NE102 Lecture Notes 2

Mts grow by the addition of the gtp – bound dimers

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Unformatted text preview: MTs grow by the addition of the GTP – bound dimers to the + end = GTP cap GTP cap stabilizes the MT GTP is hydrolyzed to GDP soon after being added. MTs shrink at the + end in the absence of a GTP cap. Centrosomes are located near the center of interphase cells (adjacent to nucleus) The – ends of MTs are anchored at centrosomes & extend outward to the periphery of the cells. Once assembled, microtubules can be released from the centrosome to organize elsewhere in the cell. Ex.) MTs in axons & dendrites of neurons. Microtubules are dynamic within cells. MT assembly and disassembly is regulated by microtubule-associated proteins (aka, MAPs) Bind & stabilize MTs Sever the middle of MTs Modulate rates of assembly/disassembly Cytoskeleton and Motor Proteins 19:00 Direct the localization & orientation of MTs Ex.) Tau = neuronal MAP involved in the pathology of several neurodegenerative diseases (e.g., Alzheimer’s Disease) Tau normally binds & regulates MT stability in neurons QUESTION: What roles do microtubules play within cells? 1. Microtubule organization affects cell structure. 2. Microtubules play a key role in chromosome segregation during cell division (i.e., mitosis) 3. Facilitate the transport of vesicles & organelles within cells. ROLE #3 of MTs HOW? MTs provide “tracks” along which “motor proteins” transport cargo. Motor proteins = proteins that bind MTs & “cargo” and carry out intracellular transport Two families of motor proteins: (1) Dynein & (2) Kinesin Two functional domains Head domain = motor domain Bind MTs & ATP Couple ATP hydrolysis to walk along MTs Tail domain = cargo domain Bind specific cargo & mediates its transport along the MT Dynein & kinesin transport cargo in specific directions along microtubules Dyneins walk towards – end Cytoskeleton and Motor Proteins 19:00 Kinesins walk towards + end ACTIN FILAMENTS Polymers of actin monomers, called G actin . Two ends: barbed end & pointed end Pointed end connects to barbed end Assembly begins with nucleation Trimer forms Growth at both ends Results in actin filament ( F actin ) with distinct polarity Actin filaments underlie the plasma membrane to provide structure. Actin filaments are anchored ot the plasma membrane via protein-protein interactions with transmembrane & adaptor proteins Actin filaments are organized in actin bundles & networks by cross-linking proteins. Cell Division Guest Lecture: Lucia Pastorino 19:00 Topics: The cell cycle Check points: role of cyclins and cyclin-dependent kinases during the cell cycle. The role for the cell cycle and related proteins in neurodegeneracy THE CELL CYCLE Cells reproduce by duplication their content and by generating 2 identical cells during the cell cycle The phases of the cell cycle Interphase Cells make sure that everything is there in content and size G1 phase – vary from cell to cell Cell makes sure that the environment is correct to undergo mitosis Centrosomes are duplicated G1 checkpoint – is environment favorable?G1 checkpoint – is environment favorable?...
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MTs grow by the addition of the GTP – bound dimers to the...

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