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BIO 230 > Lecture 3: Cell adhesion > Flashcards

Lecture 3: Cell adhesion Flashcards

1
Q

What do polarized cells do

A
  • Define inside vs outside
  • Have different functions at different cell regions
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2
Q

What does the extracellular matrix do

A

Directly bears mechanical stresses of tension and compression

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3
Q

How are mechanical STRESSES TRANSMITTED FORM CELL TO CELL

A

by cytoskeletal filaments anchored to cel-matrix and cell-cell adhesion sites

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4
Q

Connective or epithelial tissue

A

epithelial cells are cells directly connected to each other with minimal extracellular matrix

connective tissue are cess through the extracellular matrix

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5
Q

What do epithelial cells do

A

line surfaces, cavities, and organs

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6
Q

Mature polarized epithelial cells are….and what do they do

A

They are polarized
they define inside vs outside

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7
Q

What does epithelial structure and function require ?

A

junctional complexes

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8
Q

What are some types of junctional complexes ?

A

tight junctions
* tight junctions
cell -cell anchoring junctions
* adherents junction
* desmosome
channel forming junction
* gap junction
cell -matrix anchoring junction
* actin-linked cell-matrix junction
* hemidesmosome

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9
Q

What are tight junctions

A
  • they seal the gap between epithelial cells
  • prevents things from going between cells
  • form sealing strands all along the region between the two cells
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10
Q

What are adherens junctions

A

connects actin filament bundle in one cell with that in the next cell
* actin does not go through to the other side

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11
Q

What are desmosomes

A
  • connects intermediate filaments in one cell to those in the next cell
  • they don’t go through , they just anchor at specific spots
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12
Q

What are gap junction

A

allows the passage of small water- soluble molecules from cell-cell

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13
Q

What are hemidesmosomes

A

anchors intermediate filaments in the cell to extracellular matrix

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14
Q

What are Actin- linked cell- matrix junction

A

anchors actin filaments in cell to extracellular matrix

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15
Q

what are cell-cell junctions mediated by
what are cell- extracellular matrix junctions mediated by

A

*cadherins
*integrins

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16
Q

cytoskeleton may be …

A

actin/ intermediated filament

17
Q

What are cadherins

A
  • transmembrane proteins expressed by both cells
    *in a perpendicular arrangement
  • mediate cell-cell connections at adherens junction
18
Q

How do extracellular domains directly interact with each other ?

A
  • Cadherins interact homophilic interactions of their extracellular domains
  • Interactions require Ca2+
  • only one type of cadherin only interacts with other cadherins of the same type
19
Q

How do cells sort into groups based on homophobic cadherin interactions

A
  • Homophilic interactions from between cells expressing E-cadherins
  • Homophilic interactions from between cells expressing N-cadherins
  • No heterophilic interactions occur between E-cadherins & N-cadherins
  • Result: cells expressing different cadherins sort into two separate groups that do not interact
20
Q

How do Cadherin intracellular domains indirectly interact with actin

A
  • Cadherins form homophilic interactions with their extracellular domains to directly link adjacent cells
  • Cadherins indirectly interact with actin filaments
  • These interactions indirectly link the actin cytoskeleton between adjacent cells in epithelial tissues
21
Q

Which of the following most closely resembles adherens junctions mutations in the outer epithelium of Drosophila embryos?
a) Hemidesmosome mutation in the outer epithelium.
b) Calcium removal at the outer epithelium.
c) Intermediate filament depolymerization in the outer epithelium.
d) Occludin mutation in the outer epithelium.

A

b

22
Q

How do adhesion belts & sorting mediate morphogenesis ?

A
  • Adhesion belt contraction pulls cells to form a tube
  • Cells express different cadherins to establish new interactions and ensure neural tube closure
23
Q

What do adhesion belts mediate ?

A
  • morphogenesis
  • embryo development
24
Q

How do tight junctions define domains of the cell

A
  • Apical domain faces the surface, cavity, or organ
  • Basal domain
    faces the inside of the body
  • Basal & lateral domains often grouped into the basolateral domain
  • Domains are defined and maintained by tight junctions
25
Q

What forms tight junctions

A

Occludins & claudins

26
Q

How do Transmembrane occludins & claudins form homophilic interactions

A

Occludins & claudins form homophilic interactions with their extracellular domains to directly link adjacent cells
* Many rows of these proteins form a functional tight junction

27
Q

How do Tight junctions limit diffusion of membrane proteins

A
  • Remember: membrane proteins can diffuse in the plasma membrane
  • Tight junctions prevent membrane proteins from moving between the apical and basolateral domains
28
Q

How do Tight junctions regulate what enters an organism?

A
  • Tight junctions stop anything from directly diffusing from the gut lumen into connective tissue & blood
  • Active transporters must move glucose into the epithelial cell on the apical domain
  • Passive carriers in the basolateral domain allow glucose to diffuse out of the epithelial cell into the connective tissue/blood
29
Q

How do Integrins anchor actin filaments to the extracellular matrix

A
  • Integrin heterodimers directly bind extracellular matrix proteins
  • Integrins have a transmembrane domain
  • Integrins indirectly interact with actin filaments
  • Actin-integrin-extracellular matrix interactions can provide the adhesion necessary for cell migration
30
Q

Which key components of cell polarity define a functional epithelium

A

1) intracellular trafficking
2) cytoskeleton organization
+ 3) cell cohesion

31
Q

An occludin mutation in ________ cells will directly affect __________.
a) intestinal epithelial; glucose transport.
b) Drosophila embryonic; movement of the outer epithelium.
c) Drosophila embryonic; segmentation of the outer epithelium.
d) epithelial; adherens junction formation.

A

A

b- adherens
d- tight juncs

32
Q

How do polarity cues establish cell cohesion?

A
  • Adherens junctions form first
  • Adherens junctions provide polarity cues to define apical from basolateral domains
  • Tight junctions form apical to the adherens junctions
33
Q

The role of cell-matrix junctions in epithelial and connective tissue

A
  • Epithelial tissue: adhesion to the
    basal lamina extracellular matrix
  • Connective tissue: cell interaction with the extracellular matrix and cell movement

BIO 230 (5 decks)

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