L4 Microtubules Structure and Function PDF

BS31004 Cell Shape and Movement L4 : Microtubules structure and function. Alan Prescott [email protected] Microtubules are found in many different locations, and all have similar structures. Heliozoan: Actinophrys axostyle  Immune synapse Figure 16-103b Molecular Biology of...

BS31004 Cell Shape and Movement L4 : Microtubules structure and function. Alan Prescott [email protected] Microtubules are found in many different locations, and all have similar structures. Heliozoan: Actinophrys axostyle  Immune synapse Figure 16-103b Molecular Biology of the Cell (© Garland Science 2008) Singlet, doublet, and triplet microtubules. Spacing of microtubules depends on the length of the projection domain of microtubule-associated proteins. Figure 16-11 Molecular Biology of the Cell (© Garland Science 2008) Plus end Minus end Tubulin polymerisation Dynamic instability of microtubules in vitro. Microtubule dynamic instability Hook decoration of microtubules in Pillar cells of the Organ of Corti  Structure of centrosomes. CENTROSOME = TWO CENTRIOLES AND PCM Cross-section of a CENTRIOLE Cr Microtubules grow preferentially at the (+) end. Microtubules grow from the MTOC. Microtubules grow are nucleated at the minus end by gamma tubulin ring complexes  Free microtubules in neuronal cells and plant cells Free axon MT Free plant MT Fluorescence microscopy reveals growth and shrinkage of individual microtubules in vivo. Photo-bleaching of cytoskeletal filaments reveals their dynamic behaviour Figure 16-14a Molecular Biology of the Cell (© Garland Science 2008) Figure 16-14b Molecular Biology of the Cell (© Garland Science 2008) GTP-hydrolysis controls microtubule stability Tubulin mRNA regulation determines the size of the free pool Figure 16-16c Molecular Biology of the Cell (© Garland Science 2008) GTP-cap regulates stability Microtubule plus end binding proteins Microtubule dynamics visualised with GFP-EB1 & GFP-tubulin Organelle transport by microtubule motors. Microtubules extend the endoplasmic reticulum Independent Cdc42 regulation of microfilaments and microtubules to polarize a migrating cell. Microtubule motors and cell movement MAP 2 & tau regulate MT spacing Hippocampal neuron tau-green MAP 2-orange Plus-end binding proteins regulate growth and shrinkage of MT Katanin is able to sever MT DIC microscopy demonstrates microtubule-based vesicle transport in vitro.  Organelles moving on microtubules in a cell-free system + ATP Motor proteins share similar domain structures Motor domain-ATPase Linker region Cargo domain Movement of pigment granules in frog melanophores.  Model of kinesin-1-catalyzed vesicle transport. Kinesin is a plus end directed motor Kinesin-1 uses ATP to “walk” down a microtubule. Microtubule polarity is recognised by the motors Progressive kinesin movement along a microtubule Structure and function of selected members of the kinesin superfamily. Dynein-dynactin complex Dynein is a minus end directed motor Motor directionality can be determined by in vitro MT sliding assays AXONEME-GROWN MT SLIDING ON IMMOBILISED KINESIN Microtubule minus end marked by axoneme + + Kinesin moves towards - the plus end -  Flagella propel cells Cilia move material across through liquid the surface of cells Sperm and Chlamydomonas Ciliated epithelium Cross section of a Cilium Mitosis in an animal cell