Cell Junctions, Adhesion Molecules, and Extracellular Matrix Flashcards

1
Q

What are the calcium dependent CAMs?

A

cadherins

selectins

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2
Q

What are the non calcium dependent CAMs?

A

integrins

immunoglobulin superfamily molecules

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3
Q

What ligands do cadherins recognize?

A

other cadherins (same or different)

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4
Q

What ligands do selections recognize?

A

carbonhydrates

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5
Q

What ligands do integrins recognize?

A

extracellular matrix molecules

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6
Q

What ligands do Ig superfamily recognize?

A

integrins

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7
Q

What stable types of junctions do cadherins have?

A

occludens and desmosomes

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8
Q

What stable types of junctions do selectins and Ig superfamily have?

A

none

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9
Q

What types of stable type junctions do integrins have?

A

hemidesmosomes

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10
Q

Describe classical cadherins

A

major components in calcium mediated adherent junctions

typically form cis and trans homophilic dimers

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11
Q

What are the three types of classical cadherins?

A

E-cadherins
N-cadherins
P- cadherins

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12
Q

Where are e-cadherins found?

A

epithelial tissues and brain

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13
Q

Where are n-cadherins found?

A

nerve cells, muscle cells, fibroblasts, lens cells

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14
Q

Where are p-cadherins found?

A

placenta and epidermis

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15
Q

Describe non classical cadherins

A

include desmocollins and desmogleins

found in desmosomes (macula adherins)

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16
Q

Extracellular portion contains multiple copies of _______

A

cadherin domain motif

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17
Q

Intracellular portion of cadherin superfamily are varied, thus able to interact with different _______ and components that anchor the ________ to cytoskeleton

A

intracellular ligands; cadherin; cytoskeleton

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18
Q

binding between cadherins is generally _____

A

homophilic

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19
Q

homophilic binding occurs at the _______ tips of the cadherin molecules

A

n- terminal

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20
Q

Extracellular portion of cadherin consists of several copies fo a motif called a ______

A

cadherin domain

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21
Q

_____ ions bind to sites near each hinge and prevent it from flexing, so cadherin domain is rigid rod

A

Ca2+

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22
Q

When Ca2+ is removed from a cadherin domain, what happens?

A

hinges can flex, and structure becomes floppy. Conformation at N terminus changes, weakening the binding affinity and disrupting the adhesion
cadherins are then degraded

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23
Q

Cadherins typically bind to their partners with relatively _____ affinity

A

low

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24
Q

In a cadherin mediated adhesion how to strong attachments form?

A

formation of many weak bonds in parallel

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25
Q

What is sorting out?

A

cadherin dependent homophile adhesions mediate highly selective recognition, enabling cells of a similar type to stick together and to stay segregated from other types of cells

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26
Q

Appearance and disappearance of cadherins correlate with major _____ in which tissues ______

A

morphogenetic events, segregate from one another

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27
Q

What does the intracellular domain do for cytoskeleton filaments?

A

provide anchorage

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28
Q

What are the most common types of cadherins?

A

E-cadherins

29
Q

E-cadherins form ______ via a _______

A

dimers; HVA binding face

30
Q

where are the dimers found on E-cadherins?

A

tip of extracelluarl end of cadherin molecule

31
Q

What does the loss e-cadherins associate with?

A

invasive behavior of tumor cells

32
Q

What are catenins?

A

small portions that link the cytoplasm end of a cadherin with cytoplasmic actin

33
Q

What are the three forms of catenins?

A

B and y/plakoglobin catenins

a catenins

34
Q

What do B and y/plakoglobin catenins do?

A

attached to cytoplasmic end of cadherin
beta may serve as transcription cofactor
beta is attached to alpha catenin

35
Q

What does a catenin do?

A

binds directly to cytoplasmic actin

36
Q

Selectins bind to _____

A

carbohydrates

37
Q

Where is the binding site for carbohydrates?

A

located at the carbohydrate -recognition domain (CRD) at the extracellular end of the selectin

38
Q

Where are calcium binding sites located?

A

found near CRD and calcium is required for the binding activity

39
Q

Selectins are involved in the ____ of ____ from blood to tissues

A

movement of leukocytes

40
Q

What are the types of selectins?

A

P-selectins: associated with platelets
E-selectins: associated with endothelial cells
L-selectins: associated with leukocytes

41
Q

Integrins are _______ that are mainly involved in _______ interactions

A

glycoproteins; cell extracellular matrix

42
Q

What do integrins bind to?

A

extracellular matrix and cytoskeleton

43
Q

What are the two subunits of integrins?

A

one alpha subunit (17 kinds)

one beta subunit (8 kinds)

44
Q

Integrins interact with ______ sequence in _____ and _____

A

RGD
fibronectin
laminin

45
Q

What do the laminin and fibronectin in the basement membrane interact with?

A

collagen
heparan sulfate proteoglycans
entactin

46
Q

In hemidesmosomes, integrins link the _____ of cells to the _______ kai the intracellular tonofilaments

A

basal domain, extracellular matrix

47
Q

What are the members of the Ig superfamily?

A

N-CAM

I-CAM-1 and I-CAM-2

48
Q

What does N-CAM do?

A

neural adhesion molecules

mediate both homophilic and heterophilic interactions

49
Q

What does I-CAM-1 do?

A

facilitates transendothelial migration of leukocytes

50
Q

What are the categories of junctional complexes?

A

adherens
occludens
gap junctions

51
Q

What are adherens?

A

molecular complexes that anchor cells together and reinforce the physical integrity of tissues and the cells that make up the tissues
found on the basolateral surface

52
Q

What are occludens?

A

molecular complexes that establish an impermeable barrier between adjacent cells, prevents paracellular transport and saints concentration differences

53
Q

What are gap junctions?

A

composed of molecular pores that enable cells to rapidly exchange ions and small molecules that help coordinate activities amounts the cells that make up the tissue

54
Q

What are the two types of junctions?

A

zonula

macula

55
Q

What are zonula junctions?

A

either of the adherent or occludens variety
travel al the way around the circumference of the cell and link all neighboring cells to the central cell. Belt like
associated with intracellular actin

56
Q

What are macula junctions?

A

spot or snap like junction
adherens variety
associated with intracellular intermediate filaments

57
Q

What are desmosomes associated with?

A

lateral domains of epithelial cells

58
Q

What are hemidesmosomes associated with?

A

basal domains of epithelial cells

59
Q

_______ are anchoring junctions characterized by intercellular spaces which are filled with cadherin proteins: _____ and _______

A

adherens
desmogleins
desmocollins

60
Q

Cadherin proteins are anchored to cytoplasmic plaques containing:

A

desmoplakin

plakoglobin

61
Q

_____ seals gap between epithelial cells

A

tight junction

62
Q

______ connects actin filament bundle in one cell with hat in the next cell

A

adherens junctions

63
Q

______ connects intermediate filaments in one cell to those in the next cell

A

desmosomes

64
Q

_____ allows the passage of small water soluble molecules from cell to cell

A

gap junction

65
Q

______ anchors intermediate filaments in a cell to extracellular matrix

A

hemisdesmosomes

66
Q

_______ actin filaments in cell to extracellular matrix

A

actin linked cell matrix adhesion anchors

67
Q

Zonula adherens are associated with _____

A

actin microfilaments

68
Q

Macula adherens area associated with ______

A

intermediate filaments