北京大学：《细胞生物学 Cell Science》课程教学资源（PPT课件讲稿）Intermediate filament（蔡国平）

细胞科学 Science 蔡国

细胞科学 Cell Science （10.4） 蔡国平

10.4 Intermediate filament I. The molecule structure of f 1)1Onm filament showing a similar spatial pattern as MT, to which they may be connected 2) To today, IF have only been identified with certainly in animal cells(?. Plant cells) 3)The model for IF assembly and architecture Monomer (a pair of globular terminal domains,a long a-helical region Dimer(homodimer or heterodimer), in parallel, ends d aligne Tetramer, in antiparallel, basic subunit. Lacking polarity IF structure, being composed of staggered subunits Highly resistant to tensile: and more resistant to chemical disruption

10.4 Intermediate filament 1. The molecule structure of IF 1) 10nm filament showing a similar spatial pattern as MT, to which they may be connected. 2) To today, IF have only been identified with certainly in animal cells (?. Plant cells) 3) The model for IF assembly and architecture: Monomer (a pair of globular terminal domains , a long -helical region. Dimer (homodimer or heterodimer), in parallel, ends aligned Tetramer, in antiparallel, basic subunit. Lacking polarity IF structure, being composed of staggered subunits, Highly resistant to tensile and more resistant to chemical disruption

coo coiled- coil dimer COOH NHz COoH COOH Hz COOH staggered tetramer of two coiled-coil dimers two tetramers packed together eight tetramers twisted into a rope 10 nm

a heikal rod domain imino terminus arbor term rewoldament p/ote regions containing heptad repeats

Central rod domain C Polypeptide N Head Coiled-coil Dimer Tetramer Protofilament 器∞∞ Filament

A B Figure 9.44 Experimental demonstration of the dynamic character of intermediate fila- ments. These photographs show the results of an experiment in which biotin-labeled type I keratin was microinjected into cultured epithelial cells and localized 20 minutes later using immunofluorescence. The photograph in a shows the localization of the injected biotinylated keratin(as revealed by anti-biotin antibodies) that had become incorporated into filaments during the 20-minute period following injection. The photograph in b shows the distribution of intermediate filaments in the cell as revealed by anti-keratin antibodies. The dotlike pattern of fluorescence in a indicates that the injected subunits are incorporated into the existing fila- ments at sites throughout their length, rather than at their ends.(Compare with a similar ex- R以c versity Press

intermediate filaments desmosome connecting two cells 9O B 20

4)IF associated protein Filaggrin(bridge) Plakoglobin(for membrane binding spot) Desmoplakin( for desmosome)

4) IF associated protein Filaggrim (bridge) Plakoglobin (for membrane binding spot) Desmoplakin ( for desmosome)

2. IF assembly and disassembly More difficult to solubilize. can be solubilized in harsh ionic detergents such SDS But Once dissolved, IF can be depolymerized and repolymerized repeatly in vitro In vivo, IF behave dynamically. There a pool of IF subunits in cells Incorporation experiments Into the filament's interior IF dynamic quality can be seen in some cells as they enter and exit mitosis, by repolymerization or reorganization the control of dynamic equilibrium by phosphorylation and dephosphorylation of the IF subunits, for example phosphorylation of vimentin filaments by protein kinase A leads to their complete disassembly

2. IF assembly and disassembly More difficult to solubilize, can be solubilized in harsh ionic detergents such SDS. But Once dissolved, IF can be depolymerized and repolymerized repeatly in vitro. In vivo, IF behave dynamically. There a pool of IF subunits in cells. Incorporation experiments. Into the filament's interior. IF dynamic quality can be seen in some cells as they enter and exit mitosis, by repolymerization or reorganization the control of dynamic equilibrium by phosphorylation and dephosphorylation of the IF subunits, for example, phosphorylation of vimentin filaments by protein kinase A leads to their complete disassembly