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Foundations Exam 1 > ECM > Flashcards

ECM Flashcards

1
Q

two regions of ECM accumulation:

A

basal lamina (basement membrane) - subdomains of lamina interna/rara/lucida and lamina densa

stroma (deepest part of basement membrane - lamina reticularis) and connective tissue

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2
Q

three distinct regions of basement membrane from superficial to deep

A

lamina lucida/rara/interna

lamina densa

lamina reticularis (sublamina densa)/ stroma

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3
Q

name 4 major macro molecular components of ECM

A
  1. structural components: collagen (strength) and elastin (resilience)
  2. glycosaminoglycans (GAGs): complex sugars, bind water to resist compression
  3. proteoglycans: GAG + protein (covalent bond)
  4. adhesive glycoproteins: fibronectin and laminin
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4
Q

what are the two major adhesive glycoproteins of ECM

A

fibronectin and laminin

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5
Q

most abundant protein in body is? what is its structure?

A

collagen

monomer of single helix, procollagen of triple-helix, procollagen assembles into fibrils

repeating sequence of every third glycine, which fits inside helix and bond with H

many proline and lysine that can be hydroxylated to contribute to H bonding

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6
Q

4 major collagen classes

A
  1. fibril-forming: most abundant, found everywhere
  2. fibril-associated: found in cartilage
  3. network-forming: found in basal lamina
  4. transmembrane: found in hemidesmosomes
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7
Q

major types of fibril-forming collagen? (3)

A

type I: most common, found ubiquitously

type II: cartilage, invertebral disc, vitreous humor (eye)

type III: skin, blood vessels, internal organs, aorta

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8
Q

what do osteogenesis imperfecta, chondrodysplasia, and Ehler-Danlos syndrome have in common>

A

tissue-specific diseases associated with mutations in fibril-forming collagens

osteogenesis imperfecta (brittle bone) - Type I (everywhere)
chondrodysplasia - Type II (cartilage)
Ehler-Danlos syndrome (aneurism) - Type III (aorta, blood vessels)

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9
Q

describe basic biosynthesis of fibril-forming collagens

A
  1. alpha chain enters secretory pathway, becomes hydroxylated (Vitamin C dependent process)
  2. glycosylation
  3. self-assembly of 3 pro-alpha chains
  4. procollagen triple helix formation
  5. secretion as pro-peptide
  6. cleave of propeptides into tropocollagen
  7. self assembly into fibril
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10
Q

what would happen to a a patient’s ability to synthesize collagen if they have scurvy?

A

scurvy due to vitamin C deficiency

vitamin C required for hydroxylation of alpha chain

reduced collagen formation

[single glycine mutation in primary structure can also alter collagen helix and reduce collagen synthesis]

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11
Q

what type of collagen is reticular

A

Type III (aorta, skin, blood vessels, internal organs) (fibril forming)

more carbohydrates, thinner fibrils, more branched, fewer bundles

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12
Q

what two classes of collagen associate to form cartilage (bonus if you can add collagen type)

A

Fibril forming collagen (Type II)
and
Fibril-associated collagen (Type IX)

Fibril-associated collagen decorates outside of Type II (fibril forming) collagen fibrils in cartilage - interrupts triple helix to form a hinge important for joint integrity

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13
Q

epiphyseal dysplasia is due to a mutation in what kind of collagen?

A

fibril-associated collagen (Type IX) - decorates Type II (fibril forming) collagen in cartilage, important for joints

mutation leads to arthritis

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14
Q

what is the major collagen of the basal lamina

A

Network-forming collagen (Type IV collagen)

multilayered chicken-wire array

C and N termini intact (not cleaved)

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15
Q

collagen mutations are also implicated in blistering diseases (like cell junctions). Contrast the effect of Type XVII (17) collagen and Type VII (7) mutations

A

Type XVII (17) collagen is transmembrane protein —> mutation causes blistering between epithelium and basement membrane

Type VII (7) collagen is network collagen forming anchoring fibrils connecting lamina densa with connective tissue —> mutation causes blistering below basement membrane

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16
Q

which of these are TRUE?
a. type III collagen has specific staining properties from increased CHO bonding
b. networking forming collagen retain extension peptides during assembly
c. post-translational processing of collagen occurs intracellularly
d. Type I, II, III collagens can all form fibrils

A

TRUE:

a. type III collagen has specific staining properties from increased CHO bonding (*reticular)
b. networking forming collagen retain extension peptides during assembly
d. Type I, II, III collagens can all form fibrils

c. post-translational processing of collagen occurs EXTRACELLULARLY

17
Q

most assembly of elastic fibers is [intra/extra]cellulary?

A

extracellularly

elastin monomers are cross-linked to provide resilience

18
Q

what stain can be used to reveal elastin fibers

A

ocrein stain

19
Q

what is the presentation and cause of Marfan syndrome

A

Fibrillin 1 mutation

increased length of appendages, chest deformity, aorta prone to rupture (AD inheritance)

lack of recoil during development because of defect in elastin (Fibrillin is glycoprotein essential for elastin formation)

20
Q

what disorder does a mutation in Fibrillin 1 cause

A

Marfan syndrome: long appendages/limbs, aorta prone to rupture, due to lack of recoil during development

(defect in elastin)

21
Q

cause and presentation of Epidermolysis bulbosa

A

Type VII collagen anchoring fibrils disrupted

epithelium and basement membrane peeled away

22
Q

structure of glycosaminoglycans (GAGs)

A

repeating disaccharides (amino sugar and uronic acid)

negative charge (COOH and SO4/sulfate group)

binds water (osmotically active)

resist compression - found in joints, vitreous humor (places where there is a lot of water)

23
Q

3 major classes of GAGs (glycosaminoglycans)

A
  1. hyaluronic acid: non-sulfated, NOT covalently attached to protein
  2. chondroitin sulfate: sulfated (duh), covalently attached to protein
  3. heparan sulfate: sulfated (duh), covalently attached to protein
24
Q

what is the major proteoglycan found in cartilage and what is its structure?

A

aggrecan: protein + chondroitin sulfate (covalent link)

also has hyaluronic acid present (with non-covalently bonded protein)

aggrecanopathies —> skeletal disease

*proteoglycan = GAG + protein

25
Q

3 important proteoglycans and where they are found?

A
  1. aggrecan - cartilage
  2. perlecan - basal lamina
  3. syndecan - fibroblast and epithelial cell surface
26
Q

what is the role of syndecan

A

major type of proteoglycan (GAG + protein)

interacts with cytoskeleton, binds growth factors to present to receptors (mediate interaction between cell surface and ECM)

27
Q

what is the basic role of adhesive glycoproteins laminin and fibronectin?

A

binding sites for multiple ECM components and integrins

28
Q

where would you find Type IV collagen, perlecan (proteoglycan), and laminin 1?

A

lamina densa of basal lamina

29
Q

which GAG is NOT bound to protein

A

hyaluronic acid

30
Q

aggrecan (proteoglycan) is found with 2 types of collagen in cartilage which are:

A

Type II and Type IX

31
Q

how do integrins interact with cytoskeleton to stabilize cell shape and attachment?

A

integrins are dimers - both subunits bind ECM via RGD (arginine-glycine-aspartic acid) sequence on laminin and fibronectin

beta subunit binds actin of cytoskeleton, recruits FAK (focal adhesion kinase) —> forms FOCAL ADHESION (cell junction)

32
Q

what is the function of the following integrin types:
a. beta 1
b. beta 2
c. beta 3
d. alpha6beta4

A

a. beta 1: binds ECM molecules, ubiquitous
b. beta 2: found in WBC, binds endothelium
c. beta 3: found in platelets, binds fibrinogen
d. alpha6beta4: found in hemidesmosomes

33
Q

what type of mutation causes Glanzmann’s disease, a clotting disorder?

A

beta 3 integrin mutation —> inability of platelets to bind fibrinogen during clotting

glaNzmaNN’s has 3 Ns for the beta 3 iNtegrin mutation

34
Q

a mutation in integrin beta 3 causes an inability of platelets to bind fibrinogen during clotting. what is this disease called?

A

Glanzmann’s disease

35
Q

lymphocyte binding to endothelium via ____ initiates signaling pathway that changes lymphocyte beta__ integrin conformation to active state

A

lymphocyte binding to endothelium via SELECTIN initiates signaling pathway that changes lymphocyte beta2 integrin conformation to active state

intracelular and extracellular signaling can activate integrins (active conformation reveals binding sites)

*regulation of integrin esp. important for lymphocyte binding to endothelium (beta2) and platelet binding to fibrinogen (beta3)

36
Q

what collagen type is network forming (type - looking for number)

A

Type IV

37
Q

in what class of collagen are extension peptides retained?

A

network-forming (such as Type IV)

38
Q

lamina densa contains collagen type ___

A

lamina dense - collagen type IV (network forming)

**Type IV collagen RETAINS N- and C- terminal propeptide extensions

39
Q

what fiber is critically dependent on amino acid sequence Gly-X-Y

A

collagen - glycines every third (get tucked inside alpha helix)

Foundations Exam 1 (33 decks)

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