17β-Estradiol inhibits phosphorylation of stromal interaction molecule 1 (STIM1) protein: implication for store-operated calcium entry and chronic lung diseases

17β-estradiol induces hyperresponsiveness in guinea pig airway smooth muscle by inhibiting the plasma membrane Ca2+-ATPase

High serum estrogen concentrations are associated with asthma development and severity, suggesting a link between estradiol and airway hyperresponsiveness (AHR). 17β-estradiol (E2) has non-genomic effects via Ca2+ regulatory mechanisms; however, its effect on the plasma membrane Ca2+-ATPases (PMCA1 and 4) and sarcoplasmic reticulum Ca2+-ATPase (SERCA) is unknown. Hence, in the present study, we aim to demonstrate if E2 favors AHR by increasing intracellular Ca2+ concentrations in guinea pig airway smooth muscle (ASM) through a mechanism involving Ca2+-ATPases. In guinea pig ASM, Ca2+ microfluorometry, muscle contraction, and Western blot were evaluated. Then, we performed molecular docking analysis between the estrogens and Ca2+ ATPases. In tracheal rings, E2 produced AHR to carbachol. In guinea pig myocytes, acute exposure to physiological levels of E2 modified the transient Ca2+ peak induced by caffeine to a Ca2+ plateau. The incubation with PMCA inhibitors (lanthanum and carboxyeosin, CE) partially reversed the E2-induced sustained plateau in the caffeine response. In contrast, cyclopiazonic acid (SERCA inhibitor), U-0126 (an inhibitor of ERK 1/2), and choline chloride did not modify the Ca2+ plateau produced by E2. The mitochondrial uniporter activity and the capacitative Ca2+ entry were unaffected by E2. In guinea pig ASM, Western blot analysis demonstrated PMCA1 and PMCA4 expression. The results from the docking modeling demonstrate that E2 binds to both plasma membrane ATPases. In guinea pig tracheal smooth muscle, inhibiting the PMCA with CE, induced hyperresponsiveness to carbachol. 17β-estradiol produces hyperresponsiveness by inhibiting the PMCA in the ASM and could be one of the mechanisms responsible for the increase in asthmatic crisis in women.

Air-Liquid interface cultures to model drug delivery through the mucociliary epithelial barrier

Epithelial cells from mucociliary portions of the airways can be readily grown and expanded in vitro. When grown on a porous membrane at an air-liquid interface (ALI) the cells form a confluent, electrically resistive barrier separating the apical and basolateral compartments. ALI cultures replicate key morphological, molecular and functional features of the in vivo epithelium, including mucus secretion and mucociliary transport. Apical secretions contain secreted gel-forming mucins, shed cell-associated tethered mucins, and hundreds of additional molecules involved in host defense and homeostasis. The respiratory epithelial cell ALI model is a time-proven workhorse that has been employed in various studies elucidating the structure and function of the mucociliary apparatus and disease pathogenesis. It serves as a critical milestone test for small molecule and genetic therapies targeting airway diseases. To fully exploit the potential of this important tool, numerous technical variables must be thoughtfully considered and carefully executed.

Estrogenic Modulation of Ionic Channels, Pumps and Exchangers in Airway Smooth Muscle

To preserve ionic homeostasis (primarily Ca²⁺, K⁺, Na⁺, and Cl^-), in the airway smooth muscle (ASM) numerous transporters (channels, exchangers, and pumps) regulate the influx and efflux of these ions. Many of intracellular processes depend on continuous ionic permeation, including exocytosis, contraction, metabolism, transcription, fecundation, proliferation, and apoptosis. These mechanisms are precisely regulated, for instance, through hormonal activity. The lipophilic nature of steroidal hormones allows their free transit into the cell where, in most cases, they occupy their cognate receptor to generate genomic actions. In the sense, estrogens can stimulate development, proliferation, migration, and survival of target cells, including in lung physiology. Non-genomic actions on the other hand do not imply estrogen's intracellular receptor occupation, nor do they initiate transcription and are mostly immediate to the stimulus. Among estrogen's non genomic responses regulation of calcium homeostasis and contraction and relaxation processes play paramount roles in ASM. On the other hand, disruption of calcium homeostasis has been closely associated with some ASM pathological mechanism. Thus, this paper intends to summarize the effects of estrogen on ionic handling proteins in ASM. The considerable diversity, range and power of estrogens regulates ionic homeostasis through genomic and non-genomic mechanisms.

Super resolution microscopy analysis reveals increased Orai1 activity in asthma and cystic fibrosis lungs

QUESTION

In diseases such as asthma and cystic fibrosis (CF), the immune response is dysregulated and the lung is chronically inflamed. Orai1 activation is required for the initiation and persistence of inflammation. However, Orai1 expression in the lung is poorly understood. We therefore tested the hypothesis that Orai1 expression was upregulated in asthmatic and CF lungs.

MATERIALS AND METHODS

We used LungMAP to analyze single-cell RNAseq data of Orai1 and stromal interaction molecule 1 (STIM1) expression in normal human lungs. We then performed RNAscope analysis and immunostaining on lung sections from normal, asthma, and CF donors. We imaged sections by confocal and super resolution microscopy, and analyzed Orai1 and STIM1 expression in different pulmonary cell types.

RESULTS

Orai1 was broadly-expressed, but expression was greatest in immune cells. At mRNA and protein levels, there were no consistent trends in expression levels between the three phenotypes. Orai1 must interact with STIM1 in order to activate and conduct Ca2+. We therefore used STIM1/Orai1 co-localization as a marker of Orai1 activity. Using this approach, we found significantly increased co-localization between these proteins in epithelia, interstitial and luminal immune cells, but not alveoli, from asthma and CF lungs. Orai1 also aggregates as part of its activation process. Using super resolution microscopy, we also found significantly increased Orai1 aggregation in immune cells from asthmatic and CF lungs.

CONCLUSION

We found evidence that Orai1 was more active in asthma and CF than normal lungs. These data suggest that Orai1 is a relevant target for reducing pulmonary inflammation.

Hormonal Effects on Asthma, Rhinitis, and Eczema

Hormones significantly influence the pathogenesis of asthma, rhinitis, and eczema. This review aims to summarize relevant clinical considerations for practicing allergists and immunologists. The first section reviews the effects of sex hormones: estrogen, progesterone, and testosterone. The second concerns insulin production in the context of type 1 and type 2 diabetes. The third concludes with a discussion of thyroid and adrenal pathology in relationship to asthma, rhinitis, and eczema.

Sex, Cells, and Asthma

There are marked sex differences in asthma prevalence and severity. Sex hormones play a central role in these sex biases and directly interact with multiple key cells involved in the pathogenesis of asthma. Here we review the known effects of estrogen, progesterone, and testosterone on airway epithelial cells, airway smooth muscle cells, the mononuclear phagocyte system, innate lymphoid cells, eosinophils, mast cells, T cells, and B cells, all in the context of asthma. Furthermore, we explore unresolved clinical questions, such as the role of sex hormones in the link between asthma and obesity.

Gender-Dependent Phenotype in Polycystic Kidney Disease Is Determined by Differential Intracellular Ca2+ Signals

Autosomal dominant polycystic kidney disease (ADPKD) is caused by loss of function of PKD1 (polycystin 1) or PKD2 (polycystin 2). The Ca²⁺-activated Cl⁻ channel TMEM16A has a central role in ADPKD. Expression and function of TMEM16A is upregulated in ADPKD which causes enhanced intracellular Ca²⁺ signaling, cell proliferation, and ion secretion. We analyzed kidneys from Pkd1 knockout mice and found a more pronounced phenotype in males compared to females, despite similar levels of expression for renal tubular TMEM16A. Cell proliferation, which is known to be enhanced with loss of Pkd1^−/−, was larger in male when compared to female Pkd1^−/− cells. This was paralleled by higher basal intracellular Ca²⁺ concentrations in primary renal epithelial cells isolated from Pkd1^−/− males. The results suggest enhanced intracellular Ca²⁺ levels contributing to augmented cell proliferation and cyst development in male kidneys. Enhanced resting Ca²⁺ also caused larger basal chloride currents in male primary cells, as detected in patch clamp recordings. Incubation of mouse primary cells, mCCDcl1 collecting duct cells or M1 collecting duct cells with dihydrotestosterone (DHT) enhanced basal Ca²⁺ levels and increased basal and ATP-stimulated TMEM16A chloride currents. Taken together, the more severe cystic phenotype in males is likely to be caused by enhanced cell proliferation, possibly due to enhanced basal and ATP-induced intracellular Ca²⁺ levels, leading to enhanced TMEM16A currents. Augmented Ca²⁺ signaling is possibly due to enhanced expression of Ca²⁺ transporting/regulating proteins.

Large pH oscillations promote host defense against human airways infection

The airway mucosal microenvironment is crucial for host defense against inhaled pathogens but remains poorly understood. We report here that the airway surface normally undergoes surprisingly large excursions in pH during breathing that can reach pH 9.0 during inhalation, making it the most alkaline fluid in the body. Transient alkalinization requires luminal bicarbonate and membrane-bound carbonic anhydrase 12 (CA12) and is antimicrobial. Luminal bicarbonate concentration and CA12 expression are both reduced in cystic fibrosis (CF), and mucus accumulation both buffers the pH and obstructs airflow, further suppressing the oscillations and bacterial-killing efficacy. Defective pH oscillations may compromise airway host defense in other respiratory diseases and explain CF-like airway infections in people with CA12 mutations.

Effects of estrogen on STIM1/Orai1 in the sublingual gland of ovariectomized rats

BACKGROUND

Studies have shown that estrogen can protect the function of the sublingual gland, but the specific mechanism is still unclear. Besides, the STIM1/Orai1 pathway is important to secretion in the salivary gland. Here, we explore the possible effects of estrogen on sublingual gland function by observing changes of STIM1 and Orai1 levels in the sublingual glands of ovariectomized rats.

METHODS

42 adult female Sprague-Dawley rats were randomly divided into three groups: SHAM, OVX, and OVX+E (n = 14 per group). Two weeks after ovariectomy, rats were treated with estrogen (β-estradiol). The expression of STIM1 and Orai1 in the sublingual gland were observed by double label-immunohistochemistry and immunofluorescence. Calcium imaging was conducted to observe changes in cellular Ca²⁺ levels.

RESULTS

IHC and IF showed that the levels of both STIM1 and Orai1 decreased following ovariectomy, but increased to SHAM levels after estrogen treatment. By IF, STIM1 and Orai1 exhibited perfect co-localization. Calcium imaging results showed that the Ca²⁺ in the cells decreased after ovariectomy. Estrogen intervention returned levels of these proteins and Ca²⁺ to the same as those in the control group.

CONCLUSION

This study demonstrates that low estrogen status significantly reduced the expression of STIM1 and Orai1 in the sublingual gland of rats, along with cellular Ca²⁺ levels. These data provide insight into the likely mechanisms underlying sublingual gland secretion dysfunction during menopause.

Reciprocality Between Estrogen Biology and Calcium Signaling in the Cardiovascular System

17β-Estradiol (E₂) is the main estrogenic hormone in the body and exerts many cardiovascular protective effects. Via three receptors known to date, including estrogen receptors α (ERα) and β (ERβ) and the G protein-coupled estrogen receptor 1 (GPER, aka GPR30), E₂ regulates numerous calcium-dependent activities in cardiovascular tissues. Nevertheless, effects of E₂ and its receptors on components of the calcium signaling machinery (CSM), the underlying mechanisms, and the linked functional impact are only beginning to be elucidated. A picture is emerging of the reciprocality between estrogen biology and Ca²⁺ signaling. Therein, E₂ and GPER, via both E₂-dependent and E₂-independent actions, moderate Ca²⁺-dependent activities; in turn, ERα and GPER are regulated by Ca²⁺ at the receptor level and downstream signaling via a feedforward loop. This article reviews current understanding of the effects of E₂ and its receptors on the cardiovascular CSM and vice versa with a focus on mechanisms and combined functional impact. An overview of the main CSM components in cardiovascular tissues will be first provided, followed by a brief review of estrogen receptors and their Ca²⁺-dependent regulation. The effects of estrogenic agonists to stimulate acute Ca²⁺ signals will then be reviewed. Subsequently, E₂-dependent and E₂-independent effects of GPER on components of the Ca²⁺ signals triggered by other stimuli will be discussed. Finally, a case study will illustrate how the many mechanisms are coordinated to moderate Ca²⁺-dependent activities in the cardiovascular system.

Flavored e-liquids increase cytoplasmic Ca2+ levels in airway epithelia

E-cigarettes are noncombustible, electronic nicotine-delivery devices that aerosolize an e-liquid, i.e., nicotine, in a propylene glycol-vegetable glycerin vehicle that also contains flavors. While the effects of nicotine are relatively well understood, more information regarding the potential biological effects of the other e-liquid constituents is needed. This is a serious concern, because e-liquids are available in >7,000 distinct flavors. We previously demonstrated that many e-liquids affect cell growth/viability through an unknown mechanism. Since Ca²⁺ is a ubiquitous second messenger that regulates cell growth, we characterized the effects of e-liquids on cellular Ca²⁺ homeostasis. To better understand the extent of this effect, we screened e-liquids for their ability to alter cytosolic Ca²⁺ levels and found that 42 of 100 flavored e-liquids elicited a cellular Ca²⁺ response. Banana Pudding (BP) e-liquid, a representative e-liquid from this group, caused phospholipase C activation, endoplasmic reticulum (ER) Ca²⁺ release, store-operated Ca²⁺ entry (SOCE), and protein kinase C (PKCα) phosphorylation. However, longer exposures to BP e-liquid depleted ER Ca²⁺ stores and inhibited SOCE, suggesting that this e-liquid may alter Ca²⁺ homeostasis by short- and long-term mechanisms. Since dysregulation of Ca²⁺ signaling can cause chronic inflammation, ER stress, and abnormal cell growth, flavored e-cigarette products that can elicit cell Ca²⁺ responses should be further screened for potential toxicity.

The steroid hormone 20-hydroxyecdysone induces phosphorylation and aggregation of stromal interacting molecule 1 for store-operated calcium entry

Oligomerization of stromal interacting molecule 1 (STIM1) promotes store-operated calcium entry (SOCE); however, the mechanism of STIM1 aggregation is unclear. Here, using the lepidopteran insect and agricultural pest cotton bollworm (Helicoverpa armigera) as a model and immunoblotting, RT-qPCR, RNA interference (RNAi), and ChIP assays, we found that the steroid hormone 20-hydroxyecdysone (20E) up-regulates STIM1 expression via G protein-coupled receptors (GPCRs) and the 20E nuclear receptor (EcRB1). We also identified an ecdysone-response element (EcRE) in the 5'-upstream region of the STIM1 gene and also noted that STIM1 is located in the larval midgut during metamorphosis. STIM1 knockdown in larvae delayed pupation time, prevented midgut remodeling, and decreased 20E-induced gene transcription. STIM1 knockdown in a H. armigera epidermal cell line, HaEpi, repressed 20E-induced calcium ion influx and apoptosis. Moreover, 20E-induced STIM1 clustering to puncta and translocation toward the cell membrane. Inhibitors of GPCRs, phospholipase C (PLC), and inositol trisphosphate receptor (IP3R) repressed 20E-induced STIM1 phosphorylation, and we found that two GPCRs are involved in 20E-induced STIM1 phosphorylation. 20E-induced STIM1 phosphorylation on Ser-485 through protein kinase C (PKC), and we observed that Ser-485 phosphorylation is critical for STIM1 clustering, interaction with calcium release-activated calcium channel modulator 1 (Orai1), calcium ion influx, and 20E-induced apoptosis. These results suggest that 20E up-regulates STIM1 phosphorylation for aggregation via GPCRs, followed by interaction with Orai1 to induce SOCE, thereby promoting apoptosis in the midgut during insect metamorphosis.

STIM1 phosphorylation at Y316 modulates its interaction with SARAF and the activation of SOCE and ICRAC

Stromal interaction molecule 1 (STIM1) is one of the key elements for the activation of store-operated Ca2+ entry (SOCE). Hence, identification of the relevant phosphorylatable STIM1 residues with a possible role in the regulation of STIM1 function and SOCE is of interest. By performing a computational analysis, we identified that the Y316 residue is susceptible to phosphorylation. Expression of the STIM1-Y316F mutant in HEK293, NG115-401L and MEG-01 cells resulted in a reduction in STIM1 tyrosine phosphorylation, SOCE and the Ca2+ release-activated Ca2+ current (ICRAC). STIM1-Orai1 colocalization was reduced in HEK293 cells transfected with YFP-STIM1-Y316F compared to in cells with wild-type (WT) YFP-tagged STIM1. Additionally, the Y316F mutation altered the pattern of interaction between STIM1 and SARAF under resting conditions and upon Ca2+ store depletion. Expression of the STIM1 Y316F mutant enhanced slow Ca2+-dependent inactivation (SCDI) as compared to STIM1 WT, an effect that was abolished by SARAF knockdown. Finally, in NG115-401L cells transfected with shRNA targeting SARAF, expression of STIM1 Y316F induced greater SOCE than STIM1 WT. Taken together, our results provide evidence supporting the idea that phosphorylation of STIM1 at Y316 plays a relevant functional role in the activation and modulation of SOCE.

Diverse actions of estradiol on anorexigenic and orexigenic hypothalamic arcuate neurons

Contribution to Special Issue on Fast effects of steroids. There is now compelling evidence for membrane-associated estrogen receptors in hypothalamic neurons that are critical for the hypothalamic control of homeostatic functions. It has been known for some time that estradiol (E2) can rapidly alter hypothalamic neuronal activity within seconds, indicating that some cellular effects can occur via membrane initiated events. However, our understanding of how E2 signals via membrane-associated receptors and how these signals impact physiological functions is only just emerging. Thus, E2 can affect second messenger systems including calcium mobilization and a plethora of kinases to alter cell excitability and even gene transcription in hypothalamic neurons. One population of hypothalamic neurons, the anorexigenic proopiomelanocortin (POMC) neurons, has long been considered to be a target of E2's actions based on gene (Pomc) expression studies. However, we now know that E2 can rapidly alter POMC neuronal activity within seconds and activate several intracellular signaling cascades that ultimately affect gene expression, actions which are critical for maintaining sensitivity to insulin in metabolically stressed states. E2 also affects the orexigenic Neuropeptide Y/Agouti-related Peptide (NPY/AgRP) neurons in similarly rapid but antagonistic manner. Therefore, this review will summarize our current state of knowledge of how E2 signals via rapid membrane-initiated and intracellular signaling cascades in POMC and NPY/AgRP neurons to regulate energy homeostasis.

Chronic E-Cigarette Exposure Alters the Human Bronchial Epithelial Proteome

RATIONALE

E-cigarettes vaporize propylene glycol/vegetable glycerin (PG/VG), nicotine, and flavorings. However, the long-term health effects of exposing lungs to vaped e-liquids are unknown.

OBJECTIVES

To determine the effects of chronic vaping on pulmonary epithelia.

METHODS

We performed research bronchoscopies on healthy nonsmokers, cigarette smokers, and e-cigarette users (vapers) and obtained bronchial brush biopsies and lavage samples from these subjects for proteomic investigation. We further employed in vitro and murine exposure models to support our human findings.

MEASUREMENTS AND MAIN RESULTS

Visual inspection by bronchoscopy revealed that vaper airways appeared friable and erythematous. Epithelial cells from biopsy samples revealed approximately 300 proteins that were differentially expressed in smoker and vaper airways, with only 78 proteins being commonly altered in both groups and 113 uniquely altered in vapers. For example, CYP1B1 (cytochrome P450 family 1 subfamily B member 1), MUC5AC (mucin 5 AC), and MUC4 levels were increased in vapers. Aerosolized PG/VG alone significantly increased MUC5AC protein in human airway epithelial cultures and in murine nasal epithelia in vivo. We also found that e-liquids rapidly entered cells and that PG/VG reduced membrane fluidity and impaired protein diffusion.

CONCLUSIONS

We conclude that chronic vaping exerts marked biological effects on the lung and that these effects may in part be mediated by the PG/VG base. These changes are likely not harmless and may have clinical implications for the development of chronic lung disease. Further studies will be required to determine the full extent of vaping on the lung.

Gender differences in bronchiectasis: a real issue?

Gender differences in chronic respiratory disease, including cystic fibrosis and non-cystic fibrosis bronchiectasis are clinically apparent and of increasing importance. Differences in disease prevalence, severity and outcome are all described, however, the precise cause of the gender dichotomy and their associated underlying mechanisms have been poorly characterised. A lack of dedicated clinical and epidemiological research focused in this area has led to a paucity of data and therefore a lack of understanding of its key drivers. Diagnosis, disease pathogenesis and treatment response are all complex but important aspects of bronchiectasis with an evident gender bias. Broadening our understanding of the interplay between microbiology, host physiology and the environment in the context of chronic lung diseases, such as bronchiectasis, is critical to unravelling mechanisms driving the observed gender differences. In this review, epidemiological, biological and environmental evidence related to gender in bronchiectasis is summarised. This illustrates gender differences as a “real issue” with the objective of mapping out a future framework upon which a gender-tailored medical approach may be incorporated into the diagnosis, monitoring and treatment of bronchiectasis.

CF and non-CF bronchiectasis are complex multifactorial chronic pulmonary diseases demonstrating gender differences in their prevalence, severity and infections, some of which are attributable to sex hormoneshttp://ow.ly/beDf30jseK4

SPLUNC1 is an allosteric modulator of the epithelial sodium channel

Cystic fibrosis (CF) is a common genetic disease with significantly increased mortality. CF airways exhibit ion transport abnormalities, including hyperactivity of the epithelial Na+ channel (ENaC). Short-palate lung and nasal epithelial clone 1 (SPLUNC1) is a multifunctional innate defense protein that is secreted into the airway lumen. We have previously demonstrated that SPLUNC1 binds to and inhibits ENaC to maintain fluid homeostasis in airway epithelia and that this process fails in CF airways. Despite this, how SPLUNC1 actually regulates ENaC is unknown. Here, we found that SPLUNC1 caused αγ-ENaC to internalize, whereas SPLUNC1 and β-ENaC remained at the plasma membrane. Additional studies revealed that SPLUNC1 increased neural precursor cell-expressed developmentally down-regulated protein 4-2-dependent ubiquitination of α- but not β- or γ-ENaC. We also labeled intracellular ENaC termini with green fluorescent protein and mCherry, and found that extracellular SPLUNC1 altered intracellular ENaC Forster resonance energy transfer. Taken together, our data indicate that SPLUNC1 is an allosteric regulator of ENaC that dissociates αβγ-ENaC to generate a new SPLUNC1-β-ENaC complex. These data indicate a novel mode for regulating ENaC at the plasma membrane.-Kim, C. S., Ahmad, S., Wu, T., Walton, W. G., Redinbo, M. R., Tarran, R. SPLUNC1 is an allosteric modulator of the epithelial sodium channel.

Estradiol Protects Proopiomelanocortin Neurons Against Insulin Resistance

Insulin resistance is at the core of the metabolic syndrome, and men exhibit a higher incidence of metabolic syndrome than women in early adult life, but this sex advantage diminishes sharply when women reach the postmenopausal state. Because 17β-estradiol (E2) augments the excitability of the anorexigenic proopiomelanocortin (POMC) neurons, we investigated the neuroprotective effects of E2 against insulin resistance in POMC neurons from diet-induced obese (DIO) female and male mice. The efficacy of insulin to activate canonical transient receptor potential 5 (TRPC5) channels and depolarize POMC neurons was significantly reduced in DIO male mice but not in DIO female mice. However, the insulin response in POMC neurons was abrogated in ovariectomized DIO females but restored with E2 replacement. E2 increased T-type calcium channel Cav3.1 messenger RNA (mRNA) expression and whole-cell currents but downregulated stromal-interaction molecule 1 mRNA, which rendered POMC neurons more excitable and responsive to insulin-mediated TRPC5 channel activation. Moreover, E2 prevented the increase in suppressor of cytokine signaling-3 mRNA expression with DIO as seen in DIO males. As proof of principle, insulin [intracerebroventricular injection into the third ventricle (ICV)] decreased food intake and increased metabolism in female but not male guinea pigs fed a high-fat diet. The uncoupling of the insulin receptor from its downstream effector system was corroborated by the reduced expression of phosphorylated protein kinase B in the arcuate nucleus of male but not female guinea pigs following insulin. Therefore, E2 protects female POMC neurons from insulin resistance by enhancing POMC neuronal excitability and the coupling of insulin receptor to TRPC5 channel activation.

Suppression of store-operated Ca2+ entry by activation of GPER: contribution to a clamping effect on endothelial Ca2+ signaling

The G protein-coupled estrogen receptor 1 (GPER, formerly also known as GPR30) modulates many Ca2+-dependent activities in endothelial cells. However, the underlying mechanisms are poorly understood. We recently reported that GPER acts to prolong cytoplasmic Ca2+ signals by interacting with and promoting inhibitory phosphorylation of the plasma membrane Ca2+-ATPase. In the present study, we examined the role of GPER activation in modulating store-operated Ca2+ entry (SOCE) via effects on the stromal interaction molecule 1 (STIM1). GPER activation by agonist G-1 reduces the peak but prolongs the plateau of bradykinin-induced Ca2+ signals in primary endothelial cells. G-1 dose-dependently inhibits thapsigargin-induced SOCE measured by the Mn2+ quenching method. GPER heterologous expression reduces SOCE, which is further pronounced by G-1 treatment. Consistently, GPER gene silencing in endothelial cells is associated with an increase in SOCE. Treatment with G-1 reduces puncta formation by STIM1 triggered by the activation of SOCE. The effect of GPER activation to inhibit SOCE is not affected by combined nonphosphorylatable substitutions at serines 486 and 668 on STIM1, but is substantially reduced by similar substitutions at serines 575, 608 and 621. Taken together with our recently reported inhibitory actions of GPER on Ca2+ efflux, the current data contribute to a model in which GPER acts to clamp agonist-induced cytoplasmic Ca2+ signals. Kinetic modeling based on current and reported data is used to estimate the overall effect of GPER activation on point activity of endothelial nitric oxide synthase during the time course of agonist-induced total Ca2+ signals.

Identification of BPIFA1/SPLUNC1 as an epithelium-derived smooth muscle relaxing factor

Asthma is a chronic airway disease characterized by inflammation, mucus hypersecretion and abnormal airway smooth muscle (ASM) contraction. Bacterial permeability family member A1, BPIFA1, is a secreted innate defence protein. Here we show that BPIFA1 levels are reduced in sputum samples from asthmatic patients and that BPIFA1 is secreted basolaterally from healthy, but not asthmatic human bronchial epithelial cultures (HBECs), where it suppresses ASM contractility by binding to and inhibiting the Ca²⁺ influx channel Orai1. We have localized this effect to a specific, C-terminal α-helical region of BPIFA1. Furthermore, tracheas from Bpifa1^-/- mice are hypercontractile, and this phenotype is reversed by the addition of recombinant BPIFA1. Our data suggest that BPIFA1 deficiency in asthmatic airways promotes Orai1 hyperactivity, increased ASM contraction and airway hyperresponsiveness. Strategies that target Orai1 or the BPIFA1 deficiency in asthma may lead to novel therapies to treat this disease.

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Uses its C-Terminus to Regulate the A2B Adenosine Receptor

CFTR is an apical membrane anion channel that regulates fluid homeostasis in many organs including the airways, colon, pancreas and sweat glands. In cystic fibrosis, CFTR dysfunction causes significant morbidity/mortality. Whilst CFTR's function as an ion channel has been well described, its ability to regulate other proteins is less understood. We have previously shown that plasma membrane CFTR increases the surface density of the adenosine 2B receptor (A2BR), but not of the β2 adrenergic receptor (β2AR), leading to an enhanced, adenosine-induced cAMP response in the presence of CFTR. In this study, we have found that the C-terminal PDZ-domain of both A2BR and CFTR were crucial for this interaction, and that replacing the C-terminus of A2BR with that of β2AR removed this CFTR-dependency. This observation extended to intact epithelia and disruption of the actin cytoskeleton prevented A2BR-induced but not β2AR-induced airway surface liquid (ASL) secretion. We also found that CFTR expression altered the organization of the actin cytoskeleton and PDZ-binding proteins in both HEK293T cells and in well-differentiated human bronchial epithelia. Furthermore, removal of CFTR's PDZ binding motif (ΔTRL) prevented actin rearrangement, suggesting that CFTR insertion in the plasma membrane results in local reorganization of actin, PDZ binding proteins and certain GPCRs.

G protein-coupled estrogen receptor inhibits the P2Y receptor-mediated Ca(2+) signaling pathway in human airway epithelia

P2Y receptor activation causes the release of inflammatory cytokines in the bronchial epithelium, whereas G protein-coupled estrogen receptor (GPER), a novel estrogen (E₂) receptor, may play an anti-inflammatory role in this process. We investigated the cellular mechanisms underlying the inhibitory effect of GPER activation on the P2Y receptor-mediated Ca²⁺ signaling pathway and cytokine production in airway epithelia. Expression of GPER in primary human bronchial epithelial (HBE) or 16HBE14o- cells was confirmed on both the mRNA and protein levels. Stimulation of HBE or 16HBE14o- cells with E₂ or G1, a specific agonist of GPER, attenuated the nucleotide-evoked increases in [Ca²⁺]_i, whereas this effect was reversed by G15, a GPER-specific antagonist. G1 inhibited the secretion of two proinflammatory cytokines, interleukin (IL)-6 and IL-8, in cells stimulated by adenosine 5′-(γ-thio)triphosphate (ATPγS). G1 stimulated a real-time increase in cAMP levels in 16HBE14o- cells, which could be inhibited by adenylyl cyclase inhibitors. The inhibitory effects of E₂ or G1 on P2Y receptor-induced increases in Ca²⁺ were reversed by treating the cells with a protein kinase A (PKA) inhibitor. These results demonstrated that the inhibitory effects of G1 or E₂ on P2Y receptor-mediated Ca²⁺ mobilization and cytokine secretion were due to GPER-mediated activation of a cAMP-dependent PKA pathway. This study has reported, for the first time, the expression and function of GPER as an anti-inflammatory component in human bronchial epithelia, which may mediate through its opposing effects on the pro‐inflammatory pathway activated by the P2Y receptors in inflamed airway epithelia.

Melanoma-Derived Wnt5a Promotes Local Dendritic-Cell Expression of IDO and Immunotolerance: Opportunities for Pharmacologic Enhancement of Immunotherapy

The β-catenin signaling pathway has been demonstrated to promote the development of a tolerogenic dendritic cell (DC) population capable of driving regulatory T-cell (Treg) differentiation. Further studies have implicated tolerogenic DCs in promoting carcinogenesis in preclinical models. The molecular mechanisms underlying the establishment of immune tolerance by this DC population are poorly understood, and the methods by which developing cancers can co-opt this pathway to subvert immune surveillance are currently unknown. This work demonstrates that melanoma-derived Wnt5a ligand upregulates the durable expression and activity of the indoleamine 2,3-dioxygenase-1 (IDO) enzyme by local DCs in a manner that depends upon the β-catenin signaling pathway. These data indicate that Wnt5a-conditioned DCs promote the differentiation of Tregs in an IDO-dependent manner, and that this process serves to suppress melanoma immune surveillance. We further show that the genetic silencing of the PORCN membrane-bound O-acyl transferase, which is necessary for melanoma Wnt ligand secretion, enhances antitumor T-cell immunity, and that the pharmacologic inhibition of this enzyme synergistically suppresses melanoma progression when combined with anti-CTLA-4 antibody therapy. Finally, our data suggest that β-catenin signaling activity, based on a target gene expression profile that includes IDO in human sentinel lymph node-derived DCs, is associated with melanoma disease burden and diminished progression-free survival. This work implicates the Wnt-β-catenin signaling pathway as a novel therapeutic target in the melanoma immune microenvironment and demonstrates the potential impact of manipulating DC function as a strategy for optimizing tumor immunotherapy.

Lentiviral shRNA against KCa3.1 inhibits allergic response in allergic rhinitis and suppresses mast cell activity via PI3K/AKT signaling pathway

Calcium-activated potassium ion channel-3.1 (KCa3.1) plays a pivotal role in the potassium-calcium exchange involved in atopy. This study aimed to explore the impact of lentiviral-mediated shRNA silencing KCa3.1 on allergic response in a murine allergic rhinitis (AR) model. The BALB/c mice were divided into four groups: untreated AR group, negative control AR group, lentiviral KCa3.1-shRNA treated AR group and normal control group. Concentrations of ovalbumin (OVA)-specific IgE, histamine and leukotrienes C4 (LTC4) in serum, and IL-4, IL-9 and IL-17 in nasal lavage fluid (NLF) were analyzed. Goblet cells and mast cells were counted. KCa3.1 positive cells were counted after immunolabelling by immunofluorescence method. KCa3.1, Mucin 5AC (MUC5AC), and tryptase mRNA levels were determined using real-time polymerase chain reaction. Furthermore, P815 cell line was used to explore the role and mechanism of lentiviral KCa3.1-shRNA on mast cells. The results showed that LV-KCa3.1-shRNA intervention effectively attenuated allergic responses in LV-KCa3.1-shRNA treated mice. LV-KCa3.1-shRNA intervention effectively suppressed KCa3.1 levels and phosphorylation of AKT in P815 cells, leading to the downregulation of tryptase, IL-6 and IL-8 levels. LV-KCa3.1-shRNA intervention effectively attenuated the allergic responses in AR and suppressed mast cell activity by inhibiting PI3K/AKT signaling pathway.

Anchoring protein AKAP79-mediated PKA phosphorylation of STIM1 determines selective activation of the ARC channel, a store-independent Orai channel

KEY POINTS

Although both the calcium store-dependent CRAC channels and the store-independent ARC channels are regulated by the protein STIM1, CRAC channels are regulated by STIM1 in the endoplasmic reticulum, whilst ARC channels are regulated by the STIM1 constitutively resident in the plasma membrane. We now demonstrate that activation of the ARC channels, but not CRAC channels, is uniquely dependent on phosphorylation of a single residue (T389) in the extensive cytosolic domain of STIM1 by protein kinase A. We further demonstrate that the phosphorylation of the T389 residue by protein kinase A is mediated by the association of plasma membrane STIM1 with the scaffolding protein AKAP79. Together, these findings indicate that the phosphorylation status of this single residue in STIM1 represents a key molecular determinant of the relative activities of these two co-existing Ca(2+) entry channels that are known to play critical, but distinct, roles in modulating a variety of physiologically relevant activities.

ABSTRACT

The low-conductance, highly calcium-selective channels encoded by the Orai family of proteins represent a major pathway for the agonist-induced entry of calcium associated with the generation and modulation of the key intracellular calcium signals that initiate and control a wide variety of physiologically important processes in cells. There are two distinct members of this channel family that co-exist endogenously in many cell types: the store-operated Ca(2+) release-activated CRAC channels and the store-independent arachidonic acid-regulated ARC channels. Although the activities of both channels are regulated by the stromal-interacting molecule-1 (STIM1) protein, two distinct pools of this protein are responsible, with the major pool of STIM1 in the endoplasmic reticulum membrane regulating CRAC channel activity, whilst the minor pool of plasma membrane STIM1 regulates ARC channel activity. We now show that a critical feature in determining this selective activation of the two channels is the phosphorylation status of a single threonine residue (T389) within the extensive (∼450 residue) cytosolic domain of STIM1. Specifically, protein kinase A (PKA)-mediated phosphorylation of T389 of STIM1 is necessary for effective activation of the ARC channels, whilst phosphorylation of the same residue actually inhibits the ability of STIM1 to activate the CRAC channels. We further demonstrate that the PKA-mediated phosphorylation of T389 occurs at the plasma membrane via the involvement of the anchoring protein AKAP79, which is constitutively associated with the pool of STIM1 in the plasma membrane. The novel mechanism we have described provides a means for the cell to precisely regulate the relative activities of these two channels to independently modulate the resulting intracellular calcium signals in a physiologically relevant manner.

Significance of Trask protein interactions in brain metastatic cohorts of lung cancers

A class of adhesion protein that occurs in the membrane with both extracellular and intracellular domain and play vital role in maintaining multicellularity is TRASK, also called CUB-domain containing protein1, CD318 (CDCP1). Specifically, in the current study, documented aggressive grades of lung cancers and distant metastatic tissues were examined for protein interactions of Trask and compared with lung cancer variants in situ. The intracellular domain of Trask has the ability to undergo tyrosine phosphorylation and thereafter undergo increased genomic expression, as well as interact with cytoskeletal proteins in the cell periphery and other local signal transduction machinery to induce invadopodia formation and distant metastasis. We incorporated proximity ligation assay to examine protein interactions of Trask in metastatic lung cancer tissues and compare with advanced and low-grade lung cancers restricted to the primary site of origins. Here, we provide direct evidence that activated Trask, which is a phosphorylated form, binds with cytoskeletal proteins actin and spectrin. These interactions were not seen in locally growing lung cancer and cancer in situ. These interactions may be responsible for invadopodia formation and breaking free from a multicellular environment. Functional studies demonstrated interaction between Trask and the STOCs Orai1 and Stim1. Calcium release from internal stores was highest in metastatic lung cancers, suggesting this mechanism as an initial stimulus for the cells to respond chaotically to external growth factor stimulation, especially in aggressive metastatic variants of lung cancers. Recently, inhibitors of STOCs have been identified, and preclinical evidence may be obtained whether these drugs may be of benefit in preventing the deadly consequences of lung cancer.

Sex steroid signaling: implications for lung diseases

There is increasing recognition that sex hormones (estrogen, progesterone, and testosterone) have biological and pathophysiological actions in peripheral, non-reproductive organs, including the lung. Clinically, sex differences in the incidence, morbidity and mortality of lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, lung cancer and pulmonary hypertension have been noted, although intrinsic sex differences vs. the roles of sex steroids are still not well-understood. Accordingly, it becomes important to ask the following questions: 1) Which sex steroids are involved? 2) How do they affect different components of the lung under normal circumstances? 3) How does sex steroid signaling change in or contribute to lung disease, and in this regard, are sex steroids detrimental or beneficial? As our understanding of sex steroid signaling in the lung improves, it is important to consider whether such information can be used to develop new therapeutic strategies to target lung diseases, perhaps in both sexes or in a sex-specific manner. In this review, we focus on the basics of sex steroid signaling, and the current state of knowledge regarding how they influence structure and function of specific lung components across the life span and in the context of some important lung diseases. We then summarize the potential for sex steroids as useful biomarkers and therapeutic targets in these lung diseases as a basis for future translational research in the area of gender and individualized medicine.

Phospho-STIM1 is a downstream effector that mediates the signaling triggered by IGF-1 in HEK293 cells

STIM1 is a Ca(2+) sensor of the endoplasmic reticulum (ER) that triggers the activation of plasma membrane Ca(2+) channels upon depletion of Ca(2+) levels within the ER. During thapsigargin-triggered Ca(2+) store depletion, ERK1/2 phosphorylates STIM1 at Ser575, Ser608, and Ser621. This phosphorylation plays a role in the regulation of STIM1 dissociation from the microtubule plus-end binding protein EB1, an essential step for STIM1 activation by thapsigargin. However, little is known regarding the physiological role of this phosphorylation. Because IGF-1 triggers the activation of the RAF-MEK-ERK and the phosphoinositide pathways, the role of STIM1 phosphorylation in IGF-1 stimulation was studied. There was found to be phosphorylation of ERK1/2 in both the presence and the absence of extracellular Ca(2+), demonstrating that Ca(2+) influx is not essential for ERK1/2 activation. In parallel, IGF-1 triggered STIM1 phosphorylation at the aforementioned sites, an effect that was blocked by PD0325901, a MEK1/2 inhibitor used to block ERK1/2 activation. Also, STIM1-GFP was found in clusters upon IGF-1 stimulation, and STIM1-S575A/S608A/S621A-GFP strongly reduced this multimerization. Interestingly, phospho-STIM1 was mainly found in clusters when cells were treated with IGF-1, and IGF-1 triggered the dissociation of STIM1 from EB1, similarly to what has been observed for thapsigargin, suggesting that STIM1 mediates the IGF-1 signaling pathway. A study of IGF-1-stimulated NFAT translocation was therefore performed, finding that STIM1-S575A/S608A/S621A blocked this translocation, as did the fusion protein STIM1-EB1, confirming that both STIM1 phosphorylation and STIM1-EB1 dissociation are required for IGF-1-triggered Ca(2+)-dependent signaling, and demonstrating that STIM1 phosphorylation plays a role as a downstream effector of the RAF-MEK-ERK pathway and an upstream activator of Ca(2+) entry.

Dehydroepiandrosterone, its metabolites and ion channels

This review is focused on the physiological and pathophysiological relevance of steroids influencing the activities of the central and peripheral nervous systems with regard to their concentrations in body fluids and tissues in various stages of human life like the fetal development or pregnancy. The data summarized in this review shows that DHEA and its unconjugated and sulfated metabolites are physiologically and pathophysiologically relevant in modulating numerous ion channels and participate in vital functions of the human organism. DHEA and its unconjugated and sulfated metabolites including 5α/β-reduced androstane steroids participate in various physiological and pathophysiological processes like the management of GnRH cyclic release, regulation of glandular and neurotransmitter secretions, maintenance of glucose homeostasis on one hand and insulin insensitivity on the other hand, control of skeletal muscle and smooth muscle activities including vasoregulation, promotion of tolerance to ischemia and other neuroprotective effects. In respect of prevalence of steroid sulfates over unconjugated steroids in the periphery and the opposite situation in the CNS, the sulfated androgens and androgen metabolites reach relevance in peripheral organs. The unconjugated androgens and estrogens are relevant in periphery and so much the more in the CNS due to higher concentrations of most unconjugated steroids in the CNS tissues than in circulation and peripheral organs. This article is part of a Special Issue entitled "Essential role of DHEA".

The inhibition of aromatase alters the mechanical and rheological properties of non-small-cell lung cancer cell lines affecting cell migration

Tumor invasion and metastasis are key aspects of non-small cell lung cancer (NSCLC). During migration, cells undergo mechanical alterations. The mechanical phenotype of breast cancer cells is correlated with aromatase gene expression. We have previously shown that targeting aromatase is a promising strategy for NSCLC. The aim of this study was to examine morphological and mechanical changes of NSCLC cells, upon treatment with aromatase inhibitor and correlate their ability to migrate and invade. In vitro experiments were performed using H23 and A549 NSCLC cell lines and exemestane was used for aromatase inhibition. We demonstrated that exemestane reduced H23 cell migration and invasion and caused changes in cell morphology including increased vacuolar structures and greater pleomorphism. In addition, exemestane changed the distribution of α-tubulin in H23 and A549 cells in a way that might destabilize microtubules polymerization. These effects were associated with increased cell viscosity and decreased elastic shear modulus. Although exemestane caused similar effects in A549 cells regarding viscosity and elastic shear modulus, it did not affect A549 cell migration and caused an increase in invasion. The increased invasion was in line with vimentin perinuclear localization. Our data show that the treatment of NSCLC cells with an aromatase inhibitor not only affects cell migration and invasion but also alters the mechanical properties of the cells. It suggests that the different origin of cancer cells is associated with different morphological characteristics and mechanical behavior.

Estrogen and the cystic fibrosis gender gap

Cystic fibrosis (CF) is the most frequent inherited disease in Caucasian populations and is due to a defect in the expression or activity of a chloride channel encoded by the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Mutations in this gene affect organs with exocrine functions and the main cause of morbidity and mortality for CF patients is the lung pathology in which the defect in CFTR decreases chloride secretion, lowering the airway surface liquid height and increasing mucus viscosity. The compromised ASL dynamics leads to a favorable environment for bacterial proliferation and sustained inflammation resulting in epithelial lung tissue injury, fibrosis and remodeling. In CF, there exist a difference in lung pathology between men and women that is termed the "CF gender gap". Recent studies have shown the prominent role of the most potent form of estrogen, 17β-estradiol in exacerbating lung function in CF females and here, we review the role of this hormone in the CF gender dichotomy.