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Cell Bio 2382B > Actin, Intermediate Filaments, Cell Adhesion > Flashcards

Actin, Intermediate Filaments, Cell Adhesion Flashcards

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1
Q

Smooth Muscle

A
  • phosphorylate myosin light chain = persistent contraction

- regulated by extracellular signals

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2
Q

Myosin and Vesicle Transport

A
  • myosin V bound vesicles carried along actin filaments
  • actin is capped by formin
  • actin pulls on MTs to pull nucleus
  • myosin V needs cargo to be active
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3
Q

Myosin V and Yeast Budding

A
  • material transported into bud by myosin V
  • formin activated at end and entry of bud
  • actin added at (+) end = growing
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4
Q

Cytoplasmic Streaming

A
  • transport along actin cytoskeleton = cytoplasm move
  • used with diffusion in gas exchange
  • cortical cytoplasmic actin around plant cell
  • myosin V moves organelles along actin
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5
Q

Cell Migration

A
  • pushing PM forward b/c actin polymerization
  • Leading Edge = filopodia and lamellipodia
  • Stress Fibers = focal adhesions (anchors cell to substrate)
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6
Q

Chemotaxis

A
  • cells respond to cAMP
  • cells have receptor for chemoattractant around cell surface
  • activates actin polymerization at leading edge
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7
Q

Steps of Cell Movement

A
  • cell on substrate attached to focal adhesions + cAMP

1) Extension = actin polymerization at leading edge
2) Adhesion = lamellipodia forms NEW focal adhesion
3) Translocation = cell moves
4) De-adhesion & Endocytic Recycling = remove old adhesion

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8
Q

Signalling Molecules

A

Rho-GTP ==> formin
Cdc42-GTP ==> activates WASp ==> activate Arp2/3
Rac-GTP ==> activates WAVE ==> activate Arp2/3

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9
Q

Mutations to Signalling Molecules

A

Dominant-active Rho = stress fibers
Dominant-active Cdc42 = lamellipodia
Dominant-active Rac = filopodia

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10
Q

Scratch Closure Assay

A

Cdc42 –> Rac –> Rho –| Rac

  • confluent cells scratched = wound
  • control = wound closure
  • experimental (inactive form ANY signalling molecule) = wound does not close
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11
Q

Intermediate Filaments

A
  • not globular
  • not need ATP or GTP
  • no polarity
  • no motor proteins
  • tetramer = basic subunit
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12
Q

Class I of Intermediate Filaments

A

acidic keratins
epithelial cells
tissue strength

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13
Q

Class II of Intermediate Filaments

A

basic keratins
epithelial cells
tissue strength

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14
Q

Class III of Intermediate Filaments

A

desmin, GFAP, vimentin
muscle & mesenchymal cells
sarcomere organization

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15
Q

Class IV of Intermediate Filaments

A

neurofilaments
nucleus
axon organization

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16
Q

Class V of Intermediate Filaments

A

lamins
nucleus
nuclear organization

17
Q

Proteins Associated with Intermediate Filaments

A

plectin cross-links intermediate filament vimentin and MT

18
Q

Functions of Intermediate Filaments

A
  • structural support for cell (links to PM)

- lamins support nuclear membrane

19
Q

Dynamic State

A
  • proteins within filament are exchanged
  • N-terminal domain of lamin A phosphorylated at serine = disassembly and prevents reassembly
    • break nuclear membrane –> mitotic apparatus
20
Q

Tissue Integrity

A
  • transgenic mice w/ mutant keratin gene = skin blistering

- epithelial cells have IF anchored to desmosomes and hemidesmosomes

21
Q

Epithelial Cells Polarity

A
  • apical surface = microvilli

- basal surface = connect to ECM

22
Q

Tight Junctions

A
  • hold cells together to prevent material going through

- rows of occludin, claudin, JAM proteins in each cell

23
Q

Gap Junctions

A
  • hold cells together for communication
  • 6 connexins = connexon
  • 2 connexons = gap junction channel
  • channel closes when exposed to Ca2+
24
Q

Cadherins (Homophilic Interactions)

A
  • single transmembrane domain + cytosolic C-terminal tail
  • Ca2+ dependent
  • linked to intermediate filament = desmosome
  • linked to actin (via adapter proteins) = adherens junction
25
Q

Ig-Superfamily CAMs (Homophilic Interactions)

A
  • mediate Ca2+ independent homophilic interactions
26
Q

Integrins (Heterophilic Interactions)

A
  • heterodimeric transmembrane protein
  • α1β1 binds collagen
  • α5β1 binds fibronectin
  • α6β1 binds laminin
  • bind to core RGD amino acids
27
Q

Selectins (Heterophilic Interactions)

A
  • leukocyte extravasation (WBC leave bloodstream)
  • endothelial cells secrete P-selectin and PAF
  • P-selectin binds to oligosaccharides on leukocyte
  • PAF binds to PAF receptor on leukocyte – activate integrin
  • integrin binds to ICAM
  • push endothelial cells apart and enter
28
Q

Extracellular Matrix Proteins

A 
Proteoglycans = hydrophilic (absorb water)
Collagen = structural (strength)
Laminin = adhesive (recognized by integrins)
Fibronectin = adhesive (recognized by integrins)
29
Q

Extracellular Matrix Functions (5)

A
  • anchor + surround cells —> shape
  • control cell polarity, survival, differentiation
  • inhibit/facilitate cell migration
  • binding growth factors
  • activating cell surface receptors
30
Q

Integrins + Extracellular Matrix

A

Bind to ECM
Cytoskeleton (actin = stress fiber) (IF = hemidesmosome)
Active form to bind to substrate
- inactive not bind to RGD

Cell Bio 2382B (12 decks)

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