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Elements of Medicine > Extracellular Matrix > Flashcards

Extracellular Matrix Flashcards

1
Q

What is the extracellular matrix?

A

3d network of proteins and polysaccharides

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2
Q

Where is the ECM most abundant?

A

Connective tissue. Also present supporting epithelial cells and surrounding muscle, adipose, and peripheral nerve cells.

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3
Q

Two components of the basement membrane

A 
Basal Lamina (superficial)
Reticular Lamina (deep)
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4
Q

Function of Epithelia

A
  • Barrier
  • Absorption and Secretion
  • Removal of particular matter
  • Gas Exchange
  • Filtration
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5
Q

Role of ECM

A
  • Supports adhesion of cells
  • Transmits signals through adhesion receptors
  • Binds, stores, and presents growth factors
  • Shapes tissue structures
  • Guides and supports migrating cells
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6
Q

Collagen (I)

A

Fibril-forming type. Most common; found in skin, bone, tendons, cartilage, and ligaments. Perpendicular layering and lots of Gly-X-Y repeats for strength

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7
Q

Collagen Structure

A

Gly-X-Y repeats and triple helix.

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8
Q

Collagen (III)

A

Plays a role in wound repair as part of the provisional extracellular matrix / skin. Later replaced by collage I

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9
Q

Collagen (IV)

A

Network-forming variety. Found in the basal laminae. Sheet-like mesh from breaks in the Gly-X-Y. Important for filtration (kidney’s glomerulus, for ex).

Non-helical domains kept.

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10
Q

Collagen (VII)

A

Anchoring fibrils. Keeps the basement membrane intact and is crucial for the epidermis-dermis junction. Lots of Gly-X-Y repeats like collagen I but retains the non-helical domains.

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11
Q

Osteogenesis Imperfecta

A

Collagen I disorder. Incorrect formation of bones, featuring Ser-X-Y repeats instead of Gly-X-Y

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12
Q

Alport Syndrome

A

Collagen IV disorder. Progressive nephritis, hearing loss, and ocular lesions.

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13
Q

Dystrophic Epidermolysis Bulosa

A

Collagen VII disorder. Issues with dermis-epidermis anchoring. Blistering from heat/friction.

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14
Q

Glycosaminoglycans (GAGs)

A

long disaccharide chains, usually sulfated (negative charge is important for electrostatic interactions)

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15
Q

Proteoglycans

A

Long GAG chain joined to core protein. Mostly carbohydrate, little protein.

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16
Q

Location of proteoglycans

A

Extracellular matrix, membrane, floating in the cytosol. Also a major component of joint fluid.

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17
Q

Roles of Proteoglycans (4)

A
  1. regulate distribution of extracellular signaling molecules
  2. modulate signaling events at cell surface
  3. serve as structural constituents of ECM
  4. regulate movement of molecules between intracellular and extracellular compartments
18
Q

What needs to bind to fibroblast growth factor (FGF) to activate it?

A

proteoglycans bind and then it can attach to the cell surface receptor

19
Q

What is aggrecan?

A

It’s a major proteogylcan in cartilage. Its enzymatic destruction can be an early sign of arthritis.

20
Q

What does heparanase do?

A

Cleaves heparan sulfate-PG to release the sequestered growth factor.

21
Q

Fibrillin

A

elastic fiber coming in two forms (1, 2) which provides the scaffolding for tissues and sequesters growth factors.

22
Q

What protein fiber is found in the skin, lens of the eye, aorta, and periosteum (connective tissue covering the surface of bones)?

A

Fibrillin

23
Q

Marfan Syndrome

A

Mutated fibrillin-1 gene. Causes malformation of digits, limbs, and anterior chest wall. It can also cause nearsightedness and aneurysms (weakens aortic wall)

24
Q

Fibronectin

A

Protein involved in blood clotting (attaches to fibrin in clot), wound healing, platelet adhesion/aggregation, cell adhesion, binding to bacteria, and to screen for premature delivery.

25
Q

What are the forms of fibronectin and how are they created?

A
  1. Plasma form: non-adhesive, soluble and circulates in the blood.
  2. Cell/matrix form: insoluble, found on cell surfaces and involved with cell adhesion.
  • The multiple forms are generated by alternative splicing of a single gene.
26
Q

Which extracellular matrix protein has two large subunits attached by disulfide bonds?

A

Fibronectin

27
Q

Laminin

A

Three chained (alpha, beta, gamma), cross-shaped ECM protein interacting with collagen IV and proteoglycans.

28
Q

Where is laminin found?

A

basement membrane (basal lamina)

29
Q

Junctional Epidermis Bullosa

A

Laminin 5 defect at epidermis-dermis junction.

30
Q

When is the extracellular matrix degraded? (4)

A
  1. wound healing
  2. bone remodeling
  3. migration of WBCs into tissues
  4. reproduction
31
Q

Arthiritis, multiple sclerosis, tooth decay, cardiovascular disease, and COPD can all be caused by what overactive/inappropriate process?

A

Matrix degradation

32
Q

What class of enzymes can degrade the ECM?

A

Matrix Metalloproteinases (MMPs)

33
Q

What cofactors do MMPs require for their function?

A

Zn (II) or Ca (II)

34
Q

Two ways that MMPs are regulated

A
  1. proteases are secreted as inactive precursors that are activated locally.
  2. Action of proteases confined to specific areas by secreted protease inhibitors (TIMPs).
35
Q

What does TIMP stand for?

A

Tissue Inhibitors of Metalloproteinases

36
Q

Stages of wound repair?

A
  1. inflammatory phase
  2. proliferative phase
  3. remodeling phase
37
Q

Describe the inflammatory phase of would repair

A

Fibronectin is part of the clot at this phase. MMPs release the cells migrating to the wound.

38
Q

Describe the proliferative phase of wound repair

A

Cells migrate to wound and form new epidermis. Provisional ECM formed. Fibroblasts synthesize collagen III. Matrix form of fibronectin secreted. Hyaluronan, PG-released growth factors, and MMPs present and/or upregulated.

39
Q

What is hyaluronan

A

GAG which allows cells to migrate, appearing in the proliferative phase but disappearing the remodeling phase of wound repair.

40
Q

Describe the remodeling phase of wound repair

A

Normal skin is re-established. Degradation of temporary ECM and hyaluronan. Collagen I replaces collagen III.

Elements of Medicine (8 decks)

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