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D.Kurry Histology KCUMB > Lecture - 6 Cytoskeleton > Flashcards

Lecture - 6 Cytoskeleton Flashcards

1
Q

What are the three types of cytoskeleton componets?

A

Microfilaments

intermediate filaments

Microtubles

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2
Q

What are the characteristics of actin monormers and filaments

A
  • highly conserved
  • WxL = 7nm x 7 um
  • monomers “depolarized” = G- actin
  • longchain “polarized”= F acrin
  • r varieties = alpha, beta, gamma
  • actin filaments are Polarized b/c actin monomers added in the same direction
    *
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3
Q

What is actin polymerization?

A

G actin monomers have to oriented in same direction to form trimer (polarity)

Nucleation when 3 ATP-G Actins form a trimer

Trimer polmerization : adds more G actins via Additsions of ATP to the growin plus or barbed end

Causes ATP to be Hydrolized into ADP

THis action is REVERSIBLE ; Leads into treadmilling

PS: F actin is a double helical chain of G actin

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4
Q

What is treadmilling?

A

A dynamic equalibrium b/w the pointed (minus) and the (plus) barbed end.

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5
Q

How does actin monomer concentration affect G actin?

A
  • The addition of G actin filaments occur more rapidly and at a lower concentration at the plus or barb end. (5 -10 X)
    • The minus of slow growing end is the slow growing one.
  • Higher concentrations of G actin facor net addition at both ends
  • AT VERY LOW, concentrations G actin f avor disassembly of actin
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6
Q

What drugs affect polymerization and Control Tread milling?

A
  • Cytochalasins
    • Bind to barbed ends, block elongations, can inhibit movements
  • Phalloidin
    • Binds to actin filamaents and prevents dissocation
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7
Q

What is list the Actin binding proteins.

Hint there are 13 of them

A
  1. Spectrin:
  2. Dystrophin:
  3. Villin and Fimbrin:
  4. Calmodulin and Myosin 1:
  5. Alpha- Actin
  6. Filamin:

ACtin binding molecules that control treadmiling

  1. Thymosin
  2. Profilin
  3. Gelsolin
  4. Cofilin
  5. Arp 2/3
  6. Phalloidin
  7. Latrunculins
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8
Q

What is Thymosin: ?

A

• Captures actin monomers; prevents monomers from being polymerized.

actin binding molecule that controls treadmilling

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9
Q

What is Profilin?

A
  • BInds to actin monomers and prevents monomers from being polymerized
  • MAIN FUCNTION
    • FACILITATE THE EXCHANGE OF BOUND ADP FOR ATP WHICH FAVORS POLYMERIZATION
  • (only atp monomers can assemble into f actin)
  • Actin binding molecule that controls treadmilling
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10
Q

What is gelsolin?

A

Destablizes F actin and caps actin filaments

Prevents loss and addition of G actin

In presence of Calcium ion, fragments actins filaments remain vound to plus end

Actin binding molecule that controls tread milling

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11
Q

What is Spectrin?

A
  • Found in red blood cells
  • maximizes SA for O2 exchange
  • binds cortical skeleton to PM
  • Actin Binding Protein
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12
Q

What is Dystrophin

A

Binds to the cortical skeleton to PM

Actin binding protein

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13
Q

WHat are villin and Fibrin?

A

Actin bind protein

Cross links in microvilli

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14
Q

WHat is calmodulin and myosin I?

A

Cross links actin to PM in microvilli

Actin Binding Protein

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15
Q

What is alpha Actin?

A

Cross links stress fibers and connects actin to protein plasma membrane complexes.

Actin bind protein

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16
Q

What is Filamin?

A

Actin binding protein

Cross links actin at wide angles to form screen like gels

17
Q

What is cofilin?

A

Triggers the depolymerization of ADP bound actin at the minus end

It is an actin bind ing molecule that controls treadmilling

18
Q

WHat is Arp 2/3

A

Initiaties the growth of F actin from sides of existing filament-causing branching

Actin binding molecule that control treadmilling

19
Q

what is Phalloidin

A

Prevents the depolymerization by binding to actin fialments

20
Q

What are Latrunculins?

A

Binds to G actin and induces F actin depolermization

Actin molecules that control treadmilling

21
Q

What is the basic structure and assembly of intermediate fialments ?

A
  • 8-10 nm thick
  • Head and tail domains that determine function
  • central rod of two poly peptides forma dimer
    • rods aligned tail to tail and head to haed
  • Associate in a staggered antiparallel fash to form tetramers
    • b/c antiparallel association they lose their polarity
    • more stable than actin doesnt require treadmilling
  • 8 tetra wound together form Unit length filament
  • ULF connected together form an intermediate
    *
22
Q

What is the structure of microtubles

A
  • 25 micrometers in diameter
  • composed of tublin dimers
    • alpha and beta
  • protofilaments formed are from long chains of dimers
    • fast growing plus end and slow growing minus end
  • microtubles consist of 13 protofilaments arranged parallel to form a cylinder with a hollow core.
23
Q

How does treadmilling and dynamic instability relate to microtubles assembyl and dissembly?

A
  • Tublin dimers with bound GTP (energy ) assocate bind to Growing END
  • Plus end also grow more raplidly than minus end (in presence of low calcoium ion concentrion)
  • After polymerization, GTP (their energy) is hydrolyzed to GDP and the tubulin is less stable.
  • Dimers at the minus end dissociate
  • At high concentratiosn of tublin GTP the dimers are added more rapidly than GTP is hydrolzed and microtuble grows
  • If concentration of GTP tublin is drops, GTP at the plus end is hydrolyzed and dimers are lost.
24
Q

WHat are the different types if intermediate filaments?

A
  • Type I
    • acidic keratins
  • Type II
    • neutral to basic keratins
  • Type III
    • vimentin, Desmin, Glial fibrillary Protein, and preipherin
  • Type IV
    • Neurofilaments
  • Type V
    • nuclear lamins
  • Type VI
    • NEstin
25
Q

What factors inhibit microtubule polymerization?

A

Colchicines

Colcemid (stops mitosis at metaphase)

VIncrstine

Vinblastine

26
Q

What factors that affect microtublles are anticancer drugs?

A

Vincristine

Vinblastine (hodkin lympphoma)

Taxol (for breast cancer)

All of these are antimitotic drugs that inhibtit polymerization or depolyermerization of microtubles on mitotoic spindle

27
Q

WHat are functions of the cytoskeleton?

A
  • Cell movement
  • Suppport and strength for the cell
  • Phagocytosis
  • Mitotic spindle formation
  • cytokinesis
  • Cell tocell and Cell to extracellular matric adherence
  • changes in cell shape
28
Q

How do microtubles affect mitosis?

A

help split apart the homologous chromosomes in to daughter cells

  1. mitotic center
    • microtuble organizing center
    • centroles
    • radiating microtubles (anchor center to membtane
  2. Mitotic Spindle
    1. Kineteichore MicroT
    2. Polar MircoT
      3.
29
Q

What is the mechanism for Intracililary transport?

A

Kinsein move dimers from minus end to the plus end w/ raft proteins

Anterograde transport

Dynein dimers from plus to minus w/ raft proteins

retrograde transport

30
Q
  • What is the role of microtubles and motor protein in axon transport?
A
  • Microtubles serve as the monorail for transport
  • Kinesin - transports vesicles from minus to plus end
    • anterograde
  • Dynenin attached to MT and run along MT carry vesicles from plus to minus end
    • Retrograde
31
Q

How are the two kinds of myosin, kinesin, and cytoplasmic dynein different with regard to structure and function

A
32
Q
A

D.Kurry Histology KCUMB (26 decks)

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