Term
Cytoskeleton Composed of ........ |
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Definition
1) Intermediate Filaments
2) Actin Filaments
3) Microtubules |
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Term
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Definition
•Framework to maintain cell shape and structure
•Mechanism to exert mechanochemical movement
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Term
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Definition
•Rope-like fibers with 10nm diameter (intermediate between microtubules and actin).
•Provide overall mechanical strength.
•Highly evolved and diverse - ~70 functional genes associated with ~30 diseases
–Nuclear lamins, skin keratins, neurofilaments
•First discovered as keratins of hair
•Not essential for eukaryotic life - IFs missing in insects and fungi- why?
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Term
Intermediate Filament Structure |
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Definition
•Although diverse, intermediate filaments share common structure: globular amino-terminal domain, central alpha helical rod domain, COOH globular domain
•Fold into coiled coil dimers.
–Some Ifs form homopolymeric filaments
• (vimentin, desmin)
–Others form heteropolymeric filaments
• (keratins neurofilaments)
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Term
Intermediate Filaments are Apolar or Polar |
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Definition
Apolar!
Actin Filaments and Microtubules are Polar! |
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Term
Intermediate Filament Function |
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Definition
–Mechanical- Protection of cells/tissues from mechanical and non mechanical stresses. Proper distribution of organelles.
–Non mechanical--Sensors for regulating cell growth, division, and cell death
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Term
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Definition
Epidermolysis bullosa simplex (EBS),
cause reaction with desmesomes and hemidesmesomes to be less strong |
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Term
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Definition
cause epidermolytic hyperkeratosis(EH) |
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Term
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Definition
•Defects in LMNA (gene encoding Lamin A&C) implicated in 12 disorders
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Term
Hutchinson-Gilford Progeria syndrome
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Definition
•normal development for 6-12 months followed by failure to gain wt and slow growth.
Average life expectancy is 13 years with ~90% of patients dying from atheroslcerosis
most HG patients have mutation that activates a cryptic slpice site that result in in 50 amino acid frame deletion of Lamin A which accumulates and become Progerin |
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Term
Intermediate filaments vs Actin and Microtubules |
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Definition
•subunit structure- coiled-coil building block vs globular building block
•polarity- apolar IF vs polar actin filaments and microtubules
•nucleotide binding
•diversity of proteins vs diversity of functions
Essential for life - actin and tubulin genes are essential for life, IF genes are not |
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