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BIOL 3302 > cell adhesion > Flashcards

cell adhesion Flashcards

1
Q

what are the functions of cell adhesion?

A
  • allow for connections between cells to maintain tissue architecture to counteract external physical forces
  • responsible for signaling processes that relay information between cells
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2
Q

what are homophilic interactions?

A
  • binding to the same type of molecule
  • examples: cadherin, immunoglobulin-superfamily CAMs
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3
Q

what are heterophilic interactions?

A
  • binding to different type of molecule
  • examples: selectins, mucin-like CAMs, integrin
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4
Q

what is the cytoskeletal network made of?

A

actin, micro, and intermediate filaments

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5
Q

what is the velcro principle of adhesion?

A
  • low-affinity binding to ligand
  • strength coming from multiple bonds in parallel
  • allows for easy disassembly and cells to move around
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6
Q

tight junctions

A
  • type of occluding junction
  • present in vertebrates only
  • found in the apical region of epithelial cells
  • form selective barrier to solutes
  • involved in maintains the apico-basal polarity of epithelia
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7
Q

what do mucin-like CAMs, selectin, and integrin bind to?

A
  • mucin-like CAMs bind to carbohydrates
  • integrin binds to fibronectin
  • selectins have a lectin domain that bind to carbohydrates
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8
Q

tight junction is composed of _______ and ________ molecules that bind in the extracellular space to allow close apposition of the plasma membranes

A

caludin and occludin

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9
Q

__________ of a particular epithelia is a function of the number of sealing strands that it exhibits as well as the _____ protein used

A

permeability, claudin

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10
Q

which two proteins are the main responsible for controlling permeability

A

occludin and claudin

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11
Q

there are approximately __ different claudins

A

30

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12
Q

occludin is present in a ____ _____

A

single copy

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13
Q

examples of diseases affecting claudin and occludin (tight junctions)

A

hepatitis C and cholera

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14
Q

what do mutations in claudin 16 and claudin 14 cause?

A
  • claudin 16: magnesium cannot be absorbed back into body leading to convulsion
  • claudin 14: causes deafness
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15
Q

function of ZO 1, 2, 3 proteins

A

link claudin to the actin cytoskeleton to stabilize the tight junction and maintain permeability

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16
Q

two main functions of tight junctions

A

barrier and fence

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17
Q

describe barrier and fence

A

barrier: very selective, only allows specific molecules, separates and maintains extracellular compartments across epithelia
fence: separates apical and basolateral membrane proteins in discrete domains

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18
Q

proteins __ ___ intermingle with each other from basolateral to apical

A

do NOT

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19
Q

epithelial cells use tight junctions to control __________ transport

A

paracellular (passive but selective, variable and regulated)

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20
Q

adherens junctions

A
  • type of actin filament attachment sites
  • cell-cell junctions
  • involved in formation of sheets
  • include cadherins
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21
Q

classical cadherins

A

-e-cadherin (epithelial)
- n-cadherin 1 and 2 (neural)
- p-cadherin (placental)

22
Q

classical cadherins attach to actin via adaptor molecules including

A
  • alpha catenin
  • beta catenin
  • vinculin
23
Q

e-cadherins mediate

A

calcium dependent adhesion due to L cells lacking endogenous cadherin expression making them not adhere well to one another

24
Q

cadherins are relatively __ _______

A

low affinity

25
Q

describe selective cell affinity

A
  • based on the idea that cells that express the same cadherin stay together
  • tissue segregation between cells
26
Q

epithelial tumors have a requirement for _________

A

loss of cadherin

27
Q

describe why e-cadherin functions as a tumor suppressor

A

because of its loss-of-function this results in a pre-disposition towards advancing tumorigenesis

28
Q

describe the cadherin switch

A

“Cadherin switching” is the downregulation of E-cadherins and upregulation of N-cadherins and integrins in EMT (epithelial to mesenchymal transition)

29
Q

explain desmosomes

A
  • they are anchoring junctions (cell-cell junctions)
  • include the non-classical cadherins desmoglein and desmocoilin
  • they link to the intermediate filament network and help hold the nucleus in position
30
Q

what is pemphigus vulgaris?

A

it is a disease of desmosomes where the body attacks itself (auto antibodies to desmoglein 1 and 3). causes a disruption of adhesion between epithelial cells.

31
Q

what are gap junctions?

A
  • most cells are connected to each other by them
  • create adherence and electrically/chemically couple cells in collectives
  • small molecules (ex: calcium) and small second messengers (ex: cAMP) can be conducted through gap junction channels
  • play an important role in the heart tissue and neurons
32
Q

a connexon is formed from ___ ________ _________ in each cell forming a hemichannel

A

6 connexin subunits

33
Q

how do hemichannels function?

A

they can function alone in a cell or found in a register with a hemichannel from an adjacent cell forming a junction

34
Q

connexons are opened and closed (permeability) by

A

post translational modifications (phosphorylation)

35
Q

small molecules less than ______ Daltons in size can pass through gap junctions

A

1000 (1 kD)

36
Q

extracellular matrix proteins include

A

proteoglycans, collagens, and multi-adhesive matrix proteins

37
Q

what are the types of collagens?

A

sheet forming (type IV) and fibrillar (type I, I, III)

38
Q

what is a proteoglycan?

A

a covalently conjugated molecule (perlecan)

39
Q

what are examples of multi-adhesive matrix proteins?

A

laminin, fibronectin, nidogen/entactin

40
Q

what is the basal lamina?

A

it connects most epithelia and other organized groups of cells to adjacent connective tissue. it contains four multidomain proteins (laminin, collagen IV, perlecan, and nidogen).

41
Q

what amino acids make up collagen?

A

glycine, proline and hydroxyproline

42
Q

what is hydroxyproline important for?

A

the formation of vitamin C (absence of vit C can lead to scurvy)

43
Q

proteoglycan are composed of

A

large chains of sugars

44
Q

excessive production of collagen can lead to

A

struggling with breathing and fibrosis disease (can occur in liver, lungs and pancreas)

45
Q

what are the major types of glycosaminoglycans?

A

hyaluroan, dermatan sulfate, chondroitin sulfate, keratan sulfate, heparan sulfate.

46
Q

fibronectin structure is composed of

A

integrin binding, collagen binding and proteoglycan binding

47
Q

integrins are connected to the _____ cytoskeleton and are mediated by _______

A

actin, talin

48
Q

hemidesmosomes

A

use plectin to connect to intermediate filaments

49
Q

defects in ________ formation result in server blistering and diseases affecting the epithelia

A

hemidesmosome

50
Q

what is epidermolysis bullosa?

A

a blistering disorder causes by defect in hemidesmosome (1 in 50,000 births affected)

51
Q

what is kindler syndrome?

A

a disease where focal contacts are affected causing excessive proliferation with fluid resulting in blisters

BIOL 3302 (5 decks)

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