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1、PAGE 分类号 学号 2005515100045学校代码 10487 密级 博士学位论文极低密度脂蛋白受体亚型在肿瘤细胞中的变化及其意义探讨学位申请人：杨 璞指导教师：屈 伸教授学科专业：生物化学与分子生物学答辩日期：2008年5月A Thesis Submitted in Partial Fulfillment of the Requirementsfor the Degree of Doctoral of Philosophy in ScienceStudy on the variation and function of very low density lipoprotein rec

2、eptor subtypes in cancer cells Candidate:Yang PuSupervisor:Professor Qu ShenMajor :Biochemistry and Molecular BiologyHuazhong University of Science and TechnologyWuhan 430074, P.R.ChinaMay. 2008独创性声明本人声明所呈交的学位论文是我个人在导师指导下进行的研究工作及取得的研究成果。尽我所知，除文中已经标明引用的内容外，本论文不包含任何其他个人或集体已经发表或撰写过的研究成果。对本文的研究做出贡献的个人和集

3、体，均已在文中以明确方式标明。本人完全意识到，本声明的法律结果由本人承担。 学位论文作者签名：杨璞日期： 2008年5月18日学位论文版权使用授权书本学位论文作者完全了解学校有关保留、使用学位论文的规定，即：学校有权保留并向国家有关部门或机构送交论文的复印件和电子版，允许论文被查阅和借阅。本人授权华中科技大学可以将本学位论文的全部或部分内容编入有关数据库进行检索，可以采用影印、缩印或扫描等复制手段保存和汇编本学位论文。本论文属于 保密 ，在_年解密后适用本授权书。不保密。（请在以上方框内打“”）学位论文作者签名：杨璞 指导教师签名：屈伸日期：2008年5月18日 日期：2008年5月18日目

4、录一、主要缩写词1二、中文摘要3三、英文摘要7四、论文正文1、前言122、第一部分 VLDLR亚型变化与细胞生物学行为关系的探讨143、第二部分 VLDLR亚型变化影响细胞生物学行为的机制的初步探讨414、总结585、参考文献59五、综述66六、附录85七、致谢86华 中 科 技 大 学 博 士 学 位 论 文PAGE 90主 要 缩 写 词ASatherosclerosis动脉粥样硬化VLDL very low density lipoprotein极低密度脂蛋白VLDLbeta migrating very low density lipoprotein-迁移率极低密度脂蛋白VLDLRve

5、ry low density lipoprotein receptor极低密度脂蛋白受体LDLlow density lipoprotein低密度脂蛋白LDLRlow density lipoprotein receptor低密度脂蛋白受体apoER2apolipoprotein E receptor 2载脂蛋白 E受体2TRLtriglyceride-rich lipoprotein富含甘油三酯的脂蛋白CMchylomicrons乳糜微粒LRPLDL receptor related protein低密度脂蛋白受体相关受体PCRpolymerase chain reaction聚合酶链式反应

6、BSAbovine serum albumen牛血清白蛋白FBSfetal bovine serum胎牛血清Apo Eapolipoprotein E载脂蛋白 ETERTTelomerase reverse transcriptase端粒酶催化亚单位ATRA all-trans retinoic acid全反式维甲酸PMAphorbol-12-myristate-13-acetate佛波酯PKCprotein kinase C蛋白激酶CLRP1Blow density lipoprotein receptor-related protein 1B低密度脂蛋白受体相关蛋白1BSR-BI.scav

7、enger receptor class B type I 清道夫受体B族I型MSRmacrophage scavenger receptor巨噬细胞清道夫受体LR11a mosaic member of LDLR familyLR11uPAurokinase-type plasminogen activator尿激酶型纤溶酶原激活因子PAIplasminogen activator inhibitor-1型纤溶酶原激活抑制因子uPA- PAIuPA-PAI complexuPA-PAI复合物uPARurokinase-type plasminogen activator receptor尿激

8、酶型纤溶酶原激活因子受体TFPItissue factor pathway inhibitor组织因子途径抑制剂bpbase pair(s)碱基对Kbkilobase pair(s)千碱基对PBSphosphate-buffered saline磷酸缓冲液OMEMoptimize minimun essential medium优化的最低必需培养基MTT(3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide甲基噻唑基四唑DMSOdimethyl sulphoxide二甲基亚砜MMPsmatrix metalloprotei

9、nase基质金属蛋白酶VEGFvascular epidermal growth facto血管内皮(细胞)生长因子Gsk3glycogen synthase kinase糖原合酶激酶3ECMextracellular matrix细胞外基质MAPKmitogen-activated protein kinases丝裂原活化的蛋白激酶ERKextracellular signal-regulates kinase胞外信号调节激酶极低密度脂蛋白受体亚型在肿瘤细胞中的变化及其意义探讨中 文 摘 要极低密度脂蛋白受体（very low density lipoprotein receptor, VL

10、DLR）属于低密度脂蛋白受体（low density lipoprotein receptor, LDLR）超家族。VLDLR由于第16外显子的选择性剪接从而产生胞外段O-linked糖链结合域缺失的亚型，根据有无此结构域可将VLDLR分为型和型两种亚型。早期研究认为，该受体主要结合富含apoE（载脂蛋白E）的脂蛋白而参与甘油三酯的代谢；与泡沫细胞的形成及动脉粥样硬化的发生发展相关。但由于该基因敲除的小鼠仅表现体脂下降，发育迟缓，因此对该受体研究一直未引起足够重视。近年来的研究发现，因此VLDLR和LDLR家族的其他成员一样被认为是一种“瑞士军刀”样多功能受体。但是对两型受体的功能差异，特别是

11、型受体的独特功能及其生物学意义尚未阐明。我们的前期工作和已有研究资料表明：、两型受体的分布具有明显的组织细胞特异性：型受体主要分布于脂代谢旺盛的组织，而型受体则主要分布于肾脏、脾脏、肾上腺、睾丸、子宫、卵巢等非肌组织。、在分化程度不同的细胞、组织中两型受体的表达不同：在高分化的胃腺癌细胞系中，型受体低表达或不表达，而在低分化的胃腺癌细胞系中型受体高表达；同样，在多种胃腺癌组织细胞中观察到型受体的表达增多；宫颈癌病变组织中也检测到VLDLR型的高表达；另外在鸡和小鼠胚胎发育过程中VLDLR两种亚型的表达可发生变化：在胚胎发育早期以型VLDLR的表达为主，而在发育成熟的体细胞中则以型VLDLR表达

12、为主；在胚胎脑中以型VLDLR表达为主，而在成熟分化的脑组织中则以型VLDLR表达为主。、在退行性病变的纤维化脾组织中，型VLDLR则几乎消失；而在阿尔茨海默病病人的老年斑斑块中以型VLDLR表达为主；、最新研究报道认为VLDLR，尤其是型VLDLR，表达减少或不表达会导致肿瘤的形成；且型VLDLR在抑制肿瘤细胞生长方面作用更重要。这些现象强烈提示：VLDLR亚型与细胞的增殖、分化、迁移等细胞活动存在密切关系。但这种关系的生物学意义目前尚不清楚。uPA-PAI-1复合物和TFPI是VLDLR已知的两种配体， VLDLR与uPA-PAI-1复合物的结合可促进细胞增殖、迁移；而与TFPI结合可抑制

13、细胞的增殖；这些表明VLDLR与不同配体结合可影响截然相反的细胞功能，但这些配体是否通过VLDLR亚型的变化来影响细胞生物学行为尚不清楚。 本研究首先针对VLDLR亚型变化与细胞增殖、迁移之间的关系进行深入研究，探讨VLDLR 亚型的变化与细胞生物学行为的关系和意义。为探讨胃腺癌细胞SGC7901在向不同方向诱导分化过程中VLDLR亚型的表达变化与细胞生物学行为之间的关系，本实验在体外，利用全反式维甲酸（ATRA）持续诱导SGC7901细胞建立向高分化诱导变化的模型，利用佛波酯（PMA）持续诱导SGC7901细胞建立向低分化诱导变化的模型；检测端粒酶催化亚单位（TERT） mRNA的表达量判断

14、细胞分化程度。结果显示：SGC7901细胞在ATRA的持续作用下，细胞向高分化转化，型VLDLR明显减少，同时细胞增殖活性和迁移能力逐渐减弱； SGC7901细胞在PMA的持续作用下，细胞向低分化转化，型VLDLR明显升高，同时细胞增殖活性和迁移能力增强。上述结果表明型VLDLR的表达变化与肿瘤细胞分化之间存在相关性。为了深入探讨VLDLR亚型与细胞分化、增殖、迁移等的关系，本实验利用能影响细胞增殖迁移的VLDLR的配体（uPA-PAI-1、TFPI）与细胞温育，观察VLDLR亚型的表达变化与细胞生物学行为之间的关系。实验结果发现：TFPI抑制细胞增殖、迁移的同时可明显减少型VLDLR，对型V

15、LDLR无影响，并可使型VLDLR与型VLDLR的比值逐渐降低；uPA-PAI-1复合物促进细胞增殖、迁移的同时可减少型VLDLR，增加型VLDLR，并使型VLDLR与型VLDLR的比值逐渐升高。综上所述，我们的结果证实：无论是诱导分化，还是影响细胞增殖相关配体的作用，肿瘤细胞中VLDLR亚型的变化具有如下规律：在低分化、增殖、迁移能力强的细胞中同时伴有型VLDLR增加，在高分化、增殖、迁移能力弱的细胞中同时伴有型VLDLR减少。这一变化规律说明型VLDLR在促进细胞增殖、迁移，抑制细胞分化中扮演着重要角色。已有的研究表明， VLDLR在神经组织发育过程中，介导Reelin-Dab1信号途径，

16、通过SFK/PI3K-Gsk3调节细胞骨架蛋白Tau而影响细胞骨架的重构和细胞迁移；在内皮细胞增殖和迁移相关的wnt信号途径中VLDLR发挥重要的负调控作用，表明VLDLR在细胞增殖分化的wnt信号途径中发挥重要调节作用。另外，VLDLR与uPA-PAI-1复合物的结合可维持胞内ERK的磷酸化，从而促进细胞增殖、迁移；而与TFPI结合可通过通过p16ink4a和p38/JNK信号途径抑制细胞的增殖；这些表明VLDLR与不同配体的结合，调节与细胞增殖分化相关的MAPK信号体系中不同的通路，影响截然相反的细胞功能。另有研究表明，ERK的活化可使GSK-3磷酸化失活，导致-catenin在胞内聚集，

17、而-catenin可促进下游包括MMPs在内的特异基因的转录，影响细胞增殖、迁移。这些表明VLDLR与不同配体结合影响细胞功能的信号调节作用可能与MAPK、 wnt途径有关。但VLDLR亚型的变化影响细胞生物学行为的机制目前尚不清楚。根据已有研究我们推测型VLDLR影响细胞增殖、迁移与MAPK、wnt信号通路有关，因此本实验在诱导分化过程中和细胞增殖迁移调控配体的温育下，观察VLDLR可能涉及的信号途径的关键分子的活性及表达变化，初步探讨型VLDLR影响细胞生物学行为的可能机制。实验结果发现：在细胞向高分化诱导过程中和TFPI温育后型VLDLR减少，-catenin的磷酸化明显增强促进其降解从

18、而使其在胞内表达降低，同时其下游靶基因MMP-2和MMP-9的表达下调，抑制细胞增殖、迁移；而在细胞向低分化诱导过程中和uPA-PAI-1温育后型VLDLR增加，-catenin的磷酸化受到抑制增加其稳定性从而促进胞内表达上调，同时其下游靶基因MMP-2和MMP-9的表达上调，促进细胞增殖、迁移。因此型VLDLR影响细胞生物学行为变化可能与-catenin在胞内的表达上调，从而促进特异靶基因的转录有关。已有研究表明，VLDLR与uPA-PAI-1的结合可维持乳腺癌胞内ERK的磷酸化。我们的实验发现，uPA-PAI-1与细胞温育5 min即可明显增强ERK的磷酸化，这种作用可一直持续到30 mi

19、n，对ERK1的磷酸化作用在温育60 min后仍较明显。这与前述研究一致。VLDLR与TFPI结合可通过活化p38/JNK信号途径抑制细胞增殖。我们的实验发现，TFPI可抑制ERK的活化。对LDLR表达调控的研究发现，胞外分子可通过激活p38信号途径抑制ERK的活性从而下调LDLR的表达。因此我们推测，TFPI可能通过活化p38从而抑制ERK的活化。上述结果提示，uPA-PAI-1复合物可能通过型VLDLR活化胞内ERK，从而促进细胞增殖、迁移；而TFPI可能通过型VLDLR活化p38从而抑制ERK的活化，从而抑制细胞增殖、迁移。上述结果提示，型VLDLR影响细胞生物学行为的变化可能与ERK的

20、活化抑制-catenin的磷酸化降解使其在胞内表达上调，调节特异靶基因的转录有关。综上所述，型VLDLR可能通过与特定配体的结合、摄取，影响细胞内增殖、分化相关的信号途径，导致相应细胞生物学行为改变。本研究的创新之处在于初步揭示了型VLDLR的表达变化与细胞增殖、分化、迁移之间的关系及其可能涉及的信号转导途径，扩展了VLDLR功能的多样性，并对脂蛋白受体家族成员作为“瑞士军刀”样多功能受体提供了新的认识。关键词：极低密度脂蛋白受体，亚型，分化，增殖，迁移Study on the variation and function very low density lipoprotein recept

21、or subtypes in cancer cells ABSTRACTVery low density lipoprotein receptors (VLDLR), a member of low density lipoprotein receptor (LDLR) superfamily, consist of two subtypes, type I VLDLR and type II VLDLR. It is generally accepted that VLDLR plays a major role in the metabolism of triglyceride throu

22、gh binding lipoproteins enriched in apoE and has an intimate relation with atherosclerosis. There have been many attempts to study the biological phenotype in homozygous VLDLR knockout mice. However, the physiological and pathological importance of these receptors has not been clearly identified. Re

23、cently, VLDLR and many other members of the low density lipoprotein receptor family are found to bind different ligands besides lipoproteins, causing endocytosis and affecting many cellular functions. For example, VLDLR impacts the immigration and location of nerve cells during the early stages of e

24、mbryonic development by binding the signaling molecule Reln. It can also inhibit cell proliferation by interacting with tissue factor pathway inhibitor (TFPI). In addition, VLDLR plays a certain role in the invasion and metaptosis of tumor cells. And now, VLDLR and the other members of LDLR are know

25、n as the multifunctional receptor like “Swiss army knife”. Nevertheless, the functional differences between the two VLDLR subtypes need to be further clarified, especially the distinctive biological function of type VLDLR lacking the o-linked sugar domain has not been illuminated. Studies about the

26、distribution of these two VLDLR subtypes suggested that their distribution presents obvious tissue- and cell-specificity. Type I VLDLR is most highly expressed in heart, skeletal muscle and adipose tissue with active fatty acid metabolism, while type II VLDLR is predominant in non-muscle tissue, inc

27、luding kidney, spleen, adrenal gland, et al. Recent studies have shown that the two VLDLR subtypes are associated with the differentiation and development of tissues and cells. The expression pattern of the two VLDLR subtypes can be changed during embryonic development of chicken and human brain. Th

28、e type II VLDLR has been found to be the major receptor expressed in early phase of embryonic or fetal brain development, whereas type I VLDLR is mainly present in adult tissues. Other reports indicate that some tumor tissues and cells also express two VLDLR subtypes with inhomogeneity. The expressi

29、on of the type II VLDLR increases obviously in poorly differentiated adenocarcinomas. Our previous study has also found that the type II VLDLR is mainly expressed in poorly- or moderately- differentiated human gastric adenocarcinoma cell lines, but its expression is relatively low or even can not be

30、 detected in well differentiated human gastric adenocarcinoma cell lines. Our recent studies also found that the expression of type II VLDLR is higher in uterine cervix cancer tissues than that in adjacent tissues. Type I VLDLR is the major receptor in senile plaques of Alzheimer diseased brain and

31、type II VLDLR in congestive fibrotic spleen disappeared from the patients with liver cirrhosis. Genomic loss and epigenetic silencing of very-low-density lipoprotein receptor involved in gastric carcinogenesis and the O-linked sugar domain of VLDLR was demonstrated to relate with cell growth inhibit

32、ion. These studies suggest that the type II VLDLR activities may be related to certain cellular functions other than its involvement in lipoprotein metabolism. Tissue factor pathway inhibitor (TFPI) and urokinase-type plasminogen activator and plasminogen activator inhibitor 1 (uPA-PAI-1) complex ar

33、e the ligands of VLDLR, which affect different cell function through VLDLR. But whether VLDLR affect cellular function via the expression variability of two VLDLR subtypes is still unknown. Thus, we explored the expression and function of type II VLDLR during the induction of human gastric adenocarc

34、inoma cell line SGC7901 and in cells treated with two ligands of VLDLR to explore the relationship of type II VLDLR with cell function. To investigate the relationship between the expression variability of two VLDLR subtypes and cellular functions during the induction of SGC7901 cells, we use all-tr

35、ans retinoic acid (ATRA) to induce SGC7901 differentiation and phorbol-12-myristate-13-acetate (PMA) to induce a change of differentiation to relatively lower. The mRNA expression of Telomerase reverse transcriptase (TERT) acts as a marker to identify the extent of cellular differentiation. The expr

36、ession of two subtypes of VLDLR after treatment was detected by western blotting. The cells became well differentiated when induced by ATRA, accompanied by decrease in expression of type II VLDLR and gradually attenuated cell proliferation and migration. However, the cells became poorly differentiat

37、ed when induced by PMA. These cells had increased receptor expression, and enhanced cell proliferation and migration. Our data indicate that the increased expression or the activity of type II VLDLR may be associated with the poor differentiation, and the enhanced proliferation and migration of the

38、cells. Then, in order to further understand the expression of two VLDLR subtypes and the cellular function, we use two VLDLR ligands, uPA-PAI-1 complex and TFPI, which can affect cell proliferation and migration, to incubate with SGC7901 cells. In this study, we showed that cell proliferation and mi

39、gration were inhibited by TFPI, but promoted by uPA-PAI-1 complex. In addition, we also demonstrated that TFPI treatment caused a decrease, but uPA-PAI-1 complex caused an increase, in the expression of type II VLDLR, suggesting that increasing type II VLDLR activity might be associated with augment

40、ing cell proliferation and migration. In conclusion, the expression of type II VLDLR had a general phenomenon during the differentiation of cancer cells: the expression of type II VLDLR increased in lowly-differentiated cells with high proliferation and migration, but it decreased in highly-differen

41、tiated cells with low proliferation and migration. These indicate that the increased expression or the activity of type II VLDLR may be associated with the poor differentiation, and the enhanced proliferation and migration of the cells.It was reported that during the development of nervous tissue, V

42、LDLR mediates Reelin-Dab1 signal pathway, modulates tau phosphorylation through glycogen synthase kinase-3beta cascade and affects tissue remodeling and cell migration. Recent study indicates that VLDLR is a negative regulator of the wnt signaling pathway. These studies suggest that VLDLR may play a

43、n important role in wnt signal pathway. In addition VLDLR can bind with different ligands relative with proliferation, regulate different signal pathway, and affect cell function. The binding of VLDLR and urokinase-type plasminogen activator and plasminogen activator inhibitor 1 (uPA-PAI-1) complex

44、can sustain the phosphorylation of extracellular signal-regulates kinase (ERK) to promote cell proliferation and migration. But VLDLR binding with TFPI can inhibit cell proliferation through activating p38 signal pathway. The two ligands appear to have quite different effects on cell function throug

45、h VLDLR. It was reported that the activation of ERK can induce the expression of -catenin, which promote the transcription of certain target genes inclding matrix metalloproteinase (MMPs). These studies suggest that the effect of VLDLR on cell function may be related with mitogen-activated protein k

46、inases (MAPK) signal pathway and wnt signal. But it was unclear whether the two VLDLR subtypes were regulated differently and affected cell function through dinstinct signal pathway.It was speculated that the role of type II VLDLR may be related with MAPK and wnt signal pathway. So we observe the po

47、ssible signal pathway involved in the role of type II VLDLR. Our results indicated that the well differentiated cells induced by ATRA and the cells treated with TFPI with a significant decrease in type II VLDLR expression accompanied by a gradually attenuated -catenin and MMP-2 and MMP-9 expression,

48、 but in the poorly differentiated cells induced by PMA and in the cells treated with uPA-PAI-1 complex with an increase in type II VLDLR expression showed an increase in -catenin and MMP-2 and MMP-9 expression. These suggested that the role of type II VLDLR could be related with the aggregation of i

49、ntracellular -catenin, which promotes some specific target genes transcription. In our study, uPA-PAI-1 complex can rapidly activate the ERK phosphorylation of SGC7901 cells after 5 min incubation and it can sustain for at least 30 min. The phosphorylation of ERK1 can last for 1 h obviously. Thise w

50、as agreed with previous study. But TFPI can inhibit the phosphorylation of ERK. Studies about LDLR found that stress-activated p38 MAPK regulates LDL receptor expression via negatively modulation of p42/44 MAPK cascade. So it was speculated that TFPI inhibited ERK through activating p38 MAPK. These

51、results suggest that the ligand promoting cell proliferation and migration can activate ERK through type II VLDLR; but the ligand inhibiting cell proliferation and migration can reduce the phosphorylation of ERK through type I VLDLR.Our studies suggested that the role of type II VLDLR on cell functi

52、on may be related with the activation of ERK, then induce the aggregation of -catenin, promoting the transcription of some specific down-stream genes to affect cell function. These suggested that type II VLDLR may play an important role in promoting cell proliferation and migration, and inhibiting c

53、ell differentiation. In conclusion, type II VLDLR may bind and internalize specific ligand, mediate the relative signal pathway, and affect cell function. Our study revealed the relationship between type II VLDLR and cellular function and the possible related signal pathway, which provided profound

54、views of VLDLR function and new cognition of lipoprotein receptor as a cellular Swiss army knife.Keywords：very low density lipoprotein receptor, subtypes, differentiation, proliferation, migration正 文极低密度脂蛋白受体亚型在肿瘤细胞中的变化及其意义探讨前 言极低密度脂蛋白受体（very low density lipoprotein receptor, VLDLR）属于低密度脂蛋白受体（low de

55、nsity lipoprotein receptor, LDLR）超家族。VLDLR由于第16外显子的选择性剪接从而产生胞外段O-linked糖链结合域缺失的亚型，根据有无此结构域可将VLDLR分为型和型1。早期研究认为，该受体主要结合富含载脂蛋白E（apoE）的脂蛋白而参与甘油三酯的代谢2；与泡沫细胞的形成及动脉粥样硬化的发生发展相关3, 4。但由于该基因敲除的小鼠仅表现体脂下降，发育迟缓5，因此其重要性受到忽略，对该受体研究一直未引起足够重视。近年来的研究发现，VLDLR可结合多种配体与细胞信息分子，介导细胞的信号转导，进而产生不同的生物学效应，如在神经细胞通过与信号分子Reln结合影响发

56、育过程中的神经细胞的迁移和定位6；组织因子途径抑制剂（TFPI）相互作用进行信号转导，以抑制细胞增殖7-9；与尿激酶型纤溶酶原激活物/纤溶酶原激活物抑制剂1复合物（uPA-PAI-1）结合，在肿瘤细胞的浸润与转移中发挥作用6, 10, 11；还可影响细胞的生长和分化12, 13。因此VLDLR和LDLR家族的其他成员一样被认为是一种“瑞士军刀”样多功能受体14。但是对两型受体的功能差异,特别是型受体的独特功能及其生物学意义尚未阐明。我们的前期工作和已有研究资料表明：、两型受体的分布具有明显的组织细胞特异性：型受体主要分布于脂代谢旺盛的组织，而型受体则主要分布于肾脏、脾脏、肾上腺、睾丸、子宫、卵

57、巢等非肌组织1。、在分化程度不同的细胞、组织中两型受体的表达不同：在高分化的胃腺癌细胞系中，型受体低表达或不表达，而在低分化的胃腺癌细胞系中型受体高表达13；同样，在多种胃腺癌组织细胞中观察到型受体的表达增多15；宫颈癌病变组织中也检测到VLDLR型的高表达；、在退行性病变的纤维化脾组织中，型VLDLR则几乎消失16；而在阿尔茨海默病病人的老年斑斑块中以型VLDLR表达为主；另外在胚胎组织中以型受体表达为主17-20。、最新研究报道认为VLDLR，尤其是型VLDLR，表达减少或不表达会导致肿瘤的形成21；且型VLDLR在抑制肿瘤细胞生长方面作用更重要。、VLDLR-/-小鼠表现为生长发育迟缓5

58、。这些现象强烈提示：VLDLR型与细胞的增殖、分化、迁移等细胞活动存在密切关系。但这种关系的生物学意义目前尚不清楚。uPA-PAI-1复合物和TFPI是VLDLR已知的两种配体， VLDLR与uPA-PAI-1复合物的结合可促进细胞增殖、迁移；而与TFPI结合可抑制细胞的增殖；这些表明VLDLR与不同配体结合可影响截然相反的细胞功能，但这些配体是否通过VLDLR亚型的变化来影响细胞生物学行为尚不清楚。已有的研究资料表明， VLDLR在神经组织发育过程中，介导Reelin-Dab1信号途径，通过SFK/PI3K-Gsk3调节细胞骨架蛋白Tau而影响细胞骨架的重构和细胞迁移22。最近又发现，VLD

59、LR在内皮细胞增殖和迁移相关的Wnt信号途径中发挥重要的负调控作用，调节细胞功能活动23，且VLDLR基因敲除小鼠的研究资料证实这一作用并不能被其他受体完全代偿5，表明VLDLR在细胞增殖分化信号转导过程中发挥重要调节作用。另外，如VLDLR 与uPA-PAI-1复合物的结合可维持胞内ERK的磷酸，从而促进细胞增殖、迁移6, 10, 11；而TFPI可通过VLDLR上调诱导胞内JUNB和GADD45B的表达，从而通过p16ink4a和p38/JNK信号途径抑制细胞的增殖7-9；这些表明VLDLR的信号调节作用与细胞增殖分化相关的MAPK信号体系中不同的通路有关。但VLDLR与不同配体的结合可影

60、响截然相反的细胞效应，这些配体是否通过VLDLR 亚型的变化，调节不同的信号转导途径，从而影响细胞功能，目前尚不清楚。为此，本研究拟从诱导SGC7901细胞（其两型VLDLR表达都较为明显）分化和相关配体温育细胞两个方面探讨VLDLR 亚型的变化及其与细胞生物学行为的关系和意义以及可能涉及的信号途径，初步揭示VLDLR亚型在细胞增殖、分化、迁移中的作用及其作用机制，为脂蛋白受体家族功能的全面认识提供新的视野。第一部分VLDLR亚型变化与细胞生物学行为关系的探讨摘要为探讨探讨VLDLR亚型表达变化与细胞分化、增殖、迁移等生物学行为的关系，本实验在体外，利用全反式维甲酸（ATRA）持续诱导SGC7