细胞的社会关系

黏合带
紧密连接
粘着带 钙粘素
肌动蛋白纤维束
30 nm
Figure 19-8 Adhesion belts between epithelial cells in the small intestine. 显著特点：可收缩的纤维束，平行于细胞膜。细胞-细胞之间的肌动蛋白由跨膜 连接的糖蛋白（钙粘素）相连接。
锚定连接
Figure 19-6 Anchoring junctions in an epithelial tissue. 锚定 连接将相邻细胞的骨架系统或将细胞与基质相连形成一个坚挺有 序的细胞群体。
细胞内附着蛋白 跨膜连接的糖蛋白
Figure 19-7 锚定连接的蛋白组成: intracellular attachment proteins and
conventional (C) electron micrographs. Note that the cells are oriented with their apical ends down. In (B) the plane of the micrograph is parallel to the plane of the membrane, and the tight junction appears as a beltlike band of anastomosing sealing strands that encircle each cell in the sheet. The sealing strands are seen as ridges of intramembrane particles on the cytoplasmic fracture face of the membrane (the P face) or as complementary grooves on the external face of the membrane (the E face) (see Figure 19-5). In (C) the junction is seen as a series of focal connections between the outer leaflets of the two interacting plasma membranes, each connection corresponding to a sealing strand in cross-section. (B and C, from N.B. Gilula, in Cell Communication [R.P. Cox, ed.], pp. 1-29)
第十五章
细胞的社会关系： 细胞的社会关系：
细胞连接, 细胞粘着，胞外基质 细胞连接 细胞粘着 胞外基质
功能: 功能
1. 将细胞整合到特定组织上 2. 细胞连接 细胞之间的粘附和通讯 细胞连接: 3. 细胞 间质粘附 细胞-间质粘附 4. 细胞外基质的组分与功能 5. 细胞壁
细胞连接的功能分类 A Functional Classification of Cell Junctions 1. 封闭连接,Occluding junctions (紧密连接, tight junctions) 2. 锚定连接Anchoring junctions a. 肌动蛋白纤维相关的锚定连接 i. 细胞-细胞之间的连接 (e.g., 粘着带,adhesion belts) ii. 细胞-间质之间的连接 (e.g., 粘着斑,focal contacts) iii. 隔膜连接 (仅无脊椎动物) ( ) b. 中间丝相关的锚定连接 i. 细胞-细胞之间 (桥粒,desmosomes) ii. 细胞-间质之间 (半桥粒,hemidesmosomes) 3. 通讯连接(Communicating junctions) a. 间隙连接,gap junctions b. 化学突触,chemical synapses c. 胞间连丝,plasmodesmata (plants only)
Figure 19-1 Simplified drawing of a cross-section through part of the wall of the intestine. This long, tubelike organ is
constructed from epithelial tissues (red), connective tissues (green), and muscle tissues (yellow). Each tissue is an organized assembly of cells held together by cell-cell adhesions, extracellular matrix, or both.
Figure 19-4 Structure of a tight junction between epithelial cells of the small intestine. The junctions are shown schematically in (A) and in freeze-fracture (B) and
transmembrane linker proteins.
桥粒
粘连蛋白（钙黏蛋白 粘连蛋白（钙黏蛋白） 盘状致密斑
角蛋白纤维（中间纤维） 角蛋白纤维（中间纤维）
30nm 整联蛋白 层粘连蛋白
Figure 4-8
桥粒结构模式图
Figure 19-12 桥粒 桥粒.
(A) An electron micrograph of three desmosomes between two epithelial cells in the intestine of a rat. (B) An electron micrograph of a single desmosome between two epidermal cells in a developing newt（蝾螈）, showing clearly the attachment of intermediate filaments. (C) A schematic drawing of a desmosome. On the cytoplasmic surface of each interacting plasma membrane is a dense plaque composed of a mixture of intracellular attachment proteins (including plakoglobin and desmoplakins). Each plaque is associated with a thick network of keratin filaments, which are attached to the surface of the plaque. Transmembrane linker proteins, which belong to the cadherin family of cell-cell adhesion molecules, bind to the plaques and interact through their extracellular domains to hold the adjacent membranes together by a Ca2+-dependent mechanism. (A, from N.B. Gilula, in Cell Communication, pp. 1-29; B, from D.E. Kelly, JCB. 28:51-59)
Figure 19-13 The distribution of desmosomes and hemidesmosomes in epithelial cells of the small intestine. The keratin filament networks of adjacent cells are indirectly connected to one another through desmosomes and to the basal lamina through hemidesmosomes.
Tight junctions
Figure 19-2 The role of tight junctions in transcellular transport.
功能： ① 阻止可溶性物质从上皮细胞层一侧 通过胞外间隙扩散到另一侧，形成渗透 性屏障，起封闭作用。血脑屏障 ②形成上皮细胞质膜蛋白与膜脂分子侧 向扩散的屏障，从而维持上皮细胞的极 性。
嵴线
Figure 19-5 A current model of a tight junction. It is postulated that the sealing strands that hold adjacent plasma membranes together are formed by continuous strands of transmembrane junctional proteins, which make contact across the intercellular space and create a seal. In this schematic the cytoplasmic half of one membrane has been peeled back by the artist to expose the protein strands. Two peripheral proteins associated with the cytoplasmic side of tight junctions have been charaBaidu Nhomakorabeaterized, but the putative transmembrane protein has not yet been identified. In freezefracture electron microscopy the tightjunction proteins would remain with the cytoplasmic (P face) half of the lipid bilayer to give the pattern of intramembrane particles seen in Figure 19-4B, instead of staying in the other half as shown here.
Figure 19-3 Tight junctions allow cell sheets to serve as barriers to solute diffusion. (A) Schematic drawing showing how a small extracellular tracer molecule added on one side of an epithelial cell sheet cannot traverse the tight junctions that seal adjacent cells together. (B) Electron micrographs of cells in an epithelium where a small, extracellular, electron-dense tracer molecule has been added to either the apical side (on the left) or the basolateral side (on the right); in both cases the tracer is stopped by the tight junction. (B, courtesy of Daniel Friend.)