RESUMO
Nongenomic glucocorticoid (GC) and serum- and glucocorticoid-inducible kinase 1 (SGK1) signaling regulate ion transport, but CFTR has not been investigated in the intestine. We examined GC, SGK1, and phosphatidylinositol 3-kinase (PI3K) kinase signaling of CFTR ion transport in native intestine and the role of GCs on mRNA, protein, surface expression, and cyclic guanosine monophosphate (cGMP)-elicited diarrhea. Rats were treated with dexamethasone (DEXA; 2 mg/kg ip) or DMSO for 1, 4, and 24 h. Cyclic adenosine monophosphate (cAMP)-activated ion transport was examined in the presence or absence of SGK1 and PI3K inhibitors. Phosphorylation of SGK1, phosphoinositide-dependent kinase 1, and Akt kinases was confirmed by immunoblots using phosphor-specific antibodies. Tissue lysates were analyzed by mass spectrometry. CFTR and SGK1 mRNA were measured by quantitative PCR. Changes in total and surface CFTR protein were determined. The role of GC in cGMP-activated CFTR ion transport was examined. GC synergistically increased CFTR ion transport by SGK1 and PI3K signaling and increased CFTR protein without altering SGK1 or CFTR mRNA. GC induced highest levels of CFTR protein at 4 h that were associated with marked increase in surface CFTR, phosphorylation of the ubiquitin ligase neural precursor cell expressed developmentally downregulated 4-like (Nedd4-2), and 14-3-3ε, supporting their roles in surface retention and stability. Coimmunoprecipitation of CFTR, Nedd4-2, and 14-3-3ε indicated that assembly of this complex is a likely effector of the SGK and Akt pathways. Mass spectrometry identified phosphorylated peptides in relevant proteins. GC-SGK1 potently regulates CFTR in the intestine and is implicated in diarrheal disease.NEW & NOTEWORTHY This is the first study to examine the mechanisms of glucocorticoid, serum- and glucocorticoid-inducible kinase 1, and nongenomic kinase signaling of CFTR in the native intestine. We identified unique and druggable intestine-specific factors of the pathway that are targets for treating stress-induced diarrhea.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Dexametasona/toxicidade , Diarreia/etiologia , Dimetil Sulfóxido/toxicidade , Proteínas Imediatamente Precoces/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas 14-3-3/genética , Proteínas 14-3-3/metabolismo , Animais , Toxinas Bacterianas/toxicidade , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Diarreia/induzido quimicamente , Enterotoxinas/toxicidade , Proteínas de Escherichia coli/toxicidade , Regulação da Expressão Gênica/efeitos dos fármacos , Proteínas Imediatamente Precoces/genética , Masculino , Ubiquitina-Proteína Ligases Nedd4/genética , Ubiquitina-Proteína Ligases Nedd4/metabolismo , Fosfatidilinositol 3-Quinases/genética , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Transporte Proteico , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Piruvato Desidrogenase Quinase de Transferência de Acetil/genética , Piruvato Desidrogenase Quinase de Transferência de Acetil/metabolismo , Ratos , Ratos Sprague-Dawley , Trocador 3 de Sódio-Hidrogênio/genética , Trocador 3 de Sódio-Hidrogênio/metabolismoRESUMO
Whether zinc (Zn2+) regulates barrier functions by modulating tight-junction (TJ) proteins when pathogens such as Shigella alter epithelial permeability is still unresolved. We investigated the potential benefits of Zn2+ in restoring impaired barrier function in vivo in Shigella-infected mouse tissue and in vitro in T84 cell monolayers. Basolateral Shigella infection triggered a time-dependent decrease in transepithelial resistance followed by an increase in paracellular permeability of FITC-labeled dextran and altered ion selectivity. This led to ion and water loss into the intestinal lumen. Immunofluorescence studies revealed redistribution of claudin-2 and -4 to an intracellular location and accumulation of these proteins in the cytoplasm following infection. Zn2+ ameliorated this perturbed barrier by redistribution of claudin-2 and -4 back to the plasma membrane and by modulating the phosphorylation state of TJ proteins t hough extracellular signal-regulated kinase (ERK)1/2 dependency. Zn2+ prevents elevation of IL-6 and IL-8. Mice challenged with Shigella showed that oral Zn2+supplementation diminished diverse pathophysiological symptoms of shigellosis. Claudin-2 and -4 were susceptible to Shigella infection, resulting in altered barrier function and increased levels of IL-6 and IL-8. Zn2+ supplementation ameliorated this barrier dysfunction, and the inflammatory response involving ERK-mediated change of phosphorylation status for claudin-2 and -4. Thus, Zn2+ may have potential therapeutic value in inflammatory diarrhea and shigellosis. NEW & NOTEWORTHY Our study addresses whether Zn2+ could be an alternative strategy to reduce Shigella-induced inflammatory response and epithelial barrier dysfunction. We have defined a mechanism in terms of intracellular signaling pathways and tight-junction protein expression by Zn2+. Claudin-2 and -4 are susceptible to Shigella infection, whereas in the presence of Zn2+ they are resistant to infection-related barrier dysfunction involving ERK-mediated change of phosphorylation status of claudins.
Assuntos
Claudina-2/metabolismo , Claudina-4/metabolismo , Permeabilidade/efeitos dos fármacos , Zinco/farmacologia , Animais , Claudina-2/efeitos dos fármacos , Claudina-4/efeitos dos fármacos , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Enteropatias/tratamento farmacológico , Enteropatias/metabolismo , Masculino , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Proteína Quinase 3 Ativada por Mitógeno/efeitos dos fármacos , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Proteínas Quinases Ativadas por Mitógeno/efeitos dos fármacos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Junções Íntimas/efeitos dos fármacos , Junções Íntimas/metabolismo , Zinco/metabolismoRESUMO
Loss of function mutations in the actin motor myosin Vb (Myo5b) lead to microvillus inclusion disease (MVID) and death in newborns and children. MVID results in secretory diarrhea, brush border (BB) defects, villus atrophy, and microvillus inclusions (MVIs) in enterocytes. How loss of Myo5b results in increased stool loss of chloride (Cl(-)) and sodium (Na(+)) is unknown. The present study used Myo5b loss-of-function human MVID intestine, polarized intestinal cell models of secretory crypt (T84) and villus resembling (CaCo2BBe, C2BBe) enterocytes lacking Myo5b in conjunction with immunofluorescence confocal stimulated emission depletion (gSTED) imaging, immunohistochemical staining, transmission electron microscopy, shRNA silencing, immunoblots, and electrophysiological approaches to examine the distribution, expression, and function of the major BB ion transporters NHE3 (Na(+)), CFTR (Cl(-)), and SLC26A3 (DRA) (Cl(-)/HCO3 (-)) that control intestinal fluid transport. We hypothesized that enterocyte maturation defects lead villus atrophy with immature secretory cryptlike enterocytes in the MVID epithelium. We investigated the role of Myo5b in enterocyte maturation. NHE3 and DRA localization and function were markedly reduced on the BB membrane of human MVID enterocytes and Myo5bKD C2BBe cells, while CFTR localization was preserved. Forskolin-stimulated CFTR ion transport in Myo5bKD T84 cells resembled that of control. Loss of Myo5b led to YAP1 nuclear retention, retarded enterocyte maturation, and a cryptlike phenotype. We conclude that preservation of functional CFTR in immature enterocytes, reduced functional expression of NHE3, and DRA contribute to Cl(-) and Na(+) stool loss in MVID diarrhea.
Assuntos
Enterócitos/metabolismo , Jejuno/metabolismo , Síndromes de Malabsorção/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Microvilosidades/patologia , Mucolipidoses/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Miosina Tipo V/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Células CACO-2 , Antiportadores de Cloreto-Bicarbonato/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Enterócitos/ultraestrutura , Regulação da Expressão Gênica , Humanos , Transporte de Íons , Jejuno/patologia , Jejuno/ultraestrutura , Síndromes de Malabsorção/genética , Síndromes de Malabsorção/patologia , Proteínas de Membrana Transportadoras/genética , Microvilosidades/genética , Microvilosidades/metabolismo , Microvilosidades/ultraestrutura , Mucolipidoses/genética , Mucolipidoses/patologia , Cadeias Pesadas de Miosina/genética , Miosina Tipo V/genética , Fenótipo , Fosfoproteínas/metabolismo , Interferência de RNA , Transdução de Sinais , Trocador 3 de Sódio-Hidrogênio , Trocadores de Sódio-Hidrogênio/metabolismo , Transportadores de Sulfato , Fatores de Transcrição , Transfecção , Proteínas de Sinalização YAPRESUMO
In enterocytes of the small intestine, endocytic trafficking of CFTR channels from the brush border membrane (BBM) to the subapical endosomes requires the minus-end motor, myosin VI (Myo6). The subapical localization of Myo6 is dependent on myosin Ia (Myo1a) the major plus-end motor associated with the BBM, suggestive of functional synergy between these two motors. In villus enterocytes of the Myo1a KO mouse small intestine, CFTR accumulated in syntaxin-3 positive subapical endosomes, redistributed to the basolateral domain and was absent from the BBM. In colon, where villi are absent and Myo1a expression is low, CFTR exhibited normal localization to the BBM in the Myo1a KO similar to WT. cAMP-stimulated CFTR anion transport in the small intestine was reduced by 58% in the KO, while anion transport in the colon was comparable to WT. Co-immunoprecipitation confirmed the association of CFTR with Myo1a. These data indicate that Myo1a is an important regulator of CFTR traffic and anion transport in the BBM of villus enterocytes and suggest that Myo1a may power apical CFTR movement into the BBM from subapical endosomes. Alternatively, it may anchor CFTR channels in the BBM of villus enterocytes as was proposed for Myo1a's role in BBM localization of sucrase-isomaltase.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Enterócitos/metabolismo , Cadeias Pesadas de Miosina/genética , Animais , Células CACO-2 , Cloretos , Colo/citologia , Estimulação Elétrica , Endocitose , Enterócitos/citologia , Exocitose , Humanos , Intestino Delgado/citologia , Transporte de Íons , Camundongos , Camundongos Knockout , Microscopia Confocal , Microvilosidades/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Especificidade de Órgãos , Vesículas Transportadoras/metabolismoRESUMO
Microvillus inclusion disease (MVID) is an autosomal recessive condition resulting in intractable secretory diarrhea in newborns due to loss-of-function mutations in myosin Vb (Myo5b). Previous work suggested that the apical recycling endosomal (ARE) compartment is the primary location for phosphoinositide-dependent protein kinase 1 (PDK1) signaling. Because the ARE is disrupted in MVID, we tested the hypothesis that polarized signaling is affected by Myo5b dysfunction. Subcellular distribution of PDK1 was analyzed in human enterocytes from MVID/control patients by immunocytochemistry. Using Myo5b knockdown (kd) in Caco-2BBe cells, we studied phosphorylated kinases downstream of PDK1, electrophysiological parameters, and net water flux. PDK1 was aberrantly localized in human MVID enterocytes and Myo5b-deficient Caco-2BBe cells. Two PDK1 target kinases were differentially affected: phosphorylated atypical protein kinase C (aPKC) increased fivefold and phosohoprotein kinase B slightly decreased compared with control. PDK1 redistributed to a soluble (cytosolic) fraction and copurified with basolateral endosomes in Myo5b kd. Myo5b kd cells showed a decrease in net water absorption that could be reverted with PDK1 inhibitors. We conclude that, in addition to altered apical expression of ion transporters, depolarization of PDK1 in MVID enterocytes may lead to aberrant activation of downstream kinases such as aPKC. The findings in this work suggest that PDK1-dependent signaling may provide a therapeutic target for treating MVID.
Assuntos
Polaridade Celular , Enterócitos/metabolismo , Síndromes de Malabsorção/metabolismo , Microvilosidades/patologia , Mucolipidoses/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Miosina Tipo V/metabolismo , Transdução de Sinais , Proteínas Quinases Dependentes de 3-Fosfoinositídeo/antagonistas & inibidores , Proteínas Quinases Dependentes de 3-Fosfoinositídeo/metabolismo , Células CACO-2 , Estudos de Casos e Controles , Regulação para Baixo , Endossomos/metabolismo , Enterócitos/efeitos dos fármacos , Humanos , Síndromes de Malabsorção/tratamento farmacológico , Síndromes de Malabsorção/genética , Microvilosidades/genética , Microvilosidades/metabolismo , Terapia de Alvo Molecular , Mucolipidoses/tratamento farmacológico , Mucolipidoses/genética , Mutação , Cadeias Pesadas de Miosina/genética , Miosina Tipo V/genética , Fosforilação , Proteína Quinase C/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Transporte Proteico , Proteínas Proto-Oncogênicas c-akt/metabolismo , Interferência de RNA , Transdução de Sinais/efeitos dos fármacos , Transfecção , Água/metabolismoRESUMO
OBJECTIVES: Spasmolytic polypeptide-expressing metaplasia (SPEM) develops as a preneoplastic lesion in the stomachs of mice and humans after parietal cell loss. To identify the commonalities and differences between phenotypic SPEM lineages, SPEM were studied from three different mouse models of parietal cell loss: with chronic inflammation with Helicobacter felis infection; with acute inflammation with L635 treatment; and without inflammation following DMP-777 treatment. DESIGN: RNA transcripts from laser capture microdissected normal chief cells and SPEM lineages were compared using gene microarray. Alterations in transcripts were validated by quantitative real-time PCR. Clusterin and cystic fibrosis transmembrane conductance regulator (CFTR) were selected for immunohistochemical analysis in all mouse models as well as in human SPEM, intestinal metaplasia and gastric cancer. RESULTS: Transcript expression patterns demonstrated differences among the phenotypic SPEM models. Clusterin expression was significantly upregulated in all three mouse SPEM models as well as in human SPEM. The highest clusterin expression in human gastric cancers correlated with poor survival. Conversely, CFTR expression was upregulated only in SPEM with inflammation in mice. In humans, intestinal metaplasia, but not SPEM, expressed CFTR. CONCLUSIONS: While markers such as clusterin are expressed in all phenotypic SPEM lineages, distinct patterns of upregulated genes including CFTR are present in murine metaplasia associated with inflammation, indicative of progression of metaplasia towards a more intestinalised metaplastic phenotype.
Assuntos
Clusterina/metabolismo , Infecções por Helicobacter/complicações , Inflamação , Intestinos/patologia , Células Parietais Gástricas/patologia , Peptídeos , Animais , Azetidinas/farmacologia , Biomarcadores/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Modelos Animais de Doenças , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Humanos , Inflamação/tratamento farmacológico , Inflamação/etiologia , Inflamação/genética , Inflamação/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular , Microdissecção e Captura a Laser , Metaplasia/diagnóstico , Metaplasia/etiologia , Metaplasia/genética , Metaplasia/metabolismo , Camundongos , Camundongos Endogâmicos CFTR , Células Parietais Gástricas/metabolismo , Peptídeos/genética , Peptídeos/metabolismo , Piperazinas/farmacologia , Lesões Pré-Cancerosas/genética , Lesões Pré-Cancerosas/metabolismo , Regulação para CimaRESUMO
The small intestine is well known for the function of its nutrient-absorbing enterocytes; yet equally critical for the maintenance of homeostasis is a diverse set of secretory cells, all of which are presumed to differentiate from the same intestinal stem cell. Despite major roles in intestinal function and health, understanding how the full spectrum of secretory cell types arises remains a longstanding challenge, largely due to their comparative rarity. Here, we investigate the fate specification of a rare and distinct population of small intestinal epithelial cells found in rats and humans but not mice: C FTR Hi gh E xpressers (CHEs). We use pseudotime trajectory analysis of single-cell RNA-seq data from rat intestinal jejunum to provide evidence that CHEs are specified along the secretory lineage and appear to employ a second wave of Notch-based signal transduction to distinguish these cells from other secretory cell types. We further validate the general order of transcription factors that direct these cells from unspecified progenitors within the crypt and experimentally demonstrate that Notch signaling is necessary to induce CHE fate both in vivo and in vitro . Our results suggest a model in which Notch is reactivated along the secretory lineage to specify the CHE population: a rare secretory cell type with putative functions in localized coordination of luminal pH and direct relevance to cystic fibrosis pathophysiology.
RESUMO
The CFTR modulator Trikafta has markedly improved lung disease for Cystic Fibrosis (CF) patients carrying the common delta F508 (F508del-CFTR) CFTR mutation. F508del-CFTR results in an apical trafficking defect and loss of function in CFTR-expressing epithelial cells. However, Trikafta has not resulted in improved gastrointestinal function in CF patients. A humanized mouse model of F508del-CFTR was recently generated to evaluate CFTR modulators and other compounds to treat human F508del-CFTR CF intestinal disease. Short-term (4 h) treatment of rats with Dexamethasone (Dex) potently activates serum glucocorticoid kinase 1 (SGK1) and increases CFTR apical traffic and ion transport in the native intestine. This study examined CFTR localization and ion transport in intestinal segments from humanized F508del-CFTR mice following treatment with Dex in the presence/absence of Trikafta. Dex treatment improved apical CFTR localization and function but was inconsistent along intestinal segments. Combined treatment with Dex and Trikafta was superior to Dex alone but inconsistently improved CFTR localization and function. These data suggest further optimization of humanized CF mouse models will be necessary to test the efficacy of compounds to treat human CF intestinal disease.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística , Dexametasona , Animais , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/deficiência , Humanos , Camundongos , Dexametasona/farmacologia , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/deficiência , Mucosa Intestinal/metabolismo , Mucosa Intestinal/efeitos dos fármacos , Intestinos/efeitos dos fármacos , Fibrose Cística/tratamento farmacológico , Fibrose Cística/metabolismo , Fibrose Cística/genética , Ativação Enzimática/efeitos dos fármacos , Transporte Proteico/efeitos dos fármacos , Mutação , Masculino , Indóis , BenzodioxóisRESUMO
Vacuolar ATPases (V-ATPases) are highly conserved proton pumps that regulate organelle pH. Epithelial luminal pH is also regulated by cAMP-dependent traffic of specific subunits of the V-ATPase complex from endosomes into the apical membrane. In the intestine, cAMP-dependent traffic of cystic fibrosis transmembrane conductance regulator (CFTR) channels and the sodium hydrogen exchanger (NHE3) in the brush border regulate luminal pH. V-ATPase was found to colocalize with CFTR in intestinal CFTR high expresser (CHE) cells recently. Moreover, apical traffic of V-ATPase and CFTR in rat Brunner's glands was shown to be dependent on cAMP/PKA. These observations support a functional relationship between V-ATPase and CFTR in the intestine. The current study examined V-ATPase and CFTR distribution in intestines from wild-type, CFTR(-/-) mice and polarized intestinal CaCo-2BBe cells following cAMP stimulation and inhibition of CFTR/V-ATPase function. Coimmunoprecipitation studies examined V-ATPase interaction with CFTR. The pH-sensitive dye BCECF determined proton efflux and its dependence on V-ATPase/CFTR in intestinal cells. cAMP increased V-ATPase/CFTR colocalization in the apical domain of intestinal cells and redistributed the V-ATPase Voa1 and Voa2 trafficking subunits from the basolateral membrane to the brush border membrane. Voa1 and Voa2 subunits were localized to endosomes beneath the terminal web in untreated CFTR(-/-) intestine but redistributed to the subapical cytoplasm following cAMP treatment. Inhibition of CFTR or V-ATPase significantly decreased pHi in cells, confirming their functional interdependence. These data establish that V-ATPase traffics into the brush border membrane to regulate proton efflux and this activity is dependent on CFTR in the intestine.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/fisiologia , Enterócitos/metabolismo , ATPases Vacuolares Próton-Translocadoras/fisiologia , Animais , Células CACO-2 , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microvilosidades/metabolismo , Transporte Proteico/fisiologia , Ratos , Ratos Sprague-DawleyRESUMO
The CFTR High Expresser (CHE) cells express eightfold higher levels of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel compared with neighboring enterocytes and were first identified by our laboratory (Ameen et al., Gastroenterology 108: 1016, 1995). We used double-label immunofluorescence microscopy to further study these enigmatic epithelial cells in rat intestine in vivo or ex vivo. CHE cells were found in duodenum, most frequent in proximal jejunum, and absent in ileum and colon. CFTR abundance increased in CHE cells along the crypt-villus axis. The basolateral Na(+)K(+)Cl(-) cotransporter NKCC1, a key transporter involved in Cl(-) secretion, was detected at similar levels in CHE cells and neighboring enterocytes at steady state. Microvilli appeared shorter in CHE cells, with low levels of Myosin 1a, a villus enterocyte-specific motor that retains sucrase/isomaltase in the brush-border membrane (BBM). CHE cells lacked alkaline phosphatase and absorptive villus enterocyte BBM proteins, including Na(+)H(+) exchanger NHE3, Cl(-)/HCO3(-) exchanger SLC26A6 (putative anion exchanger 1), and sucrase/isomaltase. High levels of the vacuolar-ATPase proton pump were observed in the apical domain of CHE cells. Levels of the NHE regulatory factor NHERF1, Na-K-ATPase, and Syntaxin 3 were similar to that of neighboring enterocytes. cAMP or acetylcholine stimulation robustly increased apical CFTR and basolateral NKCC1 disproportionately in CHE cells relative to neighboring enterocytes. These data strongly argue for a specialized role of CHE cells in Cl(-)-mediated "high-volume" fluid secretion on the villi of the proximal small intestine.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Mucosa Intestinal/metabolismo , Intestino Delgado/citologia , Acetilcolina/farmacologia , Fosfatase Alcalina/genética , Fosfatase Alcalina/metabolismo , Animais , AMP Cíclico/farmacologia , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Mucosa Intestinal/ultraestrutura , Masculino , Microvilosidades/ultraestrutura , Transporte Proteico/efeitos dos fármacos , Proteínas Qa-SNARE/genética , Proteínas Qa-SNARE/metabolismo , Ratos , Ratos Sprague-Dawley , Trocador 3 de Sódio-Hidrogênio , Trocadores de Sódio-Hidrogênio/genética , Trocadores de Sódio-Hidrogênio/metabolismo , ATPase Trocadora de Sódio-Potássio/genética , ATPase Trocadora de Sódio-Potássio/metabolismo , Membro 2 da Família 12 de Carreador de Soluto/genética , Membro 2 da Família 12 de Carreador de Soluto/metabolismoRESUMO
The Brunner's glands of the proximal duodenum exert barrier functions through secretion of glycoproteins and antimicrobial peptides. However, ion transporter localization, function, and regulation in the glands are less clear. Mapping the subcellular distribution of transporters is an important step toward elucidating trafficking mechanisms of fluid transport in the gland. The present study examined 1) changes in the distribution of intestinal anion transporters and the aquaporin 5 (AQP5) water channel in rat Brunner's glands following second messenger activation and 2) anion transporter distribution in Brunner's glands from healthy and disease-affected human tissues. Cystic fibrosis transmembrane conductance regulator (CFTR), AQP5, sodium-potassium-coupled chloride cotransporter 1 (NKCC1), sodium-bicarbonate cotransporter (NBCe1), and the proton pump vacuolar ATPase (V-ATPase) were localized to distinct membrane domains and in endosomes at steady state. Carbachol and cAMP redistributed CFTR to the apical membrane. cAMP-dependent recruitment of CFTR to the apical membrane was accompanied by recruitment of AQP5 that was reversed by a PKA inhibitor. cAMP also induced apical trafficking of V-ATPase and redistribution of NKCC1 and NBCe1 to the basolateral membranes. The steady-state distribution of AQP5, CFTR, NBCe1, NKCC1, and V-ATPase in human Brunner's glands from healthy controls, cystic fibrosis, and celiac disease resembled that of rat; however, the distribution profiles were markedly attenuated in the disease-affected duodenum. These data support functional transport of chloride, bicarbonate, water, and protons by second messenger-regulated traffic in mammalian Brunner's glands under physiological and pathophysiological conditions.
Assuntos
Proteínas de Transporte de Ânions/metabolismo , Glândulas Duodenais/metabolismo , Água/metabolismo , Animais , Proteínas de Transporte de Ânions/análise , Aquaporina 5/análise , Aquaporina 5/metabolismo , Bicarbonatos/metabolismo , Transporte Biológico/efeitos dos fármacos , Glândulas Duodenais/química , Glândulas Duodenais/patologia , Carbacol/farmacologia , Doença Celíaca/metabolismo , Cloretos/metabolismo , AMP Cíclico/farmacologia , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/análise , Duodeno/química , Duodeno/patologia , Humanos , Masculino , Prótons , Ratos , Ratos Sprague-Dawley , Sistemas do Segundo Mensageiro/fisiologia , ATPases Vacuolares Próton-Translocadoras/análiseRESUMO
Intracellular protein traffic plays an important role in the regulation of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) chloride channels. Microtubule and actin-based motor proteins direct CFTR movement along trafficking pathways. As shown for other regulatory proteins such as adaptors, the involvement of protein motors in CFTR traffic is cell-type specific. Understanding motor specificity provides insight into the biology of the channel and opens opportunity for discovery of organ-specific drug targets for treating CFTR-mediated diseases.
Assuntos
Actinas/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Epitélio/metabolismo , Microtúbulos/metabolismo , Miosinas/metabolismo , Animais , Regulador de Condutância Transmembrana em Fibrose Cística/análise , Humanos , Transporte ProteicoRESUMO
When using organoids to assess physiology and cell fate decisions, it is important to use a model that closely recapitulates in vivo contexts. Accordingly, patient-derived organoids are used for disease modeling, drug discovery, and personalized treatment screening. Mouse intestinal organoids are commonly utilized to understand aspects of both intestinal function/physiology and stem cell dynamics/fate decisions. However, in many disease contexts, rats are often preferred over mice as a model due to their greater physiological similarity to humans in terms of disease pathophysiology. The rat model has been limited by a lack of genetic tools available in vivo, and rat intestinal organoids have proven fragile and difficult to culture long-term. Here, we build upon previously published protocols to robustly generate rat intestinal organoids from the duodenum and jejunum. We provide an overview of several downstream applications utilizing rat intestinal organoids, including functional swelling assays, whole mount staining, the generation of 2D enteroid monolayers, and lentiviral transduction. The rat organoid model provides a practical solution to the need of the field for an in vitro model which retains physiological relevance to humans, can be quickly genetically manipulated, and is easily obtained without the barriers involved in procuring human intestinal organoids.
Assuntos
Intestinos , Jejuno , Ratos , Camundongos , Humanos , Animais , Diferenciação Celular , Células-Tronco , Organoides , Mucosa IntestinalRESUMO
Cystic Fibrosis Transmembrane Conductance Regulator (CFTR), the Cl-/HCO3 - channel implicated in Cystic Fibrosis, is critical to the pathophysiology of many gastrointestinal diseases. Defects in CFTR lead to intestinal dysfunction, malabsorption, obstruction, infection, inflammation, and cancer that increases morbidity and reduces quality of life. This review will focus on CFTR in the intestine and the implications of the subpopulation of CFTR High Expresser Cells (CHEs) in Cystic Fibrosis (CF), intestinal physiology and pathophysiology of intestinal diseases.
RESUMO
Changes in intestinal luminal pH affect mucosal ion transport. The aim of this study was to compare how luminal pH and specific second messengers modulate the membrane traffic of four major ion transporters (CFTR, NHE3, NKCC1, and NBCe1) in rat small intestine. Ligated duodenal, jejunal, and ileal segments were infused with acidic or alkaline saline, 8-Br-cAMP, or the calcium agonist carbachol in vivo for 20 min. Compared with untreated intestine, lumen pH was reduced after cAMP or carbachol and increased following HCO(3)(-)-saline. Following HCl-saline, lumen pH was restored to control pH levels. All four secretory stimuli resulted in brush-border membrane (BBM) recruitment of CFTR in crypts and villi. In villus enterocytes, CFTR recruitment was coincident with internalization of BBM NHE3 and basolateral membrane recruitment of the bicarbonate transporter NBCe1. Both cAMP and carbachol recruited NKCC1 to the basolateral membrane of enterocytes, while luminal acid or HCO(3)(-) retained NKCC1 in intracellular vesicles. Luminal acid resulted in robust recruitment of CFTR and NBCe1 to their respective enterocyte membrane domains in the upper third of the villi; luminal HCO(3)(-) induced similar membrane changes lower in the villi. These findings indicate that each stimulus promotes a specific transporter trafficking response along the crypt-villus axis. This is the first demonstration that physiologically relevant secretory stimuli exert their actions in villus enterocytes by membrane recruitment of CFTR and NBCe1 in tandem with NHE3 internalization.
Assuntos
8-Bromo Monofosfato de Adenosina Cíclica/farmacologia , Ácidos/farmacologia , Bicarbonatos/farmacologia , Carbacol/farmacologia , Mucosa Intestinal/efeitos dos fármacos , Intestinos/efeitos dos fármacos , Animais , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Humanos , Mucosa Intestinal/metabolismo , Masculino , Transporte Proteico/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Simportadores de Sódio-Bicarbonato/metabolismo , Trocador 3 de Sódio-Hidrogênio , Trocadores de Sódio-Hidrogênio/metabolismo , Simportadores de Cloreto de Sódio-Potássio/metabolismo , Membro 2 da Família 12 de Carreador de SolutoRESUMO
BACKGROUND AND AIM: Lubiprostone is a chloride channel activator in clinical use for the treatment of chronic constipation, but the mechanisms of action of the drug are poorly understood. The aim of this study was to determine whether lubiprostone exerts secretory effects in the intestine by membrane trafficking of ion transporters and associated machinery. METHODS: Immunolabeling and quantitative fluorescence intensity were used to examine lubiprostone-induced trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR), sodium/potassium-coupled chloride co-transporter 1 (NKCC1), electrogenic sodium/bicarbonate co-transporter 1 (NBCe1), down-regulated in adenoma (DRA), putative anion transporter 1 (PAT1), sodium/proton exchanger 3 (NHE3), Ca(2+) activated chloride channel 2 (ClC-2) serotonin and its transporter SERT, E prostanoid receptors EP4 and EP1, sodium/potassium ATPase (Na-K-ATPase) and protein kinase A (PKA). The effects of lubiprostone on mucus exocytosis in rat intestine and human rectosigmoid explants were also examined. RESULTS: Lubiprostone induced contraction of villi and proximal colonic plicae and membrane trafficking of transporters that was more pronounced in villus/surface cells compared to the crypt. Membrane trafficking was determined by: (1) increased membrane labeling for CFTR, PAT1, NKCC1, and NBCe1 and decreased membrane labeling for NHE3, DRA and ClC-2; (2) increased serotonin, SERT, EP4, EP1 and PKA labeling in enterochromaffin cells; (3) increased SERT, EP4, EP1, PKA and Na-K-ATPase in enterocytes; and (4) increased mucus exocytosis in goblet cells. CONCLUSION: These data suggest that lubiprostone can target serotonergic, EP4/PKA and EP1 signaling in surface/villus regions; stimulate membrane trafficking of CFTR/NBCe1/NKCC1 in villus epithelia and PAT1/NBCe1/NKCC1 in colonic surface epithelia; suppress NHE3/DRA trafficking and fluid absorption; and enhance mucus-mobilization and mucosal contractility.
Assuntos
Alprostadil/análogos & derivados , Exocitose/efeitos dos fármacos , Mucosa Intestinal/efeitos dos fármacos , Mucosa Intestinal/metabolismo , Muco/efeitos dos fármacos , Muco/metabolismo , Contração Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Músculo Liso/metabolismo , Alprostadil/farmacologia , Análise de Variância , Animais , Antiporters/metabolismo , Biópsia , Canais de Cloro CLC-2 , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Imunofluorescência , Humanos , Técnicas In Vitro , Transporte de Íons , Lubiprostona , Proteínas de Membrana Transportadoras/metabolismo , Transportadores de Ânions Orgânicos/metabolismo , Proteínas de Ligação a RNA/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Prostaglandina E Subtipo EP1/metabolismo , Receptores de Prostaglandina E Subtipo EP4/metabolismo , Simportadores de Sódio-Bicarbonato/metabolismo , Trocador 3 de Sódio-Hidrogênio , Trocadores de Sódio-Hidrogênio/metabolismo , Simportadores de Cloreto de Sódio-Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Transportadores de SulfatoRESUMO
Microvillus inclusion disease (MVID), a lethal congenital diarrheal disease, results from loss of function mutations in the apical actin motor myosin VB (MYO5B). How loss of MYO5B leads to both malabsorption and fluid secretion is not well understood. Serum glucocorticoid-inducible kinase 1 (SGK1) regulates intestinal carbohydrate and ion transporters including cystic fibrosis transmembrane conductance regulator (CFTR). We hypothesized that loss of SGK1 could reduce CFTR fluid secretion and MVID diarrhea. Using CRISPR-Cas9 approaches, we generated R26CreER;MYO5Bf/f conditional single knockout (cMYO5BKO) and R26CreER;MYO5Bf/f;SGK1f/f double knockout (cSGK1/MYO5B-DKO) mice. Tamoxifen-treated cMYO5BKO mice resulted in characteristic features of human MVID including severe diarrhea, microvillus inclusions (MIs) in enterocytes, defective apical traffic, and depolarization of transporters. However, apical CFTR distribution was preserved in crypts and depolarized in villus enterocytes, and CFTR high expresser (CHE) cells were observed. cMYO5BKO mice displayed increased phosphorylation of SGK1, PDK1, and the PDK1 target PKCι in the intestine. Surprisingly, tamoxifen-treated cSGK1/MYO5B-DKO mice displayed more severe diarrhea than cMYO5BKO, with preservation of apical CFTR and CHE cells, greater fecal glucose and reduced SGLT1 and GLUT2 in the intestine. We conclude that loss of SGK1 worsens carbohydrate malabsorption and diarrhea in MVID.
RESUMO
We examined the cell-specific subcellular expression patterns for sodium- and potassium-coupled chloride (NaK2Cl) cotransporter 1 (NKCC1), Na(+) bicarbonate cotransporter (NBCe1), cystic fibrosis transmembrane conductance regulator (CFTR), and Na(+)/H(+) exchanger 3 (NHE3) to understand the functional plasticity and synchronization of ion transport functions along the crypt-villus axis and its relevance to intestinal disease. In the unstimulated intestine, all small intestinal villus enterocytes coexpressed apical CFTR and NHE3, basolateral NBCe1, and mostly intracellular NKCC1. All (crypt and villus) goblet cells strongly expressed basolateral NKCC1 (at approximately three-fold higher levels than villus enterocytes), but no CFTR, NBCe1, or NHE3. Lower crypt cells coexpressed apical CFTR and basolateral NKCC1, but no NHE3 or NBCe1 (except NBCe1-expressing proximal colonic crypts). CFTR, NBCe1, and NKCC1 colocalized with markers of early and recycling endosomes, implicating endocytic recycling in cell-specific anion transport. Brunner's glands of the proximal duodenum coexpressed high levels of apical/subapical CFTR and basolateral NKCC1, but very low levels of NBCe1, consistent with secretion of Cl(-)-enriched fluid into the crypt. The cholinergic agonist carbachol rapidly (within 10 min) reduced cell volume along the entire crypt/villus axis and promoted NHE3 internalization into early endosomes. In contrast, carbachol induced membrane recruitment of NKCC1 and CFTR in all crypt and villus enterocytes, NKCC1 in all goblet cells, and NBCe1 in all villus enterocytes. These observations support regulated vesicle traffic in Cl(-) secretion by goblet cells and Cl(-) and HCO(3)(-) secretion by villus enterocytes during the transient phase of cholinergic stimulation. Overall, the carbachol-induced membrane trafficking profile of the four ion transporters supports functional plasticity of the small intestinal villus epithelium that enables it to conduct both absorptive and secretory functions.
Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Intestino Delgado/metabolismo , Simportadores de Sódio-Bicarbonato/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Simportadores de Cloreto de Sódio-Potássio/metabolismo , Animais , Carbacol/farmacologia , Mucosa Intestinal/citologia , Mucosa Intestinal/fisiologia , Intestino Delgado/citologia , Intestino Delgado/efeitos dos fármacos , Masculino , Ratos , Trocador 3 de Sódio-Hidrogênio , Membro 2 da Família 12 de Carreador de SolutoRESUMO
Loss-of-function mutations in the nonconventional myosin Vb (Myo5b) result in microvillus inclusion disease (MVID) and massive secretory diarrhea that often begins at birth. Myo5b mutations disrupt the apical recycling endosome (ARE) and membrane traffic, resulting in reduced surface expression of apical membrane proteins. ARE disruption also results in constitutive phosphoinositide-dependent kinase 1 gain of function. In MVID, decreased surface expression of apical anion channels involved in Cl- extrusion, such as cystic fibrosis transmembrane conductance regulator (CFTR), should reduce fluid secretion into the intestinal lumen. But the opposite phenotype is observed. To explain this contradiction and the onset of diarrhea, we hypothesized that signaling effects downstream from Myo5b loss of function synergize with higher levels of glucocorticoids to activate PKA and CFTR. Data from intestinal cell lines, human MVID, and Myo5b KO mouse intestine revealed changes in the subcellular redistribution of PKA activity to the apical pole, increased CFTR phosphorylation, and establishment of apical cAMP gradients in Myo5b-defective cells exposed to physiological levels of glucocorticoids. These cells also displayed net secretory fluid fluxes and transepithelial currents mainly from PKA-dependent Cl- secretion. We conclude that Myo5b defects result in PKA stimulation that activates residual channels on the surface when intestinal epithelia are exposed to glucocorticoids at birth.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Glucocorticoides/metabolismo , Miosina Tipo V/genética , Proteínas Quinases Dependentes de 3-Fosfoinositídeo/metabolismo , Animais , Células CACO-2 , Linhagem Celular Tumoral , Canais de Cloreto/metabolismo , Diarreia/congênito , Diarreia/genética , Humanos , Síndromes de Malabsorção/genética , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Knockout , Microvilosidades/genética , Microvilosidades/patologia , Mucolipidoses/genéticaRESUMO
BACKGROUND: AP2 is a clathrin-based endocytic adaptor complex comprising α, ß2, µ2 and σ2 subunits. µ2 regulates CFTR endocytosis. The α subunit interacts with CFTR in the intestine but its physiologic significance is unclear. METHODS: CFTR short circuit current was measured in intestinal T84 cells following shRNA knock down of AP2α (AP2αKD). Clathrin-coated structures (CCS) were immunolabeled and quantified in AP2αKD intestinal Caco2BBe (C2BBe) cells. GST tagged human AP2α appendage domain was cloned and its interaction with CFTR determined by GST pull down assay. RESULT: AP2αKD in T84 cells resulted in higher CFTR current (57%) compared to control, consistent with increased functional CFTR and delayed endocytosis. Depletion of AP2α reduced CCS in C2BBe cells. Pull down assays revealed an interaction between human AP2α appendage domain and CFTR. CONCLUSION: AP2 α interacts with and modulates CFTR function in the intestine by participating in clathrin assembly and recruitment of CFTR to CCS.