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Articles by X Chen
Total Records ( 32 ) for X Chen
  J He , R Xu , X Chen , K Jia , X Zhou and K. Zhu
 

To reduce the immunogenicity of recombinant staphylokinase, structure-based mutagenesis of Glu80 residue in wild-type staphylokinase (wt-Sak) was rationally designed and carried out by a modified QuikChange site-directed mutagenesis. Sak mutants, including Sak(E80A) and Sak(E80S), were successfully expressed in E. coli DH5 as a soluble cytoplasmic proteins and accounted for more than 40% of the total cellular proteins. The expressed proteins were purified by a three-step chromatographic purification process. SDS–PAGE and HPLC analyses results indicated that the purified proteins were almost completely homogeneous and the purities of Sak mutants exceeded 97%. Analysis of fibrinolytic activity revealed that substitution of E80 residue with serine and alanine resulted in slightly increased specific activities of Sak mutants. Investigation of the immunogenicity of Sak mutants showed that the amount of specific anti-Sak IgG antibodies elicited by Sak(E80A) and Sak(E80S) in BALB/c mice decreased ~35% and 27%, respectively compared with wt-Sak. The abilities of Sak mutants to stimulate proliferation of T cells from BALB/c mice and to bind mouse anti-Sak polyclonal serum were significantly lower than those of wt-Sak. These results suggested that substitution of Glu80 residue by alanine and serine successfully eliminated part of T- and B-cell epitope of Sak molecule. Our findings suggested that simultaneous elimination of T- and B-cell epitopes was a useful method to reduce the immunogenicity of wt-Sak molecule and provided a strategy for engineering safe Sak-based fibrinolytics for the clinical treatment of acute myocardial infarction.

  R. A Leos , M. J Anderson , X Chen , J Pugmire , K. A Anderson and S. W. Limesand
 

In this study, we examined chronic norepinephrine suppression of insulin secretion in sheep fetuses with placental insufficiency-induced intrauterine growth restriction (IUGR). Glucose-stimulated insulin secretion (GSIS) was measured with a square-wave hyperglycemic clamp in the presence or absence of adrenergic receptor antagonists phentolamine () and propranolol (β). IUGR fetuses were hypoglycemic and hypoxemic and had lower GSIS responsiveness (P ≤ 0.05) than control fetuses. IUGR fetuses also had elevated plasma norepinephrine (3,264 ± 614 vs. 570 ± 86 pg/ml; P ≤ 0.05) and epinephrine (164 ± 32 vs. 60 ± 12 pg/ml; P ≤ 0.05) concentrations. In control fetuses, adrenergic inhibition increased baseline plasma insulin concentrations (1.7-fold, P ≤ 0.05), whereas during hyperglycemia insulin was not different. A greater (P ≤ 0.05) response to adrenergic inhibition was found in IUGR fetuses, and the average plasma insulin concentrations increased 4.9-fold at baseline and 7.1-fold with hyperglycemia. Unlike controls, basal plasma glucose concentrations fell (P ≤ 0.05) with adrenergic antagonists. GSIS responsiveness, measured by the change in insulin, was higher (8.9-fold, P ≤ 0.05) in IUGR fetuses with adrenergic inhibition than controls (1.8-fold, not significant), showing that norepinephrine suppresses insulin secretion in IUGR fetuses. Strikingly, in IUGR fetuses, adrenergic inhibition resulted in a greater GSIS responsiveness, because β-cell mass was 56% lower and the maximal stimulatory insulin response tended (P < 0.1) to be higher than controls. This persistent norepinephrine suppression appears to be partially explained by higher mRNA concentrations of adrenergic receptors 1D, 2A, and 2B in a cohort of fetuses that were naïve to the antagonists. Therefore, norepinephrine suppression of insulin secretion was maintained, in part, by upregulating adrenergic receptor expression, but the β-cells also appeared to compensate with enhanced GSIS. These findings may begin to explain why IUGR infants have a propensity for increased glucose requirements if norepinephrine is suddenly decreased after birth.

  S Naar King , J. T Parsons , D. A Murphy , X Chen , D. R Harris and M. E. Belzer
 

Objective  To determine if Healthy Choices, a motivational interviewing intervention targeting multiple risk behaviors, improved human immunodeficiency virus (HIV) viral load.

Design  A randomized, 2-group repeated measures design with analysis of data from baseline and 6- and 9-month follow-up collected from 2005 to 2007.

Setting  Five US adolescent medicine HIV clinics.

Participants  A convenience sample with at least 1 of 3 risk behaviors (nonadherence to HIV medications, substance abuse, and unprotected sex) was enrolled. The sample was aged 16 to 24 years and primarily African American. Of the 205 enrolled, 19 did not complete baseline data collections, for a final sample size of 186. Young people living with HIV were randomized to the intervention plus specialty care (n = 94) or specialty care alone (n = 92). The 3- and 6-month follow-up rates, respectively, were 86% and 82% for the intervention group and 81% and 73% for controls.

Intervention  Healthy Choices was a 4-session individual clinic-based motivational interviewing intervention delivered during a 10-week period. Motivational interviewing is a method of communication designed to elicit and reinforce intrinsic motivation for change.

Outcome Measure  Plasma viral load.

Results  Youth randomized to Healthy Choices showed a significant decline in viral load at 6 months postintervention compared with youth in the control condition (β = –0.36, t = –2.15, P = .03), with those prescribed antiretroviral medications showing the lowest viral loads. Differences were no longer significant at 9 months.

Conclusion  A motivational interviewing intervention targeting multiple risk behaviors resulted in short-term improvements in viral load for youth living with HIV.

Trial Registration  clinicaltrials.gov Identifier: NCT00103532

  X Chen and R. D. Cook
 

Continuum regression encompasses ordinary least squares regression, partial least squares regression and principal component regression under the same umbrella using a nonnegative parameter . However, there seems to be no literature discussing the asymptotic properties for arbitrary continuum regression parameter . This article establishes a relation between continuum regression and sufficient dimension reduction and studies the asymptotic properties of continuum regression for arbitrary under inverse regression models. Theoretical and simulation results show that the continuum seems unnecessary when the conditional distribution of the predictors given the response follows the multivariate normal distribution.

  H Yi , X Yu , P Gao , Y Wang , S. H Baek , X Chen , H. L Kim , J. R Subjeck and X. Y. Wang
 

Class A scavenger receptor (SRA), also known as CD204, has been shown to participate in the pathogenesis of atherosclerosis and the pattern recognition of pathogen infection. However, its role in adaptive immune responses has not been well defined. In this study, we report that the lack of SRA/CD204 promotes Toll-like receptor (TLR)4 agonist–augmented tumor-protective immunity, which is associated with enhanced activation of CD8+ effector T cell and improved inhibition of tumor growth. Dendritic cells (DCs) deficient in SRA/CD204 display more effective immunostimulatory activities upon TLR4 engagement than those from wild-type counterparts. Silencing of SRA/CD204 by RNA interference improves the ability of DCs to prime antigen-specific CD8+ T cells, suggesting that antigen-presenting cells, for example, DCs, play a major role in SRA/CD204-mediated immune modulation. Our findings reveal a previously unrecognized role for SRA/CD204, a non-TLR pattern recognition receptor, as a physiologic negative regulator of TLR4-mediated immune consequences, which has important clinical implications for development of TLR-targeted immunotherapeutic intervention.

  Y Liao , J Tang , M Ma , Z Wu , M Yang , X Wang , T Liu , X Chen , P. C Fletcher and W. Hao
 

Ketamine abuse has been shown to have a deleterious impact on brain function. However, the precise mechanisms of ketamine dependence-induced pathological change remain poorly understood. Although there is evidence for white matter changes in drug abuse, the presence of white matter abnormalities in chronic ketamine users has not been studied. White matter volumes were measured using in vivo diffusion tensor magnetic resonance imaging data in 41 ketamine-dependent subjects and 44 drug-free healthy volunteers. White matter changes associated with chronic ketamine use were found in bilateral frontal and left temporoparietal cortices. There was also evidence that frontal white matter fractional anisotropy correlated with the severity of drug use (as measured by estimated total ketamine consumption). We provide direct evidence for dose-dependent abnormalities of white matter in bilateral frontal and left temporoparietal regions following chronic ketamine use. The findings suggest a microstructural basis for the changes in cognition and experience observed with prolonged ketamine use. Moreover, the similarities of these changes to those observed in chronic schizophrenia have implications for the glutamate model of this illness.

  S Zhang , J Lu , X Zhao , W Wu , H Wang , Q Wu , X Chen , W Fan , H Chen , F Wang , Z Hu , L Jin , Q Wei , H Shen , W Huang and D. Lu
 

Checkpoint kinase (CHEK) 2, a tumor suppressor gene, plays an essential role in the DNA damage checkpoint response cascade. We first investigated two polymorphisms in the proximal promoter of the CHEK2 gene and evaluated their associations with the risk of lung cancer in a case–control study using 500 incident lung cancer cases and 517 cancer-free controls. We found that CHEK2 rs2236141 –48 G > A was significantly associated with lung cancer risk (P = 0.0018). Similar results were obtained in a follow-up replication study in 575 lung cancer patients and 589 controls (P = 0.042). Quantitative polymerase chain reaction showed that individuals with the G allele had lower levels of CHEK2 transcripts in peripheral blood mononuclear cells and normal lung tissues. The –48 G->A variant eliminated a methylation site and thereby relieve the transcriptional repression of CHEK2. Therefore, this polymorphism affected downstream transcription through genetic and epigenetic modifications. Luciferase reporter assays demonstrated that the major G allele significantly attenuated reporter gene expression when methylated. Electrophoretic Mobility shift assays and surface plasmon resonance revealed that the methylated G allele increased transcription factor accessibility. We used in vivo chromatin immunoprecipitation to confirm that the relevant transcription factor was Sp1. Using lung tissue heterozygous for the G/A single-nucleotide polymorphism, we found that Sp1 acted as a repressor and had a stronger binding affinity for the G allele. These results support our hypothesis that the CHEK2 rs2236141 variant modifies lung cancer susceptibility in the Chinese population by affecting CHEK2 expression.

  L Ding , L Dong , X Chen , L Zhang , X Xu , A Ferro and B. Xu
 

Background— Left ventricular (LV) remodeling is associated with the development of heart failure after myocardial infarction. Here we investigated whether integrin-linked kinase (ILK) may regulate LV remodeling and function after myocardial infarction.

Methods and Results— Adenoviral vector expressing ILK (n=25) or empty adeno-null (n=25) was injected into rat peri-infarct myocardium after left anterior descending coronary artery ligation. ILK expression was confirmed by Western blotting and immunofluorescence. Echocardiographic and hemodynamic analyses demonstrated relatively preserved cardiac function in adeno-ILK animals. ILK treatment was associated with reduced infarct scar size, increased scar thinning ratio, and preserved LV diameter, wall thickness, cardiomyocyte size, and myofilament density. Enhanced angiogenesis and reduced fibrosis were observed in the adeno-ILK group, along with reduced apoptosis as demonstrated by terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling analysis. Moreover, increased cardiomyocyte proliferation was found in adeno-ILK animals, as measured by proliferating cell nuclear antigen, Ki-67, and phosphohistone-H3 staining. At long-term follow-up, most indices of cardiac function and hemodynamics showed no difference between adeno-ILK and control animals by 9 weeks, although LV end-systolic diameter and infarct scar size were reduced in the adeno-ILK group at this time point. Additionally, ILK overexpression was found to exert a rescue effect on remodeling when administered in a delayed fashion 1 week after coronary artery ligation.

Conclusions— ILK gene therapy improves cardiac remodeling and function in rats after myocardial infarction and is associated with increased angiogenesis, reduced apoptosis, and increased cardiomyocyte proliferation. This may represent a new approach to the treatment of postinfarct remodeling and subsequent heart failure.

  Q Liu , X Chen , S. M MacDonnell , E. G Kranias , J. N Lorenz , M Leitges , S. R Houser and J. D. Molkentin
 

Protein kinase (PK)C, PKCβ, and PKC comprise the conventional PKC isoform subfamily, which is thought to regulate cardiac disease responsiveness. Indeed, mice lacking the gene for PKC show enhanced cardiac contractility and reduced susceptibility to heart failure. Recent data also suggest that inhibition of conventional PKC isoforms with Ro-32-0432 or Ro-31-8220 enhances heart function and antagonizes failure, although the isoform responsible for these effects is unknown. Here, we investigated mice lacking PKC, PKCβ, and PKC for effects on cardiac contractility and heart failure susceptibility. PKC–/– mice, but not PKCβ–/– mice, showed increased cardiac contractility, myocyte cellular contractility, Ca2+ transients, and sarcoplasmic reticulum Ca2+ load. PKC–/– mice were less susceptible to heart failure following long-term pressure-overload stimulation or 4 weeks after myocardial infarction injury, whereas PKCβ–/– mice showed more severe failure. Infusion of ruboxistaurin (LY333531), an orally available PKC/β/ inhibitor, increased cardiac contractility in wild-type and PKCβ–/– mice, but not in PKC–/– mice. More importantly, ruboxistaurin prevented death in wild-type mice throughout 10 weeks of pressure-overload stimulation, reduced ventricular dilation, enhanced ventricular performance, reduced fibrosis, and reduced pulmonary edema comparable to or better than metoprolol treatment. Ruboxistaurin was also administered to PKCβ–/– mice subjected to pressure overload, resulting in less death and heart failure, implicating PKC as the primary target of this drug in mitigating heart disease. As an aside, PKCβ triple-null mice showed no defect in cardiac hypertrophy following pressure-overload stimulation. In conclusion, PKC functions distinctly from PKCβ and PKC in regulating cardiac contractility and heart failure, and broad-acting PKC inhibitors such as ruboxistaurin could represent a novel therapeutic approach in treating human heart failure.

  Z Liu , S Yue , X Chen , T Kubin and T. Braun
 

Rationale: Polyploidy and multinucleation are characteristic features of mammalian cardiomyocytes, which develop shortly after birth when most differentiated cardiomyocytes become acytokinetic. Cardiac overload and hypertrophy further increase the degree of polyploidy of cardiomyocytes, suggesting a role in cell type–specific responses to physiological and pathological stimuli.

Objective: We sought to study the function of cyclinG1 in the regulation of polyploidy and multinucleation in cardiomyocytes.

Methods and Results: We found that expression of cyclinG1, a transcriptional target of p53, coincides with arrest of cardiomyocyte proliferation and onset of polyploidization. Overexpression of cyclinG1 promoted DNA synthesis but inhibited cytokinesis in neonatal cardiomyocytes leading to an enlarged population of binuclear cardiomyocytes. Reciprocally, inactivation of the cyclinG1 gene in mice lowered the degree of polyploidy and multinucleation in cardiomyocytes. Moreover, lack of cyclinG1 prevented the increase of polynucleated cardiomyocytes in response to pressure overload and hypertrophy.

Conclusions: CyclinG1 is an important player for the regulation of polyploidy and multinucleation in cardiomyocytes probably by inhibition of apoptosis caused by checkpoint activation.

  J Luan , J Yuan , X Li , S Jin , L Yu , M Liao , H Zhang , C Xu , Q He , B Wen , X Zhong , X Chen , H. L.Y Chan , J. J.Y Sung , B Zhou and C. Ding
 

Background: Variations in the hepatitis B virus (HBV) genome may develop spontaneously or under selective pressure from antiviral therapy. Such variations may confer drug resistance or affect virus replication capacity, resulting in failure of antiviral therapy.

Methods: A duplex PCR was used to amplify the region of the reverse transcriptase gene, the precore promoter, and the basal core promoter of the HBV genome. Four multiplex primer-extension reactions were used to interrogate 60 frequently observed HBV variants during antiviral therapy. Automated MALDI-TOF mass spectrometry (MS) was used for mutation detection. Capillary sequencing was used to confirm the MS results.

Results: The limit of quantification was 1000 HBV copies/mL for multiplex detection of HBV variants. Fifty-three variants (88.3%) were analyzed successfully in at least 90% of the sera from 88 treatment-naive patients and 80 patients with virologic breakthrough. MS was able to detect twice as many minor variants as direct sequencing while achieving close to full automation. MS and direct sequencing showed only 0.1% discordance in variant calls.

Conclusions: This platform based on multiplex primer extension and MALDI-TOF MS was able to detect 60 HBV variants in 4 multiplex reactions with accuracy and low detection limits.

  C Zhang , C Wang , X Chen , C Yang , K Li , J Wang , J Dai , Z Hu , X Zhou , L Chen , Y Zhang , Y Li , H Qiu , J Xing , Z Liang , B Ren , K Zen and C. Y. Zhang
  BACKGROUND:

Sensitive and specific biomarkers for the early detection of esophageal squamous cell carcinoma (ESCC) are urgently needed to reduce the high morbidity and mortality of the disease. The discovery of serum microRNAs (miRNAs) and their unique concentration profiles in patients with various diseases makes them attractive, novel noninvasive biomarkers for tumor diagnosis. In this study, we investigated the serum miRNA profile in ESCC patients to develop a novel diagnostic ESCC biomarker.

METHODS:

Serum samples were taken from 290 ESCC patients and 140 age- and sex-matched controls. Solexa sequencing technology was used for an initial screen of miRNAs in serum samples from 141 patients and 40 controls. A hydrolysis probe–based stem–loop quantitative reverse-transcription PCR (RT-qPCR) assay was conducted in the training and verification phases to confirm the concentrations of selected miRNAs in serum samples from 149 patients and 100 controls.

RESULTS:

The Solexa sequencing results demonstrated marked upregulation of 25 serum miRNAs in ESCC patients compared with controls. RT-qPCR analysis identified a profile of 7 serum miRNAs (miR-10a, miR-22, miR-100, miR-148b, miR-223, miR-133a, and miR-127-3p) as ESCC biomarkers. The area under the ROC curve for the selected miRNAs ranged from 0.817 to 0.949, significantly higher than for carcinoembryonic antigen (0.549; P < 0.0005). More importantly, this panel of 7 miRNAs clearly distinguished stage I/II ESCC patients from controls.

CONCLUSIONS:

This panel of 7 serum miRNAs holds promise as a novel blood-based biomarker for the diagnosis of ESCC.

  X Chen , F Gu and D. Xie
 

We describe a case of successful vegetectomy of the aortic valves for early infective endocarditis. An aortic vegetectomy was performed as an alternative to valve replacement for a 54-year-old man with three vegetations and mild regurgitation in aortic valve due to infective endocarditis. Postoperative clinical course was without signs of recurrent infection after follow-up of 19 months, and transesophageal echocardiography demonstrated aortic valve competence. We would suggest that vegetectomy with valve sparing may be a viable option in the context of early infective endocarditis involved aortic valve in selected patients.

  H Song , S. J Ramus , S. K Kjaer , R. A DiCioccio , G Chenevix Trench , C. L Pearce , E Hogdall , A. S Whittemore , V McGuire , C Hogdall , J Blaakaer , A. H Wu , D. J Van Den Berg , D. O Stram , U Menon , A Gentry Maharaj , I. J Jacobs , P. M Webb , J Beesley , X Chen , The Australian Ovarian Cancer Study Group the Australian Cancer (Ovarian) Study , J. A Doherty , J Chang Claude , S Wang Gohrke , M. T Goodman , G Lurie , P. J Thompson , M. E Carney , R. B Ness , K Moysich , E. L Goode , R. A Vierkant , J. M Cunningham , S Anderson , J. M Schildkraut , A Berchuck , E. S Iversen , P. G Moorman , M Garcia Closas , S Chanock , J Lissowska , L Brinton , H Anton Culver , A Ziogas , W. R Brewster , B. A.J Ponder , D. F Easton , S. A Gayther , P. D.P Pharoah and on behalf of the Ovarian Cancer Association Consortium (OCAC)
 

Because both ovarian and breast cancer are hormone-related and are known to have some predisposition genes in common, we evaluated 11 of the most significant hits (six with confirmed associations with breast cancer) from the breast cancer genome-wide association study for association with invasive ovarian cancer. Eleven SNPs were initially genotyped in 2927 invasive ovarian cancer cases and 4143 controls from six ovarian cancer case–control studies. Genotype frequencies in cases and controls were compared using a likelihood ratio test in a logistic regression model stratified by study. Initially, three SNPs (rs2107425 in MRPL23, rs7313833 in PTHLH, rs3803662 in TNRC9) were weakly associated with ovarian cancer risk and one SNP (rs4954956 in NXPH2) was associated with serous ovarian cancer in non-Hispanic white subjects (P-trend < 0.1). These four SNPs were then genotyped in an additional 4060 cases and 6308 controls from eight independent studies. Only rs4954956 was significantly associated with ovarian cancer risk both in the replication study and in combined analyses. This association was stronger for the serous histological subtype [per minor allele odds ratio (OR) 1.07 95% CI 1.01–1.13, P-trend = 0.02 for all types of ovarian cancer and OR 1.14 95% CI 1.07–1.22, P-trend = 0.00017 for serous ovarian cancer]. In conclusion, we found that rs4954956 was associated with increased ovarian cancer risk, particularly for serous ovarian cancer. However, none of the six confirmed breast cancer susceptibility variants we tested was associated with ovarian cancer risk. Further work will be needed to identify the causal variant associated with rs4954956 or elucidate its function.

  J Fu , X Chen , Y Zhang , H Gu and Y. Bai
  Objective

To investigate the possible role of CD147 and vascular endothelial growth factor in progression and prognosis of acute myeloid leukemia.

Methods

Immunohistochemical staining was performed to detect the expression of CD147 and vascular endothelial growth factor in paraffin-embedded sections from 62 bone marrow biopsies obtained from an equal number of patients with newly diagnosed acute myeloid leukemia.

Results

CD147 and vascular endothelial growth factor expression in the bone marrow of acute myeloid leukemia patients were significantly higher than those in normal controls (both P < 0.001). Expression of them was significantly increased in patients with a high degree of microvessel density compared with those with a low degree (CD147: P = 0.009; vascular endothelial growth factor: P = 0.01) and correlated well with bone marrow microvessel density (CD147: P = 0.01; vascular endothelial growth factor: P = 0.02). In addition, higher levels of CD147 and vascular endothelial growth factor were also found in acute myeloid leukemia patients with an unfavorable karyotype compared with those with intermediate and favorable karyotypes (both P = 0.01). Moreover, the expression of CD147 was significantly correlated with that of vascular endothelial growth factor (P < 0.001). Furthermore, the co-expression of CD147 and vascular endothelial growth factor in the bone marrow indicated a poor prognosis in acute myeloid leukemia and was an independent prognostic factor for overall survival by multivariate analysis.

Conclusions

Our data show for the first time that the co-expression of CD147 and vascular endothelial growth factor may indicate a poor prognosis in acute myeloid leukemia and may be a highly sensitive marker for predicting the clinical outcome of patients.

  V Dubois , C Van Ginneken , H De Cock , A. M Lambeir , P Van der Veken , K Augustyns , X Chen , S Scharpe and I. De Meester
 

The mRNA expression pattern of dipeptidyl peptidase (DPP) 8 and DPP9, two DPP4 homologs, was studied previously and showed a broad tissue distribution. In this study, protein expression and activity of DPP8 and DPP9 were investigated in male reproductive tissues of different mammals. Based on specific DPP activities and inhibition profiles, the proline-selective DPP activity in the bovine and rat testis could predominantly be attributed to DPP8/9 and not to DPP4. This is in contrast to the epididymis, where most of the activity was caused by DPP4. Bovine sperm preparations had very low or undetectable DPP8/9 activity. After characterization of polyclonal antibodies specific for DPP8 or DPP9, we could localize both enzymes in seminiferous tubules of the testis. A specific staining for DPP9 was found associated with spermatozoids embedded in the epithelium, just before their release into the lumen, and in spermatids. DPP8 was localized in spermatozoids in an earlier stage of maturation. These findings help to provide insight into the physiological role of DPP4-like enzymes in the male reproductive system. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials. (J Histochem Cytochem 57:531–541, 2009)

  M Liao , X Chen , J Han , S Yang , T Peng and H. Li
 

Huntingtin-associated protein-1 (HAP1) was initially identified as a binding partner of huntingtin, the Huntington's disease protein. Based on its preferred distribution among neurons and endocrine cells, HAP1 has been suggested to play roles in vesicular transportation in neurons and hormonal secretion of endocrine cells. Given that HAP1 is selectively expressed in the islets of rat pancreas, in this study, we analyzed the expression pattern of HAP1 in the islets. In rats injected intraperitoneally with streptozotocin, which can selectively destroy β-cells of the pancreatic islets, the number of HAP1 immunoreactive cells was dramatically decreased and was accompanied by a parallel decrease in the number of insulin-immunoreactive cells. Immunofluorescent double staining of pancreas sections showed that, in rat islets, HAP1 is selectively expressed in the insulin-immunoreactive β-cells but not in the glucagon-immunoreactive -cells and somatostatin immunoreactive -cells. In isolated rat pancreatic islets, ~80% of cells expressed both HAP1 and insulin. Expression of HAP1 in the INS-1 rat insulinoma cell line was also demonstrated by immunofluorescent staining. Western blotting further revealed that HAP1 in both the isolated rat pancreatic islets and the INS-1 cells also has two isoforms, HAP1A and HAP1B, which are the same as those in the hypothalamus. These results demonstrated that HAP1 is selectively expressed in β-cells of rat pancreatic islets, suggesting the involvement of HAP1 in the regulation of cellular trafficking and secretion of insulin. (J Histochem Cytochem 58:255–263, 2010)

  H Jing , H Liu , D. F Bird , T. H. C Wong , X Chen and B. Chen
 

Phylogenetic diversity (18S rRNA gene) of picoeukaryotes in Hong Kong coastal waters is dominated by heterotrophic forms and influenced by the seasonally driven combination of freshwater discharge from the Pearl River, oceanic water of the South China Sea and coastal water from the China Coastal Current.

  M Ghadami , E El Demerdash , S.A Salama , A.A Binhazim , A.E Archibong , X Chen , B.R Ballard , M.R Sairam and A. Al Hendy
 

A homozygous missense mutation, C566T, in the follicle stimulation hormone receptor (FSHR) gene has been linked to premature ovarian failure. The disease leads to infertility in a normal karyotype female with an elevated follicle stimulating hormone (FSH) and decreased serum estrogen level. Female mice carrying mutated FSHR gene, called follitropin receptor knockout (FORKO), display similar phenotype and are sterile because of a folliculogenesis block at a primary stage. We investigated the effects of bilateral intra-ovarian injection of an adenovirus expressing a normal copy of human FSHR on the reproductive system of 6–10 weeks female FORKO mice. Ad-LacZ was injected directly into each ovary of the control group. Animals were sacrificed at 2, 4, 8 and 12 weeks post-injection and tissues collected for evaluation. Treated mice showed estrogenic changes in daily vaginal smear whereas control animals remained fixated in the diestrus stage. Histological evaluation showed on average 26 ± 4 follicles/ovary in treated group with 8 ± 2 follicles at the antral stage compared with only 5 ± 2 with zero follicles at antral stage in Ad-LacZ control mice. There was no significant change in serum level of progesterone, however, estrogen level increased 2–3-fold (P < 0.02) and FSH decreased by up to 50% (P < 0.04) in treated animals. FSHR mRNA was detected in the ovaries of the treated group. In conclusion, intra-ovarian injection of an adenovirus expressing human FSHR gene is able to restore FSH responsiveness and reinitiate ovarian folliculogenesis as well as resume estrogen production in female FORKO mice. Ad-LacZ injections indicate the absence of systemic viral dissemination or germ line transmission of adenovirus DNA to offspring.

  S Li , Q Wang , Y Wang , X Chen and Z. Wang
 

It is well established that epidermal growth factor (EGF) induces the cytoskeleton reorganization and cell migration through two major signaling cascades: phospholipase C-1 (PLC-1) and Rho GTPases. However, little is known about the cross talk between PLC-1 and Rho GTPases. Here we showed that PLC-1 forms a complex with Rac1 in response to EGF. This interaction is direct and mediated by PLC-1 Src homology 3 (SH3) domain and Rac1 106PNTP109 motif. This interaction is critical for EGF-induced Rac1 activation in vivo, and PLC-1 SH3 domain is actually a potent and specific Rac1 guanine nucleotide exchange factor in vitro. We have also demonstrated that the interaction between PLC-1 SH3 domain and Rac1 play a significant role in EGF-induced F-actin formation and cell migration. We conclude that PLC-1 and Rac1 coregulate EGF-induced cell cytoskeleton remodeling and cell migration by a direct functional interaction.

  X Chen , Z Liu and J. Xu
 

Nuclear receptor coactivator 1 [NCOA1/steroid receptor coactivator (SRC)-1] and NCOA3 (SRC-3/AIB1/ACTR) constitute two thirds of the SRC (steroid receptor coactivator) family. Although in vitro experiments have suggested overlapping functions between NCOA1 and NCOA3, their in vivo functional relationship is poorly understood. In this study, NCOA1 and NCOA3 double knockout mice were generated to determine the compensatory roles of NCOA1 and NCOA3 in development. NCOA1–/– mice survived normally, whereas most NCOA3–/– embryos were viable at embryonic d 13.5 (E13.5). In contrast, the majority of double-knockout (DKO) embryos died by E13.5. NCOA1 and NCOA3 are expressed in the labyrinth, and labyrinths of NCOA1+/–;NCOA3–/– and DKO placentas were small compared with wild-type and single-knockout labyrinths. DKO labyrinths exhibited low densities of maternal blood sinuses and fetal capillaries and displayed fetomaternal blood transfusion. At the interface between maternal and fetal circulations, layer I sinusoidal trophoblast giant cells showed a reduced density of microvilli. Layer III syncytiotrophoblasts appeared to accumulate large lipid droplets and have reduced density and deepened invaginations of the intrasyncytial bays. The endothelial layer in DKO labyrinth showed abnormal morphologies and had large lipid droplets. Furthermore, disruption of NCOA1 and NCOA3 increased labyrinth trophoblast proliferation and their progenitor gene expression but decreased their differentiation gene expression. NCOA1 and NCOA3 deficiencies also affected the expression of several genes for placental morphogenesis including TGFβ-, peroxisome proliferator-activated receptor-β-, and peroxisome proliferator-activated receptor--regulated genes and for glucose transportation including GLUT1 and Cx26. These findings demonstrate that NCOA1 and NCOA3 cooperatively regulate placental morphogenesis and embryo survival.

  Y Li , W Pan , W Xu , N He , X Chen , H Liu , L Darryl Quarles , H Zhou and Z. Xiao
 

Cleidocranial dysplasia (CCD) is an autosomal dominant bone disease in humans caused by haploinsufficiency of the RUNX2 gene. The RUNX2 has two major isoforms derived from P1 and P2 promoters. Over 90 mutations of RUNX2 have been reported associated with CCD. In our study, DNA samples of nine individuals from three unrelated CCD families were collected and screened for all exons of RUNX2 and 2 kb of P1 and P2 promoters. We identified two point mutations in the RUNX2 gene in Case 1, including a nonsense mutation (c.577C>T) that has been reported previously and a silent substitution (c.240G>A). In vitro studies demonstrated that c.577C>T mutation led to truncated RUNX2 protein production and diminished stimulating effects on mouse osteocalcin promoter activity when compared with full-length Runx2-II and Runx2-I isoforms. These results confirm that loss of function RUNX2 mutation (c.577C>T) in Case 1 family is responsible for its CCD phenotype.

  H Zhang , X Chen , W. B Bollag , R. J Bollag , D. J Sheehan and C. S. Chew
 

Lasp1 is an actin-binding, signaling pathway-regulated phosphoprotein that is overexpressed in several cancers. siRNA knockdown in cell lines retards cell migration, suggesting the possibility that Lasp1 upregulation influences cancer metastasis. Herein, we utilized a recently developed gene knockout model to assess the role of Lasp1 in modulating nontransformed cell functions. Wound healing and tumor initiation progressed more rapidly in Lasp1–/– mice compared with Lasp1+/+ controls. Embryonic fibroblasts (MEFs) derived from Lasp1–/– mice also migrated more rapidly in vitro. These MEFs characteristically possessed increased focal adhesion numbers and displayed more rapid attachment compared with wild-type MEFs. Differential microarray analyses revealed alterations in message expression for proteins implicated in cell migration, adhesion, and cytoskeletal organization. Notably, the focal adhesion protein, lipoma preferred partner (LPP), a zyxin family member and putative Lasp1 binding protein, was increased about twofold. Because LPP gene disruption reduces cell migration, we hypothesize that LPP plays a role in enhancing the migratory capacity of Lasp1–/– MEFs, perhaps by modifying the subcellular localization of other motility-associated proteins. The striking contrast in the functional effects of loss of Lasp1 in innate cells compared with cell lines reveals distinct differences in mechanisms of motility and attachment in these models.

  W Cai , M Torreggiani , L Zhu , X Chen , J. C He , G. E Striker and H. Vlassara
 

Advanced glycated end-product receptor 1 (AGER1) protects against vascular disease promoted by oxidants, such as advanced glycated end products (AGEs), via inhibition of reactive oxygen species (ROS). However, the specific AGEs, sources, and pathways involved remain undefined. The mechanism of cellular NADPH oxidase (NOX)-dependent ROS generation by defined AGEs, N-carboxymethyl-lysine- and methylglyoxal (MG)-modified BSA, was assessed in AGER1 overexpressing (AGER1+ EC) or knockdown (sh-mRNA-AGER1+ EC) human aortic endothelial (EC) and ECV304 cells, and aortic segments from old (18 mo) C57BL6-F2 mice, propagated on low-AGE diet (LAGE), or LAGE supplemented with MG (LAGE+MG). Wild-type EC and sh-mRNA-AGER1+ EC, but not AGER1+ EC, had high NOX p47phox and gp91phox activity, superoxide anions, and NF-B p65 nuclear translocation in response to MG and N-carboxymethyl-lysine. These events involved epidermal growth factor receptor-dependent PKC- redox-sensitive Tyr-311 and Tyr-332 phosphorylation and were suppressed in AGER1+ ECs and enhanced in sh-mRNA-AGER1+ ECs. Aortic ROS, PKC- Tyr-311, and Tyr-332 phosphorylation, NOX expression, and nuclear p65 in older LAGE+MG mice were significantly increased above that in age-matched LAGE mice, which had higher levels of AGER1. In conclusion, circulating AGEs induce NADPH-dependent ROS generation in vascular aging in both in vitro and in vivo models. Furthermore, AGER1 provides protection against AGE-induced ROS generation via NADPH.

  L Xue , F Zhang , X Chen , J Lin and J. Shi
 

The insertion of amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors into the plasma membrane and removal via internalization are essential for regulating synaptic strength, which underlies the basic mechanism of learning and memory. The retinocollicular pathway undergoes synaptic refinement during development and shows a wide variety of long-term synaptic changes; however, still little is known about its underlying molecular regulation. Here we report a rapid developmental long-term potentiation (LTP)/long-term depression (LTD) switch and its intracellular mechanism at the rat retinocollicular pathway from postnatal day 5 (P5) to P14. Before P9, neurons always exhibited LTP, whereas LTD was observed only after P10. Blockade of GluR2/3-glutamate receptor-interacting protein (GRIP)/AMPA-receptor-binding protein (ABP)/protein interacting with C kinase 1 (PICK1) interactions with pep2-SVKI could sustain the LTP after P10. This suggests that the LTP/LTD switch relied on PDZ protein activities. Selective interruption of GluR2/3-PICK1 binding by pep2-EVKI blocked the long-lasting effects of both LTP and LTD, suggesting a role for PICK1 in the maintenance of long-term synaptic plasticity. Interestingly, synaptic expression of GRIP increased more than twofold from P7 to P11, whereas ABP and PICK1 expression levels remained stable. Blockade of spontaneous retinal input suppressed this increase and abolished the LTP/LTD switch. These results suggest that the increased GRIP synaptic expression may be a key regulatory factor in mediating the activity-dependent developmental LTP/LTD switch, whereas PICK1 may be required for both LTP and LTD to maintain their long-term effects.

  X Hu , S Kang , X Chen , C. B Shoemaker and M. M. Jin
 

A quantitative in vivo method for detecting protein-protein interactions will enhance our understanding of protein interaction networks and facilitate affinity maturation as well as designing new interaction pairs. We have developed a novel platform, dubbed "yeast surface two-hybrid (YS2H)," to enable a quantitative measurement of pairwise protein interactions via the secretory pathway by expressing one protein (bait) anchored to the cell wall and the other (prey) in soluble form. In YS2H, the prey is released either outside of the cells or remains on the cell surface by virtue of its binding to the bait. The strength of their interaction is measured by antibody binding to the epitope tag appended to the prey or direct readout of split green fluorescence protein (GFP) complementation. When two -helices forming coiled coils were expressed as a pair of prey and bait, the amount of the prey in complex with the bait progressively decreased as the affinity changes from 100 pm to 10 µm. With GFP complementation assay, we were able to discriminate a 6-log difference in binding affinities in the range of 100 pm to 100 µm. The affinity estimated from the level of antibody binding to fusion tags was in good agreement with that measured in solution using a surface plasmon resonance technique. In contrast, the level of GFP complementation linearly increased with the on-rate of coiled coil interactions, likely because of the irreversible nature of GFP reconstitution. Furthermore, we demonstrate the use of YS2H in exploring the nature of antigen recognition by antibodies and activation allostery in integrins and in isolating heavy chain-only antibodies against botulinum neurotoxin.

  B Ji , S Gaiser , X Chen , S. A Ernst and C. D. Logsdon
 

Premature intracellular activation of the digestive enzyme trypsinogen is considered to be the initiating event in pancreatitis. However, the direct consequences of intracellular trypsin activity have not previously been examined. In the current study, a mutant trypsinogen (paired basic amino acid cleaving enzyme (PACE)-trypsinogen), which is activated intracellularly by the endogenous protease PACE, was developed. This new construct allowed for the first time direct examination of the effects of intracellular trypsin on pancreatic acinar cells. We found that PACE-trypsinogen was expressed in the secretory pathway and was activated within acinar cells. Expression of PACE-trypsinogen induced apoptosis of HEK293 cells and pancreatic acinar cells, as indicated by histology, DNA laddering, PARP cleavage, and caspase-3 activation. Cell death was blocked by the trypsin inhibitor Pefabloc but not by the pancaspase inhibitor benzyloxycarbonyl-VAD, indicating that caspase-independent pathways were also involved. However, intracellular trypsin had no significant effect on the activity of the proinflammatory transcription factor NF-B. In contrast, extracellular trypsin caused cell damage and dramatically increased NF-B activity. These data indicate that localization of active trypsin determines its effects on pancreatic acinar cells. This new model will greatly improve our understanding of the role of active trypsin in pancreatitis and its associated inflammatory response.

  T. P Abeyweera , X Chen and S. A. Rotenberg
 

Engineered overexpression of protein kinase C (PKC) was previously shown to endow nonmotile MCF-10A human breast cells with aggressive motility. A traceable mutant of PKC (Abeyweera, T. P., and Rotenberg, S. A. (2007) Biochemistry 46, 2364–2370) revealed that 6-tubulin is phosphorylated in cells expressing traceable PKC and in vitro by wild type PKC. Gain-of-function, single site mutations (Ser -> Asp) were constructed at each PKC consensus site in 6-tubulin (Ser158, Ser165, Ser241, and Thr337) to simulate phosphorylation. Following expression of each construct in MCF-10A cells, motility assays identified Ser165 as the only site in 6-tubulin whose pseudophosphorylation reproduced the motile behavior engendered by PKC. Expression of a phosphorylation-resistant mutant (S165N-6-tubulin) resulted in suppression of MCF-10A cell motility stimulated either by expression of PKC or by treatment with PKC-selective activator diacylglycerol-lactone. MCF-10A cells treated with diacylglycerol-lactone showed strong phosphorylation of endogenous -tubulin that could be blocked when S165N-6-tubulin was expressed. The S165N mutant also inhibited intrinsically motile human breast tumor cells that express high endogenous PKC levels (MDA-MB-231 cells) or lack PKC and other conventional isoforms (MDA-MB-468 cells). Comparison of Myc-tagged wild type 6-tubulin and S165N-6-tubulin expressed in MDA-MB-468 cells demonstrated that Ser165 is also a major site of phosphorylation for endogenously active, nonconventional PKC isoforms. PKC-stimulated motility of MCF-10A cells was nocodazole-sensitive, thereby implicating microtubule elongation in the mechanism. These findings support a model in which PKC phosphorylates -tubulin at Ser165, leading to microtubule elongation and motility.

  M Oser , H Yamaguchi , C. C Mader , J.J Bravo Cordero , M Arias , X Chen , V DesMarais , J van Rheenen , A. J Koleske and J. Condeelis
 

Invadopodia are matrix-degrading membrane protrusions in invasive carcinoma cells. The mechanisms regulating invadopodium assembly and maturation are not understood. We have dissected the stages of invadopodium assembly and maturation and show that invadopodia use cortactin phosphorylation as a master switch during these processes. In particular, cortactin phosphorylation was found to regulate cofilin and Arp2/3 complex–dependent actin polymerization. Cortactin directly binds cofilin and inhibits its severing activity. Cortactin phosphorylation is required to release this inhibition so cofilin can sever actin filaments to create barbed ends at invadopodia to support Arp2/3-dependent actin polymerization. After barbed end formation, cortactin is dephosphorylated, which blocks cofilin severing activity thereby stabilizing invadopodia. These findings identify novel mechanisms for actin polymerization in the invadopodia of metastatic carcinoma cells and define four distinct stages of invadopodium assembly and maturation consisting of invadopodium precursor formation, actin polymerization, stabilization, and matrix degradation.

  R. E Taylor , C. J Gregg , V Padler Karavani , D Ghaderi , H Yu , S Huang , R. U Sorensen , X Chen , J Inostroza , V Nizet and A. Varki
 

The nonhuman sialic acid N-glycolylneuraminic acid (Neu5Gc) is metabolically incorporated into human tissues from certain mammalian-derived foods, and this occurs in the face of an anti-Neu5Gc "xeno-autoantibody" response. Given evidence that this process contributes to chronic inflammation in some diseases, it is important to understand when and how these antibodies are generated in humans. We show here that human anti-Neu5Gc antibodies appear during infancy and correlate with weaning and exposure to dietary Neu5Gc. However, dietary Neu5Gc alone cannot elicit anti-Neu5Gc antibodies in mice with a humanlike Neu5Gc deficiency. Other postnatally appearing anti-carbohydrate antibodies are likely induced by bacteria expressing these epitopes; however, no microbe is known to synthesize Neu5Gc. Here, we show that trace exogenous Neu5Gc can be incorporated into cell surface lipooligosaccharides (LOS) of nontypeable Haemophilus influenzae (NTHi), a human-specific commensal/pathogen. Indeed, infant anti-Neu5Gc antibodies appear coincident with antibodies against NTHi. Furthermore, NTHi that express Neu5Gc-containing LOS induce anti-Neu5Gc antibodies in Neu5Gc-deficient mice, without added adjuvant. Finally, Neu5Gc from baby food is taken up and expressed by NTHi. As the flora residing in the nasopharynx of infants can be in contact with ingested food, we propose a novel model for how NTHi and dietary Neu5Gc cooperate to generate anti-Neu5Gc antibodies in humans.

 
 
 
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