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Block Two Cell Signaling > Cellular Adhesion and Migration > Flashcards

Cellular Adhesion and Migration Flashcards

1
Q

Classes of cell junctions in animal tissues

A
  1. Anchoring junctions
  2. Occulding (tight) junctions
  3. Channel-forming junctions (gap junctions)
  4. Signal-relaying junctions
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2
Q

Anchoring junctions

A

Assemble and maintain epithelia; Transmit stresses and mechanically attach cells to their neighbors; consists of transmembrane adhesion proteins that link to cytoskeleton via intracellular anchor proteins
ex. cell-cell adhesions and cell matrix adhesions

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3
Q

Occulding (tight) junctions

A

seal gaps btwn cells in epithelia; forms selectively permeable barrier

  • keeps interstitial fluid inside animal*; always closest to apical domain
  • prevent back flow from one side of cell to other
  • forms fence btwn membrane domains (cells need to segregate proteins to appropriate domain ie basolateral or apical)
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4
Q

Channel-forming junctions (gap junctions)

A

link cytoplasm of adjacent cells

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5
Q

Signal-relaying junctions

A

allows signal relay from cell to cell at PM contact

ex. chemical synapses in nervous system and immunological synapses

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6
Q

junctions that allow cell to form epithelium

A

anchoring junctions and occluding junctions

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7
Q

cell cell attachments

A

usually mediated by cadherins

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8
Q

cell matrix attachments

A

usually mediated by integrins

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9
Q

Anchoring junction components

A

Transmembrane adhesion proteins (attach to each other btwn PMs) and intracellular adaptor proteins (attach transmembrane adhesion proteins to cytoskeletal filaments)

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10
Q

Catenins

A

Adaptor proteins that link cell adhesion receptors to cytoskeletal elements; cadherins anchor to cytoskeleton via catenins which assemble on cadherin tail

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11
Q

Actin filament attachment sites

A
  • adherence junctions (cell-cell junctions)

- Actin-linked cell-matrix adhesions (cell-matrix junctions)

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12
Q

Intermediate filament attachment sites

A
  • Desomsomes (cell-cell junctions)

- Hemidesmosomes (cell-matrix junctions)

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13
Q

Adherens junctions

A

coordinate actin-based motility of adjacent cells; form continuous adhesion belt around interacting cells in epithelial sheet; contract via myosin motor proteins; confer motile force for folding of epithelia sheets

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14
Q

Cordination of actin based motility of adjacent cells

A

coordinated by adherens junctions; oriented contraction of bundles of actin filaments running along adhesion belts causes narrowing of cells at apex

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15
Q

Desmosomes

A

link intermediate filaments from cell to cell main job is to confer mechanical strength

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16
Q

desmosomes and hemidesemosomes

A

along with intermediate filaments form network of great tensile strength; desmosomes link intermediate filaments from cell to cell hemidesmosomes link intermediate filaments to basal lamina?

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17
Q

Pemphigus

A

autoimmune disease body attacks desmosomal cadherins cells become “unglued” from each other -> severe blistering

18
Q

Cadherins

A

mediate cell cell attachment at anchoring junctions (adherens junctions and desmosomes)
CALCIUM DEPENDENT

19
Q

Cadherin structure

A

extracellular domain contains cadherin repeats which are joined by flexible hinge regions
Ca2+ binds at linker region -> prevents flexing
Ca2+ absent from linker region -> hinge region floppy

20
Q

Cadherin binding

A

cadherins on opp cells bind end to end; binding = homophilic; multiple parallel low affinity bonds allow for strong interactions and easy assembly; intracellular domains highly variable b/c high variety intracellular ligands

21
Q

homophilic binding cadherin

A

molecules of specific subtype in one cell only bind cadherins of same or closely related type

22
Q

Selective assortment of cells

A

controlled by cadherins; appearance and disappearance of specific cadherins allows cells to regroup and change their contacts to form new tissue structures

23
Q

Epithelial-mesenchymal transition

A

epithelial cells can disassemble from parent epithelium and adopt mesenchymal phenotype and migrate away as individual cells via change in expression of adhesion molecules regulated by transcription factors such as twist, snail, and slug
Important in:
-Development
- wound healing (want cells near wound to move in and loose growth inhibition
- cancer

24
Q

Origin of neural crest

A 
epithelial-mesenchymal transition
-cells from epithelial- neural tube alter their adhesive properties, twist represses transcription of e-cadherin
Migrate:
-chemotaxis
-chemorepulsion
-contact guidance
Reaggregate
25
Q

cell-cell adhesions and intracellular signaling

A

there is cross talk between adhesion machinery and cell signaling pathways

  • cells attached to other cells proliferation inhibited (contact inhibition)
  • attachments btwn cells broken proliferation stimulated (ex wound healing)
26
Q

Beta catinin

A

Dual functions serves as anchoring protein at adherens junctions and nuclear transcription factor
Cell location (nucleus vs adherens junction) dictates its fx
- relocates to nucleus during epithelial-mesenchymal transition (bc freed when transition to mesenchymal cell when loose E cadherin so relocates to nucleus)
- mislocalization -> cancer

27
Q

Occulding junction structure

A

serve as fence between apical and basolateral domains of polarized epithelial cell (ensures protein segregate to appropriate domain)
branching networks sealing strands encircle apical ends of cell in sheet
** always closest to apical part of cell**
Each strand composed of long row transmembrane adhesion proteins (Claudine and occluding) embedded in interaction PMs; extracellular domains adhere occluding extracellular space

28
Q

Claudins

A

one of two transmembrane adhesion proteins (Claudine and occluding) embedded in PM forming occluding junction; Claudins have characteristic ion-conductive properties so type Claudine determine ion-selectivity; differential expression Claudine changes permeability under diff circumstances

29
Q

alterations in claudins

A

leads to alteration in permeability can leads to internal cystitis and diabetic retinopathy
- abnormal Claudin expression may be part of pathologic process of feline idiopathic cystitis

30
Q

tight vs leaky epithelia

A

differ in permeability of their tight junctinos

  • Bladder transitional epithelium= most impermeable epithelium in animal body
  • renal tubules= allow paracellular transport
31
Q

paracellular transport

A

transport of solutes between cells

32
Q

How do tight junctions work

A

Occludins determine permeability to solute

Claudins assemble sealing strands

33
Q

Organization of cell junctions in epithelial

A

relative positions diff kinds of junctions are same in all epithelial
Most apical: Occulding junctions -> adherens junctions -> desmosomes (Most basal)
Scaffold proteins = critical components of junctional complexes

34
Q

Intacelluar scaffold proteins

A

position and organize tight junctions into correct relationship with other components of junctional complexes

35
Q

Scaffold proteins

A

critical components of junctional complexes

- help to establish apico-basal polarity and play key part in control of cell proliferation

36
Q

cell migration requires

A

making and breaking of cellular adhesion

37
Q

leukocyte migration to site of inflammation

A

1st forms attachment to vascular endothelium then transverses basement membrane and finally crawls through ECM; weak attachment of leukocyte to endothelial sure mediated by cell-surface carbohydrate biding proteins (selectins); stronger adhesions necessary for extravasation mediated by integrins

38
Q

ECM degredation

A

integral component migration; mediated by matrix matalloprotinases and serine proteases

39
Q

FAK

A

focal adhesion kinase in command and control of cell motility; form intracellular attachment through integrin

40
Q

Cell motility

A
  1. Actin polymerization at forward end
  2. Membrane delivered to leading edge
  3. Focal adhesions form at leading edge (localized integrin-mediated attachments at leading edge) providing traction (attachments form at front of lamella podia)
  4. Integrins recruit FAK at sites cell substrate adhesion
  5. Tyrosine phosphorylated by FAK creates docking sites for other signaling proteins
  6. Contraction at rear of cell
  7. Attachments at rear of cell disassembled to allow forward movement
41
Q

bovine leukocyte adhesion deficiency

A

defect in neutrophil Beta2 integrin chain; neutrophils unable to leave blood stream; autosomal recessive
-> pneumonia, enteritis, stomatitis

Block Two Cell Signaling (12 decks)

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