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Hwang CL, Okazaki K, Shibata S, Liu YL, Fu Q. Menstrual cycle effects on sympathetic neural burst amplitude distribution during orthostasis in young women. Clin Auton Res 2021; 31:767-773. [PMID: 34669075 PMCID: PMC11382632 DOI: 10.1007/s10286-021-00832-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 10/12/2021] [Indexed: 11/24/2022]
Abstract
PURPOSE Fluctuations in ovarian hormones during the menstrual cycle impact muscle sympathetic nerve activity burst frequency and burst incidence at rest. The purpose of this study was to investigate menstrual cycle effects on sympathetic neural burst amplitude distribution during an orthostatic challenge in young women. METHODS This study included 11 healthy women (33 ± 10 years [mean ± standard deviation]). Muscle sympathetic nerve activity was measured in the supine position as baseline measurement and during 5 min of 60° upright tilting, during the early follicular phase (low estrogen and progesterone) and mid-luteal phase (high estrogen and progesterone) of the menstrual cycle. Relative burst amplitude distribution of muscle sympathetic nerve activity was characterized by the mean, median, skewness, and kurtosis. RESULTS From the supine to upright position, mean and median values of relative burst amplitude increased (both P < 0.05), regardless of phases of the menstrual cycle (P = 0.5 and P = 0.7, respectively). In comparison, during the early follicular phase, skewness and kurtosis remained unchanged (P = 0.6 and P = 0.3, respectively) and kurtosis decreased (1.25 ± 1.11 supine vs. - 0.03 ± 0.73 upright; P = 0.02); there was no change in skewness during the mid-luteal phase (P = 0.4). CONCLUSIONS In response to orthostasis, while the symmetry and tailedness/peakness of burst amplitude distribution do not change during the early follicular phase, the distribution during the mid-luteal phase becomes flatter with a lower but broader peak. The latter result suggests that the firing probability of large axon action potentials in response to orthostatic challenge is higher when estrogen and progesterone levels are elevated. The role of changes in sympathetic neural burst amplitude distribution in orthostatic tolerance remains to be determined.
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Affiliation(s)
- Chueh-Lung Hwang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Avenue, Dallas, TX, 75231, USA
- Department of Physical Therapy, College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Kazunobu Okazaki
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Avenue, Dallas, TX, 75231, USA
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Shigeki Shibata
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Avenue, Dallas, TX, 75231, USA
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yu-Lun Liu
- The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Qi Fu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Avenue, Dallas, TX, 75231, USA.
- The University of Texas Southwestern Medical Center, Dallas, TX, USA.
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2
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Ferreira MJ, Sanches IC, Jorge L, Llesuy SF, Irigoyen MC, De Angelis K. Ovarian status modulates cardiovascular autonomic control and oxidative stress in target organs. Biol Sex Differ 2020; 11:15. [PMID: 32264929 PMCID: PMC7140311 DOI: 10.1186/s13293-020-00290-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 03/18/2020] [Indexed: 01/08/2023] Open
Abstract
Studies have presented conflicting findings regarding the association between both fluctuation and deprivation of ovarian hormones and cardiovascular autonomic modulation and oxidative stress and their potential impact on resting arterial pressure (AP) and cardiovascular risk. This study aimed to assess cardiovascular autonomic modulation, baroreflex sensitivity (BRS), and oxidative stress in male rats (M) and in female rats during ovulatory (FOV) and non-ovulatory phases (FNOV) of the estrous cycle and after deprivation of ovarian hormones (FO). Direct AP was recorded, and BRS was assessed by using increasing doses of phenylephrine and sodium nitroprusside. AP and heart rate variability were assessed by spectral analysis. Oxidative stress profile was evaluated in cardiac, renal, and muscle tissues. In females, the ovulatory phase and ovarian hormone deprivation induced an increase in AP (FOV and FO ~ 9 mmHg) when compared to the non-ovulatory phase. Ovariectomy promoted increased cardiac sympathovagal balance (~ 17–37%) when compared to other groups. Both FOV and FO groups presented impaired BRS, associated with higher AP variability. In general, antioxidant capacity was higher in the FNOV than in the M group. Ovarian hormone deprivation induced a decrease in catalase activity in cardiac and renal tissues and an increase in lipid peroxidation in all tissues analyzed. Positive correlations (p < 0.05) were found between vascular sympathetic modulation and lipid peroxidation in cardiac (r = 0.60), renal (r = 0.60), and muscle (r = 0.57) tissues. In conclusion, both oscillation and deprivation of ovarian hormones play an important role in cardiovascular autonomic control and oxidative stress profile in target organs, which is reflected in AP changes.
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Affiliation(s)
- Maycon Junior Ferreira
- Physiology Exercise Laboratory, Department of Physiology, Federal University of Sao Paulo (UNIFESP), Sao Paulo, Brazil
| | - Iris Callado Sanches
- Human Movement Laboratory, Sao Judas Tadeu University (USJT), Sao Paulo, SP, Brazil
| | - Luciana Jorge
- Hypertension Unit, Heart Institute, University of Sao Paulo (USP), Sao Paulo, Brazil
| | - Susana Francisca Llesuy
- University Institute of Italian Hospital, Italian Hospital of Buenos Aires (HIBA), Buenos Aires, Argentina
| | | | - Kátia De Angelis
- Physiology Exercise Laboratory, Department of Physiology, Federal University of Sao Paulo (UNIFESP), Sao Paulo, Brazil. .,Laboratory of Translational Physiology, Nove de Julho University (UNINOVE), Sao Paulo, SP, Brazil.
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Abstract
CFTR protein is an ion channel regulated by cAMP-dependent phosphorylation and expressed in many types of epithelial cells. CFTR-mediated chloride and bicarbonate secretion play an important role in the respiratory and gastrointestinal systems. Pharmacological modulators of CFTR represent promising drugs for a variety of diseases. In particular, correctors and potentiators may restore the activity of CFTR in cystic fibrosis patients. Potentiators are also potentially useful to improve mucociliary clearance in patients with chronic obstructive pulmonary disease. On the other hand, CFTR inhibitors may be useful to block fluid and electrolyte loss in secretory diarrhea and slow down the progression of polycystic kidney disease.
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Affiliation(s)
- Olga Zegarra-Moran
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Via Gerolamo Gaslini 5, 16147, Genoa, Italy
| | - Luis J V Galietta
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Via Gerolamo Gaslini 5, 16147, Genoa, Italy.
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4
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Dittrich NP, Kummer W, Clauss WG, Fronius M. Luminal acetylcholine does not affect the activity of the CFTR in tracheal epithelia of pigs. Int Immunopharmacol 2015; 29:166-72. [DOI: 10.1016/j.intimp.2015.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Revised: 08/05/2015] [Accepted: 08/06/2015] [Indexed: 11/29/2022]
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5
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Roomans GM. Pharmacological Approaches to Correcting the Ion Transport Defect in Cystic Fibrosis. ACTA ACUST UNITED AC 2012; 2:413-31. [PMID: 14719993 DOI: 10.1007/bf03256668] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cystic fibrosis (CF) is a lethal genetic disease caused by a mutation in a membrane protein, the cystic fibrosis transmembrane conductance regulator (CFTR), which mainly (but not exclusively) functions as a chloride channel. The main clinical symptoms are chronic obstructive lung disease, which is responsible for most of the morbidity and mortality associated with CF, and pancreatic insufficiency. About 1000 mutations of the gene coding for CFTR are currently known; the most common of these, present in the great majority of the patients (Delta508) results in the deletion of a phenylalanine at position 508. In this mutation, the aberrant CFTR is not transported to the membrane but degraded in the ubiquitin-proteasome pathway. The aim of this review is to give an overview of the pharmacologic strategies currently used in attempts to overcome the ion transport defect in CF. One strategy to develop pharmacologic treatment for CF is to inhibit the breakdown of DeltaF508-CFTR by interfering with the chaperones involved in the folding of CFTR. At least in in vitro systems, this can be accomplished by sodium phenylbutyrate, or S-nitrosoglutathione (GSNO), and also by genistein or benzo[c]quinolizinium compounds. It is also possible to stimulate CFTR or its mutated forms, when present in the plasma membrane, using xanthines, genistein, and various other compounds, such as benzamidizoles and benzoxazoles, benzo[c]quinolizinium compounds or phenantrolines. Experimental results are not always unambiguous, and adverse effects have been incompletely tested. Some clinical tests have been done on sodium phenyl butyrate, GSNO and genistein, mostly in respect to other diseases, and the results demonstrate that these drugs are reasonably well tolerated. Their efficiency in the treatment of CF has not yet been demonstrated, however. An alternative strategy is to compensate for the defective chloride transport by CFTR by stimulation of other chloride channels. This can be done via purinergic receptors. A phase I study using a stable uridine triphosphate analog has recently been completed. A second alternative strategy is to attempt to maintain hydration of the airway mucus by inhibiting Na(+) uptake by the epithelial Na(+) channel using amiloride or stable analogs of amiloride. Clinical tests so far have been inconclusive. A number of other suggestions are currently being explored. The minority of patients with CF who have a stop mutation may benefit from treatment with gentamicin. The difficulties in finding a pharmacologic treatment for CF may be due to the fact that CFTR has additional functions besides chloride transport, and interfering with CFTR biosynthesis or activation implies interference with central cellular processes, which may have undesirable adverse effects.
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Affiliation(s)
- Godfried M Roomans
- Department of Medical Cell Biology, University of Uppsala, Uppsala, Sweden.
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6
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Al-Nakkash L, Springsteel MF, Kurth MJ, Nantz MH. Activation of CFTR by UCCF-029 and genistein. Bioorg Med Chem Lett 2008; 18:3874-7. [PMID: 18595696 DOI: 10.1016/j.bmcl.2008.06.051] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 06/05/2008] [Accepted: 06/16/2008] [Indexed: 10/21/2022]
Abstract
The mechanism of action of a novel CFTR activator UC(CF)-029 on NIH3T3 cells stably expressing DeltaF508-CFTR was investigated and its effects compared to those of genistein, a known CFTR activator. This study shows that UC(CF)-029 and genistein have differing efficacies. The efficacy of UC(CF)-029 in the presence of forskolin (10microM) is approximately 50% that of genistein; however, the EC(50)'s for both drugs are comparable; 3.5microM for UC(CF)-029 and 4.4muM for genistein. Using NIH3T3 cells stably transfected with K1250A-CFTR we find that CFTR channel open time is unaffected by UC(CF)-029 or genistein, supporting the hypothesis that these compounds stabilize the open state by inhibiting ATP hydrolysis at NBD2. Our data suggest that the ability of UC(CF)-029 to augment DeltaF508-CFTR channel activity necessitates further interest.
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Affiliation(s)
- Layla Al-Nakkash
- Department of Physiology, Midwestern University, 19555 N 59th Avenue, Glendale, AZ 85308, USA.
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7
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Pereira M, Parker J, Stratford F, McPherson M, Dormer R. Activation mechanisms for the cystic fibrosis transmembrane conductance regulator protein involve direct binding of cAMP. Biochem J 2007; 405:181-9. [PMID: 17381427 PMCID: PMC1925253 DOI: 10.1042/bj20061879] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 03/23/2007] [Accepted: 03/23/2007] [Indexed: 11/17/2022]
Abstract
The CFTR [CF (cystic fibrosis) transmembrane conductance regulator] chloride channel is activated by cyclic nucleotide-dependent phosphorylation and ATP binding, but also by non-phosphorylation-dependent mechanisms. Other CFTR functions such as regulation of exocytotic protein secretion are also activated by cyclic nucleotide elevating agents. A soluble protein comprising the first NBD (nucleotide-binding domain) and R-domain of CFTR (NBD1-R) was synthesized to determine directly whether CFTR binds cAMP. An equilibrium radioligand-binding assay was developed, firstly to show that, as for full-length CFTR, the NBD1-R protein bound ATP. Half-maximal displacement of [3H]ATP by non-radioactive ATP at 3.5 microM and 3.1 mM was demonstrated. [3H]cAMP bound to the protein with different affinities from ATP (half-maximal displacement by cAMP at 2.6 and 167 microM). Introduction of a mutation (T421A) in a motif predicted to be important for cyclic nucleotide binding decreased the higher affinity binding of cAMP to 9.2 microM. The anti-CFTR antibody (MPNB) that inhibits CFTR-mediated protein secretion also inhibited cAMP binding. Thus binding of cAMP to CFTR is consistent with a role in activation of protein secretion, a process defective in CF gland cells. Furthermore, the binding site may be important in the mechanism by which drugs activate mutant CFTR and correct defective DeltaF508-CFTR trafficking.
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Key Words
- camp
- cyclic nucleotide
- cystic fibrosis transmembrane conductance regulator
- ligand binding
- mutation
- protein secretion
- bca, bicinchoninic acid
- 8-cpt, 8-(4-chlorophenyl)thio
- cf, cystic fibrosis
- cftr, cf transmembrane conductance regulator
- epac, exchange protein directly activated by camp
- gef, guanine exchange factor
- iptg, isopropyl β-d-thiogalactoside
- nbd, nucleotide-binding domain
- ni-nta, ni2+-nitrilotriacetate
- pde, cyclic nucleotide phosphodiesterase
- pka, protein kinase a (or camp-dependent protein kinase)
- pka-i, pka inhibitor peptide
- pka-r, regulatory subunit of pka
- tnp-atp, 2′-o-(trinitrophenyl)-atp
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Affiliation(s)
- Malcolm M. C. Pereira
- Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff CF14 4XN, U.K
| | - Jody Parker
- Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff CF14 4XN, U.K
| | - Fiona L. L. Stratford
- Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff CF14 4XN, U.K
| | - Margaret McPherson
- Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff CF14 4XN, U.K
| | - Robert L. Dormer
- Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff CF14 4XN, U.K
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8
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Adams JM, Legan SJ, Ott CE, Jackson BA. Modulation of hypoglycemia-induced increases in plasma epinephrine by estrogen in the female rat. J Neurosci Res 2005; 79:360-7. [PMID: 15614787 DOI: 10.1002/jnr.20369] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Clinical studies have demonstrated that estrogen replacement therapy suppresses stress-induced increases in plasma catecholamines. The present study determined whether normal circulating levels of estrogen can modulate hypoglycemia-induced increases in plasma epinephrine (EPI). In anesthetized female rats, insulin-induced hypoglycemia (0.25 U/kg) increased plasma EPI concentration to a significantly greater extent in 14-day ovariectomized (OVEX) rats compared to that in sham-operated controls. In 17beta-estradiol (E2)-replaced OVEX rats, the hypoglycemia-induced rise in plasma EPI was reduced significantly when compared to that in vehicle-replaced OVEX rats. OVEX and E2 replacement had no effect on tyrosine hydroxylase or phenylethanolamine N-methyltransferase mRNA levels in the adrenal medulla. In isolated adrenal medullary chromaffin cells, agonist-induced increases in intracellular Ca2+ were unaffected by 48-hr exposure to 10 nM E2. In contrast, acute (3-min) exposure to micromolar concentrations of E2 dose-dependently and reversibly inhibited agonist-induced Ca2+ transients. In addition, in OVEX rats, a constant infusion of E2 significantly reduced the insulin-induced increase in plasma EPI concentration compared to that in vehicle-infused controls. These data demonstrate that physiologic levels of circulating E2 can modulate hypoglycemia-induced increases in plasma EPI. This effect seems independent of steroid influence on adrenal medullary secretion or biosynthesis. In contrast, acute exposure to high levels of E2 can also suppress hypoglycemia-induced increases in plasma epinephrine, due at least in part to inhibition of stimulus-secretion coupling.
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Affiliation(s)
- Julye M Adams
- Department of Physiology, University of Kentucky, College of Medicine, Lexington, Kentucky 40536-0298, USA
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9
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Abstract
The transactivation domain of the cAMP response element-binding protein (CREB) consists of two major domains. The glutamine-rich Q2 domain, which interacts with the general transcription factor TAFII130/135, is sufficient for the recruitment of a functional RNA polymerase II complex and allows basal transcriptional activity. The kinase-inducible domain, however, mediates signal-induced activation of CREB-mediated transcription. It is generally believed that recruitment of the coactivators CREB-binding protein (CBP) and p300 after signal-induced phosphorylation of this domain at serine-133 strongly enhances CREB-dependent transcription. Transcriptional activity of CREB can also be potentiated by phosphoserine-133-independent mechanisms, and not all stimuli that provoke phosphorylation of serine-133 stimulate CREB-dependent transcription. This review presents an overview of the diversity of stimuli that induce CREB phosphorylation at Ser-133, focuses on phosphoserine-133-dependent and -independent mechanisms that affect CREB-mediated transcription, and discusses different models that may explain the discrepancy between CREB Ser-133 phosphorylation and activation of CREB-mediated transcription.
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Affiliation(s)
- Mona Johannessen
- Department of Biochemistry, Institute of Medical Biology, University of Tromsø, N-9037, Norway
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10
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Sangiuolo F, D'Apice MR, Gambardella S, Di Daniele N, Novelli G. Toward the pharmacogenomics of cystic fibrosis – an update. Pharmacogenomics 2004; 5:861-78. [PMID: 15469408 DOI: 10.1517/14622416.5.7.861] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasians, with a frequency of ∼ 1 in 3000 live births. The mutated gene is a defective chloride channel in epithelial cells, named cystic fibrosis transmembrane conductance regulator (CFTR). Several different protocols for the scanning of the entire gene have aided molecular diagnosis and improved our understanding of the disorder’s pathophysiology, but also showed the disease’s complexity. Therefore, CF phenotype remains difficult to predict from CFTR mutation data alone: several studies have suggested that additional genes could modulate its clinical outcome. Gene replacement therapy is still far from being used in patients with CF, mostly due to the difficulties with targeting the appropriate cells. In this review, we summarize recent advances, both in the pharmacological and gene therapy field, aimed for the treatment of the disease.
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Affiliation(s)
- Federica Sangiuolo
- Department of Biopathology and Diagnostic Imaging, Tor Vergata University, Roma, Italy
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Vais H, Zhang R, Reenstra WW. Dibasic phosphorylation sites in the R domain of CFTR have stimulatory and inhibitory effects on channel activation. Am J Physiol Cell Physiol 2004; 287:C737-45. [PMID: 15140750 DOI: 10.1152/ajpcell.00504.2003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To better understand the mechanisms by which PKA-dependent phosphorylation regulates CFTR channel activity, we have assayed open probabilities (P(o)), mean open time, and mean closed time for a series of CFTR constructs with mutations at PKA phosphorylation sites in the regulatory (R) domain. Forskolin-stimulated channel activity was recorded in cell-attached and inside-out excised patches from transiently transfected Chinese hamster ovary cells. Wild-type CFTR and constructs with a single Ser-to-Ala mutation as well as octa (Ser-to-Ala mutations at 8 sites) and constructs with one or two Ala-to-Ser mutations were studied. In cell-attached patches, Ser-to-Ala mutations at amino acids 700, 795, and 813 decreased P(o), whereas Ser-to-Ala mutations at 737 and 768 increased P(o). In general, differences in P(o) were due to differences in mean closed time. For selected constructs with either high or low values of P(o), channel activity was measured in excised patches. With 1 mM ATP, P(o) was similar to that observed in cell-attached patches, but with 10 mM ATP, all constructs tested showed elevated P(o) values. ATP-dependent increases in P(o) were due to reductions in mean closed time. These results indicate that R-domain phosphorylation affects ATP binding and not the subsequent steps of hydrolysis and channel opening. A model was developed whereby R-domain phosphorylation, in a site-dependent manner, alters equilibrium between forms of CFTR with low and high affinities for ATP.
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Affiliation(s)
- Horia Vais
- Division of Medical Genetics, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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DeCarvalho ACV, Gansheroff LJ, Teem JL. Mutations in the nucleotide binding domain 1 signature motif region rescue processing and functional defects of cystic fibrosis transmembrane conductance regulator delta f508. J Biol Chem 2002; 277:35896-905. [PMID: 12110684 DOI: 10.1074/jbc.m205644200] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), an ATP binding cassette (ABC) transporter that functions as a phosphorylation- and nucleotide-regulated chloride channel, is mutated in cystic fibrosis (CF) patients. Deletion of a phenylalanine at amino acid position 508 (DeltaF508) in the first nucleotide binding domain (NBD1) is the most prevalent CF-causing mutation and results in defective protein processing and reduced CFTR function, leading to chloride impermeability in CF epithelia and heterologous systems. Using a STE6/CFTRDeltaF508 chimera system in yeast, we isolated two novel DeltaF508 revertant mutations, I539T and G550E, proximal to and within the conserved ABC signature motif of NBD1, respectively. Western blot and functional analysis in mammalian cells indicate that mutations I539T and G550E each partially rescue the CFTRDeltaF508 defect. Furthermore, a combination of both revertant mutations resulted in a 38-fold increase in CFTRDeltaF508-mediated chloride current, representing 29% of wild type channel activity. The G550E mutation increased the sensitivity of CFTRDeltaF508 and wild type CFTR to activation by cAMP agonists and blocked the enhancement of CFTRDeltaF508 channel activity by 2 mm 3-isobutyl-1-methylxanthine. The data show that the DeltaF508 defect can be significantly rescued by second-site mutations in the nucleotide binding domain 1 region, that includes the LSGGQ consensus motif.
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Affiliation(s)
- Ana C V DeCarvalho
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306, USA
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deCarvalho ACV, Ndi CP, Tsopmo A, Tane P, Ayafor J, Connolly JD, Teem JL. A Novel Natural Product Compound Enhances cAMP-Regulated Chloride Conductance of Cells Expressing CFTRΔF508. Mol Med 2002. [DOI: 10.1007/bf03402077] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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14
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McCarty NA, Standaert TA, Teresi M, Tuthill C, Launspach J, Kelley TJ, Milgram LJH, Hilliard KA, Regelmann WE, Weatherly MR, Aitken ML, Konstan MW, Ahrens RC. A phase I randomized, multicenter trial of CPX in adult subjects with mild cystic fibrosis. Pediatr Pulmonol 2002; 33:90-8. [PMID: 11802244 DOI: 10.1002/ppul.10041] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
CPX (8-cyclopentyl-1,3-dipropylxanthine) is a novel compound currently under development as a potential treatment for cystic fibrosis (CF). The drug has been shown to increase chloride efflux and CFTR trafficking in vitro in CF airway cells. This phase I multicenter, single-dose, placebo-controlled trial was performed at four institutions. Thirty-seven subjects homozygous for the Delta F(508) allele were studied in an escalating dose protocol of seven single-dose cohorts (1, 3, 10, 30, 100, 300, and 1,000 mg) to evaluate the safety, pharmacokinetics, and efficacy of CPX. Efficacy was determined using nasal transepithelial potential difference and sweat chloride measurements prior to dosing and at 1, 2, and 4 hr postdose. The incidence of adverse events in the treatment group was similar to that with placebo, indicating safety of the single doses studied. One serious adverse event (an acute pulmonary exacerbation) occurred 13 days after dosing, and was not considered related to the study drug. The maximal plasma CPX concentration and total amount of CPX absorbed appeared to be linearly related to dose, but was highly variable throughout the dose range studied, suggesting inconsistent absorption. There was no apparent effect of single-dose administration on either nasal transepithelial potential difference or sweat chloride measurements. The positive safety and pharmacokinetic findings of this study support continued development of CPX as a potential therapeutic for CF.
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Affiliation(s)
- Nael A McCarty
- Department of Physiology, Emory University, Atlanta, Georgia, USA.
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15
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Niskanen L, Laitinen T, Tuppurainen M, Saarikoski S, Kröger H, Alhava E, Hartikainen J. Does postmenopausal hormone replacement therapy affect cardiac autonomic regulation in osteoporotic women? Menopause 2002; 9:52-7. [PMID: 11791086 DOI: 10.1097/00042192-200201000-00008] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Postmenopausal hormone replacement therapy (HRT) has been associated with reduced risk of cardiovascular disease; however, the mechanisms remain obscure, and it is not known whether this applies to regimens containing both estrogen and progestin. One possibility is that estrogen would act via enhancement of cardiac autonomic regulation. DESIGN In this prospective, controlled study of 6-months duration, 22 osteoporotic, postmenopausal women in the intervention group were treated with combined estradiol hemihydrate corresponding to estradiol 2 mg and norethisterone acetate 1 mg with or without clodronate (HRT group). Nine women in the control group received clodronate only. Indices of heart rate variability (HRV) by power spectral analyses and baroreceptor sensitivity (BRS) by phenylephrine test were measured before and after 3 and 6 months of treatment. RESULTS The total power of HRV remained identical within the groups, although it was higher at 3 and 6-month measurements in the control group than the HRT group. This was mainly due to lower very low frequency and high frequency power in the HRT group. However, no changes in the low frequency/high frequency-ratio of HRV, an index of sympathovagal balance, were observed between and within the groups. Further, during the intervention, no significant changes in BRS (baseline and 6 months: 5.0 +/- 2.1 and 5.1 +/- 2.5 ms/mmHg) within the HRT group was observed. CONCLUSIONS The impact of estrogen and progesterone on cardiac autonomic regulation seems to be quite modest. Therefore, cardiac morbidity and mortality are probably not mediated by their effects on cardiac autonomic regulation. However, the effects of estrogen alone or more selective estrogen receptor modulators need yet to be clarified in future studies.
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Affiliation(s)
- Leo Niskanen
- Department of Medicine, Building Number 5, Kuopio University Hospital, PO Box 1777, FIN-70211 Kuopio, Finland.
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El-Mas MM, Afify EA, Mohy El-Din MM, Omar AG, Sharabi FM. Testosterone facilitates the baroreceptor control of reflex bradycardia: role of cardiac sympathetic and parasympathetic components. J Cardiovasc Pharmacol 2001; 38:754-63. [PMID: 11602822 DOI: 10.1097/00005344-200111000-00012] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Reported clinical and experimental findings have shown that baroreflex control of heart rate is attenuated in women compared with men. This study investigated whether the sexual dimorphism in baroreflex function relates to the ability of the male hormone testosterone to facilitate baroreflex responsiveness. Relative contributions of the vagal and sympathetic autonomic components to testosterone modulation of baroreflex function were also investigated. Baroreflex curves relating changes in heart rate to increases or decreases in blood pressure evoked by phenylephrine and sodium nitroprusside, respectively, were constructed in sham-operated rats and castrated rats with and without testosterone replacement. Slope of the curves was taken as an index of baroreflex sensitivity (BRS PE and BRS NP ). Castration (for 10 days) significantly reduced plasma testosterone levels and attenuated reflex bradycardia, as indicated by significantly smaller BRS PE in castrated rats compared with values in sham-operated rats (-0.85 +/- 0.07 vs. -1.51 +/- 0.10 beats/min per mm Hg). Testosterone replacement in castrated rats restored plasma testosterone and BRS PE to levels similar to those of sham-operated rats. Muscarinic blockade by atropine caused 55% reduction in BRS PE in sham-operated rats, an effect that was significantly (p < 0.05) attenuated in castrated rats and restored to intact levels after testosterone supplementation. beta-Adrenergic blockade by propranolol caused slight and insignificant decreases in BRS PE. Castration and testosterone supplementation had no effect on BRS NP, ruling out a modulatory effect of testosterone on reflex tachycardia. These data provide the first experimental evidence of a favorable role for testosterone in baroreceptor control of reflex bradycardia. Further, baroreflex modulation by testosterone appears to be autonomically mediated and involves an enhancement of cardiomotor vagal activity.
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Affiliation(s)
- M M El-Mas
- Department of Pharmacology, Faculty of Pharmacy, University of Alexandria, Alexandria, Egypt.
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17
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Webe WM, Segal A, Vankeerberghen A, Cassiman JJ, Van Driessche W. Different activation mechanisms of cystic fibrosis transmembrane conductance regulator expressed in Xenopus laevis oocytes. Comp Biochem Physiol A Mol Integr Physiol 2001; 130:521-31. [PMID: 11913463 DOI: 10.1016/s1095-6433(01)00427-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP sensitive Cl- channel that is defective in cystic fibrosis (CF). The most frequent mutation, namely deltaF508-CFTR, accounts for 66% of CF. Here we show that cAMP-activation of CFTR occurs via at least two distinct pathways: activation of CFTR molecules already present in the plasma membrane and protein kinase A (PKA)-mediated vesicular transport of new CFTR molecules to the plasma membrane and functional insertion into the membrane. We investigated the mechanisms that are responsible for these activation pathways using the Xenopus laevis oocytes expression system. We expressed CFTR and recorded continuously membrane current (Im), conductance (Gm) and capacitance (Cm), which is a direct measure of membrane surface area. Expression of CFTR alone did not change the plasma membrane surface area. However, activation of CFTR with cAMP increased Im, Gm and Cm while deltaF508-CFTR-expressing oocytes showed no response on cAMP. Inhibition of protein kinase A or buffering intracellular Ca2+ abolished the cAMP-induced increase in Cm while increases of Im and Gm were still present. ATP or the xanthine derivative 8-cyclopentyl-1,3-dipropylxanthine (CPX) did not further activate CFTR. Insertion of pre-formed CFTR into the plasma membrane could be prevented by compounds that interfere with intracellular transport mechanisms such as primaquine, brefeldin A, nocodazole. From these data we conclude that cAMP activates CFTR by at least two distinct pathways: activation of CFTR already present in the plasma membrane and exocytotic delivery of new CFTR molecules to the oocyte membrane and functional insertion into it.
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Affiliation(s)
- W M Webe
- Laboratory of Physiology, K U Leuven, Belgium.
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18
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Jankowski M, Rachelska G, Donghao W, McCann SM, Gutkowska J. Estrogen receptors activate atrial natriuretic peptide in the rat heart. Proc Natl Acad Sci U S A 2001; 98:11765-70. [PMID: 11562484 PMCID: PMC58804 DOI: 10.1073/pnas.201394198] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In this study, semiquantitative reverse transcription-PCR analysis showed that estrogen receptor alpha (ERalpha) and beta (ERbeta) mRNAs are developmentally regulated in the rat heart. We found that ERalpha mRNA was low in all heart chambers of 4-day-old rats, but was elevated in the atria (6- to 18-fold) and ventricles (3- to 4-fold) of adult rats. Western blotting analysis confirmed that these differences were efficiently translated into 67-kDa ERalpha protein. ERbeta mRNA was expressed at its highest level in the left atrium and was 3- to 4-fold lower in other heart chambers of 4-day-old animals. In adult rats ERbeta was decreased dramatically in the left atrium (20-fold) and, to a lesser extent in the other heart chambers (2- to 4-fold). Significant ER changes occurred already in the first week after birth. Accordingly, estrogen regulation in cells from neonatal hearts, as reported in several studies, may not correspond to that occurring in fully differentiated adult hearts, because of an altered degree of ER expression. In adult rats, ovariectomy decreases atrial ERalpha, the atria/body weight ratio, and atrial natriuretic peptide (ANP) transcription. Treatment of ovariectomized rats with 17-beta-estradiol (25 microg, 10 days, s.c.) reversed these changes. In addition, there was no effect of ovariectomy and 17-beta-estradiol supplementation on systolic blood pressure, but in ovariectomized rats a decreased heart rate followed 17-beta-estradiol administration. Similar to the effects on ERalpha in the atria, ovariectomy lowered plasma ANP levels, and 17-beta-estradiol administration restored ANP in the plasma of ovariectomized rats. Changes in plasma ANP correlated with changes in ANP content in the right atrium, as demonstrated by RIA. Increased ANP expression and secretion in response to ERalpha activation may be a protective mechanism in the heart.
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Affiliation(s)
- M Jankowski
- Laboratory of Cardiovascular Biochemistry, Centre de Recherche, Centre Hospitalier de l'Université de Montréal, Hôtel-Dieu, Montréal, QC, Canada.
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19
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Bulteau L, Dérand R, Mettey Y, Métayé T, Morris MR, McNeilly CM, Folli C, Galietta LJ, Zegarra-Moran O, Pereira MM, Jougla C, Dormer RL, Vierfond JM, Joffre M, Becq F. Properties of CFTR activated by the xanthine derivative X-33 in human airway Calu-3 cells. Am J Physiol Cell Physiol 2000; 279:C1925-37. [PMID: 11078708 DOI: 10.1152/ajpcell.2000.279.6.c1925] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pharmacological activation of the cystic fibrosis gene protein cystic fibrosis transmembrane conductance regulator (CFTR) was studied in human airway epithelial Calu-3 cells, which express a high level of CFTR protein as assessed by Western blot and in vitro phosphorylation. Immunolocalization shows that CFTR is located in the apical membrane. We performed iodide efflux, whole cell patch-clamp, and short-circuit recordings to demonstrate that the novel synthesized xanthine derivative 3, 7-dimethyl-1-isobutylxanthine (X-33) is an activator of the CFTR channel in Calu-3 cells. Whole cell current activated by X-33 or IBMX is linear, inhibited by glibenclamide and diphenylamine-2-carboxylate but not by DIDS or TS-TM calix[4]arene. Intracellular cAMP was not affected by X-33. An outwardly rectifying Cl(-) current was recorded in the absence of cAMP and X-33 stimulation, inhibited by DIDS and TS-TM calix[4]arene. With the use of short-circuit recordings, X-33 and IBMX were able to stimulate a large concentration-dependent CFTR transport that was blocked by glibenclamide but not by DIDS. Our results show that manipulating the chemical structure of xanthine derivatives offers an opportunity to identify further specific activators of CFTR in airway cells.
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Affiliation(s)
- L Bulteau
- Laboratoire de Physiologie des Régulations Cellulaires, Unité Mixte de Recherche 6558, 86022 Poitiers, France
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20
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Ji HL, Chalfant ML, Jovov B, Lockhart JP, Parker SB, Fuller CM, Stanton BA, Benos DJ. The cytosolic termini of the beta- and gamma-ENaC subunits are involved in the functional interactions between cystic fibrosis transmembrane conductance regulator and epithelial sodium channel. J Biol Chem 2000; 275:27947-56. [PMID: 10821834 DOI: 10.1074/jbc.m002848200] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epithelial sodium channel (ENaC) and cystic fibrosis transmembrane conductance regulator (CFTR) are co-localized in the apical membrane of many epithelia. These channels are essential for electrolyte and water secretion and/or reabsorption. In cystic fibrosis airway epithelia, a hyperactivated epithelial Na(+) conductance operates in parallel with defective Cl(-) secretion. Several groups have shown that CFTR down-regulates ENaC activity, but the mechanisms and the regulation of CFTR by ENaC are unknown. To test the hypothesis that ENaC and CFTR regulate each other, and to identify the region(s) of ENaC involved in the interaction between CFTR and ENaC, rENaC and its mutants were co-expressed with CFTR in Xenopus oocytes. Whole cell macroscopic sodium currents revealed that wild type (wt) alphabetagamma-rENaC-induced Na(+) current was inhibited by co-expression of CFTR, and further inhibited when CFTR was activated with a cAMP-raising mixture (CKT). Conversely, alphabetagamma-rENaC stimulated CFTR-mediated Cl(-) currents up to approximately 6-fold. Deletion mutations in the intracellular tails of the three rENaC subunits suggested that the carboxyl terminus of the beta subunit was required both for the down-regulation of ENaC by activated CFTR and the up-regulation of CFTR by ENaC. However, both the carboxyl terminus of the beta subunit and the amino terminus of the gamma subunit were essential for the down-regulation of rENaC by unstimulated CFTR. Interestingly, down-regulation of rENaC by activated CFTR was Cl(-)-dependent, while stimulation of CFTR by rENaC was not dependent on either cytoplasmic Na(+) or a depolarized membrane potential. In summary, there appear to be at least two different sites in ENaC involved in the intermolecular interaction between CFTR and ENaC.
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Affiliation(s)
- H L Ji
- Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama 35294-0005, USA
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21
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Luo J, Zhu T, Evagelidis A, Pato MD, Hanrahan JW. Role of protein phosphatases in the activation of CFTR (ABCC7) by genistein and bromotetramisole. Am J Physiol Cell Physiol 2000; 279:C108-19. [PMID: 10898722 DOI: 10.1152/ajpcell.2000.279.1.c108] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Genistein and bromotetramisole (Br-t) strongly activate cystic fibrosis transmembrane conductance regulator (CFTR; ABCC7) chloride channels on Chinese hamster ovary cells and human airway epithelial cells. We have examined the possible role of phosphatases in stimulation by these drugs using patch-clamp and biochemical methods. Genistein inhibited the spontaneous rundown of channel activity that occurs after membrane patches are excised from cAMP-stimulated cells but had no effect on purified protein phosphatase type 1 (PP1), PP2A, PP2B, PP2C, or endogenous phosphatases when assayed as [(32)P]PO(4) release from prelabeled casein, recombinant GST-R domain fusion protein, or immunoprecipitated full-length CFTR. Br-t also slowed rundown of CFTR channels, but, in marked contrast to genistein, it did inhibit all four protein phosphatases tested. Half-maximal inhibition of PP2A and PP2C was observed with 0.5 and 1.5 mM Br-t, respectively. Protein phosphatases were also sensitive to (+)-p-Br-t, a stereoisomer of Br-t that does not inhibit alkaline phosphatases. Br-t appeared to act exclusively through phosphatases since it did not affect CFTR channels in patches that had low apparent endogenous phosphatase activity (i.e., those lacking spontaneous rundown). We conclude that genistein and Br-t act through different mechanisms. Genistein stimulates CFTR without inhibiting phosphatases, whereas Br-t acts by inhibiting a membrane-associated protein phosphatase (probably PP2C) that presumably allows basal phosphorylation to accumulate.
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Affiliation(s)
- J Luo
- Department of Physiology, McGill University, Montréal, Québec H3G 1Y6, Canada S7N 0W0
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22
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Wang F, Zeltwanger S, Hu S, Hwang TC. Deletion of phenylalanine 508 causes attenuated phosphorylation-dependent activation of CFTR chloride channels. J Physiol 2000; 524 Pt 3:637-48. [PMID: 10790148 PMCID: PMC2269903 DOI: 10.1111/j.1469-7793.2000.00637.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
In cell-attached patches stimulated with cAMP agonists, the single-channel open probability (Po) of the phenylalanine 508-deleted cystic fibrosis transmembrane conductance regulator (DeltaF508-CFTR) channel, the most common disease-associated mutation in cystic fibrosis, was abnormally low (a functional defect). To investigate the mechanism for the poor response of DeltaF508-CFTR to cAMP stimulation, we examined, in excised inside-out patches, protein kinase A (PKA)-dependent phosphorylation activation and ATP-dependent gating of wild-type (WT) and DeltaF508-CFTR channels expressed in NIH3T3 mouse fibroblasts. For WT-CFTR, the activation time course of CFTR channel current upon addition of PKA and ATP followed a sigmoidal function with time constants that decreased as [PKA] was increased. The curvilinear relationship between [PKA] and the apparent activation rate suggests an incremental phosphorylation-dependent activation of CFTR at multiple phosphorylation sites. The time course of PKA-dependent activation of DeltaF508-CFTR channel current also followed a sigmoidal function, but the rate of activation was at least 7-fold slower than that with WT channels. This result suggests that deletion of phenylalanine 508 causes attenuated PKA-dependent phosphorylation of the CFTR chloride channel. Once DeltaF508-CFTR channels were maximally activated with PKA, the mutant channel and WT channel had indistinguishable steady-state Po values, ATP dose-response relationships and single-channel kinetics, indicating that DeltaF508-CFTR is not defective in ATP-dependent gating. By measuring whole-cell current density, we compared the number of functional channels in WT- and DeltaF508-CFTR cell membrane. Our data showed that the estimated channel density for DeltaF508-CFTR was approximately 10-fold lower than that for WT-CFTR, but the cAMP-dependent whole-cell current density differed by approximately 200-fold. We thus conclude that the functional defect (a decrease in Po) of DeltaF508-CFTR is as important as the trafficking defect (a decrease in the number of functional channels in the plasma membrane) in cystic fibrosis pathogenesis.
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Affiliation(s)
- F Wang
- Department of Physiology, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA
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23
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Abstract
Cystic fibrosis (CF) is an autosomal inherited disorder caused by over 800 different mutations in the CFTR gene. The most common mutation, delta F508, causes a trafficking arrest in the endoplasmic reticulum and the CFTR protein is degraded. Restoration of CFTR trafficking in vitro restores cAMP-mediated chloride transport at the cell surface. The hypothesis of this discussion is that the short chain fatty acids, butyrate and 4-phenylbutyrate, up-regulate mature CFTR at the plasma membrane. Evidence that these compounds regulate CFTR production and maturation in part through effects on molecular chaperones in CF cells in culture is discussed. The oral drug, 4-phenylbutyrate, was tested in a Phase I clinical trial in CF subjects and further trials are underway. Other new therapeutic approaches directed at different classes of mutations in CFTR are also discussed. Chemical and pharmacologic agents that regulate endogenous gene expression at different steps in the biosynthetic processing pathway of a membrane glycoprotein will be needed to comprehensively treat a complex inherited disorder like cystic fibrosis.
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Affiliation(s)
- P L Zeitlin
- Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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24
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Leung GP, Wong PY. Activation of cystic fibrosis transmembrane conductance regulator in rat epididymal epithelium by genistein. Biol Reprod 2000; 62:143-9. [PMID: 10611078 DOI: 10.1095/biolreprod62.1.143] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The effect of genistein on anion secretion via cystic fibrosis transmembrane conductance regulator (CFTR) in cultured rat cauda epididymal epithelia was studied by short-circuit current (Isc) technique. Genistein added apically stimulated a concentration-dependent rise in Isc due to Cl(-) and HCO(3)(-) secretion. The genistein-induced Isc was observed in basolaterally permeabilized monolayers, suggesting that the Isc response was mediated by the apical anion channel. The response could be blocked by the nonspecific Cl(-) channel blocker, diphenylamine-2-carboxylate (DPC), but not by the Ca(2+)-activated Cl(-) channel blocker, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). Genistein did not increase intracellular cAMP, but H-89, a protein kinase A inhibitor, completely abolished the Isc response to genistein. Moreover, pretreatment of the tissues with MDL-12330A, an adenylate cyclase inhibitor, markedly attenuated the Isc response to genistein, but the response was restored upon the addition of exogenous cAMP. Ca(2+), protein kinase C, tyrosine kinase, and protein phosphatase signalling pathways were not involved in the action of genistein. It is speculated that genistein stimulates anion secretion by direct interaction with CFTR. This requires a low level of phosphorylation of CFTR by basal protein kinase A activity. It is suggested that genistein may provide therapeutic benefit to male infertility associated with cystic fibrosis.
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Affiliation(s)
- G P Leung
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People's Republic of China
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25
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Abstract
Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel is associated with a wide spectrum of disease. In the search for modulators of CFTR, pharmacological agents that interact directly with the CFTR Cl- channel have been identified. Some agents stimulate CFTR by interacting with the nucleotide-binding domains that control channel gating, whereas others inhibit CFTR by binding within the channel pore and preventing Cl- permeation. Knowledge of the molecular pharmacology of CFTR might lead to new treatments for diseases caused by the dysfunction of CFTR.
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Affiliation(s)
- T C Hwang
- Department of Physiology, Dalton Cardiovascular Research Center, University of Missouri-Columbia, Columbia, MO 65211, USA.
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26
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Affiliation(s)
- P L Zeitlin
- The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-2533,
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27
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Abstract
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.
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Affiliation(s)
- D C Gadsby
- Laboratory of Cardiac/Membrane Physiology, and Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York, USA
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