膽固醇代謝ppt課件

1、膽固醇代謝平衡調(diào)控,提綱,膽固醇的生物學(xué)功能 膽固醇相關(guān)疾病 膽固醇的生物合成 膽固醇在血液中的運輸 家族型高膽固醇血癥 NPC疾病 膽固醇的降解與清除 膽固醇代謝的負(fù)反饋調(diào)控機(jī)制SCAP-SREBP途徑 膽固醇代謝的負(fù)反饋調(diào)控機(jī)制HMGCR降解途徑 飲食膽固醇吸收的分子途徑,Cholesterol（膽固醇,一、膽固醇的生物學(xué)功能,Membrane Fluidity Bile Acids Hormones、Vitamin D Synapse Hedgehog Modification Signal Transduction,哺乳動物細(xì)胞模式圖,膜上的微結(jié)構(gòu)域,Cholesterol and c

2、holesterol derivatives,雌激素,雄激素,脂肪酸、糖等提供能量（ATP） 膽固醇并不提供能量,二、膽固醇相關(guān)疾病,Cholesterol is the major cause of atherosclerosis,From He J. et al., N Engl J Med, (2005), 353: 1124-1134,中國死亡原因統(tǒng)計,蒙娜麗莎患有高膽固醇,意大利帕勒莫大學(xué)的病理解剖學(xué)教授弗蘭克，研究認(rèn)為蒙娜麗莎飲食不健康，患有高膽固醇癥。 正是眼部的脂肪瘤，造成了蒙娜麗莎這副神秘莫測的表情。畫中的她（或者說達(dá)芬奇的這個模特）正在為自己體內(nèi)過高的膽固醇而擔(dān)憂,膽結(jié)石,

3、老年癡呆癥,Cholesterol and Diseases,Niemann-Pick Type C Disease,糖尿病/肥胖癥,From IMS Health, MIDAS,藥品銷售排行榜,三、膽固醇的生物合成,Cholesterol is not required in the diet,Cholesterol is an essential molecule but is not required in the diet because all cells can synthesize it from simple precursors,Cholesterol is made fro

4、m acetyl-CoA in four stages,all of its carbon atoms are provided by a single precursor acetate,Stage 1,Three acetate units condense to form a six carbon intermediate, mevalonate,Two molecules of acetate-CoA condense forming acetoacetyl-CoA. Acetoacetyl-CoA condenses with acetyl-CoA to yield b-hydrox

5、y-b-methylglutaryl-CoA (HMG-CoA,The final step the reduction of HMG-CoA to mevalonate, catalyzed by HMG-CoA reductase,Stage 2,Conversion of mevalonate into activated isoprene units Isoprene containing molecules are important intermediates in cholesterol biosynthesis,Stage 3,Polymerization of six 5-c

6、arbon isoprene units to form the 30-carbon linear structure of squalene,Cyclization of squalene forms the four rings of the steroid nucleus. Subsequent modifications leads to the final product, cholesterol,Stage 4,Most of the cholesterol made in the liver is exported,Much of cholesterol synthesis ta

7、kes place in the liver Most is exported,Cholesterol is exported in three forms,1. Bile salts amphipathic cholesterol derivatives that aid lipid digestion 2. Cholesterol to bile 3. Cholesteryl esters transported and secreted in lipoprotein particles to other tissues that use cholesterol or are stored

8、 in the liver,四、膽固醇在血液中的運輸,Cholesteryl ester formation,Formed in the liver Converting cholesterol to a more hydrophobic form,Cholesterol transport: the problem,Cholesterol and cholesteryl esters are essentially insoluble in water These molecules must be moved from the tissue of origin to the tissues

9、 in which they are stored or are consumed,Cholesterol transport: the solution,Cholesterol and cholesteryl esters are carried in the blood plasma from one tissue to another as plasma lipoproteins,Cholesterol esters enter cells by receptor mediated endocytosis,五、家族型高膽固醇血癥,LDL receptor (LDLR) 突變,家族性高膽固

10、醇血癥 (Familial Hypercholesterolemia, FH,雜合子患者血清總膽固醇較正常人高出12倍 純合子患者血清總膽固醇較正常人高出68倍,雜合子患者發(fā)生率為1/500 純合子患者發(fā)生率為1/1,000,000,雜合子患者男性3040歲時，患CAD， 23% 患者在50歲以前死于CAD，50% 患者在60歲時明顯的CAD癥狀； 純合子患者十幾歲時，有嚴(yán)重的心血管事件甚至死亡,LDLR突變-黃色瘤,FH患者,LDLR突變-眼底脂質(zhì)滲出,正常人,六、 Niemann-Pick type C(NPC) 疾病,溶酶體堆積型疾?。↙ysosomal Storage Disorder

11、s） 膽固醇在溶酶體中堆積 進(jìn)行性神經(jīng)細(xì)胞死亡、肝脾腫大、小腦共濟(jì)失調(diào)、癡呆、語言吞咽困難、青春期之前死亡 1：120，000發(fā)病，攜帶者1：100 NPC1（大的膜蛋白）或NPC2（小的可溶蛋白）基因突變 臨床嘗試用環(huán)化糊精進(jìn)行治療,正常細(xì)胞,NPC1突變細(xì)胞,七、膽固醇的降解與清除,Degradation of cholesterol,The ring structure of cholesterol cannot be metabolized to CO2 and H2O in humans The intact sterol ring is eliminated from the bo

12、dy by: Conversion to bile acids, which are excreted in feces Secretion of cholesterol into the bile, which transports it to the intestine for elimination,Steroid hormones are formed from cholesterol,All steroid hormones are derived form cholesterol In the cortex of adrenal glands two classes of horm

13、ones are synthesized mineralocorticoids and glucocorticoids In the male and female gonads sex hormones are produced Sex hormones include progesterone, androgens and estrogens,八、膽固醇代謝的負(fù)反饋調(diào)控機(jī)制,一）SCAP-SREBP途徑,脂質(zhì)代謝的關(guān)鍵蛋白質(zhì)及其功能調(diào)控的臨床意義,Insig,SREBP膜結(jié)合的轉(zhuǎn)錄因子,Wang X, Briggs MR, Hua X, Yokoyama C, Goldstein JL,

14、Brown MS. Nuclear protein that binds sterol regulatory element of low density lipoprotein receptor promoter. II. Purification and characterization. J Biol Chem. 1993 Jul 5;268(19):14497-504. Yokoyama C, Wang X, Briggs MR, Admon A, Wu J, Hua X, Goldstein JL, Brown MS. SREBP-1, a basic-helix-loop-heli

15、x-leucine zipper protein that controls transcription of the low density lipoprotein receptor gene. Cell. 1993 Oct 8;75(1):187-97. Wang X, Sato R, Brown MS, Hua X, Goldstein JL. SREBP-1, a membrane-bound transcription factor released by sterol-regulated proteolysis. Cell. 1994 Apr 8;77(1):53-62,25-Hy

16、droxycholesterol,irradiation,Mutant cells survive (25-RA,Amphotericin B,irradiation,Cholesterol auxotrophs (M19,S2P cDNA to CHO cells,Briefly incubated with LDL, Amphotericin B selection,irradiation,Low fluorescent LDL uptake,irradiation,SRD-12B,DeBose-Boyd RA, Brown MS, Li WP, Nohturfft A, Goldstei

17、n JL, Espenshade PJ. Transport-dependent proteolysis of SREBP: relocation of site-1 protease from Golgi to ER obviates the need for SREBP transport to Golgi. Cell. 1999 Dec 23;99(7):703-12. Nohturfft A, Yabe D, Goldstein JL, Brown MS, Espenshade PJ. Regulated step in cholesterol feedback localized t

18、o budding of SCAP from ER membranes. Cell. 2000 Aug 4;102(3):315-23,Sterol Regulated Transport of SCAP,Purification Scheme for SCAP-interacting Proteins,Yang et al., Cell (2002) 489-500,Two Insigs: Insig-1 and Insig-2,A.Sequence Alignment,B.Hydropathy Plot,Yabe et al., PNAS (2002) 12753-8,Insig,九、膽固

19、醇代謝的負(fù)反饋調(diào)控機(jī)制,二）HMGCR降解途徑,From He J. et al., N Engl J Med, (2005), 353: 1124-1134. and IMS Health, MIDAS,藥品銷售排行榜,HMG-CoA Reductase (HMGCR): the Rate-Limiting Enzyme in Cholesterol Biosynthetic Pathway,Proposed Model for INSIG-mediated Regulation ofHMG CoA Reductase and SCAP,Sterol-Regulated Degradatio

20、n of HMG-CoA Reductase is Blocked by Inhibitors of the 26S Proteasome,Working Hypothesis for Sterol-Regulated Degradation of HMG-CoA Reductase,Sterol-Stimulated Ubiquitinaion of HMGCR Requires Insig,Sever, Song, Yabe, et al., JBC, 2003,Amino Acid Sequence of the HMG-CoA Reductase Membrane Domain,Lys

21、ines 89 and 248 are Required for the Sterol-Regulated Ubiquitination and Degradation of HMGCR,Strategy for Purifying the E3 of HMG-CoA Reductase,E3 Activity Co-immunoprecipitates with Insig-1 in Sterol-Treated Cells,Identification of gp78 and VCP as Insig-1-associating proteins,Molecular Pathway for

22、 Sterol-regulated Degradation of HMGCR,Song et al., Mol Cell, 2005,What are other proteins involved in this pathway,Identification of Ufd1 as a gp78 interacting protein,IP: Endogenous gp78,IP: Endogenous gp78,Transfect & CoIP IP: Flag-Ufd1,A,B,C,Ufd1 is required for the ubiquitination of endogenous

23、HMGCR,Ufd1 enhances the E3 activity of gp78 in vitro,Dual roles of Ufd1: Enhancing E3 activity and Promoting degradation,Cao et al., Cell Metab, 2007,十、飲食膽固醇吸收的分子途徑,De novo Cholesterol Synthesis is a Energy-Consuming Process,18 Acetyl-CoA,Cholesterol,27 NADPH 11 O2 18 ATP,Cholesterol Biosynthesis an

24、d Absorption in Human,300-500 mg,Dietary Absorption,Biosynthesis,600-900 mg,1000 mg,Biliary re-absorption,Dietary Cholesterol Absorption by Intestinal Enterocytes,Cholesterol Ester,Hydrolysis,Cholesterol,Cholesterol,Cholesterol Ester,Chylomicron,Intestinal lumen,Lymph,ACAT2,ER,Enterocyte,Tight Junct

25、ion,NPC1L1,2004 Identification of NPC1L1,Human Niemann Pick C1 Like 1 (NPC1L1,NPC1L1 mediates the re-absorption of cholesterol from bile,NPC1L1 recycles between PM and ERC responding to cholesterol level,A,B,Overexpression of NPC1L1 increases free cholesterol uptake,Knocking down of NPC1L1 protein in L02 cells attenuates the uptake of free cholesterol,Structures of different sterols,Sterol Absorption,50% cholesterol,Sterol-specificity for NPC1L1-mediated internalization,A,B,Hypothesis: NPC1L1 mediates cholesterol uptake through vesicle endocytosis,NPC1L1,Cholesterol,Cytoskeleton i