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38 Cards in this Set
- Front
- Back
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What is the cytoskeleton?
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An organized intracellular network of 3 protein filament types
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What 3 protein filaments make up the cytoskeleton?
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-Actin filaments
-Intermediate filaments -Microtubules |
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What is the function of the cytoskeleton?
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Provides mechanical support and movement of whole cells and the structures within them.
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What is each component of the cytoskeleton composed of?
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Actin filaments = globular Actin
Intermed fils = intermediate fibrous proteins Microtubules = tubulin heterodimer subunits |
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How does the cytoskeleton behave?
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Dynamically
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What is a major difference between IF and Actins other than size?
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Actin filaments are ATPases, IFs have no NTPase capability.
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2 cell structures that are made up by intermediate filaments:
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-Cell/cell desmosome junctions
-Cell/matrix junctions |
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What structures are Actin filaments found in?
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-Cell/cell ADHERENS junctions
-Actin/myosin contractions |
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3 Important roles of IFs in cells:
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-Form ropelike hammock to cradle the nucleus
-Give mechanical strength to cell -Give structure to nuclear envelope |
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6 Types of Intermediate filaments:
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DGKNNV
-Nuclear lamins -Vimentin -Desmin -Glial fibrillary acidic protein -Keratins -Neurofilaments |
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In what type of cell would IFs be concentrated generally?
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In cells under mechanical stress
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What type of cell junctions involve IFs?
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Desmosomes
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What cancers are Keratin Positive?
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-Breast
-GI |
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What cancers are Vimentin positive?
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Sarcoma
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What disease is caused by an autosomal dominant mutation of genes for Lamins A/C?
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Emery-Dreifuss Muscular Dystrophy
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Loss of which IFs will result in
-Loss of life -Degraded function |
Loss of life = lamins
All others just degrade function |
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Where exactly do Lamin Bs reside?
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Attached to their lamin b receptors (LBR) on the nuclear side of inner nuclear membrane.
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What is attached to Lamin B?
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Lamins A/C - they interact w/ B on one side, and organize chromatin on their other side.
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What happens when lamin B is phosphorylated?
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It depolymerizes the lamins
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Symptoms of EmeryDreifuss Muscular Dystrophy:
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-Peripheral heterochromatin detached from inner nu membrane
-Progressive muscle weakness -Joint contractures -Cardiomyopathy |
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What results from genetic defect in Keratin genes?
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Blistering disease which leads to infections
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What function of IFs is essential for preventing blisters?
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Its ability to distribute shear force across cells.
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What is the name for blistering disease?
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Epidermolysis bullosa simplex
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What parts of IF molecules are:
-Conserved -Variable |
Conserved = alpha helical domains that allow subunits to bind to each other.
Variable = N and C-terminus ends |
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What do the variable N and C-terminal ends of IFs confer?
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Diversity of function
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How much IF in nondividing cells is free?
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1-5%
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How do soluble IF monomers assemble into dimers?
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By packing to form a nonpolarized high-tensile, insoluble filament.
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What do the IF filaments join togehter to form?
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Staggared antiparallel tetramers
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What mediates assembly and disassembly of IFs?
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Phosphorylation and dephosphorylation
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In which filaments is the N terminal essential for assembly?
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-Vimentin
-Neurofilaments -Lamins |
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How do IFs link to membranes and the cytoskeleton?
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By IF binding proteins
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What disease is mutated neurofilament protein a risk factor for?
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Amyotrophic lateral sclerosis
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Are IFs polarized or nonpolarized?
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Nonpolarized
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What is the structure of a homodimer of IFs like?
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Parallel coiled-coil
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What is the structure of the tetramer like?
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Staggered tetramer of two Antiparallel coiled coil homodimers
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How are neurofilaments crosslinked?
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By their C-terminal extensions
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Are IFs associated with motor proteins?
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No
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What happens when the globular heads of IFs are phosphorylated?
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They disassemble
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