LEC38: Cells in Tissues: Junctions, Adhesion, and Extracellular Matrix Flashcards Preview

MCG > LEC38: Cells in Tissues: Junctions, Adhesion, and Extracellular Matrix > Flashcards

Flashcards in LEC38: Cells in Tissues: Junctions, Adhesion, and Extracellular Matrix Deck (44):
1

what is epithelia

majority of cell in body are epithelia 

line channels on inside and outside of body - i.e. in pancreas, gut, skin 

form sheets, display polarized structure, w/ apical border exposed or lining channel and basal surface on basal lamina 

2

are epithalial cells polarized

yes 

polarization maintained by specialized cell junctions that bind the cells to each other, help separate distinct membrane domains

3

kinds of cells in body

epithelia

connective tissue

muscle cells

nervous cells

blood cells

4

ell adhesion moecules

1) cadherins 

2) IG superfamily 

3) integrins

4) selectins

5

homophilic vs heterophilic binding

homophilic- same adhesion molecule binding (i.e. cadherins) 

heterophilic- diff molecules (integrins on the cell, laminin on ECM)

6

cell adhesion molecule functions inside cells

1) inside cells, bind to adapter proteins that interact w/ cytoskeleton, thereby connecting outside of cell to cellular machinery:

binding regulates cell migration, cell proliferation, cell death 

2) associate in clusters in a lateral fashion, creating junctions of cell adhesion molecules 

7

ECM functions

1) hold tissues together - multiadhesive proteins

2) provide cushioning (cartilage) and strength (tendons) - via proteoglycans 

3) acts as reservoir for growth factors 

4) resist tensile/stretching forces via proteins like collagen

8

what comprises ECM?

proteins and carbohydrates such as proteoglycans 

all ECM components are highly networked w/ each other, and w/ receptors on cell surface, i.e. integrins 

composition of ECM varies by tissue

9

purpose of epithelial cells' polarized cellular organization

divide body cavities, provide barriers between gut and blood and blood brain barrier 

polarization allows for diff functions like absorption of nutrients on 1 membrane, secretion from another membrane 

10

what is on apical surface of epithelial cells

villi 

for absorption

11

cell junctions in epithelial cells

1) tight junctions 

2) anchoring junctions: adherens, desmosomes, hemidesmosomes

3) communicating junctions: gap junctions

4) integrins

12

tight junctions function? structure?

exist directly under microvilli 

seal epithelial cells together in sheets

prevents passage of small molecules 

13

tight junctions made of?

claudins, occludins

14

anchoring junctions function

join cells to each other and to ECCM

1) adherens junctions and desmosomes

2) focal adhesions and hemidesmosomes

 

15

adherens junctions and desmosomes functions

made by homophilic interactions among cadherens

hold cells together by connecting to a linker protein, alpha and beta catenin, in the middle of cytoskeletons of 2 cells 

impact polarity of epithelial cells also 

16

nature of caderins throughout the body?

tissue specific localizations - diff kinds of cadherins in diff parts of the body

cancer cells can move throughout the body if/when they lose their specific cadherins 

17

focal adhesions?

integrin proteins that bind to the ECM outside and attach to actin inside the cell 

controls interaction of integrin w/ the ECM, outside of cell 

impact physiological processes

18

desmosomes connect with what?

anchoring junctions that connect with cadherins and IF, so bind indirectly to actin

 

19

hemidesmosomes are made of?

IF

bind inside the cell, and to the ECM via integrin

20

gap junctions function?

cell - cell communication 

allwo for electrical coupling between cells

21

what are cadherins

what does their loss result in

large glycoproteins that link by a homophilic (same cadherin) mechanism 

link to actin cytoskeleton via adapter proteins, catenins (alpha and beta catenin) 

disruption of cytoskeletal interaction via adapters -> loss of adhesion

22

integrins function

cell matrix receptors on cells 

are abdunant on cell surfaces, bind ligand w/ low affinity 

activate signaling pathways upon ligand binding 

comprise alpha and beta subunits held together noncovalently

Ca2+ or Mg2+ needed for ligand binding

23

what integrain is a hemidesmosome connection

a6b4 interacts w/ IFs a hemidesmosomes 

exception to integrins connecting to bundled actin filaments

24

what mediates actin-integrin interaction

anchor proteins - talin, a-actinin, filamin 

linkage leads to clustering and formaiton of focal adhesions

25

what are selectins?

lectins (carb binding) that media Ca2+-dependent cell-cell adhesion in bloodstream 

L-selectin in WBC, P-selectin in platelets 

each binds to a specific carb on another cell 

26

how do WBC travel around the blood

during inflammation, endothelial cells express E-selectin 

as travel around blood, WBC bind to an epithelial cell via selectins (i.e. E-selectin), selectins collaborate w/ integrtins

WBC then roll over cells til get to integrins, where WBC are stopped, and go through endothelial cells and into tissue 

so selectins mediate weak binding at first, integrins mediate strong binding to WBC

27

what is ECM

space between cells 

a misture of proteins and polysaccharides 

high ECM in bone and cartilage, low ECM in brain and spinal cord

28

what forms bone/teeth

calcified ECM

29

how is ECM in tendon

trannsparent

30

what is basal lamina

form of the ECM at interface of epithelia and connective tissues

31

where is basal lamina found

underlies epithelial cell sheets and tubes 

around muscle cells, fat cells, schwann cells 

separates these cells from CT and serves as highly selective filter

32

what does basal lamina influence

cell polarity, metabolism, survival, proliferation, idfferentiation 

serves as highway for migration

33

what forms BL

cells that sit on it

34

what is basement membrane

structure connected to BL by type IV collagen to underlying CT 

35

proteins of the BL?

type IV collagen 

multiadhesive proteins, laminin 

proteoglycan, perlecan 

nidogen

these form a meshlike structure

36

laminin is?

heterotrimeric multiadhesive matrix protein found in all BL 

interacts w/ integrins on 1 end, collagen on other end 

helps integrate structures

37

most abundant protein in body?

collagen

38

ollagen structure

triple stranded helical conformation, forms a rope-like structure 

can resist tensile forces 

in tendons, are in parallel bundles, aligned along major axis of tendon

39

proteoglycan structure and function

type of GAG 

hydrate to a high degree, become gel-like to resist compressive forces 

easily form gels

40

how are collagen in bone, cornea?

arranged in parallel bundles that lie on top of other bundles at right angles 

collagen XVIII is in basal laminae of blood vessels 

Collagen XVIII cleavage -> endostatin, which inhibits angioenesis

41

what is fibronectin structure, function?

modular protein that binds to other matrix molecules and receptors on cells - binds integrins on 1 end, collagen on other end, integrates binding btwn them

42

structure, funciton of elastin?

found on skin, blood vessels, lungs 

elastic fibers allow for recoil after transient stretch 

rich in glycine, proline, hydroxyproline 

sheated by microfibrils ocntaining fibrillin

43

what causes Marfan's syndrome?

mutation in fibrillin I gene 

fibrillin I usually binds to an intert form of TGF-beta, keeps it firmly inactive 

patients w/ fibrillin I mutation means cells cannot form TGF beta in its inactive form, instead get overactive TGF beta and overactivity of the growth factor

leads to defects in tissues rich in elastic fibers, such as aorta, which is prone to rupture; loose joints, weakness in blood vessels, tallness 

 

44

what re: fibronectin makes cancer cells more mobile 

cancer cells make less fibronectin -> are more mobile 

are not anchorage dependent 

Decks in MCG Class (77):