Term
Minus ends of microtubules |
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Definition
are usually embedded in microtubule organizing center (MTOC) - Centriole/centrosome/ basal body / spindle pole body
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Term
Like actin, rate limiting step in microtubule formation........ |
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Definition
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Term
Not all Microtubules have (-) ends in MTOC
(Exceptions) |
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Definition
•fungi have spindle pole body imbedded in nuclear membrane but no centrioles
•plant cells and vertebrate oocytes have no centrosomes
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Term
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Definition
–Cilia and flagella
–Adult axon microtubules
–Marginal microtubule bands in RBCs
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Term
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Definition
–Spindle microtubules
–Cytoplasmic microtubules
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Term
Dynamic Properties of Microtubules |
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Definition
•Guanine nucleotide at + end of microtubule.
–Only GTP-tubulin has a strong tendency to form microtubules.
–After GTP-tub polymerizes, the GTP gradually hydrolyzes to GDP. Microtubules capped with GDP rapidly depolymerize.
•Microtubule binding proteins can contribute to growth and shrinkage.
•Drugs
–Colchicine, vinblastine, nocodozole (destabilize microtubules)
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Term
Structural difference between GTP-tubulin and GDP-tubulin |
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Definition
-probably responsible for the rapid depolymerization of microtubules with GDP-cap |
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Term
Does dynamic instability serve any purpose? |
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Definition
1) Organizing principle for cell morphogenesis
2)Capture of chromosomes in mitotic prophase
3) Propulsive Force
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Term
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Definition
•Have nine microtubule doublets arranged in a circle
•Develop from a basal body/centriole with nine microtubule triplets.
•Classified into 8 groups but all have either either 9+2 or 9+0 arrangement of microtubules.
Mobile or non-mobile
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Term
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Definition
•9+2 arrangement of microtubules
•Present on ciliated epithelia and sperm use dynein motor for movement
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Term
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Definition
•mostly 9+0 arrangement of microtubules
•present on the apical surface of most no-proliferating cells.
•often have sensory role.
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Term
physiological role of cilia |
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Definition
Immotile-cilia syndrome.
Kartagene Syndrome
•Due to mutation in dynein motor heavy chain
•patents present with:
–respiratory problems (immotile respiratory cilia)
–sterility (immotile sperm)
–situs inversus:
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Term
primary cilia as sensory organelles |
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Definition
•Autosomal dominant polycystic kidney disease (PKD)
–Most common single gene genetic disease, affecting 1/400-1/500 adults. Caused by development of renal cysts. Patients often present with hypertension, pain, or urinary tract infections. Dominant mutations in two genes, PKD1 and PKD2 are responsible for most of the cases.
•Current Treatment
–Kidney transplantation and or dialysis (8-10% of dialysis patients have PDK)
•Hypothesis:
–primary cilia in renal epithelium monitor fluid flow through renal tubules and regulate cell proliferation via calcium signaling. Loss of cilia function blocks the signaling pathway leading to cell proliferation and cyst formation.
•Treatment
–Several drugs are in clinical trials - Vasopressin receptor antagonists and the mTor inhibitor, rapamycin
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Term
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Definition
•Minus end motor (moves to minus end of microtubule -retrograde movement)
•Directs vesicle movement along microtubules towards microtubule organizing center - retrograde movement. Usually associated with the dynactin complex
• Also has role in mitotic spindle and chromosome segregation
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Term
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Definition
•Plus end motor (moves to plus end of microtubule -anteriograde movement)
•Directs vesicle movement along microtubules away from microtubule organizing center - anteriograde movement
• large collection of kinesin-like proteins
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Term
Physiological roles for kinesin-related proteins |
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Definition
•assembly and function of mitotic and meiotic spindle.
•membrane movement
•assembly of cilia
•signaling
•transport of RNAs and proteins
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Term
Communication between actin and microtubules |
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Definition
Ex.
–cell migration - growing microtubule ends traffic actin regulators
–myosin V-dependent spindle orientation in yeast
–vesicle trafficking
–immunological synapse
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Term
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Definition
Long range movement- microtubule motors
Short range movement- actin motors
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