The β2-adrenergic receptor associates with CXCR4 multimers in human cancer cells

While the existence and functional role of class C G-protein-coupled receptors (GPCR) dimers is well established, there is still a lack of consensus regarding class A and B GPCR multimerization. This lack of consensus is largely due to the inherent challenges of demonstrating the presence of multimeric receptor complexes in a physiologically relevant cellular context. The C-X-C motif chemokine receptor 4 (CXCR4) is a class A GPCR that is a promising target of anticancer therapy. Here, we investigated the potential of CXCR4 to form multimeric complexes with other GPCRs and characterized the relative size of the complexes in a live-cell environment. Using a bimolecular fluorescence complementation (BiFC) assay, we identified the β2 adrenergic receptor (β2AR) as an interaction partner. To investigate the molecular scale details of CXCR4-β2AR interactions, we used a time-resolved fluorescence spectroscopy method called pulsed-interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). PIE-FCCS can resolve membrane protein density, diffusion, and multimerization state in live cells at physiological expression levels. We probed CXCR4 and β2AR homo- and heteromultimerization in model cell lines and found that CXCR4 assembles into multimeric complexes larger than dimers in MDA-MB-231 human breast cancer cells and in HCC4006 human lung cancer cells. We also found that β2AR associates with CXCR4 multimers in MDA-MB-231 and HCC4006 cells to a higher degree than in COS-7 and CHO cells and in a ligand-dependent manner. These results suggest that CXCR4-β2AR heteromers are present in human cancer cells and that GPCR multimerization is significantly affected by the plasma membrane environment.

Impact of obesity paradox between genders on in-hospital mortality in cardiogenic shock: a retrospective cohort study

Background

In a few studies, obesity was associated with better outcomes in patients with cardiogenic shock (CS). Although this phenomenon, the “obesity paradox”, reportedly manifests differently based on sex in other disease entities, it has not yet been investigated in CS patients.

Methods and results

1,227 patients with CS from The REtrospective and prospective observational Study to investigate Clinical oUtcomes and Efficacy of left ventricular assist device for Korean patients with cardiogenic shock (RESCUE) registry in Korea were analyzed. The study population was classified into obese and non-obese groups according to Asian-Pacific criteria (BMI >25.0 kg/m2 for obese). Clinical impact of obesity on in-hospital mortality according to sex was analyzed using logistic regression analysis and restricted cubic spline curves. In-hospital mortality rate was significantly lower in obese men than non-obese men (34.2% vs. 24.1%, p=0.004) while the difference was not significant in women (37.3% vs. 35.8%, p=0.884). As a continuous variable, higher BMI showed a protective effect in men conversely, BMI was not associated with clinical outcomes in women. Comparing to normal-weight patients, obesity was associated with a decreased risk of in-hospital death in men (multivariable-adjusted OR 0.63, CI 0.43–0.92, p=0.016), not in women (multivariable-adjusted OR 0.94, 95% CI 0.55–1.61, p=0.828). Interaction P value for the association between BMI and sex was 0.023.

Conclusions

Obesity paradox exists and apparently occurs in men among CS patients. The differential effect of BMI on in-hospital mortality was observed according to sex.

Funding Acknowledgement

Type of funding sources: None.

Functional Rescue of Inactivating Mutations of the Human Neurokinin 3 Receptor Using Pharmacological Chaperones

G protein-coupled receptors (GPCRs) facilitate the majority of signal transductions across cell membranes in humans, with numerous diseases attributed to inactivating GPCR mutations. Many of these mutations result in misfolding during nascent receptor synthesis in the endoplasmic reticulum (ER), resulting in intracellular retention and degradation. Pharmacological chaperones (PCs) are cell-permeant small molecules that can interact with misfolded receptors in the ER and stabilise/rescue their folding to promote ER exit and trafficking to the cell membrane. The neurokinin 3 receptor (NK3R) plays a pivotal role in the hypothalamic–pituitary–gonadal reproductive axis. We sought to determine whether NK3R missense mutations result in a loss of cell surface receptor expression and, if so, whether a cell-permeant small molecule NK3R antagonist could be repurposed as a PC to restore function to these mutants. Quantitation of cell surface expression levels of seven mutant NK3Rs identified in hypogonadal patients indicated that five had severely impaired cell surface expression. A small molecule NK3R antagonist, M8, increased cell surface expression in four of these five and resulted in post-translational receptor processing in a manner analogous to the wild type. Importantly, there was a significant improvement in receptor activation in response to neurokinin B (NKB) for all four receptors following their rescue with M8. This demonstrates that M8 may have potential for therapeutic development in the treatment of hypogonadal patients harbouring NK3R mutations. The repurposing of existing small molecule GPCR modulators as PCs represents a novel and therapeutically viable option for the treatment of disorders attributed to mutations in GPCRs that cause intracellular retention.

Connecting nutritional deprivation and pubertal inhibition via GRK2-mediated repression of kisspeptin actions in GnRH neurons

BACKGROUND

Perturbations in the timing of puberty, with potential adverse consequences in later health, are increasingly common. The underlying neurohormonal mechanisms are unfolded, but nutritional alterations are key contributors. Efforts to unveil the basis of normal puberty and its metabolic control have focused on mechanisms controlling expression of Kiss1, the gene encoding the puberty-activating neuropeptide, kisspeptin. However, other regulatory phenomena remain ill-defined. Here, we address the putative role of the G protein-coupled-receptor kinase-2, GRK2, in GnRH neurons, as modulator of pubertal timing via repression of the actions of kisspeptin, in normal maturation and conditions of nutritional deficiency.

METHODS

Hypothalamic RNA and protein expression analyses were conducted in maturing female rats. Pharmacological studies involved central administration of GRK2 inhibitor, βARK1-I, and assessment of gonadotropin responses to kisspeptin or phenotypic and hormonal markers of puberty, under normal nutrition or early subnutrition in female rats. In addition, a mouse line with selective ablation of GRK2 in GnRH neurons, aka G-GRKO, was generated, in which hormonal responses to kisspeptin and puberty onset were monitored, in normal conditions and after nutritional deprivation.

RESULTS

Hypothalamic GRK2 expression increased along postnatal maturation in female rats, especially in the preoptic area, where most GnRH neurons reside, but decreased during the juvenile-to-pubertal transition. Blockade of GRK2 activity enhanced Ca+2 responses to kisspeptin in vitro, while central inhibition of GRK2 in vivo augmented gonadotropin responses to kisspeptin and advanced puberty onset. Postnatal undernutrition increased hypothalamic GRK2 expression and delayed puberty onset, the latter being partially reversed by central GRK2 inhibition. Conditional ablation of GRK2 in GnRH neurons enhanced gonadotropin responses to kisspeptin, accelerated puberty onset, and increased LH pulse frequency, while partially prevented the negative impact of subnutrition on pubertal timing and LH pulsatility in mice.

CONCLUSIONS

Our data disclose a novel pathway whereby GRK2 negatively regulates kisspeptin actions in GnRH neurons, as major regulatory mechanism for tuning pubertal timing in nutritionally-compromised conditions.

MKRN3 inhibits the reproductive axis through actions in kisspeptin-expressing neurons

The identification of loss-of-function mutations in MKRN3 in patients with central precocious puberty in association with the decrease in MKRN3 expression in the medial basal hypothalamus of mice before the initiation of reproductive maturation suggests that MKRN3 is acting as a brake on gonadotropin-releasing hormone (GnRH) secretion during childhood. In the current study, we investigated the mechanism by which MKRN3 prevents premature manifestation of the pubertal process. We showed that, as in mice, MKRN3 expression is high in the hypothalamus of rats and nonhuman primates early in life, decreases as puberty approaches, and is independent of sex steroid hormones. We demonstrated that Mkrn3 is expressed in Kiss1 neurons of the mouse hypothalamic arcuate nucleus and that MKRN3 repressed promoter activity of human KISS1 and TAC3, 2 key stimulators of GnRH secretion. We further showed that MKRN3 has ubiquitinase activity, that this activity is reduced by MKRN3 mutations affecting the RING finger domain, and that these mutations compromised the ability of MKRN3 to repress KISS1 and TAC3 promoter activity. These results indicate that MKRN3 acts to prevent puberty initiation, at least in part, by repressing KISS1 and TAC3 transcription and that this action may involve an MKRN3-directed ubiquitination-mediated mechanism.

SUN-100 Mice Lacking Paternally Expressed DLK1 Reach Puberty at a Lower Body Weight Than Littermate Controls

Body fat content along with a variety of genetic, environmental and psychosocial factors are responsible for the development and maintenance of reproductive function, especially in females. Epidemiologic studies indicate a relationship between increased body mass index and earlier puberty in girls. In contrast, a significant delay in puberty and menarche is seen in girls who are very physically active and have markedly diminished body fat. This link between reproduction and metabolism was reinforced with the recent report of loss-of-function mutations in the Delta-like homolog 1 (DLK1) gene in girls with central precocious puberty (CPP) and increased body fat. DLK1 is a paternally expressed gene located on chromosome 14q32.2 in a locus associated with Temple syndrome (TS), an imprinting disorder caused mainly by maternal parental disomy (mUPD). Dlk1 knockout mice display pre- and postnatal growth retardation, a phenotype that overlaps with human mUPD14. However, precocious puberty, a common finding associated with TS, was not carefully characterized in these mice. We used a Dlk1 deficient mouse model to determine the effects of Dlk1 on pubertal maturation. We confirmed by RT-qPCR that Dlk1 mRNA was undetectable in the mediobasal hypothalamus, where kisspeptin and other regulators of puberty are expressed, of Dlk^+/p- mice (which inherited the mutant allele from their father) whereas it was present in Dlk^+/+ mice. As reported previously, body weight was significantly lower in juvenile male and female Dlk^+/p- mice, compared to wild-type littermate controls. Interestingly, mutant and control female mice achieved vaginal opening, a marker of puberty onset, at a similar age (Dlk^+/p-: 29.8 ± 1.5 days, n=11 vs. Dlk^+/+: 29.1 ± 0.7 days, n=15, p=0.6) despite a considerably lower body weight in the Dlk1 deficient mice at the time of vaginal opening (Dlk^+/p-: 10.1 ± 0.8 g vs. Dlk^+/+: 14.3 ± 0.3 g, p<0.0001). Similarly, in the Dlk^+/p- males, preputial separation occurred at a lower body weight than in controls (Dlk^+/p-: 12.4 ± 0.3 g, n=9 vs. Dlk^+/+: 14.1 ± 0.2 g, n=19, p<0.0001). We hypothesize that the lack of Dlk1 at the hypothalamic level may be attenuating the effect of the low body weight on determining pubertal onset. These findings suggest that DLK1 is an important link between body weight and pubertal development in mice, as has been shown in humans.

Effects of AIF-1 inflammatory factors on the regulation of proliferation of breast cancer cells

The purpose of this study was to explore the effect of Allograft Inflammatory Factor 1 (AIF-1) on the regulation of proliferation of breast cancer cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), cell culture and counting, and mass spectrometry were performed. The biologically active high-purity recombinant protein rhAIF-1 was obtained by optimizing the rhAIF-1 protein purification system, and MDA-MB-231 and MDA-MB-361 breast cancer cell lines were used. After adding to the culture medium, rhAIF-1 was found to promote cell proliferation in dose-dependent and time-dependent manners. The purified protein rhAIF-1 was marked with rhodamine and incubated with the cells. Confocal imaging analysis revealed that the foreign protein was localized in the cytoplasm, and rhAIF-1 was unevenly distributed in the cytoplasm. Although AIF-1 accumulates around the nucleus, it can not enter the nucleus, suggesting that other factors might be involved in the regulation of cell proliferation. In order to find the possible interacting protein of rhAIF-1, protein immunoprecipitation technique and mass spectrometry were employed, and it was indicated that ADAM28m was the possible interacting protein of rhAIF-1. The interaction between rhAIF-1 and ADAM28m was validated by immunoprecipitation along with Western blotting. It was found that rhAIF-1 could precipitate ADAM28m protein by immunoprecipitation. The results indicated that IF-1 participates in the development of breast cancer by interacting with ADAM28m and activating downstream signaling pathways. It was concluded that AIF-1 provides a new idea for the molecular mechanism of breast cancer cell proliferation and acts as a new target for the prevention and treatment of breast cancer in the future.

Tac1 Signaling Is Required for Sexual Maturation and Responsiveness of GnRH Neurons to Kisspeptin in the Male Mouse

The tachykinins substance P (SP) and neurokinin A (Tac1) have emerged as novel regulators of kisspeptin/GnRH release. Recently, we documented that SP modulates reproductive function in the female mouse. Here, we extended this characterization to the male mouse. Tac1-/- male mice showed delayed puberty onset. They also presented significantly decreased expression levels of Pdyn (dynorphin) and Nos1 (nitric oxide synthase) in the mediobasal hypothalamus and elevated Gnrh1 levels. Unexpectedly, the response of Tac1-/- mice to central kisspeptin or senktide (neurokinin B receptor-agonist) administration was significantly decreased compared with controls, despite the preserved ability of GnRH neurons to stimulate luteinizing hormone release as demonstrated by central N-methyl-D-aspartate receptor administration, suggesting a deficit at the GnRH neuron level. Importantly, we demonstrated that kisspeptin receptor and SP receptor (NK1R) heterodimerize, indicating that changes in the SP tone could alter the responsiveness of GnRH neurons to kisspeptin. Finally, electrophysiological recordings from arcuate Kiss1 neurons showed that, although virtually all Kiss1 neurons responded to NKB and senktide, only half responded to an NK1R agonist and none to the neurokinin A receptor agonist at a 1-μM dose. In summary, we provide compelling evidence for a role of Tac1 in the control of reproductive function in the male mouse, suggesting a predominant central action that may involve a change in the balance of neural factors that control GnRH expression.

Monitoring G protein-coupled receptor activation using an adenovirus-based β-arrestin bimolecular fluorescence complementation assay

G protein-coupled receptors (GPCRs) are the largest family of cell-surface receptors and are involved in a variety of pathological conditions including cancer and cardiovascular, metabolic, neurological, and autoimmune diseases. GPCRs are being intensively investigated as targets for therapeutic intervention, and the β-arrestin recruitment assay has become a popular tool for analyzing GPCR activation. Here, we report a high-throughput method for cloning GPCR cDNAs into adenoviral bimolecular fluorescence complementation (BiFC) vectors and performing the β-arrestin BiFC assay in cells transduced with recombinant adenoviruses. An analysis of the activation of somatostatin receptor 2 (SSTR2) with the adenovirus-based β-arrestin BiFC assay showed that the assay is suitable for quantifying SSTR2 activation in response to specific agonists or antagonists. Furthermore, the adenovirus-based β-arrestin BiFC assay was able to detect the activation of a broad range of GPCRs. Collectively, our data indicate that the adenovirus-based β-arrestin BiFC assay can serve as a simple and universal platform for studying GPCR activation and thus will be useful for high-throughput screening of drugs that target GPCRs.

AdHTS: a high-throughput system for generating recombinant adenoviruses

The need for efficient high-throughput gene delivery system for mammalian cells is rapidly increasing with the growing request for functional genomics studies and drug discoveries in various physiologically relevant systems. However, plasmid-based gene delivery has limitations in transfection efficiency and available cell types. Viral vectors have great advantages over plasmid-based vectors, but construction of recombinant viruses remains to be a big hurdle for high-throughput applications. Here we demonstrate a rapid and simple high-throughput system for constructing recombinant adenoviruses which have been used as efficient gene delivery tools in mammalian systems in vitro and in vivo. By combining Gateway-based site-specific recombination with Terminal protein-coupled adenovirus vector, the adenovirus high-throughput system (AdHTS) generates multiple recombinant adenoviruses in 96-well plates simultaneously without the need for additional cloning or recombination in bacteria or mammalian cells. The AdHTS allows rapid and robust cloning and expression of genes in mammalian cells by removing shuttle vector construction, bacterial transformation, or selection and by minimizing effort in plaque isolation. By shortening the time required to convert whole cDNA library into desired viral vector constructs, the AdHTS would greatly facilitate functional genomics and proteomics studies in various mammalian systems.

Expression of anti-neuroexcitation peptide III of scorpion Buthus martensii Karsch BmK ANEP III in plants

Anti-neuroexcitation peptide III of Buthus martensii Karsch (BmK ANEP III) has better anti-epileptic and anticonvulsive effects in the test animal models. The present study is aimed at developing transgenic tomato and tobacco lines overproducing the ANEP III protein. Using the molecular cloning technique, the plant expression vector pBI-ANEP III was constructed successfully. The ANEP III expression cassette included a double CaMV 35S promoter with omega enhancers, the ANEP III gene with the Kozak sequence, the ER retention signal and the NOS terminator. Recombinant plasmids were transferred into Agrobacterium tumefaciens EHA105 by freeze-thaw transformation methods. By the Agrobacterium-mediated leaf disc transformation method, tobacco (Nicotiana tabacum) and tomato (Lycopersicum esculentum) lines were transformed. Transformants were screened and confirmed by PCR, RT-PCR and western blotting analysis. It was demonstrated that the ANEP III gene was successfully expressed in the genomic DNA of transgenic plants. The ANEP III protein was detected by immunofluorescence analysis, and the results confirmed the high amount of ANEP III protein, being 0.81 and 1.08% of total soluble proteins in transgenic tobacco and tomato. The study of plants with high expression levels of ANEP III has an important theoretical and practical significance and provides valuable information for establishing a new, economical and effective system for industrial protein production.

Redox regulation of the tumor suppressor PTEN by glutathione

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expressed in Saccharomyces cerevisiae was reversibly oxidized by hydrogen peroxide and reduced by cellular reductants. Reduction of hPTEN was delayed in each of S. cerevisiae gsh1Delta and gsh2Delta mutants. Expression of gamma-glutamylcysteine synthetase Gsh1 in the gsh1Delta mutant rescued regeneration rate of hPTEN. Oxidized hPTEN was reduced by glutathione in a concentration- and time-dependent manner. Glutathionylated PTEN was detected. Incubation of 293T cells with BSO and knockdown expression of GCLc in HeLa cells by siRNA resulted in the delay of reduction of oxidized PTEN. Also, in HeLa cells transfected with GCLc siRNA, stimulation with epidermal growth factor resulted in the increase of oxidized PTEN and phosphorylation of Akt. These results suggest that the reduction of oxidized hPTEN is mediated by glutathione.

Effects of dietary supplementation of lipophilic fraction from Panax ginseng on cGMP and cAMP in rat platelets and on blood coagulation

We have studied the effect of dietary supplementation with 25 mg (0.0025% of the total diet) of a lipophilic fraction (LF) from Panax ginseng on rat platelet aggregation induced by collagen or thrombin, and on blood coagulation. When platelets prepared from 15% corn oil plus LF-administered rats (COLF) were stimulated by thrombin (0.1 units/ml) and collagen (100 micrograms/ml), the cGMP level was significantly increased as compared with those from 15% corn oil only-administered rats (CO). The levels of cAMP in COLF were decreased by thrombin, but was increased by collagen. Furthermore, the levels of both cGMP and cAMP were also increased by the exogenous addition of LF to thrombin- and collagen-stimulated platelets. These results mean that LF increases cGMP directly and cAMP indirectly, and thus inhibits thrombin- or collagen-induced rat platelet aggregation. Both the thrombin time (TT) and activated partial thromboplastin time (APTT) were prolonged more in citrated platelet-poor plasma from COLF than in that from CO. The level of lipids such as triglyceride, total cholesterol, high density lipoprotein-cholesterol and low density lipoprotein-cholesterol was decreased in serum from COLF more than in that of CO. Thus, these results suggest that dietary LF regulates the levels of cGMP and cAMP, and prolongs the time interval (TT, APTT) between the conversion of fibrinogen to fibrin. Accordingly, our data demonstrate that dietary LF has an antithrombotic effect in vivo.

Effect of ginsenoside Rb1 on rat liver phosphoproteins induced by carbon tetrachloride

We investigated the effects of ginsenoside Rb1 (G-Rb1), a major saponin from Panax ginseng C. A. MEYER, on rat liver protein phosphorylation after intraperitoneal administration of CCl4 alone or together with G-Rb1. We found that 118, 63, and 34kDa proteins were prominently phosphorylated in liver homogenates prepared from CCl4-administered rats, while these protein-phosphorylations were inhibited in the homogenate prepared from the G-Rb1 plus CCl4-administration group. When inhibitors of protein kinases were exogenously added to the homogenates from either the CCl4-administered group or the G-Rb1 plus CCl4-administered group, their phosphorylations were inhibited much more by W-7, an inhibitor of Ca2+/calmodulin-dependent protein kinase (CaM-PK), than by H-7, an inhibitor of protein kinase C (C-kinase). Interestingly, only 34kDa was phosphorylated in homogenates prepared from the corn oil-, G-Rb1-, and G-Rb1 plus CCl4-administered groups by the exogenous addition of sodium fluoride (NaF), an inhibitor of glycogen synthase. Additionally, G-Rb1 inhibited the Ca(2+)-accumulation induced by CCl4 both in liver homogenates and microsomes. The above results imply that G-Rb1 inhibits the CCl4-induced protein phosphorylations by modulating CaM-PK rather than C-kinase, and that 34kDa protein may play a different biological role in cellular environment from 118 and 63kDa proteins. Therefore, a study in which G-Rb1 is employed as a modulator of critical CCl4-induced phenomena ranging from the disturbance of Ca2+ concentration to protein phosphorylation may be successfully applicable to investigate the diverse physiological functions of liver.

Experimental IgA nephropathy. Enhanced deposition of glomerular IgA immune complex in proteinuric states

BACKGROUND

IgA nephropathy is induced by the IgA-immune complex (IC). IgA nephropathy associated with heavy proteinuria is considered a more progressive form of the disease. To elucidate the mechanism by which the latter condition occurs, we investigated the effect of proteinuria on the glomerular deposition of IgA-IC.

EXPERIMENTAL DESIGN

BALB/c female mice that had been made proteinuric by adriamycin or bovine serum albumin (BSA) were injected with TEPC-15 hybridoma-derived IgA anti-phosphorylcholine (PC) and individual specific antigens. The 6-hour clearance kinetics of IgA were measured, and the accumulation of IgA deposits and the third complement component (C3) in the glomerulus were analyzed.

RESULTS

The clearance kinetics of 125I-IgA injected together with a specific antigen, PC-conjugated BSA (BSA-PC), showed only a minimal distinction between the experimental (proteinuric) and the control (nonproteinuric) groups of mice. However, analysis of renal tissue by immunofluorescence and light microscopic autoradiography revealed markedly enhanced mesangial IgA-IC deposition in the proteinuric mice receiving IgA and one of three specific antigens, BSA-PC, PC-conjugated cytochrome-c, and a pneumococcal C-polysaccharide. Immunofluorescence also showed augmented mesangial C3 deposition in proteinuric mice that received IgA/PC-conjugated cytochrome-c or IgA/pneumococcal C-polysaccharide. In addition, adriamycin or BSA per se did not influence glomerular IgA-IC localization.

CONCLUSIONS

Glomerular localization of nephritogenic IgA-IC was comparably enhanced in mice with proteinuria induced by various methods. Thus, a vicious cycle for the progression of IgA nephropathy might ensue in proteinuric states.

Novel assay method for mitoxantrone in plasma, and its application in cancer patients

Mitoxantrone is an anthracene derivative that acts as a cytostatic in a variety of cancers. A quantitative analytical method has been established for the determination of mitoxantrone in plasma. The method employed C18 reversed-phase ion-pair chromatography with an isocratic mobile phase of 50.0% methanol in 10 mM phosphate buffer (pH 3.0) plus 0.09% 1-pentanesulphonic acid and ultraviolet detection. Sample preparation consisted of two extraction steps using same organic solvent system at different pH to remove plasma impurities efficiently. Potential adsorption of mitoxantrone onto glassware was considered. Silanization of all glassware with 5% dichlorodimethylsilane in chloroform increased the extraction recovery in plasma from 50 to 85% with high reproducibility. Mitoxantrone was unstable in human plasma. To maintain plasma sample integrity, each millilitre of sample should be fortified with 0.1 ml of 5% vitamin C (in citrate buffer) and kept frozen until analysis. Using this new method, the calibration curve of mitoxantrone in plasma in the range of interest (1-500 ng/ml) showed good linearity (r = 0.996) and precision (both between-day and within-day coefficients of variation less than 10%). The lower detection limit of this assay method was 1 ng. The application of this method allowed us to study the stability of mitoxantrone in plasma, and the pharmacokinetics of mitoxantrone in nasopharyngeal carcinoma patients receiving 12 mg/m2. The study revealed a prolonged terminal phase half-life for mitoxantrone.