Angiotensin(1-7) activates MAS-1 and upregulates CFTR to promote insulin secretion in pancreatic β-cells: the association with type 2 diabetes

OBJECTIVE

The beneficial effect of angiotensin(1-7) (Ang(1-7)), via the activation of its receptor, MAS-1, has been noted in diabetes treatment; however, how Ang(1-7) or MAS-1 affects insulin secretion remains elusive and whether the endogenous level of Ang(1-7) or MAS-1 is altered in diabetic individuals remains unexplored. We recently identified an important role of cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated Cl- channel, in the regulation of insulin secretion. Here, we tested the possible involvement of CFTR in mediating Ang(1-7)'s effect on insulin secretion and measured the level of Ang(1-7), MAS-1 as well as CFTR in the blood of individuals with or without type 2 diabetes.

METHODS

Ang(1-7)/MAS-1/CFTR pathway was determined by specific inhibitors, gene manipulation, Western blotting as well as insulin ELISA in a pancreatic β-cell line, RINm5F. Human blood samples were collected from 333 individuals with (n = 197) and without (n = 136) type 2 diabetes. Ang(1-7), MAS-1 and CFTR levels in the human blood were determined by ELISA.

RESULTS

In RINm5F cells, Ang(1-7) induced intracellular cAMP increase, cAMP-response element binding protein (CREB) activation, enhanced CFTR expression and potentiated glucose-stimulated insulin secretion, which were abolished by a selective CFTR inhibitor, RNAi-knockdown of CFTR, or inhibition of MAS-1. In human subjects, the blood levels of MAS-1 and CFTR, but not Ang(1-7), were significantly higher in individuals with type 2 diabetes as compared to those in non-diabetic healthy subjects. In addition, blood levels of MAS-1 and CFTR were in significant positive correlation in type-2 diabetic but not non-diabetic subjects.

CONCLUSION

These results suggested that MAS-1 and CFTR as key players in mediating Ang(1-7)-promoted insulin secretion in pancreatic β-cells; MAS-1 and CFTR are positively correlated and both upregulated in type 2 diabetes.

Magnesium implantation or supplementation ameliorates bone disorder in CFTR-mutant mice through an ATF4-dependent Wnt/β-catenin signaling

Magnesium metal and its alloys are being developed as effective orthopedic implants; however, the mechanisms underlying the actions of magnesium on bones remain unclear. Cystic fibrosis, the most common genetic disease in Caucasians caused by the mutation of CFTR, has shown bone disorder as a key clinical manifestation, which currently lacks effective therapeutic options. Here we report that implantation of magnesium-containing implant stimulates bone formation and improves bone fracture healing in CFTR-mutant mice. Wnt/β-catenin signaling in the bone is enhanced by the magnesium implant, and inhibition of Wnt/β-catenin by iCRT14 blocks the magnesium implant to improve fracture healing in CFTR-mutant mice. We further demonstrate that magnesium ion enters osteocytes, increases intracellular cAMP level and activates ATF4, a key transcription factor known to regulate Wnt/β-catenin signaling. In vivo knockdown of ATF4 abolishes the magnesium implant-activated β-catenin in bones and reverses the improved-fracture healing in CFTR-mutant mice. In addition, oral supplementation of magnesium activates ATF4 and β-catenin as well as enhances bone volume and density in CFTR-mutant mice. Together, these results show that magnesium implantation or supplementation may serve as a potential anabolic therapy for cystic fibrosis-related bone disease. Activation of ATF4-dependent Wnt/β-catenin signaling in osteocytes is identified as a previously undefined mechanism underlying the beneficial effect of magnesium on bone formation.

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Magnesium implant ameliorates bone defects and improves the impaired bone fracture healing in CFTR-deficient mice.

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Oral magnesium supplementation improves bone quality in CFTR-deficient mice.

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Extracellular Mg²⁺ enters bone cells through Mg²⁺ channels and transporters.

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Mg²⁺ elevates cAMP level to activate ATF4-dependent Wnt/β-catenin signalingin bone cells.

Effect of SARS and COVID-19 outbreaks on urology practice and training

INTRODUCTION

The objective was to investigate the changes in urology practice during coronavirus disease 2019 (COVID-19) pandemic with a perspective from our experience with severe acute respiratory syndrome (SARS) in 2003.

METHODS

Institutional data from all urology centres in the Hong Kong public sector during the COVID-19 pandemic (1 Feb 2020-31 Mar 2020) and a non-COVID-19 control period (1 Feb 2019-31 Mar 2019) were acquired. An online anonymous questionnaire was used to gauge the impact of COVID-19 on resident training. The clinical output of tertiary centres was compared with data from the SARS period.

RESULTS

The numbers of operating sessions, clinic attendance, cystoscopy sessions, prostate biopsy, and shockwave lithotripsy sessions were reduced by 40.5%, 28.5%, 49.6%, 44.8%, and 38.5%, respectively, across all the centres reviewed. The mean numbers of operating sessions before and during the COVID-19 pandemic were 85.1±30.3 and 50.6±25.7, respectively (P=0.005). All centres gave priority to cancer-related surgeries. Benign prostatic hyperplasia-related surgery (39.1%) and ureteric stone surgery (25.5%) were the most commonly delayed surgeries. The degree of reduction in urology services was less than that during SARS (47.2%, 55.3%, and 70.5% for operating sessions, cystoscopy, and biopsy, respectively). The mean numbers of operations performed by residents before and during the COVID-19 pandemic were 75.4±48.0 and 34.9±17.2, respectively (P=0.002).

CONCLUSION

A comprehensive review of urology practice during the COVID-19 pandemic revealed changes in every aspect of practice.

CFTR promotes malignant glioma development via up-regulation of Akt/Bcl2-mediated anti-apoptosis pathway

Cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP‐activated Cl^‐ channel, is extensively expressed in the epithelial cells of various tissues and organs. Accumulating evidence indicates that aberrant expression or mutation of CFTR is related to carcinoma development. Malignant gliomas are the most common and aggressive intracranial tumours; however, the role of CFTR in the development of malignant gliomas is unclear. Here, we report that CFTR is expressed in malignant glioma cell lines. Suppression of CFTR channel function or knockdown of CFTR suppresses glioma cell viability whereas overexpression of CFTR promotes it. Additionally, overexpression of CFTR suppresses apoptosis and promotes glioma progression in both subcutaneous and orthotopic xenograft models. Cystic fibrosis transmembrane conductance regulator activates Akt/Bcl2 pathway, and suppression of PI3K/Akt pathway abolishes CFTR overexpression–induced up‐regulation of Bcl2 (MK‐2206 and LY294002) and cell viability (MK‐2206). More importantly, the protein expression level of CFTR is significantly increased in glioblastoma patient samples. Altogether, our study has revealed a mechanism by which CFTR promotes glioma progression via up‐regulation of Akt/Bcl2‐mediated anti‐apoptotic pathway, which warrants future studies into the potential of using CFTR as a therapeutic target for glioma treatment.

KDM3A and KDM4C Regulate Mesenchymal Stromal Cell Senescence and Bone Aging via Condensin-mediated Heterochromatin Reorganization

Epigenomic changes and stem cell deterioration are two hallmarks of aging. Accumulating evidence suggest that senescence of mesenchymal stromal cells (MSCs) perpetuates aging or age-related diseases. Here we report that two H3K9 demethylases, KDM3A and KDM4C, regulate heterochromatin reorganization via transcriptionally activating condensin components NCAPD2 and NCAPG2 during MSC senescence. Suppression of KDM3A or KDM4C by either genetic or biochemical approach leads to robust DNA damage response and aggravates cellular senescence, whereas overexpression of KDM3A/KDM4C or NCAPD2 promotes heterochromatin reorganization and blunts DNA damage response. Moreover, MSCs derived from Kdm3a−/− mice exhibit defective chromosome organization and exacerbated DNA damage response, which are associated with accelerated bone aging. Consistently, analysis of human bone marrow MSCs and transcriptome database reveals inverse correlation of KDM3A/KDM4C and/or NCAPD2/NCAPG2 with aging. Taken together, the present finding unveils that H3K9 demethylases function as a surveillance mechanism to restrain DNA damage accumulation in stem cells during aging.

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KDM3A and KDM4C restrain DNA damage response during MSC senescence

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KDM3A and KDM4C promote heterochromatin reorganization via induction of condensin

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Loss of Kdm3a exacerbates MSC senescence and bone aging in mice

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Chronological aging of human MSCs is associated with reduced expression of KDM3A and KDM4C

The Mechanosensitive Ion Channel Piezo1 Significantly Mediates In Vitro Ultrasonic Stimulation of Neurons

Ultrasound brain stimulation is a promising modality for probing brain function and treating brain disease non-invasively and with high spatiotemporal resolution. However, the mechanism underlying its effects remains unclear. Here, we examine the role that the mouse piezo-type mechanosensitive ion channel component 1 (Piezo1) plays in mediating the in vitro effects of ultrasound in mouse primary cortical neurons and a neuronal cell line. We show that ultrasound alone could activate heterologous and endogenous Piezo1, initiating calcium influx and increased nuclear c-Fos expression in primary neurons but not when pre-treated with a Piezo1 inhibitor. We also found that ultrasound significantly increased the expression of the important proteins phospho-CaMKII, phospho-CREB, and c-Fos in a neuronal cell line, but Piezo1 knockdown significantly reduced this effect. Our findings demonstrate that the activity of mechanosensitive ion channels such as Piezo1 stimulated by ultrasound is an important contributor to its ability to stimulate cells in vitro.

Emergency attendances and hospitalisations for complications after transrectal ultrasound-guided prostate biopsies: a five-year retrospective multicentre study

INTRODUCTION

Transrectal ultrasound-guided (TRUS) prostate biopsy is an established procedure for diagnosis of prostate cancer. Complications after TRUS biopsy are not well reported in Hong Kong. This study evaluated the 5-year incidences of TRUS biopsy complications and potential risk factors for those complications.

METHODS

This was a retrospective review of biopsies performed from 2013 to 2017 in two local hospitals, using data retrieved from electronic medical records. The primary outcome was the occurrence of complications requiring either emergency attendances or hospitalisations within 30 days after biopsy. Potential risk factors were examined using multiple logistic regression analysis.

RESULTS

In total, 1699 men were included (mean age ± standard deviation: 67 ± 7 years; median prostate-specific antigen level: 7.9 μg/L [interquartile range, 5.5-12.6 μg/L]); 4.3% had pre-biopsy bacteriuria. Overall, 5.7% and 3.8% of post-biopsy complications required emergency attendances and hospitalisations, respectively. Gross haematuria and rectal bleeding requiring emergency attendances developed in 2.1% and 0.4% of men; 0.8% and 0.4% required hospitalisations. Furthermore, 1.5% of men developed acute urinary retention requiring hospitalisations; 1.9% and 1.2% had post-biopsy infections requiring emergency attendances and hospitalisations, respectively, and 0.9% had urosepsis requiring hospitalisations. Prostate volume >48 cc was associated with an increased risk of post-biopsy retention (odds ratio 2.75, 95% confidence interval: 1.23-4.17).

CONCLUSIONS

The rate of overall complications after TRUS biopsy was low. The most common complications requiring emergency attendances and hospitalisations were gross haematuria and acute urinary retention, respectively. Prostate volume >48 cc increased the risk of post-biopsy urinary retention.

Progenitor Cells Derived from Drain Waste Product of Open-Heart Surgery in Children

Human cardiac progenitor cells isolated from the same host may have advantages over other sources of stem cells. The aim of this study is to establish a new source of human progenitor cells collected from a waste product, pericardiac effusion fluid, after open-heart surgery in children with congenital heart diseases. The fluid was collected every 24 h for 2 days after surgery in 37 children. Mononuclear cells were isolated and expanded in vitro. These pericardial effusion-derived progenitor cells (PEPCs) exhibiting cardiogenic lineage markers, were highly proliferative and enhanced angiogenesis in vitro. Three weeks after stem cell transplantation into the ischemic heart in mice, cardiac ejection fraction was improved significantly without detectable progenitor cells. Gene expression profiles of the repaired hearts revealed activation of several known repair mechanisms including paracrine effects, cell migration, and angiogenesis. These progenitor cells may have the potential for heart regeneration.

MRP4 sustains Wnt/β-catenin signaling for pregnancy, endometriosis and endometrial cancer

Rationale: Abnormal Wnt/β-catenin signaling in the endometrium can lead to both embryo implantation failure and severe pathogenic changes of the endometrium such as endometrial cancer and endometriosis. However, how Wnt/β-catenin signaling is regulated in the endometrium remains elusive. We explored possible regulation of Wnt/β-catenin signaling by multi-drug resistance protein 4 (MRP4), a potential target in cancer chemotherapy, and investigated the mechanism.

Methods: Knockdown of MRP4 was performed in human endometrial cells in vitro or in a mouse embryo-implantation model in vivo. Immunoprecipitation, immunoblotting and immunofluorescence were used to assess protein interaction and stability. Wnt/β-catenin signaling was assessed by TOPflash reporter assay and quantitative PCR array. Normal and endometriotic human endometrial tissues were examined. Data from human microarray or RNAseq databases of more than 100 participants with endometriosis, endometrial cancer or IVF were analyzed. In vitro and in vivo tumorigenesis was performed.

Results: MRP4-knockdown, but not its transporter-function-inhibition, accelerates β-catenin degradation in human endometrial cells. MRP4 and β-catenin are co-localized and co-immunoprecipitated in mouse and human endometrium. MRP4-knockdown in mouse uterus reduces β-catenin levels, downregulates a series of Wnt/β-catenin target genes and impairs embryo implantation, which are all reversed by blocking β-catenin degradation. Analysis of human endometrial biopsy samples and available databases reveals significant and positive correlations of MRP4 with β-catenin and Wnt/β-catenin target genes in the receptive endometrium in IVF, ectopic endometriotic lesions and endometrial cancers. Knockdown of MRP4 also inhibits in vitro and in vivo endometrial tumorigenesis.

Conclusion: A previously undefined role of MRP4 in stabilizing β-catenin to sustain Wnt/β-catenin signaling in endometrial cells is revealed for both embryo implantation and endometrial disorders, suggesting MRP4 as a theranostic target for endometrial diseases associated with Wnt/β-catenin signaling abnormality.

Activation of the epithelial sodium channel (ENaC) leads to cytokine profile shift to pro-inflammatory in labor

The shift of cytokine profile from anti‐ to pro‐inflammatory is the most recognizable sign of labor, although the underlying mechanism remains elusive. Here, we report that the epithelial sodium channel (ENaC) is upregulated and activated in the uterus at labor in mice. Mechanical activation of ENaC results in phosphorylation of CREB and upregulation of pro‐inflammatory cytokines as well as COX‐2/PGE₂ in uterine epithelial cells. ENaC expression is also upregulated in mice with RU486‐induced preterm labor as well as in women with preterm labor. Interference with ENaC attenuates mechanically stimulated uterine contractions and significantly delays the RU486‐induced preterm labor in mice. Analysis of a human transcriptome database for maternal–fetus tissue/blood collected at onset of human term and preterm births reveals significant and positive correlation of ENaC with labor‐associated pro‐inflammatory factors in labored birth groups (both term and preterm), but not in non‐labored birth groups. Taken together, the present finding reveals a pro‐inflammatory role of ENaC in labor at term and preterm, suggesting it as a potential target for the prevention and treatment of preterm labor.

CFTR is required for the migration of primordial germ cells during zebrafish early embryogenesis

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene affect fertility in both sexes. However, the involvement of CFTR in regulating germ cell development remains largely unknown. Here, we used zebrafish model to investigate the role of CFTR in primordial germ cells (PGCs) development. We generated a cftr frameshift mutant zebrafish line using CRISPR/Cas9 technique and investigated the migration of PGCs during early embryo development. Our results showed that loss of Cftr impairs the migration of PGCs from dome stages onward. The migration of PGCs was also perturbed by treatment of CFTRinh-172, a gating-specific CFTR channel inhibitor. Moreover, defected PGCs migration in cftr mutant embryos can be partially rescued by injection of WT but not other channel-defective mutant cftr mRNAs. Finally, we observed the elevation of cxcr4b, cxcl12a, rgs14a and ca15b, key factors involved in zebrafish PGCs migration, in cftr-mutant zebrafish embryos. Taken together, the present study revealed an important role of CFTR acting as an ion channel in regulating PGCs migration during early embryogenesis. Defect of which may impair germ cell development through elevation of key factors involved in cell motility and response to chemotactic gradient in PGCs.

Defective CFTR- β-catenin interaction promotes NF-κB nuclear translocation and intestinal inflammation in cystic fibrosis

While inflammation with aberrant activation of NF-κB pathway is a hallmark of cystic fibrosis (CF), the molecular mechanisms underlying the link between CFTR defect and activation of NF-κB-mediated pro-inflammatory response remain elusive. Here, we investigated the link between CFTR defect and NF-κB activation in ΔF508cftr^−/− mouse intestine and human intestinal epithelial cell lines. Our results show that the NF-κB/COX-2/PGE₂ pathway is activated whereas the β-catenin pathway is suppressed in CF mouse intestine and CFTR-knockdown cells. Activation of β-catenin pathway by GSK3 inhibitors suppresses CFTR mutation/knockdown-induced NF-κB/COX-2/PGE₂ pathway in ΔF508 mouse intestine and CFTR-knockdown cells. In contrast, suppression of β-catenin signaling induces the nuclear translocation of NF-κB. In addition, CFTR co-localizes and interacts with β-catenin while CFTR mutation disrupts the interaction between NF-κB and β-catenin in mouse intestine. Treatment with proteasome inhibitor MG132 completely reverses the reduced expression of β-catenin in Caco-2 cells. Collectively, these results indicate that CFTR stabilizes β-catenin and prevents its degradation, defect of which results in the activation of NF-κB-mediated inflammatory cascade. The present study has demonstrated a previously unsuspected interaction between CFTR and β-catenin that regulates NF-κB nuclear translocation in mouse intestine. Therefore, our study provides novel insights into the physiological function of CFTR and pathogenesis of CF-related diseases in addition to the NF-κB-mediated intestinal inflammation seen in CF.

Cystic fibrosis transmembrane conductance regulator-emerging regulator of cancer

Mutations of cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis, the most common life-limiting recessive genetic disease among Caucasians. CFTR mutations have also been linked to increased risk of various cancers but remained controversial for a long time. Recent studies have begun to reveal that CFTR is not merely an ion channel but also an important regulator of cancer development and progression with multiple signaling pathways identified. In this review, we will first present clinical findings showing the correlation of genetic mutations or aberrant expression of CFTR with cancer incidence in multiple cancers. We will then focus on the roles of CFTR in fundamental cellular processes including transformation, survival, proliferation, migration, invasion and epithelial-mesenchymal transition in cancer cells, highlighting the signaling pathways involved. Finally, the association of CFTR expression levels with patient prognosis, and the potential of CFTR as a cancer prognosis indicator in human malignancies will be discussed.

CD147 regulates extrinsic apoptosis in spermatocytes by modulating NFκB signaling pathways

CD147 null mutant male mice are infertile with arrested spermatogenesis and increased apoptotic germ cells. Our previous studies have shown that CD147 prevents apoptosis in mouse spermatocytes but not spermatogonia. However, the underlying mechanism remains elusive. In the present study, we aim to determine the CD147-regulated apoptotic pathway in mouse spermatocytes. Our results showed that immunodepletion of CD147 triggered apoptosis through extrinsic apoptotic pathway in mouse testis and spermatocyte cell line (GC-2 cells), accompanied by activation of non-canonical NFκB signaling and suppression of canonical NFκB signaling. Furthermore, CD147 was found to interact with TRAF2, a factor known to regulate NFκB and extrinsic apoptotic signaling, and interfering CD147 led to the decrease of TRAF2. Consistently, depletion of CD147 by CRISPR/Cas9 technique in GC-2 cells down-regulated TRAF2 and resulted in cell death with suppressed canonical NFκB and activated non-canonical NFκB signaling. On the contrary, interfering of CD147 had no effect on NFκB signaling pathways as well as TRAF2 protein level in mouse spermatogonia cell line (GC-1 cells). Taken together, these results suggested that CD147 plays a key role in reducing extrinsic apoptosis in spermatocytes, but not spermatogonia, through modulating NFκB signaling pathway.

CFTR is a potential marker for nasopharyngeal carcinoma prognosis and metastasis

While there is an increasing interest in the correlation of cystic fibrosis transmembrane conductance regulator (CFTR) and cancer incidence, the role of CFTR in nasopharyngeal carcinoma (NPC) development remains unknown. In this study, we aimed to explore the prognostic value of CFTR in NPC patients. The expression of CFTR was determined in NPC cell lines and tissues. Statistical analysis was utilized to evaluate the correlation between CFTR expression levels and clinicopathological characteristics and prognosis in 225 cases of NPC patients. The results showed that CFTR was down-regulated in NPC tissues and cell lines. Low expression of CFTR was correlated with advanced stage (p = 0.026), distant metastasis (p < 0.001) and poor prognosis (p < 0.01). Multivariate analysis identified CFTR as an independent prognostic factor (p = 0.003). Additionally, wound healing and transwell assays revealed that overexpression of CFTR inhibited NPC cell migration and invasion, whereas knockdown of CFTR promoted cell migration and invasion. Thus, the current study indicates that CFTR, as demonstrated to play an important role in tumor migration and invasion, may be used as a potential prognostic indicator in NPC.

Abnormal CFTR Affects Glucagon Production by Islet α Cells in Cystic Fibrosis and Polycystic Ovarian Syndrome

Glucagon, produced by islet α cells, functions to increase blood glucose. Abnormal glucose levels are often seen in cystic fibrosis (CF), a systematic disease caused by mutations of the CF transmembrane conductance regulator (CFTR), and in polycystic ovarian syndrome (PCOS), an endocrine disorder featured with hyperandrogenism affecting 5-10% women of reproductive age. Here, we explored the role of CFTR in glucagon production in α cells and its possible contribution to glucagon disturbance in CF and PCOS. We found elevated fasting glucagon levels in CFTR mutant (DF508) mice compared to the wildtypes. Glucagon and prohormone convertase 2 (PC2) were also upregulated in CFTR inhibitor-treated or DF508 islets, as compared to the controls or wildtypes, respectively. Dihydrotestosterone (DHT)-induced PCOS rats exhibited significantly lower fasting glucagon levels with higher CFTR expression in α cells compared to that of controls. Treatment of mouse islets or αTC1-9 cells with DHT enhanced CFTR expression and reduced the levels of glucagon and PC2. The inhibitory effect of DHT on glucagon production was blocked by CFTR inhibitors in mouse islets, and mimicked by overexpressing CFTR in αTC1-9 cells with reduced phosphorylation of the cAMP/Ca2+ response element binding protein (p-CREB), a key transcription factor for glucagon and PC2. These results revealed a previously undefined role of CFTR in suppressing glucagon production in α-cells, defects in which may contribute to glucose metabolic disorder seen in CF and PCOS.

Huwe1 Regulates the Establishment and Maintenance of Spermatogonia by Suppressing DNA Damage Response

Spermatogenesis is sustained by a heterogeneous population of spermatogonia that includes the spermatogonial stem cells. However, the mechanisms underlying their establishment from gonocyte embryonic precursors and their maintenance thereafter remain largely unknown. In this study, we report that inactivation of the ubiquitin ligase Huwe1 in male germ cells in mice led to the degeneration of spermatogonia in neonates and resulted in a Sertoli cell-only phenotype in the adult. Huwe1 knockout gonocytes showed a decrease in mitotic re-entry, which inhibited their transition to spermatogonia. Inactivation of Huwe1 in primary spermatogonial culture or the C18-4 cell line resulted in cell degeneration. Degeneration of Huwe1 knockout spermatogonia was associated with an increased level of histone H2AX and an elevated DNA damage response that led to apparent mitotic catastrophe but not apoptosis or senescence. Blocking this increase in H2AX prevented the degeneration of Huwe1-depleted cells. Taken together, these results reveal a previously undefined role of Huwe1 in orchestrating the physiological DNA damage response in the male germline that contributes to the establishment and maintenance of spermatogonia.

Glucose-Sensitive CFTR Suppresses Glucagon Secretion by Potentiating KATP Channels in Pancreatic Islet α Cells

The secretion of glucagon by islet α cells is normally suppressed by high blood glucose, but this suppressibility is impaired in patients with diabetes or cystic fibrosis (CF), a disease caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), a cyclic adenosine monophosphate-activated Cl- channel. However, precisely how glucose regulates glucagon release remains controversial. Here we report that elevated glucagon secretion, together with increased glucose-induced membrane depolarization and Ca2+ response, is found in CFTR mutant (DF508) mice/islets compared with the wild-type. Overexpression of CFTR in AlphaTC1-9 cells results in membrane hyperpolarization and reduced glucagon release, which can be reversed by CFTR inhibition. CFTR is found to potentiate the adenosine triphosphate-sensitive K+ (KATP) channel because membrane depolarization and whole-cell currents sensitive to KATP blockers are significantly greater in wild-type/CFTR-overexpressed α cells compared with that in DF508/non-overexpressed cells. KATP knockdown also reverses the suppressive effect of CFTR overexpression on glucagon secretion. The results reveal that by potentiating KATP channels, CFTR acts as a glucose-sensing negative regulator of glucagon secretion in α cells, a defect of which may contribute to glucose intolerance in CF and other types of diabetes.

Amplification of FSH signalling by CFTR and nuclear soluble adenylyl cyclase in the ovary

The cAMP/PKA pathway is one of the most important signalling pathways widely distributed in most eukaryotic cells. The activation of the canonical cAMP/PKA pathway depends on transmembrane adenylyl cyclase (tmAC). Recently, soluble adenylyl cyclase (sAC), which is activated by HCO₃^- or Ca²⁺ , emerges to provide an alternative way to activate cAMP/PKA pathway with the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated Cl^- /HCO₃^- -conducting anion channel, as a key player. This review summarizes new progress in the investigation of the CFTR/HCO₃^- -dependent sAC signalling and its essential role in various reproductive processes, particularly in ovarian functions. We present the evidence for a CFTR/HCO₃^- -dependent nuclear sAC signalling cascade that amplifies the FSH-stimulated cAMP/PKA pathway, traditionally thought to involve tmAC, in granulosa for the regulation of oestrogen production and granulosa cell proliferation. The implication of the CFTR/HCO₃^- /sAC pathway in amplifying other receptor-activated cAMP/PKA signalling in a wide variety of cell types and pathophysiological processes, including aging, is also discussed.

CCR6 is required for ligand-induced CatSper activation in human sperm

CatSper channel has been considered the principal sperm Ca²⁺ channel responsible for the cytosolic Ca²⁺ elevation required for various sperm functions necessary for fertilization [1–4]. However, the mechanism underlying the activation of CatSper channel by various physiological ligands remain incompletely understood. We have recently demonstrated the expression of C-C chemokine receptor 6 (CCR6) in sperm and Ca²⁺ influx upon binding of human β-defensin 1 (DEFB1) to CCR6, which is important for sperm motility [5]. In the present study, we have demonstrated that CCR6 receptor and CatSper channel are both required for the Ca²⁺ entry/current induced by physiological ligands DEFB1, chemokine (C-C motif) ligand 20 (CCL20) and progesterone in human sperm. CCR6 is co-localized and interacts with CatSper in human sperm. Ca²⁺ influx mediated by CCR6 and CatSper is required for essential sperm functions, including motility, hyperactivation and acrosome reaction, which are impaired in infertile sperm showing reduced levels of CCR6 and CatSper. The present finding suggests a critical role of CCR6 receptor in mediating ligand-induced, CatSper-dependent Ca²⁺ influx required for various sperm functions and thus male fertility.

Upregulation of CFTR in patients with endometriosis and its involvement in NFκB-uPAR dependent cell migration

Endometriotic tissues exhibit high migration ability with the underlying mechanisms remain elusive. Our previous studies have demonstrated that cystic fibrosis transmembrane conductance regulator (CFTR) acts as a tumor suppressor regulating cell migration. In the present study, we explored whether CFTR plays a role in the development of human endometriosis. We found that both mRNA and protein expression levels of CFTR and urokinase-type plasminogen activator receptor (uPAR) were significantly increased in ectopic endometrial tissues from patients with endometriosis compared to normal endometrial tissues from women without endometriosis and positively correlated. In human endometrial Ishikawa (ISK) cells, overexpression of CFTR stimulated cell migration with upregulated NFκB p65 and uPAR. Knockdown of CFTR inhibited cell migration. Furthermore, inhibition of NFκB with its inhibitors (curcumin or Bay) significantly reduced the expression of uPAR and cell migration in the CFTR-overexpressing ISK cells. Collectively, the present results suggest that the CFTR-NFκB-uPAR signaling may contribute to the progression of human endometriosis, and indicate potential targets for diagnosis and treatment.

Mammalian TRAPPIII Complex positively modulates the recruitment of Sec13/31 onto COPII vesicles

The Transport protein particle (TRAPP) complex is a tethering factor for COPII vesicle. Of three forms of TRAPP (TRAPPI, II and III) complexes identified so far, TRAPPIII has been largely considered to play a role in autophagy. While depletion of TRAPPIII specific subunits caused defects in the early secretory pathway and TRAPPIII might interact with components of the COPII vesicle coat, its exact role remains to be determined. In this study, we studied the function of TRAPPIII in early secretory pathway using a TRAPPIII-specific subunit, TRAPPC12, as starting point. We found that TRAPPC12 was localized to the ER exit sites and ERGIC. In cells deleted with TRAPPC12, ERGIC and to a lesser extent, the Golgi became dispersed. ER-to-Golgi transport was also delayed. TRAPPC12, but not TRAPPC8, bound to Sec13/Sec31A tetramer but each Sec protein alone could not interact with TRAPPC12. TRAPPIII positively modulated the assembly of COPII outer layer during COPII vesicle formation. These results identified a novel function of TRAPPIII as a positive modulator of the outer layer of the COPII coat.

Epigenetic Modification of the CCL5/CCR1/ERK Axis Enhances Glioma Targeting in Dedifferentiation-Reprogrammed BMSCs

The success of stem cell-mediated gene therapy in cancer treatment largely depends on the specific homing ability of stem cells. We have previously demonstrated that after in vitro induction of neuronal differentiation and dedifferentiation, bone marrow stromal cells (BMSCs) revert to a primitive stem cell population (De-neu-BMSCs) distinct from naive BMSCs. We report here that De-neu-BMSCs express significantly higher levels of chemokines, and display enhanced homing abilities to glioma, the effect of which is mediated by the activated CCL5/CCR1/ERK axis. Intriguingly, we find that the activated chemokine axis in De-neu-BMSCs is epigenetically regulated by histone modifications. On the therapeutic front, we show that De-neu-BMSCs elicit stronger homing and glioma-killing effects together with cytosine deaminase/5-fluorocytosine compared with unmanipulated BMSCs in vivo. Altogether, the current study provides an insight into chemokine regulation in BMSCs, which may have more profound effects on BMSC function and their application in regenerative medicine and cancer targeting.

COPI-TRAPPII activates Rab18 and regulates its lipid droplet association

The transport protein particle (TRAPP) was initially identified as a vesicle tethering factor in yeast and as a guanine nucleotide exchange factor (GEF) for Ypt1/Rab1. In mammals, structures and functions of various TRAPP complexes are beginning to be understood. We found that mammalian TRAPPII was a GEF for both Rab18 and Rab1. Inactivation of TRAPPII-specific subunits by various methods including siRNA depletion and CRISPR-Cas9-mediated deletion reduced lipolysis and resulted in aberrantly large lipid droplets. Recruitment of Rab18 onto lipid droplet (LD) surface was defective in TRAPPII-deleted cells, but the localization of Rab1 on Golgi was not affected. COPI regulates LD homeostasis. We found that the previously documented interaction between TRAPPII and COPI was also required for the recruitment of Rab18 to the LD We hypothesize that the interaction between COPI and TRAPPII helps bring TRAPPII onto LD surface, and TRAPPII, in turn, activates Rab18 and recruits it on the LD surface to facilitate its functions in LD homeostasis.

Implant-derived magnesium induces local neuronal production of CGRP to improve bone-fracture healing in rats

Orthopedic implants containing biodegradable magnesium have been used for fracture repair with considerable efficacy; however, the underlying mechanisms by which these implants improve fracture healing remain elusive. Here we show the formation of abundant new bone at peripheral cortical sites after intramedullary implantation of a pin containing ultrapure magnesium into the intact distal femur in rats. This response was accompanied by substantial increases of neuronal calcitonin gene-related polypeptide-α (CGRP) in both the peripheral cortex of the femur and the ipsilateral dorsal root ganglia (DRG). Surgical removal of the periosteum, capsaicin denervation of sensory nerves or knockdown in vivo of the CGRP-receptor-encoding genes Calcrl or Ramp1 substantially reversed the magnesium-induced osteogenesis that we observed in this model. Overexpression of these genes, however, enhanced magnesium-induced osteogenesis. We further found that an elevation of extracellular magnesium induces magnesium transporter 1 (MAGT1)-dependent and transient receptor potential cation channel, subfamily M, member 7 (TRPM7)-dependent magnesium entry, as well as an increase in intracellular adenosine triphosphate (ATP) and the accumulation of terminal synaptic vesicles in isolated rat DRG neurons. In isolated rat periosteum-derived stem cells, CGRP induces CALCRL- and RAMP1-dependent activation of cAMP-responsive element binding protein 1 (CREB1) and SP7 (also known as osterix), and thus enhances osteogenic differentiation of these stem cells. Furthermore, we have developed an innovative, magnesium-containing intramedullary nail that facilitates femur fracture repair in rats with ovariectomy-induced osteoporosis. Taken together, these findings reveal a previously undefined role of magnesium in promoting CGRP-mediated osteogenic differentiation, which suggests the therapeutic potential of this ion in orthopedics.

MycN Is Critical for the Maintenance of Human Embryonic Stem Cell-Derived Neural Crest Stem Cells

The biologic studies of human neural crest stem cells (hNCSCs) are extremely challenging due to the limited source of hNCSCs as well as ethical and technical issues surrounding isolation of early human embryonic tissues. On the other hand, vast majority of studies on MycN have been conducted in human tumor cells, thus, the role of MycN in normal human neural crest development is completely unknown. In the present study, we determined the role of MycN in hNCSCs isolated from in vitro-differentiating human embryonic stem cells (hESCs). For the first time, we show that suppression of MycN in hNCSCs inhibits cell growth and cell cycle progression. Knockdown of MycN in hNCSCs increases the expression of Cdkn1a, Cdkn2a and Cdkn2b, which encodes the cyclin-dependent kinases p21^CIP1, p16 ^INK4a and p15^INK4b. In addition, MycN is involved in the regulation of human sympathetic neurogenesis, as knockdown of MycN enhances the expression of key transcription factors involved in sympathetic neuron differentiation, including Phox2a, Phox2b, Mash1, Hand2 and Gata3. We propose that unlimited source of hNCSCs provides an invaluable platform for the studies of human neural crest development and diseases.

CFTR-regulated MAPK/NF-κB signaling in pulmonary inflammation in thermal inhalation injury

The mechanism underlying pulmonary inflammation in thermal inhalation injury remains elusive. Cystic fibrosis, also hallmarked with pulmonary inflammation, is caused by mutations in CFTR, the expression of which is temperature-sensitive. We investigated whether CFTR is involved in heat-induced pulmonary inflammation. We applied heat-treatment in 16HBE14o- cells with CFTR knockdown or overexpression and heat-inhalation in rats in vivo. Heat-treatment caused significant reduction in CFTR and, reciprocally, increase in COX-2 at early stages both in vitro and in vivo. Activation of ERK/JNK, NF-κB and COX-2/PGE2 were detected in heat-treated cells, which were mimicked by knockdown, and reversed by overexpression of CFTR or VX-809, a reported CFTR mutation corrector. JNK/ERK inhibition reversed heat-/CFTR-knockdown-induced NF-κB activation, whereas NF-κB inhibitor showed no effect on JNK/ERK. IL-8 was augmented by heat-treatment or CFTR-knockdown, which was abolished by inhibition of NF-κB, JNK/ERK or COX-2. Moreover, in vitro or in vivo treatment with curcumin, a natural phenolic compound, significantly enhanced CFTR expression and reversed the heat-induced increases in COX-2/PGE2/IL-8, neutrophil infiltration and tissue damage in the airway. These results have revealed a CFTR-regulated MAPK/NF-κB pathway leading to COX-2/PGE2/IL-8 activation in thermal inhalation injury, and demonstrated therapeutic potential of curcumin for alleviating heat-induced pulmonary inflammation.

Dynamically Regulated CFTR Expression and Its Functional Role in Cutaneous Wound Healing

The physiological role of cystic fibrosis transmembrane conductance regulator (CFTR) in keratinocytes and skin wound healing is completely unknown. The present study shows that CFTR is expressed in the multiple layers of keratinocytes in mouse epidermis and exhibits a dynamic expression pattern in a dorsal skin wound healing model, with diminishing levels observed from day 3 to day 5 and re-appearing from day 7 to day 10 after wounding. Knockdown of CFTR in cultured human keratinocytes promotes cell migration but inhibits differentiation, while overexpression of CFTR suppresses migration but enhances differentiation, indicating an important role of CFTR in regulating keratinocyte behavior. In addition, we have demonstrated a direct association of CFTR with epithelial junction formation as knockdown of CFTR downregulates the expression of adhesion molecules, such as E-cadherin, ZO-1 and β-catenin, and disrupts the formation of cell junction, while overexpression of CFTR enhances cell junction formation. More importantly, we have shown that ΔF508cftr-/- mice with defective CFTR exhibit delayed wound healing as compared to wild type mice, indicating that normal function of CFTR is critical for wound repair. Taken together, the present study has revealed a previously undefined role of CFTR in regulating skin wound healing processes, which may have implications in injury repair of other epithelial tissues.

Down-regulated CFTR During Aging Contributes to Benign Prostatic Hyperplasia

Benign prostatic hyperplasia (BPH) is a hyper-proliferative disease of the aging prostate; however, the exact mechanism underlying the development of BPH remains incompletely understood. The present study investigated the possible involvement of the cystic fibrosis transmembrane conductance regulator (CFTR), which has been previously shown to negatively regulate nuclear factor-κB (NF-κB)/cyclooxygenase 2 (COX2)/prostaglandin E2 (PGE2) pathway, in the pathogenesis of BPH. Our results showed decreasing CFTR and increasing COX2 expression in rat prostate tissues with aging. Furthermore, suppression of CFTR led to increased expression of COX2 and over-production of PGE2 in a normal human prostate epithelial cell line (PNT1A) with elevated NF-κB activity. PGE2 stimulated the proliferation of primary rat prostate stromal cells but not epithelial cells, with increased PCNA expression. In addition, the condition medium from PNT1A cells after inhibition or knockdown of CFTR promoted cell proliferation of prostate stromal cells which could be reversed by COX2 or NF-κB inhibitor. More importantly, the involvement of CFTR in BPH was further demonstrated by the down-regulation of CFTR and up-regulation of COX2/NF-κB in human BPH samples. The present results suggest that CFTR may be involved in regulating PGE2 production through its negative regulation on NF-κB/COX2 pathway in prostate epithelial cells, which consequently stimulates cell growth of prostate stromal cells. The overstimulation of prostate stromal cell proliferation by down-regulation of CFTR-enhanced PGE2 production and release during aging may contribute to the development of BPH.

Up-regulation of Bcl-2 by CD147 Through ERK Activation Results in Abnormal Cell Survival in Human Endometriosis

CONTEXT

Human endometriosis (EMS) is characterized by insufficient apoptosis. Our previous studies have shown elevated CD147 expression in human endometriotic tissues and its involvement in endometrial cell apoptosis. However, the exact underlying mechanism remains elusive.

OBJECTIVE

The objective was to examine the correlation of the highly expressed CD147 with anti-apoptotic factor Bcl-2 in human endometriotic tissues and to determine the CD147-regulated apoptotic pathway in human endometrial epithelial cell line (HES).

DESIGN

This was a laboratory study using human tissue analysis and HES cell culture.

SETTING

The setting was an academic research center and hospital.

PATIENTS

Patients were 30 women with ovarian EMS and 12 women without EMS.

INTERVENTIONS

mRNA levels of CD147 and Bcl-2 were evaluated in endometriotic tissues by quantitative real-time PCR. HES cells were transfected with pcDNA3.0-CD147 overexpressing plasmid or immune-depleted by CD147 antibody.

MAIN OUTCOME MEASURES

Main outcome measures were reverse transcription, quantitative real-time PCR, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, and Western blotting.

RESULTS

In human endometriotic tissues, Bcl-2 was up-regulated and positively correlated with CD147 expression, accompanied by activated ERK signaling. In HES cells, overexpression of CD147 increased viable cells and up-regulated Bcl-2 expression by activation of ERK signaling. Interference with CD147 function suppressed ERK signaling and decreased Bcl-2 expression, followed by accumulation of apoptotic factors, including cleaved caspase-9, cleaved caspase-3, and cleaved poly ADP-ribose polymerase.

CONCLUSIONS

The presently found strong correlations between Bcl-2 and CD147, ERK, and CD147 in human endometriotic lesions and the demonstrated reduced cell apoptosis through CD147-ERK-Bcl-2 intrinsic apoptosis signaling axis suggest that this CD147-regulated signaling may contribute to the enhanced cell survival in the progression of human EMS.

FSH regulates fat accumulation and redistribution in aging through the Gαi/Ca(2+)/CREB pathway

Increased fat mass and fat redistribution are commonly observed in aging populations worldwide. Although decreased circulating levels of sex hormones, androgens and oestrogens have been observed, the exact mechanism of fat accumulation and redistribution during aging remains obscure. In this study, the receptor of follicle-stimulating hormone (FSH), a gonadotropin that increases sharply and persistently with aging in both males and females, is functionally expressed in human and mouse fat tissues and adipocytes. Follicle-stimulating hormone was found to promote lipid biosynthesis and lipid droplet formation; FSH could also alter the secretion of leptin and adiponectin, but not hyperplasia, in vitro and in vivo. The effects of FSH are mediated by FSH receptors coupled to the Gαi protein; as a result, Ca²⁺ influx is stimulated, cAMP-response-element-binding protein is phosphorylated, and an array of genes involved in lipid biosynthesis is activated. The present findings depict the potential of FSH receptor-mediated lipodystrophy of adipose tissues in aging. Our results also reveal the mechanism of fat accumulation and redistribution during aging of males and females.

The cystic fibrosis transmembrane conductance regulator as a biomarker in non-small cell lung cancer

An increased risk of non-small cell lung cancer (NSCLC) in cystic fibrosis (CF) patients and carriers of CF transmembrane conductance regulator (CFTR) mutations has been proposed. However, the role of CFTR in lung cancer remains controversial. In the present study, CFTR expression was assessed in 165 NSCLC tumors and 22 normal lung samples with validation in an independent series of 131 samples. The effect of gain and loss of CFTR on the malignant behavior of NSCLC was examined. The effect of CFTR manipulation on tumor metastasis was examined in a mouse model. Expression of CFTR was downregulated in NSCLC (p=0.041). Low CFTR expression was correlated with advanced stage (p<0.001) and lymph node metastasis (p=0.009). Low CFTR expression was significantly associated with poor prognosis (overall survival: 45 vs. 36 months, p<0.0001; progression-free survival: 41 vs. 30 months, p=0.007). Knockdown of CFTR in NSCLC cells enhanced malignant behavior (epithelial-mesenchymal transition, invasion and migration); in contrast, overexpression of CFTR suppressed cancer progression in vitro and in vivo. The tumor-suppressing effect of CFTR was associated with inhibition of multiple uPA/uPAR-mediated malignant traits in culture. These results show that CFTR plays a role in inhibition of NSCLC metastasis and suggest that CFTR may serve as a novel indicator for predicting adverse prognosis and metastasis in NSCLC patients.

Defective CFTR-regulated granulosa cell proliferation in polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) is one of the most frequent causes of female infertility, featured by abnormal hormone profile, chronic oligo/anovulation, and presence of multiple cystic follicles in the ovary. However, the mechanism underlying the abnormal folliculogenesis remains obscure. We have previously demonstrated that CFTR, a cAMP-dependent Cl(-) and HCO3 (-) conducting anion channel, is expressed in the granulosa cells and its expression is downregulated in PCOS rat models and human patients. In this study, we aimed to investigate the possible involvement of downregulation of CFTR in the impaired follicle development in PCOS using two rat PCOS models and primary culture of granulosa cells. Our results indicated that the downregulation of CFTR in the cystic follicles was accompanied by reduced expression of proliferating cell nuclear antigen (PCNA), in rat PCOS models. In addition, knockdown or inhibition of CFTR in granulosa cell culture resulted in reduced cell viability and downregulation of PCNA. We further demonstrated that CFTR regulated both basal and FSH-stimulated granulosa cell proliferation through the HCO3 (-)/sAC/PKA pathway leading to ERK phosphorylation and its downstream target cyclin D2 (Ccnd2) upregulation. Reduced ERK phosphorylation and CCND2 were found in ovaries of rat PCOS model compared with the control. This study suggests that CFTR is required for normal follicle development and that its downregulation in PCOS may inhibit granulosa cell proliferation, resulting in abnormal follicle development in PCOS.

New insights into germ cell migration and survival/apoptosis in spermatogenesis: Lessons from CD147

CD147, also named basigin (Bsg) or extracellular matrix (ECM) metalloproteinase inducer (EMMPRIN), is a highly glycosylated protein first identified as a tumor cell surface molecule. In cancer, it is well established that CD147 promotes metastasis by stimulating the production of MMPs. Recent studies have also suggested that it may be associated with tumor growth and angiogenesis. Interestingly, CD147 is expressed in germ cells of different development stages in the testis and its knockout mice are infertile, indicating an essential role of CD147 in spermatogenesis. While the detailed involvement of CD147 in spermatogenesis remains elusive, our recent findings have revealed a dual role of CD147 in germ cell development. On the one hand, it regulates the migration of spermatogonia and spermatocytes via the induction of MMP-2 production; on the other hand, it specifically regulates the survival/apoptosis of spermatocytes but not spermatogonia through a p53-independent pathway. In this review, we aim to provide an overview on the functions of CD147, comparing its roles in cancer and the testis, thereby providing new insights into the regulatory mechanisms underlying the process of spermatogenesis.

Regulation of miR-101/miR-199a-3p by the epithelial sodium channel during embryo implantation: involvement of CREB phosphorylation

In our previous study, we have demonstrated that the epithelial sodium channel (ENaC) mediates the embryo-derived signals leading to the activation of CREB and upregulation of cyclooxygenase type 2 (COX2) required for embryo implantation. This study aims to investigate whether microRNAs (miRNAs) are involved in the ENaC-induced upregulation of COX2 during embryo implantation. The results show that the levels of miR-101 and miR-199a-3p, two COX2 targeting miRNAs, are reduced by ENaC activation, and increased by ENaC inhibition or knock-down of ENaC subunit (ENaCα) in human endometrial surface epithelial (HES) cells or in mouse uteri during implantation. Phosphorylation of CREB is induced by the activation of ENaC, and blocked by ENaC inhibition or knockdown in HES cells. Knockdown of ENaCα or CREB in HES cells or in mouse uterus in vivo results in increases in miR-101 and miR-199a-3p, accompanied with decreases in COX2 protein levels and reduction in implantation rate. The downregulation of COX2 caused by knockdown of ENaC or CREB can be recovered by the inhibitors of miR-101 or miR-199a-3p in HES cells. These results reveal a novel molecular mechanism modulating COX2 expression during embryo implantation via ENaC-dependent CREB activation and COX2-targeting miRNAs.

Deficient human β-defensin 1 underlies male infertility associated with poor sperm motility and genital tract infection

Genital tract infection and reduced sperm motility are considered two pivotal etiological factors for male infertility associated with leukocytospermia and asthenozoospermia, respectively. We demonstrate that the amount of human β-defensin 1 (DEFB1) in sperm from infertile men exhibiting either leukocytospermia or asthenozoospermia, both of which are associated with reduced motility and reduced bactericidal activity in sperm, is much lower compared to that in normal fertile sperm. Interference with DEFB1 function also decreases both motility and bactericidal activity in normal sperm, whereas treatment with recombinant DEFB1 markedly restores DEFB1 expression, bactericidal activity, sperm quality, and egg-penetrating ability in sperm from both asthenozoospermia and leukocytospermia patients. DEFB1 interacts with chemokine receptor type 6 (CCR6) in sperm and triggers Ca(2+) mobilization, which is important for sperm motility. Interference with CCR6 function also reduces motility and bactericidal activity of normal sperm. The present finding explains a common defect in male infertility associated with both asthenozoospermia and leukocytospermia, indicating a dual role of DEFB1 in defending male fertility. These results also suggest that the expression of DEFB1 and CCR6 may have diagnostic potential and that treatment of defective sperm with recombinant DEFB1 protein may be a feasible therapeutic approach for male infertility associated with poor sperm motility and genital tract infection.

CFTR interacts with ZO-1 to regulate tight junction assembly and epithelial differentiation through the ZONAB pathway

Mutations in CFTR lead to dysfunction of tubular organs, which is currently attributed to impairment of its conductive properties. We now show that CFTR regulates tight junction assembly and epithelial cell differentiation through modulation of the ZO-1-ZONAB pathway. CFTR colocalizes with ZO-1 at the tight junctions of trachea and epididymis, and is expressed before ZO-1 in Wolffian ducts. CFTR interacts with ZO-1 through the CTFR PDZ-binding domain. In a three-dimensional (3D) epithelial cell culture model, CFTR regulates tight junction assembly and is required for tubulogenesis. CFTR inhibition or knockdown reduces ZO-1 expression and induces the translocation of the transcription factor ZONAB (also known as YBX3) from tight junctions to the nucleus, followed by upregulation of the transcription of CCND1 and downregulation of ErbB2 transcription. The epididymal tubules of cftr(-/-) and cftr(ΔF508) mice have reduced ZO-1 levels, increased ZONAB nuclear expression, and decreased epithelial cell differentiation, illustrated by the reduced expression of apical AQP9 and V-ATPase. This study provides a new paradigm for the etiology of diseases associated with CFTR mutations, including cystic fibrosis.

Glucose-induced electrical activities and insulin secretion in pancreatic islet β-cells are modulated by CFTR

The cause of insulin insufficiency remains unknown in many diabetic cases. Up to 50% adult patients with cystic fibrosis (CF), a disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), develop CF-related diabetes (CFRD) with most patients exhibiting insulin insufficiency. Here we show that CFTR is a regulator of glucose-dependent electrical acitivities and insulin secretion in β-cells. We demonstrate that glucose elicited whole-cell currents, membrane depolarization, electrical bursts or action potentials, Ca(2+) oscillations and insulin secretion are abolished or reduced by inhibitors or knockdown of CFTR in primary mouse β-cells or RINm5F β-cell line, or significantly attenuated in CFTR mutant (DF508) mice compared with wild-type mice. VX-809, a newly discovered corrector of DF508 mutation, successfully rescues the defects in DF508 β-cells. Our results reveal a role of CFTR in glucose-induced electrical activities and insulin secretion in β-cells, shed light on the pathogenesis of CFRD and possibly other idiopathic diabetes, and present a potential treatment strategy.

Emerging role of cystic fibrosis transmembrane conductance regulator as an epigenetic regulator: linking environmental cues to microRNAs

Although microRNAs (miRNAs) have been recognized as one of the important epigenetic mechanisms that regulate gene expression in response to changes in the environment, the links between environmental cues and changes in miRNAs remain largely unknown. Localized to the cell membrane and recognized as an anion channel, the cystic fibrosis transmembrane conductance regulator (CFTR) has recently been shown to mediate important signalling pathways leading to activation of miRNAs. This brief review summarizes the related findings and discusses the emerging role of CFTR as an epigenetic regulator, possibly involved in a wide spectrum of physiological and pathological processes.

Disrupted interaction between CFTR and AF-6/afadin aggravates malignant phenotypes of colon cancer

How mutations or dysfunction of CFTR may increase the risk of malignancies in various tissues remains an open question. Here we report the interaction between CFTR and an adherens junction molecule, AF-6/afadin, and its involvement in the development of colon cancer. We have found that CFTR and AF-6/afadin are co-localized at the cell-cell contacts and physically interact with each other in colon cancer cell lines. Knockdown of CFTR results in reduced epithelial tightness and enhanced malignancies, with increased degradation and reduced stability of AF-6/afadin protein. The enhanced invasive phenotype of CFTR-knockdown cells can be completely reversed by either AF-6/afadin over-expression or ERK inhibitor, indicating the involvement of AF-6/MAPK pathway. More interestingly, the expression levels of CFTR and AF-6/afadin are significantly downregulated in human colon cancer tissues and lower expression of CFTR and/or AF-6/afadin is correlated with poor prognosis of colon cancer patients. The present study has revealed a previously unrecognized interaction between CFTR and AF-6/afadin that is involved in the pathogenesis of colon cancer and indicated the potential of the two as novel markers of metastasis and prognostic predictors for human colon cancer.