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Articles by D Lu
Total Records ( 5 ) for D Lu
  C Wu , Z Hu , D Yu , L Huang , G Jin , J Liang , H Guo , W Tan , M Zhang , J Qian , D Lu , T Wu , D Lin and H. Shen
 

Recent three genome-wide association studies have mapped a lung cancer susceptibility locus to chromosome 15q25 in Caucasians. However, the reported risk single nucleotide polymorphisms (SNPs) are extremely rare in Asians, arguing against any of these being causative variants. This study sought to identify other variants on 15q25 associated with lung cancer susceptibility in Chinese. Two-stage case-control studies were conducted in subjects derived from both Northern and Southern China. The first-stage, consisting of 576 cases and 576 controls, was to discover novel risk variants using a haplotype-tagging SNP approach, and these variants were then replicated in the second-stage, consisting of 2,989 cases and 2,880 controls. Associations were estimated by logistic regression models, and function of the variants was examined by biochemical assays. We found that the three risk SNPs reported in Caucasians were not associated with lung cancer risk in Chinese. However, we identified four novel SNPs (rs2036534C>T, rs667282C>T, rs12910984G>A, and rs6495309T>C) that were associated with significantly increased lung cancer risk and smoking behavior, which were all confirmed in the replication analyses [odds ratios (95% confidence intervals) in the dominant model: 1.39 (1.23–1.57; P = 2.3 x 10–7), 1.52 (1.35–1.71; P = 2.0 x 10–12), 1.44 (1.28–1.63; P = 2.7 x 10–9), and 1.43 (1.27–1.61; P = 2.6 x 10–9), respectively]. We characterized the rs6495309T>C change in the CHRNA3 promoter as a functional variant because it affected the Oct-1 binding ability, resulting in increased CHRNA3 expression. These results support 15q25 as a susceptibility region for lung cancer in Chinese but underscore the difference in genetic markers among different ethnic populations. [Cancer Res 2009;69(12):5065–72]

  J Liu , C Huan , M Chakraborty , H Zhang , D Lu , M. S Kuo , G Cao and X. C. Jiang
 

Rationale: Sphingomyelin synthase (SMS)2 contributes to de novo sphingomyelin (SM) biosynthesis and plasma membrane SM levels. SMS2 deficiency in macrophages diminishes nuclear factor B and mitogen-activated protein kinase activation induced by inflammatory stimuli.

Objective: The effects of SMS2 deficiency on the development of atherosclerosis are investigated.

Methods and Results: We measured cholesterol efflux from macrophages of wild-type (WT) and SMS2 knockout (KO) mice. We transplanted SMS2 KO mouse bone marrow into low-density lipoprotein (LDL) receptor (LDLr) knockout mice (SMS2–/–->LDLr–/–), creating a mouse model of SMS2 deficiency in the macrophages. We found that SMS2 deficiency caused significant induction of cholesterol efflux in vitro and in vivo. Moreover, we found that SMS2 KO mice had less interleukin-6 and tumor necrosis factor in the circulation before and after endotoxin stimulation, compared with controls. More importantly, after 3 months on a western-type diet, SMS2–/–->LDLr–/– mice showed decreased atherosclerotic lesions in the aortic arch, root (57%, P<0.001), and the entire aorta (42%, P<0.01), compared with WT->LDLr–/– mice. Analysis of plaque morphology revealed that SMS2–/–->LDLr–/– mice had significantly less necrotic core area (71%, P<0.001), less macrophage content (37%, P<0.01), and more collagen content (35%, P<0.05) in atherosclerotic lesions. We also found that SMS2–/–->LDLr–/– mice had significantly lower free cholesterol and cholesteryl ester levels in the brachiocephalic artery than WT->LDLr–/– mice (33 and 52%, P<0.01 and P<0.001, respectively).

Conclusions: SMS2 deficiency in the macrophages reduces atherosclerosis in mice. Macrophage SMS2 is thus a potential therapeutic target for treatment of this disease.

  D Lu , S Fillet , C Meng , Y Alguel , P Kloppsteck , J Bergeron , T Krell , M. T Gallegos , J Ramos and X. Zhang
 

The majority of bacterial gene regulators bind as symmetric dimers to palindromic DNA operators of 12–20 base pairs (bp). Multimeric forms of proteins, including tetramers, are able to recognize longer operator sequences in a cooperative manner, although how this is achieved is not well understood due to the lack of complete structural information. Models, instead of structures, of complete tetrameric assembly on DNA exist in literature. Here we present the crystal structures of the multidrug-binding protein TtgV, a gene repressor that controls efflux pumps, alone and in complex with a 42-bp DNA operator containing two TtgV recognition sites at 2.9 Å and 3.4 Å resolution. These structures represent the first full-length functional tetrameric protein in complex with its intact DNA operator containing two continuous recognition sites. TtgV binds to its DNA operator as a highly asymmetric tetramer and induces considerable distortions in the DNA, resulting in a 60° bend. Upon binding to its operator, TtgV undergoes large conformational changes at the monomeric, dimeric, and tetrameric levels. The structures here reveal a general model for cooperative DNA binding of tetrameric gene regulators and provide a structural basis for a large body of biochemical data and a reinterpretation of previous models for tetrameric gene regulators derived from partial structural data.

  S. M Malakauskas , W. M Kourany , X. Y Zhang , D Lu , R. D Stevens , T. R Koves , H. E Hohmeier , D. M Muoio , C. B Newgard and T. H. Le
 

Collectrin is a downstream target of the transcription factor hepatocyte nuclear factor-1 (HNF-1), which is mutated in maturity-onset diabetes of the young subtype 3 (MODY3). Evidence from transgenic mouse models with collectrin overexpression in pancreatic islets suggests divergent roles for collectrin in influencing β-cell mass and insulin exocytosis. To clarify the function of collectrin in the pancreas, we used a mouse line with targeted deletion of the gene. We examined pancreas morphology, glucose homeostasis by ip glucose tolerance testing (IPGTT) and insulin tolerance testing (IPITT), and pancreas function by in vivo acute-phase insulin response determination and glucose-stimulated insulin secretion from isolated islets. We find no difference in either pancreas morphology or function between wild-type and collectrin-deficient animals (Tmem27–/y). However, we note that by 6 months of age, Tmem27–/y mice exhibit increased insulin sensitivity by IPITT and decreased adiposity by dual-energy x-ray absorptiometry scanning compared with wild-type. We have previously reported that Tmem27–/y mice exhibit profound aminoaciduria due to failed renal recovery. We now demonstrate that Tmem27–/y animals also display inappropriate excretion of some short-chain acylcarnitines derived from amino acid and fatty acid oxidation. We provide further evidence for compensatory up-regulation of oxidative metabolism in Tmem27–/y mice, along with enhanced protein turnover associated with preserved lean mass even out to 1.5 yr of age. Our studies suggest that collectrin-deficient mice activate a number of adaptive mechanisms to defend energy homeostasis in the setting of ongoing nutrient losses.

 
 
 
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