低密度脂蛋白受体相关蛋白5(LRP5)与骨质疏松症

从低密度脂蛋白受体相关蛋白 5 (L RP5 )基因的发现及分子结构、组织分布及功能等几个方面 ,综述 L RP5与骨质密度及骨质疏松症之间的关系 ,旨在阐明 L RP5基因与骨质疏松症发病密切相关 ,为进一步研究和开发治疗骨质疏松症药物提供研究思路     

低密度脂蛋白受体相关蛋白5（LRP5）与骨质疏松症

从低密度脂蛋白受体相关蛋白5(LRP5)基因的发现及分子结构、组织分布及功能等几个方面，综述LRP5与骨质密度及骨质疏松症之间的关系。旨在阐明LRP5基因与骨质疏松症发病密切相关，为进一步研究和开发治疗骨质疏松症药物提供研究思路。     

低密度脂蛋白受体相关蛋白5与骨量相关性的研究进展

骨最受多种遗传及环境因素共同影响,其中遗传因素对骨密度的影响大于60%.近年的研究显示,低密度脂蛋白受体相关蛋白5(LRP5)与成骨细胞分化、骨密度和/或骨质疏松性骨折关系密切.LRP5参与的骨量调控机制为骨质疏松症等疾病提供了新的治疗靶点,针对以上机制研制特异性激动剂或拈抗剂对开发新型抗骨质疏松药物具有重要意义.     

低密度脂蛋白受体相关蛋白与纤溶系统

低密度脂蛋白受体相关蛋白(LRP)是近年新发现的一种细胞表面蛋白,为低密度脂蛋白受体(LDLR)家族的一员,能与多种配体结合,参与纤溶系统多种成分的代谢,从而调节纤溶系统功能的稳定。     

低密度脂蛋白受体相关蛋白5在骨中发挥调节骨量的作用

人类骨骼受低密度脂蛋白受体相关蛋白5(low-density lipoprotein receptor-related protein 5,LRP5)的影响。有研究发现,骨质疏松症-假神经胶质瘤综合征(osteoporosis-pseudoglioma syndrome)的个体携带功能缺失的Lrp5基因突变,而Lrp5基因的杂合子错义突变则在显性遗传的骨量增多(high bone mass,HBM)个体中被发现。为探讨Lrp5如何影响骨性质,Cui等繁育了一系列Lrp5基因敲入(knock-in)或敲除(knockout)小鼠,结果发现:(1)遗传性敲入致HBM的Lrp5等位基因使小鼠骨量增多。(2)在骨细胞中敲入致HBM的Lrp5等位基因也同样能增加骨量。(3)在     

低密度脂蛋白受体基因Hinc多态性与胆囊结石病关系研究

目的　研究低密度脂蛋白受体 (L DL R)基因多态性与胆囊结石 (gallstone,GS)病之间的关系。方法　应用聚合酶链反应及 Hinc 内切酶限制性片段长度多态性方法 ,检测了 132例 GS患者和 80名对照的 L DL R基因第 12外显子 Hinc 多态性分布。结果　 GS组患者 H2 等位基因频率为 0 .76 ,显著高于对照组的 0 .6 2 (P<0 .0 5 ) ;GS组和对照组的 H2 H2 基因型血浆总胆固醇 (TC)和低密度脂蛋白 -胆固醇(L DL- C)较 H1 H1 基因型降低 (P<0 .0 1)。结论　L DL R基因第 12外显子 Hinc 多态性 H2 等位基因与 GS病发生以及 GS患者低血 L DL- C可能有关 ,L DL R基因可能属于结石基因族成员之一。     

软骨细胞膜蛋白低密度脂蛋白受体相关蛋白1低表达的意义

BACKGROUND: Tumor necrosis factor α, as a pathogenic factor, induces the inflammatory reaction mainly via the activation of the nuclear factor kappa B signaling pathway. Low density lipoprotein receptor-related protein 1 (LRP1) is involved in the regulation of the inflammatory reaction induced by cytokines.     

Heymann肾炎受体相关蛋白融合蛋白的实验研究

通过Heymann肾炎受体相关蛋白的研究 ,探讨Heymann肾炎的分子发病机制。运用基因重组技术 ,将编码受体相关蛋白羧基端 10 8个氨基酸多肽 (RAP3 2 4 )的cDNA克隆到大肠杆菌高效表达载体pGEX。通过异丙基硫代 β D半乳糖苷 (IPTG )诱导 ,表达了分子量为 44× 10 3 的融合蛋白。经GST Sepharose4B亲和层析柱 ,纯化了融合蛋白。表达产物经Westernblot分析。羧基端受体相关蛋白融合蛋白在pGEX中得到高效表达 ,其分子量为 44× 10 3 。每升培养液纯化到 2 0～ 30mg的融合蛋白。Westernblot分析表明抗RAP3 2 4 融合蛋白的抗血清识别天然肾小管刷状缘膜抗原FXIA中分子量约 44× 10 3 的带。间接免疫荧光显示该融合蛋白抗体结合于肾小管刷状缘。表明受体相关蛋白羧基端 10 8氨基酸多肽链上存在致肾炎的病理性表型。     

动脉粥样硬化性脑梗塞与低密度脂蛋白受体基因NcoI、AvaⅡ多态性的关系

目的 探讨动脉粥样硬化性脑梗死（atherosclerotic cerebral infarction,ACI)与低密度脂蛋白受体（low density lipoprotein receptor,LDL-R)基因NcoI、AvaⅡ多态性的关系。方法 用聚合酶链反应技术检测113名辽宁藉汉族健康人和77例ACI患者的LD－R基因NcoI、AvaⅡ多态性及血脂、载脂蛋白的含量。结果 LDL－R基因NcoI、AvaⅡ等位基因频率健康人N^ 为0．667、A^ 为0．230；ACI组N^ 为0．662、A^ 为0．125。A^-A^-与N^ N^ 联合存在时ACI的发病相对风险率（RR）为5．56（P＜0．001），引起血清TG、TC、LDL－C、LP（a)升高的相对风险率依次为4．29、7．67、9．33、3．09（P＜0．05）。结论 LDL－R基因A^-A^-与N^ N^ 联合存在影响血脂、脂蛋白的含量，与ACI密切相关。     

Seven novel sequence variants in the human low density lipoprotein receptor related protein 5 (LRP5) gene

We identified seven novel polymorphisms in the human low density lipoprotein receptor related protein 5 (LRP5) gene. Two of them are predicted to replace amino acid in LRP5 protein (c.314A>G: Q89R and c.4037T>C: V1330A), whereas three are silent mutations in the coding region (c.2268T>C: N740N, c.3405A>G: V1119V, and c.4137C>T: D1363D) and two are polymorphisms in introns (IVS10+6T>C and IVS17‐30G>A). Since LRP5 recognizes apolipoprotein E and is genetically linked with type 1 diabetes, these novel polymorphisms will be useful in genetic studies of hyperlipoproteinemia and diabetes. To our knowledge, this is the first report in the literature of sequence variants in the human LRP5 gene. ©2002 Wiley‐Liss, Inc.     

Characterization of low density lipoprotein receptor (LDLR) gene mutations in Albania

Introduction

Familial hypercholesterolaemia (FH) is a clinical syndrome characterised by elevated serum total cholesterol (TCHOL) levels due to an increase in low-density lipoprotein (LDL) cholesterol, by tendon xanthomata and clinical manifestations of ischaemic heart disease in early life. Typically, it results from mutations in the low-density lipoprotein receptor (LDLR) gene. So far, more than 800 mutations have been reported for the LDLR gene and account for FH. The nature of LDLR gene mutations varies among different ethnicities. Until now no mutations of LDLR have been reported in the Albanian population.

Material and methods

We assessed the contribution of the LDLR gene mutations as causes of FH in an Albanian population. Fifty probands with a clinical diagnosis of FH were included. We analysed all the exons and the promoter of the LDLR gene by using restriction isotyping or direct sequencing.

Results

Twenty-one patients were heterozygous for the 1646G>A mutation (FH Genoa) in exon 11 and 9 patients were heterozygous for the 81T>C mutation in exon 2 of the LDLR gene.

Conclusions

This report describes two LDLR gene mutations accounting for FH in Albania (1646G>A, 81T>C).     

Genetics of the low density lipoprotein receptor:

Fibroblast low density lipoprotein (LDL) plasma membrane receptor activity, measured as 125I-LDL association (plasma membrane binding plus intracellular accumulation) and degradation was determined in cell strains from 14 monozygotic (MZ) and 21 like-sexed dizygotic (DZ) normolipidemic twin pairs. The twins were between 57 and 62 years old and had liver apart for an average of 38 years (range 0-60). The intrapair differences were significantly smaller in MZ than in DZ twin pairs in fibroblast 125I-LDL association as well as degradation assays (P less than 0.05). These findings suggest a genetic influence on normal variation in LDL receptor activity in vitro. In two MZ pairs discordant for psoriasis, the psoriatic twin had markedly lower LDL receptor activity than the cotwin.     

Lp(a) lipoprotein enters cultured fibroblasts independently of the plasma membrane low density lipoprotein receptor

Lp(a) lipoprotein shares the apoB antigen with low density lipoprotein (LDL). The Lp(a) antigen is unique for Lp(a) lipoprotein. Fibroblast association (i.e. plasma membrane binding plus intracellular accumulation), plasma membrane binding, intracellular accumulation and degradation of 125I-Lp(a) lipoprotein were studied in strains from subjects with or without autosomal dominant hypercholesterolemia (HC). Subjects without HC (non-HCs) have cell surface receptors for low density lipoprotein (LDL receptors). On the average, HC heterozygotes have half-normal LDL receptor activity and "receptor-negative" HC homozygous cell strains lack functional receptors. Fibroblast processing of 125I-Lp(a) lipoprotein was compared to fibroblast processing of 125I-LDL. LDL receptor-dependent processing of 125I-LDL was saturated at about 50 microgram apo 125I-LDL.ml-1 in non-HC fibroblasts. 125I-Lp(a) lipoprotein was, however, largely processed independently of receptor mechanisms by non-HC cells (highest concentration examined 150 microgram apo 125I-Lp(a) lipoprotein . ml-1). Lp(a) lipoprotein did not interfere with 125I-LDL for fibroblast association, but inhibited 125I-LDL degradation. The interference with 125I-LDL degradation was time dependent. Only slightly higher 125I-Lp(a) lipoprotein processing values were found in non-HC and HC heterozygous strains than in "receptor-negative" HC homozygous strains. However, non-HC cells had more than tenfold higher 125I-LDL processing values than "receptor-negative" HC homozygous cells.     

两个家族性高胆固醇血症纯合子家系低密度脂蛋白受体基因分析

目的：分析家族性高胆固醇血症（familial hypercholesterolemia,FH)低密度脂蛋白受体（low density lipoprotein receptor,LDLR)的基因突变。方法：提取5个彼此无亲缘关系临床诊断为FH的纯合子患儿及其家系成员的基因组DNA,用聚合酶链反应－单链构象多态性分析方法,对LDLR基因的启动子和全部18个外显子进行突变检测,并对结果异常者进行DNA测序。结果：在两个家系分别发现A606T和C263R两种突变。结论：LDLR基因在以上两位点的突变可引起FH,中国FH患者的LDLR基因可能存在特有的突变位点。     

Characterization and geographic distribution of the low density lipoprotein receptor (LDLR) gene mutations in northwestern Greece

Familial Hypercholesterolaemia (FH) is a clinical syndrome characterised by elevated serum total cholesterol levels due to an increase in low density lipoprotein (LDL) cholesterol, by tendon xanthomata and clinical manifestations of ischaemic heart disease in early life. Typically, it results from mutations in the low-density lipoprotein receptor (LDLR) gene. So far, over 600 mutations have been reported for the LDLR gene and account for FH. The nature of LDLR gene mutations is different in various ethnicities and has also regional distribution within each ethnicity. Eleven mutations have already been described in the Greek population. This report describes seven LDLR gene mutations accounting for FH in Northwestern Greece (81T>G, 517T>C, 858C>A, 1285G>A, 1352T>C, 1646G>A and 1775G>A) and their geographic distribution. We have recently described one of these mutations (1352T>C) as a novel point mutation in a Greek family originating from Northwestern Greece. Furthermore, two previously identified mutations (81T>C, 1775G>A) were also detected in the Greek FH patients for the first time. The 1775G>A mutation was responsible for all the homozygous patients in our area, indicating a founder effect. These data will favor the development of tailed information and screening programs in Northwestern Greece for the primary prevention of cardiovascular disease in FH patients.     

A 9.6 kilobase deletion in the low density lipoprotein receptor gene in Norwegian familial hypercholesterolemia subjects

Haplotype analysis of the low density lipoprotein receptor (LDLR) gene was performed in Norwegian subjects heterozygous for familial hypercholesterolemia (FH). Southern blot analysis of genomic DNA, using an exon 18 specific probe and the restriction enzyme NcoI, showed that two out of 57 unrelated FH subjects had an abnormal 3.6 kb band. Further analyses revealed that this abnormal band was due to a 9.6 kb deletion that included exons 16 and 17. The 5' deletion breakpoint was after 245 bp of intron 15, and the 3' deletion breakpoint was in exon 18 after nucleotide 3390 of cDNA. Thus, both the membrane-spanning and cytoplasmatic domains of the receptor had been deleted. A polymerase chain reaction (PCR) method was developed to identify this deletion among other Norwegian FH subjects. As a result of this screening one additional subject was found out of 124 subjects screened. Thus, three out of 181 (1.7%) unrelated Norwegian FH subject possessed this deletion. The deletion was found on the same haplotype in the three unrelated subjects, suggesting a common mutagenic event. The deletion is identical to a deletion (FH-Helsinki) that is very common among Finnish FH subjects. However, it is not yet known whether the mutations evolved separately in the two countries.     

家族性高胆固醇血症纯合子家系低密度脂蛋白受体功能检测及基因突变分析

目的：分析家庭性高胆固醇血症（familial hypercholesterolemia,FH）患者低密度脂蛋白受体（low density lipoprotein receptor,LDLR）的功能改变及基因突变。方法：分离FH患者外周血淋巴细胞，用流式细胞仪观察淋巴细胞结合和摄取荧光标记的低密度脂蛋白的情况。抽提FH患者外周血基因组DNA为模板，进行聚合酶链反应－单链构象多态性分析（polymerase chain reaction-single strand conformation polymorphism,PCR-SSCP）及DNA序列分析。结果：对一家两例临床诊断为FH纯合子的患儿及其父母的外周血淋巴细胞LDLR功能进行了分析，发现均表现为低密度脂蛋白（LDL）摄取和结合障碍。进一步从基因水平进行了研究，发现LDLR基因突变是位于第6外显子编码第297位氨基酸的碱基发生缺失，导致移码突变并使得终止密码子TGA在第369位提前出现，从而不能表达正常的LDLR，体内胆固醇的代谢发生障碍。结论：对1例家庭性高胆固醇血症纯合子家系应用流式细胞仪方法初步发现LDLR功能缺陷，进一步结合PCR－SSCP方法证实其LDLR存在新的突变类型。     

Genetics of the low density lipoprotein receptor:

Fibroblast association (plasma membrane binding plus intracellular accumulation) and degradation of radioiodinated low density lipoprotein (125I-LDL) index plasma membrane LDL receptor activity. Cultured fibroblasts from 23 subjects affected with familial hypercholesterolemia (HC) and from 95 subjects without HC (non-HCs) were tested for 125I-LDL association and degradation. Both LDL receptor activity indices were twice as high in non-HC and HC heterozygous cell strains. This is compatible with a major gene effect on LDL receptor activity. However, a considerable overlap between non-HC and HC heterozygous values was found in the 125I-LDL association assay [median (range) 970 (330-2500), and 450 (250-490), respectively] and in the degradation assay [median (range) 810 (280-2020), and 470 (160-790), respectively]. The values are expressed as ng 125I-LDL X mg cell protein-1 X 4.5 h-1. These great overlaps in the LDL receptor activity indices support the view that the influence of LDL receptor activity on the HC phenotype may be smaller than believed previously. Furthermore, for the diagnosis of HC, these LDL receptor activity assays are far more expensive and have less sensitivity and specificity than simple serum cholesterol determination. The LDL receptor-dependent 125I-LDL association values for the HC heterozygous individuals clustered into four groups. Family data supported the hypothesis that this variation could be due to four different LDL receptor variants, each coded for by different alleles at the LDL receptor locus. If confirmed, this finding may have implications for the understanding of the variable expression of HC and also of the genetic impact on lipoprotein metabolism and susceptibility to atherosclerosis in non-HCs.