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

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

1
Q

what is epithelia

A

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

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2
Q

are epithalial cells polarized

A

yes

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

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3
Q

kinds of cells in body

A

epithelia

connective tissue

muscle cells

nervous cells

blood cells

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4
Q

ell adhesion moecules

A

1) cadherins
2) IG superfamily
3) integrins
4) selectins

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5
Q

homophilic vs heterophilic binding

A

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

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

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6
Q

cell adhesion molecule functions inside cells

A

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

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7
Q

ECM functions

A

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

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8
Q

what comprises ECM?

A

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

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9
Q

purpose of epithelial cells’ polarized cellular organization

A

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

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10
Q

what is on apical surface of epithelial cells

A

villi

for absorption

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11
Q

cell junctions in epithelial cells

A

1) tight junctions
2) anchoring junctions: adherens, desmosomes, hemidesmosomes
3) communicating junctions: gap junctions
4) integrins

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12
Q

tight junctions function? structure?

A

exist directly under microvilli

seal epithelial cells together in sheets

prevents passage of small molecules

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13
Q

tight junctions made of?

A

claudins, occludins

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14
Q

anchoring junctions function

A

join cells to each other and to ECCM

1) adherens junctions and desmosomes
2) focal adhesions and hemidesmosomes

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15
Q

adherens junctions and desmosomes functions

A

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

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16
Q

nature of caderins throughout the body?

A

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

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17
Q

focal adhesions?

A

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

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18
Q

desmosomes connect with what?

A

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

19
Q

hemidesmosomes are made of?

A

IF

bind inside the cell, and to the ECM via integrin

20
Q

gap junctions function?

A

cell - cell communication

allwo for electrical coupling between cells

21
Q

what are cadherins

what does their loss result in

A

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
Q

integrins function

A

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
Q

what integrain is a hemidesmosome connection

A

a6b4 interacts w/ IFs a hemidesmosomes

exception to integrins connecting to bundled actin filaments

24
Q

what mediates actin-integrin interaction

A

anchor proteins - talin, a-actinin, filamin

linkage leads to clustering and formaiton of focal adhesions

25
Q

what are selectins?

A

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
Q

how do WBC travel around the blood

A

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
Q

what is ECM

A

space between cells

a misture of proteins and polysaccharides

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

28
Q

what forms bone/teeth

A

calcified ECM

29
Q

how is ECM in tendon

A

trannsparent

30
Q

what is basal lamina

A

form of the ECM at interface of epithelia and connective tissues

31
Q

where is basal lamina found

A

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
Q

what does basal lamina influence

A

cell polarity, metabolism, survival, proliferation, idfferentiation

serves as highway for migration

33
Q

what forms BL

A

cells that sit on it

34
Q

what is basement membrane

A

structure connected to BL by type IV collagen to underlying CT

35
Q

proteins of the BL?

A

type IV collagen

multiadhesive proteins, laminin

proteoglycan, perlecan

nidogen

these form a meshlike structure

36
Q

laminin is?

A

heterotrimeric multiadhesive matrix protein found in all BL

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

helps integrate structures

37
Q

most abundant protein in body?

A

collagen

38
Q

ollagen structure

A

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
Q

proteoglycan structure and function

A

type of GAG

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

easily form gels

40
Q

how are collagen in bone, cornea?

A

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
Q

what is fibronectin structure, function?

A

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
Q

structure, funciton of elastin?

A

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
Q

what causes Marfan’s syndrome?

A

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
Q

what re: fibronectin makes cancer cells more mobile

A

cancer cells make less fibronectin -> are more mobile

are not anchorage dependent

MCG (77 decks)

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