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biochem > EXAM 3 STARTS: Cell adhesion > Flashcards

EXAM 3 STARTS: Cell adhesion Flashcards

1
Q

how do cells define their capacity for adhesive interactions

A

by selectively expressing plasma membrane receptors with limited ligan-binding activity

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2
Q

how are receptors expressed

A

mostly genetically but sometimes by extracellular stimuli

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3
Q

what is the second principle of adhesion

A

many adhesion proteins bind one main ligand and many ligands bind a single type of receptor

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4
Q

what makes the integrin family of receptors an exception to one-to-one pairing

A

they bind more than one ligand and some ligands, such as fibronectin, bind more than one integrin. they also bind ahdesion proteins on the surface of other cells including Ig-CAMs and one cadherin

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5
Q

describe how cadherins prefer to bind and what does binding require

A

prefer to bind themselves so they promote the adhesion of like cells. it requires Ca2+

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6
Q

describe how selectins bind

A

anionic polysaccharides like those on mucins. generally these interactions bind together two different types of cells

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7
Q

describe how Ig-CAMs bind

A

they bind other cell surface adhesion proteins. may occur between the same or different cell types

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8
Q

how do cells modulate adhesion

A

by controlling the surface density, state of aggregation, and state of activation of their adhesion receptors

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9
Q

what does surface density reflect

A

level of synthesis, partitioning of adhesion molecules between the plasma membrane and intracellular storage compartments

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10
Q

how can cells sort themselves

A

according to the type and level of cadherins they express

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11
Q

what are cadherins

A

calcium dependent adhesion molecules

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12
Q

what do cadherins do

A

establish and maintain intercellular connections
- spatial segregation of cell types

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13
Q

what anchors cadherins into the cell

A

a complex of proteins called catenins

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14
Q

what forms the adherens junctions

A

cadherin-catenin complex

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15
Q

where do catenins bind

A

the actin cytoskeleton of the cell

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16
Q

how well do cell surface adhesion proteins bind their ligands

A

weakly in comparison to other molecular interactions

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17
Q

what do rapid, reversible binding of ligands (transient adhesion) allow for

A

-white blood cells to roll along the endothelium of blood vessels
- fibroblasts to migrate through CT

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18
Q

where do many adhesion receptors interact

A

within the cytoskeleton inside the cell

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19
Q

what do adapter proteins link

A

cadherins and integrins to actin filaments or intermediate filaments

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20
Q

what is the purpose of adapter protein linkage of cadherins and integrins to actin filaments or intermediate filaments

A

provide mechanical continuity from cell to cell in muscles and epithelia, allowing them to transmit forces and resist mechanical disruption

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21
Q

what does the association of ligands and adhesion receptors activate

A

intracellular signal transduction pathways, leading to changes in gene expression, cellular differentiation, secretion, motility, receptor activation and cell division

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22
Q

how do cells attach to the underlying extracellular matrix

A

-focal adhesions- attach the actin cytoskeleton to fibers of fibronectin
- hemidesmosomes- connect intermediate filaments to basal laminae

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23
Q

where are integrin-containing cell matrix junctions found

A

highly motile cells such as keratinocytes and in immobile strongly adherent cells such as epithelila
- weakly adherent

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24
Q

where are hemidesmosomes found

A

mainly on the basal surface of epithelial cells

25
Q

what do hemidesmosomes do

A

firmly anchor epithelial cells to underlying basal lamina

26
Q

what does the cytosolic side of a hemidesmosome consist of

A

a plaque composed of adapter proteins which are attached to the ends of keratin filaments

27
Q

what is integrin alpha6beta4 localized to and what does it bind to

A

localized to hemidesmosomes and binds to plectin within the plaques and to laminin

28
Q

how do cell-matrix junctions increase the overall rigidity of epithelial tissues

A

by interconnecting the intermediate filaments of the cytoskeleton with the fibers of the basal lamina

29
Q

where is E-cadherin expressed

A

on all early mammilian embryonic cells, even at the 1-cell stage. later- restricted to epithelial tissues of embryos and adults

30
Q

where is P-cadherin expressed

A

trophoblast cells ( placental cells of the mammilian embryo that contact the uterine wall) and on the uterine wall epithelium

31
Q

what does P cadherin do

A

facilitates the connection of the embryo to the uterus

32
Q

what do protocadherins do

A

separate the notochord from the other mesodermal tissues during xenopus gastrulation

33
Q

where is N-cadherin expressed

A

first on mesodermal cells in the gastrulating embryo as they lose their E-cadherin expression. also highly expressed on cells of the developing CNS

34
Q

what does EP-cadherin do

A

critical for maintaining adhesion between the blastomeres of the xenopus blastula and is required for the normal movements of gastrulation

35
Q

what are protocadherins

A

calcium dependent adhesion proteins that differ from the classic cadhering in that they lack connections to the cytoskeleton through catenins

36
Q

what is homophilic binding

A

-cadherin joins cells together by binding same type of cadherin
example: E-cadherins will stick best to other cells with E-cadherin and will sort out from cells containing N-cadherin

37
Q

how can cadherins be restricted in their expression

A

spatially

38
Q

what are the functions of the basal lamina

A
  • molecular filter
    -cell barrier
  • molecular scaffolding to aid in regeneration after injury
39
Q

how does the basal lamina act as a molecular filter

A

retaining proteins in the blood while filtering toxic substances into the urine

40
Q

how does the basal lamina act as a cell barrier (example)

A

ameloblasts and odontoblasts separated by a BM during tooth development

41
Q

what does vinculin do when interacting with Arp2/3

A

at focal adhesions the leading edge promotes protrusion of the membrane

42
Q

what does vinculin do in traction force generation

A

links integrins to the actin cytoskeleton and bears the forces exerted during motility

43
Q

how does vinculin interact with PIP2

A

induces a conformational change that reduces vinculin interaction with actin, therby promoting the disassembly of focal adhesions

44
Q

how do t-cells use cell adhesion receptors

A

in process of antigen presentation

45
Q

how does mechanical tension activate signaling pathways at adhesion sites

A

exposure of cryptic sites, tension can affect protein conformation to expose protein binding sites or sites for kinases or other protein modifications

46
Q

how does RhoA regulate adhesion maturation through Rock and mDia

A

-adhesion of fibronecting activates RhoA through p115/RhoGEF and LARG, leading to rock mediated myosin stimulation.
-GEF-H1, LARG, and mDia are recruited and promote actin polymerization
-B1 and alphav integrin subtypes cooperate to regulate RhoA signaling and adhesion maturation

47
Q

how do cells transition to a motile state

A

de-adhesion of cells from the ECM by inhibition of cell-matrix interactions and by destruction of matrix components

48
Q

what do the main class of disintegrins contain

A

integrin-binding RGD sequence in ECM proteins

49
Q

what do disintegrins do

A

bind to integrins on the surface of cells and competitively inhibit binding of cells to matrix components

50
Q

what does the secondary class of disintegrins contain

A

2 proteases: ADAMs and MMPs

51
Q

what are ADAMs and what do they do

A

membrane bound proteases that catalyze shedding of transmembrane proteins
-soluble enzyme that cleaves non-fibrillary ECM proteins

52
Q

what do tight junctions do

A

seal gap between epithelial cells

53
Q

what do adherens junctions do

A

connect actin filaments between cells

54
Q

what do desmosomes do

A

connects intermediate filaments between cells

55
Q

what do gap junctions do

A

allow passage of small water soluble molecules from cell to cell

56
Q

what do hemidesmosomes do

A

anchor intermediate filaments in cell to ECM

57
Q

what are the cell- cell junction types and what is their transmembrane adhesion protein

A

adherens and desmosome and cadherin

58
Q

what are the cell-matrix junction types and what is their transmembrane adhesion protein

A

actin-linked cell-matric adhesion and hemidesmosomes and they use integrins

biochem (34 decks)

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