Cell Adhesion

Question 1

tight junction seals

Answer 1

gap between epithelial cells

Question 2

adherent junction connects

Answer 2

actin filament bundle in one cell with that in the next cell

Question 3

desmosomes connect

Answer 3

intermediate filaments in one cel to those in the next cell

Question 4

gap junctions allow for the passage of

Answer 4

small water soluble molecules from cell to cell

Question 5

actin linked cell matrix adhesion anchors

Answer 5

actin filaments in cell to extracellular matrix

Question 6

hemidesmosome anchors

Answer 6

intermediate filaments in a cell to extracellular matrix

Question 7

first principle of adhesion

Answer 7

cells define their capacity for adhesive interactions by selectively expressing plasma membrane receptors (cell adhesion molecules, aka: CAMs) with limited ligand-binding activity. Generally, expression of the proper mix of receptors is part of a genetic program for the differentiation of the cell. In some cases, extracellular stimuli control expression of adhesion receptors. For example, endothelial cells produce E-selectin only when stimulated by inflammatory hormones or endotoxin

Question 8

second principle of adhesion

Answer 8

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

Question 9

if this one-to-one pairing were the rule, adhesion would be simple indeed. However, many exceptions exist, particularly in the

Answer 9

integrin family of receptors

Question 10

these integrin receptors generally bind

Answer 10

more than one ligand, and some ligands, such as fibronectin, bind more than one integrin

Question 11

Most cadherins prefer to bind

Answer 11

themselves

Question 12

cadherins promote the adhesion of

Answer 12

like cells

Question 13

homophilic interactions

Answer 13

association of like receptors on two cells

Question 14

cadherin reactions require

Answer 14

ca

Question 15

Selectins bind

Answer 15

anionic polysaccharides like those on mucins

Question 16

Generally, such interactions bind together

Answer 16

two different types of cells

Question 17

Most Ig-CAMs bind

Answer 17

other cell surface adhesion proteins

Question 18

heterophilic interactions

Answer 18

association of unlike receptors on two cells

Question 19

These heterophilic interactions may occur between

Answer 19

the same or different cell types

Question 20

integrins stand apart because they bind

Answer 20

a variety of ligands

Question 21

variety of ligands includes

Answer 21

matrix macromolecules, such as fibronectin and laminin; soluble proteins, such as fibrinogen in blood; and adhesion proteins on the surface of other cells, including Ig-CAMs and one cadherin

Question 22

third principle of adhesion

Answer 22

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

Question 23

Surface density reflects not only the level of synthesis but also the

Answer 23

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

Question 24

endothelial cells express P-selectin constitutively but store it internally in membranes of cytoplasmic vesicles. When inflammatory cytokines activate endothelial cells, these vesicles

Answer 24

fuse with the plasma membrane, exposing P-selectin on the cell surface, where it binds white blood cells

Question 25

cadherins control the

Answer 25

selective assortment of cells

Question 26

cells can sort themselves out according to

Answer 26

the type and level of cadherins they express

Question 27

cadherins

Answer 27

calcium-dependent adhesion molecules. Cadherins are critical for establishing and maintaining intercellular connections, and they appear to be crucial to the spatial segregation of cell types and to the organization of animal form (Takeichi 1987). Cadherins interact with other cadherins on adjacent cells, and they are anchored into the cell by a complex of proteins called catenins (Figure 3.31). The cadherin-catenin complex forms the classic adherens junctions that connect epithelial cells together. Moreover, since the catenins bind to the actin cytoskeleton of the cell, they integrate the epithelial cells together into a mechanical unit.

Question 28

fourth principle of adhesion

Answer 28

The rates of ligand binding and dissociation are important determinants of cellular adhesion

Question 29

Many cell surface adhesion proteins (including members of the Ig-CAM, cadherin, integrin, and selectin families) bind their ligands

Answer 29

weakly in comparison with other specific macromolecular interactions, such as the interaction of antigens and antibodies, hormones and receptors, or transcription factors and DNA

Question 30

In some cases, this makes good biological sense. Rapidly reversible interactions allow white blood cells to

Answer 30

roll along the endothelium of blood vessels

Question 31

Transient adhesion also allows fibroblasts to

Answer 31

migrate through connective tissue

Question 32

On the other hand, the interactions of cells in epithelia and muscle appear to be more stable, perhaps owing to

Answer 32

multiple weak interactions between clustered adhesion proteins cooperating to stabilize adherens junctions and desmosomes

Question 33

The combined strength of these bonds is said to increase the “---” of the interaction

Answer 33

avidity

Question 34

fifth principle of adhesion

Answer 34

Many adhesion receptors interact with the cytoskeleton inside the cell

Question 35

Adapter proteins link cadherins and integrins to (2)

Answer 35

actin filaments or intermediate filaments

Question 36

These interactions provide mechanical continuity from cell to cell in muscles and epithelia, allowing them to t

Answer 36

ransmit forces and resist mechanical disruption

Question 37

sixth principle of adhesion

Answer 37

Association of ligands with adhesion receptors can activate intracellular signal transduction pathways, leading to changes in gene expression, cellular differentiation, secretion, motility, receptor activation, and cell division

Question 38

Signaling through adhesion receptors allows cells to

Answer 38

respond appropriately to physical interactions with the surrounding matrix or cells

Question 39

Cells attach to the underlying extracellular matrix through two types of integrin-dependent junctions:

Answer 39

focal adhesions | hemidesmosomes

Question 40

focal adhesions

Answer 40

attach the actin cytoskeleton to fibers of fibronectin

Question 41

hemidesmosomes

Answer 41

connect intermediate filaments to basal laminae

Question 42

Integrin-containing cell matrix junctions are found in (2)

Answer 42

highly motile cells such as skin keratinocytes, which are weakly adherent, and in immobile, strongly adherent cells such as epithelia

Question 43

hemidesmosomes are found mainly on the

Answer 43

basal surface of epithelial cells

Question 44

hemidesmosomes firmly anchor epithelial cells to the

Answer 44

underlying basal lamina

Question 45

what does the cytosolic side of hemidesosomes consist of?

Answer 45

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

Question 46

Integrin α6β4 is localized to

Answer 46

hemidesmosomes

Question 47

Integrin α6β4 is thought to bind to

Answer 47

an adapter protein, plectin, within the plaques and to the extracellular-matrix protein laminin

Question 48

by interconnecting the intermediate filaments of the cytoskeleton with the fibers of the basal lamina, these cell-matrix junctions increase the

Answer 48

overall rigidity of epithelial tissues

Question 49

adhesion proteins play a role in (3)

Answer 49

platelet function development health/disease

Question 50

E-cadherin (epithelial cadherin, also called uvomorulin and L-CAM) is expressed on

Answer 50

all early mammalian embryonic cells, even at the 1-cell stage

Question 51

Later, this molecule is restricted to

Answer 51

epithelial tissues of embryos and adults

Question 52

P-cadherin (placental cadherin) appears to be expressed primarily on the (2)

Answer 52

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

Question 53

It is possible that P-cadherin facilitates the connection of the

Answer 53

embryo to the uterus since P-cadherin on the uterine cells is seen to contact P-cadherin on the trophoblast cells of mouse embryos

Question 54

N-cadherin (neural cadherin) is first seen on

Answer 54

mesodermal cells in the gastrulating embryo as they lose their E-cadherin expression

Question 55

N-cadherin is also highly expressed on the cells of the

Answer 55

developing central nervous system

Question 56

EP-cadherin (C-cadherin) has been found to be critical for maintaining

Answer 56

adhesion between the blastomeres of the Xenopus blastula and is required for the normal movements of gastrulation

Question 57

Protocadherins are calcium-dependent adhesion proteins that differ from the classic cadherins in that they

Answer 57

lack connections to the cytoskeleton through catenins

Question 58

Protocadherins have been found to be very important in

Answer 58

separating the notochord from the other mesodermal tissues during Xenopus gastrulation

Question 59

Cadherins join cells together by binding to the

Answer 59

same type of cadherin on another cell

Question 60

cells with E-cadherin stick best to other cells with

Answer 60

E-cadherin, and they will sort out from cells containing N-cadherin in their membranes.

Question 61

This pattern is called

Answer 61

Homophilic binding

Question 62

how can cadherins be restricted in their expression?

Answer 62

spacially

Question 63

what are the three functional roles of the basal lamina?

Answer 63

1. molecular filter (retaining proteins in the blood while filtering toxic substances into the urine) 2. cell barrier (ex. ameloblasts and odontoblasts separated by a basement membrane during tooth development) 3. molecular scaffolding to aid in regeneration after injury

Question 64

what do T cell use in the process of antigen presentation?

Answer 64

adhesion receptors

Question 65

how are adhesion molecules used in antigen recognition?

Answer 65

colonel expansion

Question 66

what process do cell adhesion receptors participate in?

Answer 66

sensation and response to mechanical forces

Question 67

This transition to a motile state requires de-adhesion of cells from the extracellular matrix by (2)

Answer 67

inhibition of cell-matrix interactions | destruction of matrix components

Question 68

One class of de-adhesion factors comprises small peptides, called

Answer 68

disintegrins

Question 69

disintegrins contain the integrin-binding RGD sequence present in many

Answer 69

ECM proteins

Question 70

By binding to integrins on the surface of cells, disintegrins competitively inhibit

Answer 70

binding of cells to matrix components

Question 71

The disintegrins present in snake venoms, which prevent platelets from aggregating, are partly responsible for the

Answer 71

anticoagulant property of venoms

Question 72

what does the second class of de-adhesion factors contains two types of proteases contain? (2)

Answer 72

ADAMs (ADAM-TS) | matrix-specific metalloproteinases (MMPs)

Question 73

ADAMs

Answer 73

membrane bound proteases that catalyze shedding of transmembrane proteins

Question 74

ADAM-TS

Answer 74

a soluble enzyme that cleaves non-fibrillary ECM proteins

Question 75

By degrading ECM matrix components, these enzymes facilitate

Answer 75

cell migration