第 7 章 细胞质基质与内膜系统

1. 第7章 细胞质基质与内膜系统 Cytosol and Endomembrane system

2. The Compartmentalization in Eukaryotic Cells • Membranes divide the cytoplasm of eukaryotic cells into distincttree categories : (1) the endomembrane system: ER, Golgi complex,Lys., secretory vesicles. (2). mitochondria, chloroplasts, peroxisomes, and the nucleus. (3) the cytosol

3. A. Cytosol and its functions

4. 1. Cytosol (cytoplasmic matrix) concept • Cytosol: The region of fluid content of the cytoplasm outside of the membranous organelles. Aqueous solution of large and small molecules including filaments of cytoskeleton which act as organizer for some order. • The Cytosol is the site of protein synthesis and degradation or modification. It also performs most of the cell’s intermediary metabolism.

5. Macromolecular crowding The crowded state of the cytoplasm in (a) eukaryotic and (b) E. coli cells

6. 2. Functions of Cytosol • Performs most of the cell’s intermediary metabolism. 如糖酵解、磷酸戊糖途径、糖醛酸途径等 • The synthesis site of some protein and fatty acid • The cytoskeleton relatedfunctions: • 维持细胞形态、细胞运动、胞内物质运输及能量传递；细胞质基质结构体系的组织者 • The cytomembrane relatedfunctions: • 细胞质基质产生区室化；依 靠细胞膜或细胞器膜上的泵蛋白和离子通道维持细胞内外跨膜的离子梯度 • The modification or selective degradation of proteins.

7. The modifications of proteins • Covalent bonding between coenzyme /prosthetic group and enzymes. • Phosphorylation and phosphorylation • Methylation • Acylation.

8. Control for the life of protein N 端第一个氨基酸残基是决定蛋白质寿命的信号:Met/Ser/ Thr/ Ala/Val/Cys/Gly/Pro (stable) Ubiquitin-and proteasome-mediated proteins degradation pathway

9. 2004 :The Nobel Prize for chemistry • 发现泛素调节的蛋白质降解

10. Degradation for degeneration and misfolded proteins 细胞质基质中的变性蛋白质、错误折叠的蛋白质、 含有被氧化或其他非正常修饰氨基酸的蛋白质，不管其 N 端氨基酸残基是否稳定，常常很快被降解清除

11. Help degeneration and misfolded proteins to refold 热休克蛋白（heat shock protein， HSP）：一类进化上高度保守的蛋 白质家族，作为分子伴 侣（molecular chaperone）发挥多种作用，协助细胞内蛋白质合成、分选、折叠与装配等

12. B. Endomembrane system and functions • Endomembrane System : The structure, functions and so that biogenesisrelationship organelles including ER, Golgi complex, lysosome, endosomes, secretory vesicles. They are found in all eukaryotic cells.

13. The Dynamic Nature of the Endomebrane System • Most organelles are part of a dynamic system in which vesicles move between compartments. • Biosynthetic parthways move proteins, carbohydrates and lipids within the cell. • Secretory pathways discharge proteins from cells. • Endocytic parthways move materials into cells. • Sorting signals are recognized by receptors and target proteins to specific sites.

14. 1. Structure of Endoplasmic Reticulum (ER) • 胰腺外分泌细胞中发达的糙面内质网，内质网膜及外核膜上附有核糖体; • 黄体细胞有丰富的光面内质网 • Cos-7 细胞经双重荧光染色显示的内质网的分布：绿色显示两种形式的内质网，叠加色（黄）显示糙面内质网区 ◆Two basic types of Endoplasmic reticulum.

15. ◆ Special type of endoplasmic reticulum ● 微粒体 (microsome) ● 肌质网 (sarcoplasmic reticulum)

16. 2. The functions of Endoplasmic Reticulum (ER) Proteins synthesized on ribosomes of rER include: • secretory proteins, • integral membrane proteins, • soluble proteins of organelles. ◆Protein synthesis is main function of rough endoplasmic reticulum

17. ◆Smooth endoplasmic reticulum is an important site of lipid synthesis 合成磷脂所需要的3 种酶活性部位都定位在内质网膜的细胞质基质侧

18. ◆The Proposed mechanisms 0f transport of cholesterol and phospholipids between Donor and target membranes. A. 通过膜泡转运脂质 B. 通过PEP 介导的脂质转运 C. 膜嵌入蛋白介导的膜间直接接触

19. ◆ Membrane lipidsasymmetry? 磷脂转位蛋白或称转位酶（flippase）

20. ◆ The modification and processing of Protein • Protein glycosylation (ER and Golgi body) • Disulfide bond formationIn and rearrangement (ER) • Protein folding and assembly of multimeric protein complex. • Specific protein hydrolysis and protein cleavage (ER ,Golgi and secretory vacuole )

21. ◆ Protein glycosylation N-linked glycosylation vs O-linked glycosylation N -连接糖基化与之直接结合的糖是N -乙酰葡糖胺 O -连接糖基化与之直接结合的糖是N -乙酰半乳糖胺

22. 在内质网发生的蛋白质N-连接糖基化的加工，转移至高尔基体后还会经过一系列复 杂的修饰

23. Biosynthesis of the oligosaccharide precursor (Glc)3 (Man)9 (GlcNAc)2

24. Addition and initial processing of N- linked oligosaccharides. (Man)8 (GlcNAc)2 高甘露糖型寡聚糖

25. ◆Action of protein disulfide isomerase

26. ◆Hemagglutinin folding and assembly

27. ◆ Quality control of newly synthesized proteins Secretory carrier membrane protein (SCAMP) : 1. The secretory pathway:newly synthesized proteins entering ER lumen; Correctly folded protein transport to Golgi and secretory vesicles and retrograde transport to ER; 2. Ubiquitin-proteasome pathway: Dislocate misfolded proteins from ER to cytosol, Ubiquitination and Proteasome degradation

28. ◆ Other functions of Endoplasmic reticulum • Liver cells detoxification 细胞色素P-450

29. Ca2 + storage and release

30. glycogen synthesis and decomposition • Sterols hormone synthesis

31. （3） Endoplasmic reticulum stress 在各种应激因素（错误折叠或未折叠蛋白质在ER 腔内聚集、Ca2+ 平衡紊乱、缺氧、异常糖基化和病毒感染等）作用下，主要通过3 条途径引发内质网应激（ERS）反应，影响特定基因表达。如果内质网功 能持续紊乱，细胞将最终启动凋亡程序. Unfolded Protein Response，UPR, Sterol Regulatory Element Binding Protein,SREBP, Endoplasmic Reticulum Overload Response, EOR

32. ◆ Unfolded protein response，UPR 三种ER跨膜蛋白介导UPR：inositol-requiring enzyme 1; PKR-like ER kinase,PERK，PKR ---dsRNA activating PK; Activating transcription factor 6.

33. Choleserol-sensitive control of SREBP

34. The cell apoptosis triggered by ERS reaction Nature , 2006, 443, 796-802

35. C. Golgi complex ◆ The structure and polarity of Golgi complex

36. Mark reaction-- biochemistry polarity • Regional differences in membrane composition across the Golgi stack a) Cis cisternae of Golgi complex: reduced osmium tetroxide; b)Reaction for enzyme mannosidaseII , localized in the medial; c) Reaction for enzyme nucleoside diphosphatase , localized in the trans cisternae.

37. Two model of Explain Golgi structure organization vesicular transport model and cisternal maturation model

38. ◆ The functions of Golgi complex • Golgi body is intracellular hub of macromolecules processing and transport • Golgi complex processes and sorts secreted and membrane proteins • Sorting Some lipids into plasmic membrane and lysosome membrane. • Golgi body is intracellular carbohydrate synthesis factory.

39. 1. Golgi body and cells secretory activity 发生在高尔基体TGN区的蛋白质分选途径

40. 2. Protein glycosylation and its modification • The core carbohydrate of N-linked oligosaccharides is assembled in the rER. • Modifications to N-linked oligosaccharides are completed in the Golgi complex. • O-linked oligosaccharides takes place in Golgi complex.

41. N -连接寡糖在高尔基体各膜囊区间的加工过程 • The Golgi networks are processing and sorting stations where proteins are modified, segregated and then shipped in different directions.

42. 3. Biological function of Protein glycosylation • 糖基化的蛋白质其寡糖链具有促进蛋白质折叠和增强糖蛋白稳定性的作用 • 蛋白质糖基化修饰利于高尔基体进行分选与包装，保证糖蛋白从 rER 至高尔基体膜囊单向转移 • 细胞内一些负责糖链合成与加工的酶类均由管家基因编码；细胞表面、细胞外基质密集存在的寡糖链，直接介导细胞间的双向通讯，或参与分化、发育等多种过程 • 多羟基糖侧链还可能影响蛋白质的水溶性及蛋白质所带电荷的性质

43. 4. Assembly of Proteoglycans in the golgi complex 由一个或 多个糖氨聚糖 (glycosaminoglycan)结合到核心蛋白的丝氨酸Ser残基上，直接与Ser羟基结合的不是N-乙酰半乳糖胺而是木糖（xylose） Golgi complex plays a key role in the assembly of the carbohydrate component of glycoproteins and glycolipids.

44. 5. Proteolytic processing of proproteins in secretion pathways • 无生物活性的蛋白原（proprotein）进入高 尔基体后，切除N 端或两端的序列形成成熟多肽。如胰岛素、胰高血糖素及血清蛋白等 • 含有多个相同氨基酸序列的前体，在高尔基体中被水解形成同种有活性的多肽，如神经肽等 • 同一种蛋 白质前体在不同的细胞中可能以不同的方式加工，产生不同种类的多肽，增加了细胞信号分子的多样 性

46. D. Lysosome 图 溶酶体的发现过程（酸性磷酸酶存在于膜结合小泡中） 左：造成膜泡破裂及酸性磷酸酶释放的条件 右：鼠肝线粒体分离组分置于低渗条件下检测的酸性磷酸酶活性曲线

47. 1. Characteristics of Lysosomes • ◆ Heterogenous organelles • primary lysosome • secondary lysosome • residual body

48. ◆ Lysosomes contain plenty acid hydrolases that can digest every kind of biological molecule. ---the principal sites of intracellular digestion. • Marker enzyme: acid phosphatase • ◆ Lysosome membrane: • H+-pumps; • Glycosylated proteins; • Transport proteins

49. 2. The functions of Lysosomes • Lysosomes are Digestive organells of cell • Lysosomes are involved in three major cell functions: • ① endocytosis ; • ②phagocytosis; • ③autophagy. • .

50. ◆The digestive processes are mediated by the lys. 清除无用的生物大分子、衰老的细胞器及衰老 损伤和死 亡的细胞 Aaron Ciechanover. Nature Reviews Molecular Cell Biology, 2005, 6, 79-87