding domains (NBDs), both of which bind and hydrolyze ATP. It appears that in a single open-close gating cycle, an individual CFTR channel hydrolyzes one ATP molecule at the NH2-terminal NBD to open the channel, and then binds and hydrolyzes a second ATP molecule at the COOH-terminal NBD to close the channel. This complex coordinated behavior of the two NBDs is orchestrated by multiple protein kinase A-dependent phosphorylation events, at least some of which occur within the third large cytoplasmic domain, called the regulatory domain. Two or more kinds of protein phosphatases selectively dephosphorylate distinct sites. Under appropriately controlled conditions of progressive phosphorylation or dephosphorylation, three functionally different phosphoforms of a single CFTR channel can be distinguished on the basis of channel opening and closing kinetics. Recording single CFTR channel currents affords an unprecedented opportunity to reproducibly examine, and manipulate, individual ATP hydrolysis cycles in a single molecule, in its natural environment, in real time.

Intracellular CFTR: localization and function

Intracellular CFTR: Localization and Function. Physiol. Rev. 79, Suppl.: S175-S191, 1999. - There is considerable evidence that CFTR can function as a chloride-selective anion channel. Moreover, this function has been localized to the apical membrane of chloride secretory epithelial cells. However, because cystic fibrosis transmembrane conductance regulator (CFTR) is an integral membrane protein, it will also be present, to some degree, in a variety of other membrane compartments (including endoplasmic reticulum, Golgi stacks, endosomes, and lysosomes). An incomplete understanding of the molecular mechanisms by which alterations in an apical membrane chloride conductance could give rise to the various clinical manifestations of cystic fibrosis has prompted the suggestion that CFTR may also play a role in the normal function of certain intracellular compartments. A variety of intracellular functions have been attributed to CFTR, including regulation of membrane vesicle trafficking and fusion, acidification of organelles, and transport of small anions. This paper aims to review the evidence for localization of CFTR in intracellular organelles and the potential physiological consequences of that localization.

Physiological basis of cystic fibrosis: a historical perspective

Physiological Basis of Cystic Fibrosis: A Historical Perspective. Physiol. Rev. 79, Suppl.: S3-S22, 1999. - Cystic fibrosis made a relatively late entry into medical physiology, although references to conditions probably reflecting the disease can be traced back well into the Middle Ages. This review begins with the origins of recognition of the symptoms of this genetic disease and proceeds to briefly review the early period of basic research into its cause. It then presents the two apparently distinct faces of cystic fibrosis: 1) as that of a mucus abnormality and 2) as that of defects in electrolyte transport. It considers principal findings of the organ and cell pathophysiology as well as some of the apparent conflicts and enigmas still current in understanding the disease process. It is written from the perspective of the author, whose career spans back to much of the initial endeavors to explain this fatal mutation.

Genomic cloning, molecular characterization, and functional analysis of human CLCA1, the first human member of the family of Ca2+-activated Cl- channel proteins

We have cloned and molecularly and functionally characterized the first human member of the family of Ca2+-activated Cl- channels, human (h) CLCA1. The 31,902-bp gene is located on chromosome 1p22-31 and is preceded by a canonic promoter region that contains an L1 transposable element. In contrast to all previously known homologs in other species, hCLCA1 is exclusively expressed in intestinal basal crypt epithelia and goblet cells, suggesting that it does not represent the human counterpart of any of them. Expression of the 914-amino-acid hCLCA1 protein in HEK 293 cells yielded a 125-kDa precursor that was processed to yield two cell-surface-associated subunits, a 90-kDa protein and a group of 37- to 41-kDa proteins. Four transmembrane domains were established within the 90-kDa subunit. HEK 293 cells transfected with CLCA1 exhibited an increase in whole-cell Ca2+-sensitive Cl- currents that were outwardly rectified and inhibited by 4,4'-diisothiocyanatostilbene-2, 2'-disulfonic acid, dithiothreitol, and niflumic acid. Cell-attached patch recordings of transfected cells revealed single channels with a slope conductance of 13.4 pS. These findings suggest that human CLCA1 mediates a Ca2+-activated Cl- conductance in the human intestine and make it an interesting candidate as a modulating factor in the pathogenesis of cystic fibrosis.

Functional expression of a truncated Ca(2+)-activated Cl- channel and activation by phorbol ester

We have isolated a niflumic acid-insensitive, Ca(2+)-activated Cl- channel (CaCC) from bovine trachea that migrates at 38 kDa (p38) on reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, a cloned CaCC isolated from a tracheal cDNA expression library by screening with an antibody raised against p38 has a primary cDNA transcript of 2712 base pairs that codes for a 100-kDa protein and is not susceptible to dithiothreitol reduction. To test the hypothesis that the functional channel may be a much smaller posttranslationally processed form of the 100-kDa protein, we generated a mutant construct (CaCCX, 42.5-kDa protein) truncated at the NH2 and COOH termini. The whole cell currents of wild-type (wt) CaCC and CaCCX expressed in Xenopus oocytes were 10-fold higher than those of water-injected oocytes and were further increased by ionomycin or A-23187 and inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and dithiothreitol. Whole cell currents in wtCaCC- and CaCCX-expressing oocytes could also be activated by phorbol 12-myristate 13-acetate and could be inhibited by chelerythrine chloride, suggesting that the cloned CaCC is regulated by protein kinase C. These results suggest that a smaller form of the full-length CaCC can form a functional channel.

Nonneoplastic disorders of the eccrine glands

Eccrine glands are uniquely susceptible to a variety of pathologic processes. Alteration in the rate of sweat secretion manifests as hypohidrosis and hyperhidrosis. Obstruction of the eccrine duct leads to miliaria. The excretion of drugs into eccrine sweat may be a contributory factor in neutrophilic eccrine hidradenitis (NEH), syringosquamous metaplasia (SSM), coma bulla, and erythema multiforme (EM). Alterations in the electrolyte composition of eccrine sweat can be observed in several systemic diseases, most notably cystic fibrosis. This article summarizes current knowledge of eccrine gland pathophysiology.

Calcium-stimulated Cl- secretion in Calu-3 human airway cells requires CFTR

Human airway serous cells secrete antibiotic-rich fluid, but, in cystic fibrosis (CF), Cl(-)-dependent fluid secretion is impaired by defects in CF transmembrane conductance regulator (CFTR) Cl- channels. Typically, CF disrupts adenosine 3',5'-cyclic monophosphate (cAMP)-mediated Cl- secretion but spares Ca(2+)-mediated secretion. However, in CF airway glands, Ca(2+)-mediated secretion is also greatly reduced. To determine the basis of Ca(2+)-mediated Cl- secretion in serous cells, we used thapsigargin to elevate intracellular Ca2+ concentration ([Ca2+]i) in Calu-3 cells, an airway cell line bearing some similarities to serous cells. Cells were cultured using conventional and air interface methods. Short-circuit current (Isc) and transepithelial conductance (Gte) were measured in confluent cell layers. Thapsigargin stimulated large, sustained changes (delta) in Isc and Gte, whereas forskolin stimulated variable and smaller increases. delta Isc was decreased by basolateral bumetanide, quinidine, barium, or diphenylamine-2-carboxylate (DPAC) but was unaffected by high apical concentrations of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 4,4'-dinitrostilbene-2,2'-disulfonic acid, and calixarene. Isc was measured after permeabilizing the basolateral membrane and establishing transmembrane ion gradients. Unstimulated apical membranes displayed high Cl- conductance (GCl) that was decreased by DPAC but not by DIDS. Apical GCl could be increased by elevating intracellular cAMP concentration but not [Ca2+]i. We conclude that CFTR channels are the exclusive GCl pathway in the apical membrane and display approximately 60% of maximum conductance at rest. Thus elevated [Ca2+]i increases K+ conductance to force Cl- through open CFTR channels. We hypothesize that loss of CFTR channels causes diminution of cholinergically mediated gland secretions in CF.

Cystic fibrosis affects specific cell type in sweat gland secretory coil

The sweat gland has three distinct cell types: a myoepithelial (ME) cell, a beta-adrenergic-insensitive (beta-I) cell, and a beta-adrenergic-sensitive (beta-S) cell. Using intracellular microelectrodes, we sought to functionally identify the specific cell type(s) affected in cystic fibrosis (CF). We found that in CF secretory coils 1) the ME calls are unaffected, as indicated by normal cell membrane potentials and spontaneous and cholinergically induced depolarizing potentials, 2) the beta-I cells showed normal physiological properties, including a relatively smaller cell membrane potential (approx -25 mV) and a Ba(2+)-inhibitable cholinergic response, and, in contrast, 3) the beta-S cell is abnormal, as shown by the lack of a beta-adrenergically activated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- conductance (GCl). Lack of CFTR GCl in this cell type does not affect either the magnitude of cell membrane potential (approx -56 mV) or the relative cell membrane GCl or the cholinergic response, as compared with that of normal beta-S cells. We conclude that, of the three cell types in secretory coil, only the beta-S cell is specifically affected in the CF secretory tissue of the human sweat gland.

Distinct cellular mechanisms of cholinergic and beta-adrenergic sweat secretion

The cholinergic and beta-adrenergic sweat secretions from human sweat glands differ with respect to secretory rates and their susceptibility to cystic fibrosis (CF). Using the cultured beta-adrenergic-sensitive sweat secretory cell, we sought to determine the intracellular electrophysiological mechanisms underlying these functional differences. We found that the cholinergic agonist methacholine (10(-6) M) induced a Ca(2+)-dependent biphasic membrane potential (Vm) response: an initial hyperpolarization and a secondary depolarization. The initial hyperpolarization was independent of bath Cl- and dependent on transmembrane K+ gradient. However, the secondary depolarization of Vm was dependent on bath Cl-. In contrast, the beta-adrenergic agonist isoproterenol (10(-5) M) induced a monophasic depolarization of Vm. This depolarization was 1) dependent on bath Cl-, 2) independent of K+ conductance (GK) blocker Ba2+ (5mM), 3) unaffected by the methacholine-induced secondary depolarization of Vm, and 4) absent in cells derived from CF subjects. These results indicated that the cholinergic agonist-induced secretion mainly involves the activation of Ca(2+)-dependent GK and Cl- conductance (GCl), whereas the beta-adrenergic secretion seems to mainly depend on the activation of cystic fibrosis transmembrane conductance regulator-GCl.

Intracellular free Ca2+ dynamic changes to histamine are reduced in cystic fibrosis human tracheal gland cells

This study documents a difference between cystic fibrosis human (CF-HTG) and normal human (HTG) tracheal gland cells: the ability of histamine to induce an increase of intracellular free calcium concentration [Ca2+]i was abnormally reduced in CF-HTG cells. The magnitude of the [Ca2+]i peak rise in response to histamine is smaller in CF-HTG cells than in HTG cells, and the percentage of CF-HTG cells that increase [Ca2+]i is decreased compared with HTG cells. In contrast to histamine, the human neutrophil elastase (HNE) stimulation of both CF-HTG and HTG cells generated [Ca2+]i asynchronous oscillations and the magnitude of the peak [Ca2+]i response as well as the percentage of responding cells were similar for both groups. By videomicroscopy observations, the secretory response (exocytosis of secretion granules) of CF-HTG cells occurred with HNE, but not with histamine, thus suggesting that [Ca2+]i asynchronous oscillations may be linked to the exocytosis process in human tracheal gland cells.

Symptom Outcome After Functional Endoscopic Sinus Surgery in Patients with Cystic Fibrosis: A Prospective Study

Twenty-nine consecutive patients with cystic fibrosis were offered functional endoscopic sinus surgery. Twenty-six of these patients underwent surgery. A symptom questionnaire was obtained from the patient or parent before surgery. At the end of the study this symptom questionnaire was again administered to the same individual, and 21 completed it. There were 14 male and 7 female patients, with a mean age of 12.3 years and a median age of 8.7 years. Mean follow-up was 34.3 months. Results for the following symptoms were significant: nasal airway obstruction was improved ( p < 0.0002), olfactory function was improved ( p < 0.0037), purulent nasal discharge was decreased ( p < 0.001), and activity level was increased ( p < 0.001). Other parameters are also reported in the text. In summary, this study prospectively studies the effects of functional endoscopic sinus surgery on symptoms in patients with cystic fibrosis. The study points out several significant areas of symptom improvement and supports the selective use of functional endoscopic sinus surgery in patients with cystic fibrosis. Indications for surgery are provided.

Cyclic AMP-related and cation-affected human platelet chloride transport regulation

Cystic fibrosis has been characterized as a defect in the regulation of cyclic AMP-dependent transepithelial chloride transport. The activation of cyclic AMP-dependent protein kinase A by cyclic AMP occurs normally in cystic fibrosis cells, but they fail to transport chloride ions in response to protein kinase A stimulation. Defective chloride secretion and abnormal electrolyte transport occurs in several organs including the lung, sweat glands, intestine and pancreas. The present work was aimed at exploring whether the same or similar regulatory systems are functional in platelets, and if they are altered or deficient in individuals with cystic fibrosis. Chloride transport in platelets from normal subjects and from cystic fibrosis patients was measured by cell sizing techniques where chloride permeability is the limiting factor. In platelets from healthy volunteers, the chloride channel blocker, 5-nitro-2-(3-phenylpropylamino) benzoic acid, inhibits the transport in a dose-dependent manner. The preservation of chloride transport capability is shown to be dependent upon the presence of either Ca2+ or two divalent cation substitutes, Cd2+ or Cu2+. It is also shown that in normal subjects 0.1 mumol/l prostaglandin E1, which elevates cyclic AMP 6 times and abolishes platelet aggregation, significantly enhances the rate constant of the transport. Furthermore, in five out of nine cystic fibrosis patients studied, platelet chloride transport did not respond to stimulation by prostaglandin E1.

A novel mutation in the cystic fibrosis gene in patients with pulmonary disease but normal sweat chloride concentrations

BACKGROUND

Many patients with chronic pulmonary disease similar to that seen in cystic fibrosis have normal (or nondiagnostic) sweat chloride values. It has been difficult to make the diagnosis of cystic fibrosis in these patients because no associated mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene has been identified.

METHODS

We evaluated 23 patients with pulmonary disease characteristic of cystic fibrosis but with sweat chloride concentrations in the normal range. Mutations in the CFTR gene were sought by direct sequencing of polymerase chain reaction-amplified nasal epithelial messenger RNA and by testing the functioning of affected epithelium.

RESULTS

A cytidine phosphate guanosine dinucleotide C-to-T point mutation in intron 19 of the CFTR gene, termed 3849 + 10 kb C to T, was identified in 13 patients from eight unrelated families. This mutation was found in patients from three different ethnic groups with three different extended haplotypes. The mutation leads to the creation of a partially active splice site in intron 19 and to the insertion into most CFTR transcripts of a new 84-base-pair "exon," containing an in-frame stop codon, between exons 19 and 20. Normally spliced transcripts were also detected at a level approximately 8 percent of that found in normal subjects. This mutation is associated with abnormal nasal epithelial and sweat acinar epithelial function.

CONCLUSIONS

We have identified a point mutation in intron 19 of CFTR and abnormal epithelial function in patients who have cystic fibrosis-like lung disease but normal sweat chloride values. The identification of this mutation indicates that this syndrome is a form of cystic fibrosis. Screening for the mutation should prove diagnostically useful in this population of patients.

Escherichia coli heat-stable enterotoxin-mediated colonic Cl- secretion is absent in cystic fibrosis

BACKGROUND/AIMS

Calcium- and adenosine 3',5'-cyclic monophosphate (cAMP)-mediated Cl- secretions in the human colon are abnormal in cystic fibrosis, but the effect of guanosine 3',5'-cyclic monophosphate (cGMP) is unknown. This study examined the effects of the cGMP activator Escherichia coli heat-stable enterotoxin (STa) on rectal ion transport of controls and subjects with cystic fibrosis.

METHODS

In vivo rectal potential difference (PD) was measured in response to 10(-7) mol/L STa in adult cystic fibrosis (n = 6) and control subjects (n = 7). Cl- transport was also evaluated in 24-hour primary cultures of human colonocytes using 6-methoxy-quinolyl-acetoethyl ester in response to STa (1 mumol/L) and 8-bromo-cGMP (100 mumol/L) with or without Cl- transport inhibitors.

RESULTS

Whereas STa increased rectal potential difference in controls, there was no effect in cystic fibrosis subjects. STa stimulated the cGMP concentration in rectal biopsy specimens from both control and cystic fibrosis subjects approximately twofold. In vitro Cl- transport in non-cystic fibrosis colonocytes increased threefold and fivefold with STa and 8-bromo-cGMP, respectively. These transport increases were inhibited by furosemide and the Cl- channel blocker diphenylamine-2-carboxylate.

CONCLUSIONS

Human colonocytes secrete Cl- in response to STa and cGMP in normal subjects, but this response is absent in cystic fibrosis.

Screening for CF mutations in adult cystic fibrosis patients with a directed and optimized SSCP strategy

Twenty adolescent and adult cystic fibrosis (CF) patients have been studied for the presence of mutations in the CFTR gene. Mutations other than deltaF508 have been detected by comparison to the single-stranded conformation polymorphism (SSCP) pattern of known mutations in eight exons, in which 80% of the more common mutations are present. Each mutation was confirmed by direct sequencing. For each of the analyzed exons, optimal SSCP conditions have been determined that allow all available known mutations in that exon to be distinguished from each other. This approach allowed mutations to be defined in 75% of the non deltaF508 alleles and 92% of all CF alleles in this cohort.

Oncogene-mediated propagation of tracheal epithelial cells from two cystic fibrosis fetuses with different mutations. Characterization of CFT-1 and CFT-2 cells in culture

Primary tracheal epithelial cells obtained from two fetuses with cystic fibrosis (CF) were successfully transfected with a plasmid vector recombined with the large T oncogene of SV40. The resulting tracheal cells were propagated in culture for up to 25 passages and retained the mutations of the CF genes carried by the two fetuses, one heterozygous for the S549N and N1303K substitutions (CFT-1 cells), and the other homozygous for the most common deletion delta F508 (CFT-2 cells). The transfected cells: (a) expressed the SV40 large T oncogene, as determined by immunofluorescence and Northern blot analysis; (b) retained typical epithelial morphology, as assessed by the presence of microvilli, desmosomes, gap junctions, and cytokeratin expression; (c) were fully responsive to the cAMP-stimulating agents isoproterenol, forskolin and vasoactive intestinal peptide for cAMP production and PKA activation; (d) do not produce any tumour in the athymic nude mice; (e) were diploid and tetraploid with a normal chromosomal complement at early passages, and (f) exhibited the abnormal regulation of chloride conductance characteristic of CF. These results indicate that CFT-1 and CFT-2 cells constitute a suitable model for: (a) comparison of the maturation and function of the CFTR protein mutated in the two nucleotide-binding domains; (2) analysis of the biochemical defect in CF epithelial airway cells, (c) development of new therapeutic agents, and correction of the CF defect by gene replacement therapy in vitro.

Chloride and potassium conductances of cultured human sweat ducts

The purpose of this study was to characterize the ion conductances, in particular those for Cl- and K+, of human sweat duct cells grown in primary culture. Sweat duct cells from healthy individuals were grown to confluence on a dialysis membrane, which was then mounted in a mini-Ussing chamber and transepithelial and intracellular potentials were measured under open-circuit conditions. Under control conditions the epithelia developed mucosa-negative transepithelial potentials, Vte, of about -10 mV. The apical membrane potential, Va, was -25 mV to -30 mV (n = 97) in most cells, but several cells had a higher potential of about -55 mV (n = 29). Mucosal amiloride (10 mumol/l) hyperpolarized Va from -31 +/- 1 mV to a new sustained level of -46 +/- 2 mV (n = 36). These changes were accompanied by increase in the fractional resistance of the apical membrane, fRa, and decreases of Vte and the equivalent short-circuit current, Isc. In amiloride-treated tissues an increase in mucosal K+ concentration (5 mmol/l to 25 mmol/l) depolarized Va by 5 +/- 1 mV (n = 8), while the same step on the serosal side depolarized Va by 20 +/- 2 mV (n = 8). A Cl- channel blocker 3',5-dichlorodiphenylamine-2-carboxylate DCl-DPC; 10 mumol/l) depolarized Va by 5 +/- 1 mV (n = 6), an effect that was lost after amiloride application. The blocker had no effect from the serosal side. Reduction of mucosal Cl- (from 120 to 30 or 10 mmol/l) depolarized Va by 9-11 mV (n = 35), an effect that was often followed by a secondary hyperpolarization of 10-30 mV (n = 27).(ABSTRACT TRUNCATED AT 250 WORDS)

Mislocalization of delta F508 CFTR in cystic fibrosis sweat gland

Misprocessing and mislocalization of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) has been described for the major CF-causing mutation (delta F508) in heterologous expression systems in vitro. We have generated monoclonal antibodies (mAbs) to CFTR with the aim of localizing the protein and its CF variants in vivo. Of the tissues where CFTR was observed, only the sweat gland is readily available and does not undergo secondary changes due to CF disease pathology. Sweat ducts from CF patients homozygous for delta F508 did not show the typical apical membrane staining seen in control biopsies. This demonstrates that the biosynthetic arrest and intracellular retention of delta F508 CFTR initially observed in vitro does occur in vivo and emphasizes the need to focus efforts on understanding the mislocalization.