6 - Cell Motility, cemotaxis and intermediate filaments

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Describe the mechanism by which a cell can sense signals and transduce the info through a transduction pathway to the cytoskeleton in order to cause changes to a cell shape
signals fromsoluble factors, other cells, the extracellular matrix -> signal transduction pathways -> cytoskeleton -> organisation and movement of prganells/ cell shape, movement and contraction
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What is chemotaxis?
the ability to sense and move towards or away from a directional signal (is important for multiple responses in the human body including wound healing (fibroblast migration) and for inflammatory response (macrophage migration)
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how do keratocytes move?
extension of lamelipodia (pushes membrane forward)->new focal adhesions on PM->translocation(acto-myosin bundles contract pushing cell forward)->trailing edge detaches&retracts into cell body(internalises membranes&integrins&transports back to front
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Key consituents of cilia and flagella? howcan they be distinguished?
highly motile structures containing microtubules and dynein - can be distinguished by beating patterns/flagella longer
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How does role of centrosome differ in ciliated and non-ciliated cells>
In a non-ciliated cell centrosome sits in middle of cell and nucleating microtubules to push organelles/chromosomes around. In ciliated cells it moves to PM to create cilia and flagella
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Describe structureof cilia/flagella
basal body sits in the cytoplasm of the cell&tethers &nucleates the axoneme (main body)through a region called the transitional zone(the basal body has nine pairs of triplets/axoneme has 9 pairs of doublets&2 central MTs which are not linked)
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Why is the structure of cila/flagella important?
arrangement is crucial for bending of the axoneme. They bend because they are normally crosslinked by nexin.
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What is the defining feature of intermediate filament (IF) proteins?
a 310-355 residue coiled-coil domain in each IF molecule which is flanked by N- and C-terminal blobs
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What are cytokeratins?
a complex family of >19 cellular proteins in human epithelia and further 8 (so called hard keratins) in hair and nails. Only found in vertebrates
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How do cyotkeratins work? what do the do?
attach to the plasma-membrane through desmosomes and extracellular matrix through hemi-desmosomes (see next 5 lectures) and can provide mechanical strength to epithelial cells and their derivatives (hair, skin, nails) especially when cross-linked
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What are type 3 intermediate filament proteins?
In skeletal muscle, desmin and synemin provide a mechanical scaffold to the sarcomere. In smooth muscle desmin cross-links at dense bodies to provide a resistive force to stretching
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what are neurofilaments?
obligate heterodimers consisting of NF-L (light), NF-M (medium) and NF-H (heavy) subunits-required for structural support in axons and glial cells and are frequently bound to, and transported by, microtubules
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What are nuclear lamins?
Nuclear lamins (A, B, C) form dimers in isolation. These then associate to form a meshwork. A and C lamin are splice variants transcribed from the same gene, differing at the C-terminus. The C-terminus of B lamin is covalently attached to the membran
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What are laminopathies?
Mutations in lamin A cause several diseases by default in gene expression e.g. Hutchinson-Gilford Progeria (premature ageing syndrome)
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Card 2

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What is chemotaxis?

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the ability to sense and move towards or away from a directional signal (is important for multiple responses in the human body including wound healing (fibroblast migration) and for inflammatory response (macrophage migration)

Card 3

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how do keratocytes move?

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Preview of the front of card 3

Card 4

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Key consituents of cilia and flagella? howcan they be distinguished?

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Card 5

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How does role of centrosome differ in ciliated and non-ciliated cells>

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