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MSK Week 6 > 2.6.1. Part 1 of 2 Collagen and Proteoglycan (Collagen Only) > Flashcards

2.6.1. Part 1 of 2 Collagen and Proteoglycan (Collagen Only) Flashcards

1
Q

Difference between the purposes of collagen and elastin

A

Collagen provides tensile strength

Elastin provides elasticity

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2
Q

What does laminin do?

A

provides meshwork and anchor points

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3
Q

What is the most abundant protein in the body?

A

Collagen

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4
Q

Where are different types of collagen found? Provide the pneumonic

A

Be So Totally Cool, Read Books

Bone, Skin, Tendon, Cartilage (incl hyaline), Reticulin, Blood vessels

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5
Q

Discuss what falls into the category of Type I collagen and how much of it we see in the body

A

accounts for 90% of the total body collagen and occurs in the skin, bone, tendons, cornea, soft tissues, and scars.

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6
Q

Which collagen type has the least amount of ccarbohydrate? Most amount?

A

Type I has the least, Type IV has the most

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7
Q

Osteogenesis Imperfecta is caused by genetic defects in what collagen type?

A

Type 1

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8
Q

Where does Type II cartilage occur? What chain type is associated with it?

A

occurs in cartilage (made by chondrocytes) and vitreous humor.

Chain type c3

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9
Q

Type II is the major type found in cartilage. But where do we also find it?

A

Skin and tendon

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10
Q

Where do we find Type III collagen and what is it chain type?

A

Chain type d3

occurs mainly in blood vessel walls, other hollow organs, and fetal skin. Found in scars and all adult soft tissues, but not in bone or tendons

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11
Q

Two collagen types have something structurally unique about them. Which ones and what is the difference?

A

Type III and IV contain disulfide bridges between chains whereas type I and II do not.

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12
Q

What disease is associated with defects in type III collagen?

A

Ehlers-Danlos Type 4 disease

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13
Q

Defects associated with Ehlers-Danlos?

A 
Aortic rupture
GI tract
Pregnancy problems
Skin fragility
Poor wound healing
Surgical problems
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14
Q

Describe Type IV collagen and the chain type

A

e3 chain type

the collagen of basement membranes (mesh-forming; creates hexagonal lattices).

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15
Q

What is the chain type for Type I collagen?

A

a2b

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16
Q

Why can Type IV cartilage allow for interruptions in the triple helix?

A

Due to high carbohydrate content

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17
Q

Defects in Type IV can cause what?

A

Alport syndrome

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18
Q

What is Alport disease characterized by?

A

Alport syndrome is a genetic condition characterized by kidney disease, hearing loss, and eye abnormalities.

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19
Q

What causes Goodpasture’s syndrome?

A

Autoantibodies target Type IV collagen

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20
Q

What characterizes Goodpasture’s syndrome?

A

group of acute illnesses involving the kidneys and lungs

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21
Q

What types of scars have collagen deposition and in what arrangement is it deposited?

A

collagen synthesis is increased in hypertrophic scar formation (w/parallel arrangement), and drastically increased in keloid scar formation (w/disorganized arrangement)

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22
Q

Primary shape of collagen?

A

Rod

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23
Q

Secondary shape of collagen?

A

Regular - 3 polypeptide chains with at least one stretch wound together to form a triple-helix

24
Q

How soluble is collagen in water?

A

It has low solubility in water

25
Q

How many exons are there in fibrillar collagen genes?

A

42

26
Q

All Collagen has a central region that encodes what? What repeating unit is associated with this stretch?

A

All collagens have a central region that encodes a 1014 amino acid stretch with the repeating unit (Gly-X-Y) 338 times

27
Q

What two amino acids are present in the Y position of the repeating units in Collagen?

Recall: All collagens have a central region that encodes a 1014 amino acid stretch with the repeating unit (Gly-X-Y) 338 times

A

Hydroxyproline and hydroxylysine

28
Q

Recall: All collagens have a central region that encodes a 1014 amino acid stretch with the repeating unit (Gly-X-Y) 338 times

What is usually in the x position?

A

Proline

29
Q

What is important about the y residues?

Recall: All collagens have a central region that encodes a 1014 amino acid stretch with the repeating unit (Gly-X-Y)338

A

Hydroxylation of the Y residues results in a polar surface that stabilizes the overall structure by forming H-bonds with water

30
Q

What residues are positioned in the central axis between the helices?

A

Glycine

31
Q

When is procollagen formed?

A

Procollagen is formed from preprocollagen after removal of the signal peptides in the ER

32
Q

What are the domains of preprocollagen?

A

Globular (N and C terminal)

Triple helical

Non-triple helical

33
Q

What exactly causes, in procollagen, Ehlers-Danlos Type VII?

A

Failure to cleave the N-terminal domain due to a defective N-terminal peptidase results in Ehlers-Danlos type VII

34
Q

A defect in which terminal of the collagen is worst? Why?

A

C terminal defect due to the direction of the helix coiling.

35
Q

The presence of what amino acid is a good indicator of collagen synthesis?

A

Glycine

36
Q

What parts of collagen synthesis occur inside the fibroblasts?

A

Synthesis
Hydroxylation
Glycosylation
Exocytosis

37
Q

What occurs during the synthesis step of collagen formation? Where in the fibroblast does it occur?

A

Synthesis (RER)

Translation of alpha chains (pre-procollagen), usually as Gly-X-Y, where X = proline and Y = lysine

38
Q

What occurs during the hydroxylation step of collagen formation? Where in the fibroblast does it occur?

A

Hydroxylation (RER)

Specific Pro and Lys residues are hydroxylated

39
Q

What cofactors are required for hydroxylation?

A

This requires Vitamin C and Fe2+ as cofactors

40
Q

What happens with a deficiency of Vitamin C?

A

Scurvy

41
Q

What characterizes scurvy?

A

Scurvy often presents itself initially as symptoms of malaise and lethargy, followed by formation of spots on the skin, spongy gums, and bleeding from the mucous membranes.

42
Q

What happens during the glycosylation step of collagen synthesis? Where in the fibroblast does it occur?

A

Glycosylation (RER)
Pro-alpha-chain hydroxylysine residues are glycosylated
Procollagen is formed via hydrogen and disulfide bonds (this is where the triple helix takes shape - after this shape is made, no more modification can occur on the individual fibers!)

43
Q

What causes Osteogenesis Imperfecta in the synthesis of collagen process?

A

Glycosylation process

Problems forming this triple helix leads to Osteogenesis Imperfecta

44
Q

Describe the exocytosis step out of the fibroblast. What is important about the status of the collagen?

A

Procollagen is exocytosed into the ECM

Note that the molecule is still in its “pro” form - if it was cleaved before, it couldn’t be transported out :(

45
Q

What steps of colagen synthesis occur outside of the fibroblast?

A

Proteolytic processing

Cross-linking

46
Q

Describe proteolytic processing

A

Disulfide-rich terminal regions are cleaved within procollagen, transforming it into an insoluble tropocollagen

47
Q

What occurs during the cross linking phase? What happens when there is a problem in this process?

A

Many staggered tropocollagen molecules are reinforced by covalent lysine-hydroxylysine cross-linkages

Problems with cross-linking results in Ehlers-Danlos

48
Q

What other ingredients besides the developing collagen is important for the cross linking step?

A

This is accomplished by the Cu2+ containing lysyl oxidase (NOT HYDROXYLASE) , thus creating collagen fibrils

49
Q

What happens with a deficiency in lysyl hydroxylase?

A

ED type VI

50
Q

ED Type VI phenotype?

A

skin bruising, hyperextensible skin, joint hypermobility

51
Q

What happens with a Cu2+ deficiency?

A

Cu2+ deficiency presents with connective tissue dysfunction, because collagen synthesis isn’t properly executed

52
Q

Types of ED and what causes them?

A

Hypermobility type (joint instability) = most common type

Classical type (joint and skin symptoms) = caused by a mutation in Type 5 collagen

Vascular type (vascular & organ rupture) = caused by deficient Type 3 collagen

53
Q

What happens with a deficiency in ascorbic acid?

A

scurvy [decreased hydroxyproline synthesis]

54
Q

Describe the general manifestations of osteogenesis imperfecta

A

multiple fractures w/minimal trauma, that may occur during the birthing process

hearing loss (b/c the ossicles are abnormally formed)

dental imperfections due to the lack of dentin

55
Q

Describe Type I Osteogenesis Imperfecta. What clinical signs do we see and how can we test for it?

A

Type I: mild form; blue sclera, mild to moderate decrease in the bone mass, generally normal life span. Autosomal dominant, decrease in the amount of Type I collagen; fractures seen in infancy and childhood, decrease over time, but non-deforming

May incorrectly assume child abuse

the blue sclera results from the translucency of the CT over the choroidal veins

56
Q

Discuss type II osteogenesis imperfecta. What causes it, how does it present, and how can we diagnosis it?

A

Type II: perinatal lethal form; dark sclera, severe bone fragility, absent calvarial mineralization, bony compression.

Caused by exon skipping mutations and deletions, and glycine substitutions due to point mutations.

AD inheritance as well, diagnosed in utero by ultrasound

Undermineralized bones, marked bowing of extremities, flattened vertebral bodies (can be seen on x-ray)

57
Q

What is Menkes Disease? How does it present and what causes it?

A

A type of CT disease caused by impaired copper absorption and transport

Leads to DECREASED lysyl oxidase activity (requires Cu2+ as a cofactor)

Due to the inability to tie the loose ends of collagen molecules, brittle, “”kinky” hair is seen, along with growth retardation and hypotonia

MSK Week 6 (19 decks)

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