Induced Expression of Endogenous CXCR4 in iPSCs by Targeted CpG Demethylation Enhances Cell Migration Toward the Ligand CXCL12.

Poor homing of cells after transplantation is an unresolved common issue in cardiac cell therapies. To enhance stem cell homing, the ligand CXC motif chemokine 12 (CXCL12) and its specific receptor CXC receptor type 4 (CXCR4) have been employed as a system in this study to show that induced expression of the endogenous CXCR4 gene in mouse-induced pluripotent stem cells (iPSCs) improved the cell migration. Loci-specific epigenome editing in the form of CpG demethylation at CXCR4 promoter region of the mouse iPSCs was accomplished with CXCR4b-TAL-Tet1c, chimeric fusion proteins of the catalytic domain of ten-eleven translocation 1 (TET1) to the C-terminal end of the DNA binding domains of predesigned synthetic transcription activator-like effectors (TALEs) that recognize specific DNA sequences within the mouse CXCR4 promoter region. Infection of the mouse iPSCs with the engineered CXCR4b-TAL-Tet1c in the form of lentiviral particles induced the loci-specific CpG demethylation and subsequent activation of CXCR4 expression in mouse iPSCs. As expected, the CXCR4-overexpressing iPSCs exhibited 3.9-fold greater migration than the control iPSCs did without alteration of the stemness and activated phosphorylation of AKT significantly. These results set a sound foundation for subsequent in vivo iPSCs transplantation studies in rodent models of acute myocardial infarction and heart failure. We show that TALEs can enhance the expression of CXCR4 by CpG methylation, and may retain the stemness. Migration of iPSCs activated by CXCL12 is associated with significant phosphorylation of AKT, not ERK1/2.

High glucose instigates tubulointerstitial injury by stimulating hetero-dimerization of adiponectin and angiotensin II receptors.

Abnormal expression and dysfunction of adiponectin and the cognate receptors are involved in diabetes and diabetic kidney disease (DKD), whereas angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) alleviate diabetic albuminuria and prevent development of DKD through upregulation of adiponectin expression. Here we report that high glucose stimulates expression of angiotensin II (AngII) receptors (AT1 and AT2) in renal proximal tubular epithelial cells (NRK-52E). These receptors underwent hetero-dimerization with adiponectin receptor AdipoR1 and AdipoR2, respectively. High glucose inhibited the dimerization between AT1 and AT2. Interestingly, these hetero-dimers instigated tubulointerstitial injury by inhibiting the cytoprotective action of the adiponectin receptors. These modes of receptor-receptor hetero-dimerization may contribute to high glucose-induced renal tubulointerstitial injury and could be potential therapeutic targets.

3-O-(Z)-coumaroyloleanolic acid overcomes Cks1b-induced chemoresistance in lung cancer by inhibiting Hsp90 and MEK pathways.

Expression of CDC28 protein kinase regulatory subunit 1 (Cks1), an adaptor for cyclin-dependent kinases, is tightly regulated at transcriptional and posttranslational levels. Increased expression of Cks1 has been documented to be attributable to cancer progression, chemoresistance, and chemosensitivity. Here we report that ectopic overexpression of Cks1b in human lung cancer cells (Cks1b-OE) induces chemoresistance of the cells to cisplatin (CDDP) and doxorubicin (DOX) through mechanisms independent of its canonical Skp2-p27 pathway. Further dissection with application of shRNA and selective inhibitors reveals that Hsp90 and MEK1/2 are the critical components of the non-canonical pathways responsible for the Cks1b-induced chemoresistance. Interestingly, inhibition of either Hsp90 or MEK1/2 rendered a similar magnitude of antitumor activity by resensitization of the chemoresistant Cks1b-OE cells to CDDP and DOX, suggesting that both Hsp90 and MEK1/2 are essential to Cks1b for induction of chemoresistance. Moreover, 3-O-(Z)-coumaroyloleanolic acid (3-COA), an active ingredient of oleanolic acid in the leaves of E. oldhamii Maxim, that has been shown to have antitumor activity against A549 lung cancer cells, mimicked PU-H71, a Hsp90-specific inhibitor, in antitumor activity when used alone or in combination with CDDP or DOX in Cks1b-OE cells and recurrent primary human lung cancer cells both in vitro and in vivo, suggesting that 3-COA is a novel Hsp90 inhibitor. Our data report for the first time that Cks1b employs Hsp90 and MEK1/2 pathways in lung cancer cells to develop chemoresistance and identify 3-COA as a potential antitumor drug for clinical treatment of chemoresistant lung cancer.

Manipulation of prostate cancer metastasis by locus-specific modification of the CRMP4 promoter region using chimeric TALE DNA methyltransferase and demethylase.

Prostate cancer is the most commonly diagnosed non-cutaneous cancer and one of the leading causes of cancer death for North American men. Whereas localized prostate cancer can be cured, there is currently no cure for metastatic prostate cancer. Here we report a novel approach that utilizes designed chimeric transcription activator-like effectors (dTALEs) to control prostate cancer metastasis. Transfection of dTALEs of DNA methyltransferase or demethylase induced artificial, yet active locus-specific CpG and subsequent histone modifications. These manipulations markedly altered expression of endogenous CRMP4, a metastasis suppressor gene. Remarkably, locus-specific CpG demethylation of the CRMP4 promoter in metastatic PC3 cells abolished metastasis, whereas locus-specific CpG methylation of the promoter in non-metastatic 22Rv1 cells induced metastasis. CRMP4-mediated metastasis suppression was found to require activation of Akt/Rac1 signaling and down-regulation of MMP-9 expression. This proof-of-concept study with dTALEs for locus-specific epigenomic manipulation validates the selected CpG methylation of CRMP4 gene as an independent biomarker for diagnosis and prognosis of prostate cancer metastasis and opens up a novel avenue for mechanistic research on cancer biology.

Aloperine executes antitumor effects against multiple myeloma through dual apoptotic mechanisms.

BACKGROUND: Aloperine, a natural alkaloid constituent isolated from the herb Sophora alopecuroides displays anti-inflammatory properties in vitro and in vivo. Our group previously demonstrated that aloperine significantly induced apoptosis in colon cancer SW480 and HCT116 cells. However, its specific target(s) remain to be discovered in multiple myeloma (MM) and have not been investigated. METHODS: Human myeloma cell lines (n = 8), primary myeloma cells (n = 12), drug-resistant myeloma cell lines (n = 2), and animal models were tested for their sensitivity to aloperine in terms of proliferation and apoptosis both in vitro and in vivo, respectively. We also examined the functional mechanisms underlying the apoptotic pathways triggered by aloperine. RESULTS: Aloperine induced MM cell death in a dose- and time-dependent manner, even in the presence of the proliferative cytokines interleukin-6 and insulin-like growth factor I. Mechanistic studies revealed that aloperine not only activated caspase-8 and reduced the expression of FADD-like interleukin-1ß-converting enzyme (FLICE)-like inhibitory protein long (FLIPL) and FLICE-inhibitory proteins (FLIPS) but also activated caspase-9 and decreased the expression of phosphorylated (p)-PTEN. Moreover, co-activation of the caspase-8/cellular FLICE-inhibitory protein (cFLIP)- and caspase-9/p-PTEN/p-AKT-dependent apoptotic pathways by aloperine caused irreversible inhibition of clonogenic survival. Aloperine induce more MM apoptosis with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or borterzomib. A U266 xenograft tumor model and 5T33 MM cells recapitulated the antitumor efficacy of aloperine, and the animals displayed excellent tolerance of the drug and few adverse effects. CONCLUSIONS: Aloperine has multifaceted antitumor effects on MM cells. Our data support the clinical development of aloperine for MM therapy.

Zero-valent iron enhanced methanogenic activity in anaerobic digestion of waste activated sludge after heat and alkali pretreatment.

Heat or alkali pretreatment is the effective method to improve hydrolysis of waste sludge and then enhance anaerobic sludge digestion. However the pretreatment may inactivate the methanogens in the sludge. In the present work, zero-valent iron (ZVI) was used to enhance the methanogenic activity in anaerobic sludge digester under two methanogens-suppressing conditions, i.e. heat-pretreatment and alkali condition respectively. With the addition of ZVI, the lag time of methane production was shortened, and the methane yield increased by 91.5% compared to the control group. The consumption of VFA was accelerated by ZVI, especially for acetate, indicating that the acetoclastic methanogenesis was enhanced. In the alkali-condition experiment, the hydrogen produced decreased from 27.6 to 18.8 mL when increasing the ZVI dosage from 0 to 10 g/L. Correspondingly, the methane yield increased from 1.9 to 32.2 mL, which meant that the H2-utilizing methanogenes was enriched. These results suggested that the addition of ZVI into anaerobic digestion of sludge after pretreated by the heat or alkali process could efficiently recover the methanogenic activity and increase the methane production and sludge reduction.

Folate-mediated mitochondrial targeting with doxorubicin-polyrotaxane nanoparticles overcomes multidrug resistance.

Resistance to treatment with anticancer drugs is a significant obstacle and a fundamental cause of therapeutic failure in cancer therapy. Functional doxorubicin (DOX) nanoparticles for targeted delivery of the classical cytotoxic anticancer drug DOX to tumor cells, using folate-terminated polyrotaxanes along with dequalinium, have been developed and proven to overcome this resistance due to specific molecular features, including a size of approximately 101 nm, a zeta potential of 3.25 mV and drug-loading content of 18%. Compared with free DOX, DOX hydrochloride, DOX nanoparticles, and targeted DOX nanoparticles, the functional DOX nanoparticles exhibited the strongest anticancer efficacy in vitro and in the drug-resistant MCF-7/Adr (DOX) xenograft tumor model. More specifically, the nanoparticles significantly increased the intracellular uptake of DOX, selectively accumulating in mitochondria and the endoplasmic reticulum after treatment, with release of cytochrome C as a result. Furthermore, the caspase-9 and caspase-3 cascade was activated by the functional DOX nanoparticles through upregulation of the pro-apoptotic proteins Bax and Bid and suppression of the antiapoptotic protein Bcl-2, thereby enhancing apoptosis by acting on the mitochondrial signaling pathways. In conclusion, functional DOX nanoparticles may provide a strategy for increasing the solubility of DOX and overcoming multidrug-resistant cancers.

Enhanced high-solids anaerobic digestion of waste activated sludge by the addition of scrap iron.

Anaerobic digestion of waste activated sludge usually requires pretreatment procedure to improve the bioavailability of sludge, which involves considerable energy and high expenditures. This study proposes a cost-effective method for enhanced anaerobic digestion of sludge without a pretreatment by directly adding iron into the digester. The results showed that addition of Fe(0) powder could enhance 14.46% methane yield, and Fe scrap (clean scrap) could further enhance methane yield (improving rate 21.28%) because the scrap has better mass transfer efficiency with sludge and liquid than Fe(0) powder. The scrap of Fe with rust (rusty scrap) could induce microbial Fe(III) reduction, which resulted in achieving the highest methane yield (improving rate 29.51%), and the reduction rate of volatile suspended solids (VSS) was also highest (48.27%) among Fe powder, clean scrap and rusty scrap. PCR-DGGE proved that the addition of rusty scrap could enhance diversity of acetobacteria and enrich iron-reducing bacteria to enhance degradation of complex substrates.

Enhanced anaerobic digestion of waste activated sludge digestion by the addition of zero valent iron.

Anaerobic digestion is promising technology to recover energy from waste activated sludge. However, the sludge digestion is limited by its low efficiency of hydrolysis-acidification. Zero valent iron (ZVI) as a reducing material is expected to enhance anaerobic process including the hydrolysis-acidification process. Considering that, ZVI was added into an anaerobic sludge digestion system to accelerate the sludge digestion in this study. The results indicated that ZVI effectively enhanced the decomposition of protein and cellulose, the two main components of the sludge. Compared to the control test without ZVI, the degradation of protein increased 21.9% and the volatile fatty acids production increased 37.3% with adding ZVI. More acetate and less propionate are found during the hydrolysis-acidification with ZVI. The activities of several key enzymes in the hydrolysis and acidification increased 0.6-1 time. ZVI made the methane production raise 43.5% and sludge reduction ratio increase 12.2 percent points. Fluorescence in situ hybridization analysis showed that the abundances of hydrogen-consuming microorganisms including homoacetogens and hydrogenotrophic methanogens with ZVI were higher than the control, which reduced the H2 accumulation to create a beneficial condition for the sludge digestion in thermodynamics.

Inheritable stimulatory effects of caffeine on steroidogenic acute regulatory protein expression and cortisol production in human adrenocortical cells.

Caffeine is the most widely consumed psychoactive substance in the world. It can elevate the level of glucocorticoid which is involved in metabolism regulation, stress response, and immune function. However, the specific mechanism has yet to be elucidated. Glucocorticoid is steroid hormone synthesized in adrenal cortex and the key rate-limiting step in its biosynthesis is mediated by steroidogenic acute regulatory protein (StAR). This study was designed to investigate the direct effects and inheritable epigenetic mechanisms of caffeine on cortisol production and StAR expression in human adrenocortical cells. The human adrenocortical cell line NCI-H295A was cultured with 0.4-40µM caffeine. There was a significant increase of the cortisol production in cells. In both acutely and chronically caffeine-treated cell groups, mRNA and protein expressions of StAR were stimulated in a dose-dependent manner. DNA methylation detection via bisulfite-sequencing PCR (BSP) uncovered a single site CpG demethylation at nt -682 within the StAR promoter region. Then we investigated how long the increased StAR expression and the single CpG demethylation could last. The caffeine was withdrawn after 48h of treatment and then the cells were continually subcultured for up to 5 and 10 passages, respectively. The results showed that the StAR expression at post-caffeine passage 10 still increased, as compared with that in the control. The caffeine-induced demethylation at nt -682 in StAR promoter underwent a similar time course as StAR expression does. The present study reveals the direct effect and possible inheritable epigenetic mechanism of caffeine on steroidogenesis in human adrenocortical cells and has implications for our understanding of the consumption of caffeine.

Nicotine induced CpG methylation of Pax6 binding motif in StAR promoter reduces the gene expression and cortisol production.

Steroidogenic acute regulatory protein (StAR) mediates the rate-limiting step in the synthesis of steroid hormones, essential to fetal development. We have reported that the StAR expression in fetal adrenal is inhibited in a rat model of nicotine-induced intrauterine growth retardation (IUGR). Here using primary human fetal adrenal cortex (pHFAC) cells and a human fetal adrenal cell line NCI-H295A, we show that nicotine inhibits StAR expression and cortisol production in a dose- and time-dependent manner, and prolongs the inhibitory effect on cells proliferating over 5 passages after termination of nicotine treatment. Methylation detection within the StAR promoter region uncovers a single site CpG methylation at nt -377 that is sensitive to nicotine treatment. Nicotine-induced alterations in frequency of this point methylation correlates well with the levels of StAR expression, suggesting an important role of the single site in regulating StAR expression. Further studies using bioinformatics analysis and siRNA approach reveal that the single CpG site is part of the Pax6 binding motif (CGCCTGA) in the StAR promoter. The luciferase activity assays validate that Pax6 increases StAR gene expression by binding to the glucagon G3-like motif (CGCCTGA) and methylation of this site blocks Pax6 binding and thus suppresses StAR expression. These data identify a nicotine-sensitive CpG site at the Pax6 binding motif in the StAR promoter that may play a central role in regulating StAR expression. The results suggest an epigenetic mechanism that may explain how nicotine contributes to onset of adult diseases or disorders such as metabolic syndrome via fetal programming.

Angiotensin II activates AMPK for execution of apoptosis through energy-dependent and -independent mechanisms.

At the cellular level, 5'-AMP-activated protein kinase (AMPK) serves as a critical link between energy homeostasis and the regulation of fundamental biological activities, including apoptosis. Angiotensin (Ang) II plays a key role in fibrotic lung remodeling. We recently demonstrated that Ang II induces apoptosis in pulmonary artery endothelial cells (PAEC) through the Ang type 2 receptor (AT(2)). AT(2) activates Src-homology two-domain-containing phosphatase-2 (SHP-2) in a signaling cascade leading to Bcl-x(L) mRNA destabilization and initiation of intrinsic apoptosis. We investigated the requirement of AMPK and ATP generation for Ang II-induced apoptosis in PAEC. Ang II activated AMPK, which was required for ATP generation. Inhibition of ATP production by compound C, an AMPK inhibitor, or by oligomycin suppressed Ang II-induced apoptosis. Experiments in Chinese hamster ovary-K1 cells expressing ectopic AT(2) (wild-type, mutant D90A, or carboxy terminal truncated mutant tC319) demonstrated that AT(2) activation of AMPK required the active conformation of the receptor and the carboxy terminal 44 amino acids. AMPK associated with and activated SHP-2 and was required for Bcl-x(L) mRNA destabilization. These are the first findings demonstrating that AMPK is activated by Ang II to produce ATP required for apoptosis. Our data also indicate that AMPK plays an energy-independent role by mediating SHP-2 activation.

Nitro-oleic acid inhibits angiotensin II-induced hypertension.

RATIONALE: Nitro-oleic acid (OA-NO(2)) is a bioactive, nitric-oxide derived fatty acid with physiologically relevant vasculoprotective properties in vivo. OA-NO(2) exerts cell signaling actions as a result of its strong electrophilic nature and mediates pleiotropic cell responses in the vasculature. OBJECTIVE: The present study sought to investigate the protective role of OA-NO(2) in angiotensin (Ang) II-induced hypertension. METHODS AND RESULTS: We show that systemic administration of OA-NO(2) results in a sustained reduction of Ang II-induced hypertension in mice and exerts a significant blood pressure lowering effect on preexisting hypertension established by Ang II infusion. OA-NO(2) significantly inhibits Ang II contractile response as compared to oleic acid (OA) in mesenteric vessels. The improved vasoconstriction is specific for the Ang II type 1 receptor (AT(1)R)-mediated signaling because vascular contraction by other G-protein-coupled receptors is not altered in response to OA-NO(2) treatment. From the mechanistic viewpoint, OA-NO(2) lowers Ang II-induced hypertension independently of peroxisome proliferation-activated receptor (PPAR)gamma activation. Rather, OA-NO(2), but not OA, specifically binds to the AT(1)R, reduces heterotrimeric G-protein coupling, and inhibits IP(3) (inositol-1,4,5-trisphosphate) and calcium mobilization, without inhibiting Ang II binding to the receptor. CONCLUSIONS: These results demonstrate that OA-NO(2) diminishes the pressor response to Ang II and inhibits AT(1)R-dependent vasoconstriction, revealing OA-NO(2) as a novel antagonist of Ang II-induced hypertension.

Expression and activation of the reprogramming transcription factors.

Recently, a series of exciting reports have revealed that terminally differentiated somatic cells can be reprogrammed to generate induced pluripotent stem (iPS) cells via overexpression of a cocktail of transcription factors such as Oct3, Sox2, Klf4, and c-Myc or Oct3, Sox2, Nanog, and Lin28. Most recently, these iPS cells has been used to generate viable, live-born progeny by tetraploid complementation. Reprogramming of iPS cells inaugurates a new era of biology and medicine, it inevitably brings new challenges, e.g., how these factors induce reprogramming and how their expression is regulated. To facilitate iPS cell research, this review focuses on how expression and activation of these transcription factors are regulated.

Rab1 GTPase and dimerization in the cell surface expression of angiotensin II type 2 receptor.

The physiological function of angiotensin II (Ang II) is mediated through the Ang II type 1 (AT1R) and type 2 (AT2R) receptors. Our previous studies have demonstrated that cell surface targeting of AT1R is regulated by Rab and Sar1 GTPases and the F(x)(6)LL motif in the membrane-proximal C terminus. However, the molecular mechanisms underlying the export of nascent AT2R remain poorly defined. In this report, we determined the role of Rab1 GTPase, which specifically controls protein transport from the endoplasmic reticulum (ER) to the Golgi, and receptor dimerization in the biosynthesis of AT2R. Cell surface expression of AT2R was augmented by transient expression of Rab1 and attenuated by dominant-negative Rab1 mutants and small interfering RNA-mediated knockdown of Rab1. Consistently, AT2R inhibition of epidermal growth factor-activated extracellular signal-regulated kinase 1/2 was significantly reduced by the Rab1 mutants, indicating that endogenous Rab1 modulates the cell surface targeting and signaling of AT2R. It is of interest to note that Rab1 augmented the overall expression of AT2R and its mRNA, whereas the Rab1 mutants attenuated the total AT2R expression and enhanced ubiquitin-dependent AT2R degradation. Furthermore, our previously characterized ER export-deficient AT1R mutant in which the F(x)(6)LL motif was mutated formed both homodimers and heterodimers with AT2R. Dimerization of the AT1R mutant with AT2R blocked AT2R trafficking to the cell surface, suggesting constitutive dimerization of both receptors in the ER and an important role of dimerization in ER export of the receptors. These data demonstrate for the first time that Rab1 GTPase and dimerization modulate export traffic from the ER to the cell surface of newly synthesized AT2R.

Nicotine-induced prenatal overexposure to maternal glucocorticoid and intrauterine growth retardation in rat.

Overexposure to glucocorticoid during fetal development can result in intrauterine growth retardation (IUGR) as well as other diseases after birth. The purpose of this study is to investigate the possibility of glucocorticoid disturbance-mediated nicotine-induced IUGR after chronic prenatal exposure. Nicotine at 1.0mg/kg twice a day was administered subcutaneously to pregnant rats from gestational day (GD) 8 to GD 15 (mid-gestation) or GD 21 (late-gestation). Placental weights and fetal developmental parameters were recorded. Corticosterone levels were determined by radioimmunoassay. The mRNA expressions of adrenal steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side chain cleavage (P450scc) and placental 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD-2) were determined using real-time quantitative RT-PCR. The results showed that prenatal chronic nicotine exposure causes IUGR in rats (P<0.01); in response to nicotine exposure, maternal serum corticosterone levels were elevated at mid- and late-gestations (P<0.05); mRNA expressions of StAR and P450scc increased in maternal adrenals (P<0.05 or 0.01) but decreased in fetal adrenals (P=0.16 or 0.11). Furthermore, the mRNA levels of placental 11 beta-HSD-2 were reduced at mid- and late-gestations (P<0.05). These results suggest that nicotine-induced IUGR is associated with the disturbances of glucocorticoid homeostasis in maternal and fetal rats. A possible underlying mechanism is that long term nicotine administration leads to fetal overexposure to maternal glucocorticoid by the combined effect of increased maternal glucocorticoid level and impaired placental barrier to it, all of which eventually leads to the fetal adrenocortical dysfunction and IUGR.

The P2X7 receptor: a novel biomarker of uterine epithelial cancers.

OBJECTIVE: To determine expression of the P2X(7) receptor in normal and in cancer uterine tissues. The rationale was that the receptor P2X(7) regulates constitutive apoptosis in uterine epithelial cells, and previous studies showed diminished P2X(7)-mediated apoptosis in cancer uterine cells compared with normal cells. METHODS: A clinical, experimental feasibility study. Normal (n = 42) and cancer uterine tissues (n = 47) were obtained from a total of 72 women ages 25 to 75. End points for P2X(7) mRNA were quantitative PCR and in situ hybridization, and end points for P2X(7) protein were Western blots and immunostaining using anti-P2X(7) antibody. RESULTS: (a) In normal uteri, P2X(7) mRNA and protein were expressed predominantly in the epithelial (endometrial, endocervical, and ectocervical) cells. (b) Expression of the P2X(7) mRNA and protein was absent from endometrial and endocervical adenocarcinoma tissues and from cervical squamous cell carcinoma tissues. (c) In cervical dysplasia, P2X(7) protein was absent in the dysplastic lesions. (d) Semiquantitative analysis using P2X(7) mRNA (normalized in each tissue to the constitutive glyceraldehyde-3-phosphate dehydrogenase) and P2X(7) protein levels (normalized in each tissue to the constitutive tubulin) revealed that P2X(7) mRNA and/or protein levels can distinguish uterine normal from cancer tissues at high degrees of sensitivity (92%, 100%) and specificity (100%, 90%). SUMMARY AND CONCLUSIONS: (a) Levels of the P2X(7) are lower in uterine epithelial cancer tissues than in the corresponding normal tissues. (b) The data suggest that tissue P2X(7) mRNA and protein levels could be used as a novel biomarker to differentiate normal and cancer uterine epithelial tissues.

A truncated P2X7 receptor variant (P2X7-j) endogenously expressed in cervical cancer cells antagonizes the full-length P2X7 receptor through hetero-oligomerization.

A truncated naturally occurring variant of the human receptor P2X7 was identified in cancer cervical cells. The novel protein (P2X7-j), a polypeptide of 258 amino acids, lacks the entire intracellular carboxyl terminus, the second transmembrane domain, and the distal third of the extracellular loop of the full-length P2X7 receptor. The P2X7-j was expressed in the plasma membrane; it showed diminished ligand-binding and channel function capacities and failed to form pores and mediate apoptosis in response to treatment with the P2X7 receptor agonist benzoyl-ATP. The P2X7-j interacted with the full-length P2X7 in a manner suggesting heterooligomerization and blocked the P2X7-mediated actions. Interestingly, P2X7-j immunoreactivity and mRNA expression were similar in lysates of human cancer and normal cervical tissues, but full-length P2X7 immunoreactivity and mRNA expression were higher in normal than in cancer tissues, and cancer tissues lacked 205-kDa P2X7 immunoreactivity suggesting lack of P2X7 homo(tri)-oligomerization. These results identify a novel P2X7 variant with apoptosis-inhibitory actions, and demonstrate a distinct regulatory property for a truncated variant to antagonize its full-length counterpart through hetero-oligomerization. This may represent a general paradigm for regulation of a protein function by its variant.

Alterations of placental cytochrome P450 1A1 and P-glycoprotein in tobacco-induced intrauterine growth retardation in rats.

AIM: To investigate the alterations of placental P-glycoprotein (P-gp) and cytochrome P450 1A1 (CYP1A1) at different gestational days (GD), and to explore the possible significance of placental P-gp and CYP1A1 in tobacco smoke-induced intrauterine growth retardation (IUGR) in rats. METHODS: An IUGR model was produced by passive tobacco smoking from GD7 to parturition (GD21) and predicted using fetal development parameters. Placental structure and function were monitored by observing pathological alteration and antioxidative function, including the content of malondialdehyde and the activities of superoxide dismutase and catalase (CAT). The expressions of CYP1A1 and P-gp (mdr 1a and mdr 1b) were detected using a reverse transcription polymerase chain reaction and immunohistochemistry. RESULTS: Placental pathological changes occurred and the malondialdehyde content increased, whereas the activities of superoxide dismutase and CAT lowered, when compared to their controls. In the rat placenta of the tobacco group, the level of CYP1A1 mRNA increased significantly; the level of mdr1a mRNA increased significantly at GD21 but not at GD14, whereas the level of mdr1b mRNA in different term remained stable; the expression of P-gp increased significantly only in full-term placenta. CONCLUSION: The expression of placental CYP1A1 and P-gp increased in tobacco-induced IUGR. Overexpression of placental CYP1A1 can attribute to the metabolism of tobacco and the generation of reactive metabolites, which can trigger IUGR. As a compulsory mechanism, upregulation of P-gp might decrease tobacco exposure to a developing fetus with IUGR.

Unconventional homologous internalization of the angiotensin II type-1 receptor induced by G-protein-independent signals.

Internalization of a G-protein-coupled receptor (GPCR) is essential to the desensitization, endocytosis, and signal transduction of the receptor. It has been the general view that conventional homologous internalization of a GPCR requires activation of the G-protein(s) coupled to the receptor. However, whether and how GPCR-mediated G-protein-independent signals trigger receptor internalization remains unknown, although G-protein-independent internalization has been reported. Here we show that an angiotensin II (Ang II) type-1 (AT1) receptor mutant incapable of activating any G-protein still undergoes normal internalization. Substitution of Asp125 with Ala and Arg126 with Leu at the highly conserved DRY motif of the AT1 receptor disabled the ability of the receptor to activate G-proteins, as shown by various Ang II binding studies, GDP-GTP exchange, and inositol phosphate production assays. Surprisingly, the mutant internalized normally in the presence of Ang II and transactivated the epidermal growth factor receptor (EGFR). Similar to the wild-type receptor, overexpression of a dominant-negative K220R mutant GRK2 diminished the internalization of D125A-R126L but not the transactivation of EGFR. These data indicate that G-protein-independent specific signals may also trigger homologous internalizations of the AT1 receptor through beta-arrestin-dependent and -independent pathways, suggesting a possible mechanism for G-protein-independent activation of G-protein-coupled receptor kinases (GRKs). This may represent a general mechanism for triggering GPCR internalization.