BFCP1 S18

S18: ECM

3 components of ECM

1. Fibrous proteins

2. Carbs

3. Multi-adhesive proteins

Fibronectin vs fibrilin

Fibronectin: important multiadhesive protein

Fibrilin: works independently to bind GFs like TGFB (microfibril) or binds elastin (elastic fiber)

Collagen, fibrilin, and elastin are examples of ________

fibrous proteins

proteoglycans and GAGS are examples of _______

carbs

fibronectins, integrins, and laminins are examples of _______

multi-adhesive proteins

Difference in function of the ECM in connective tissue vs BM

Connective tissue: 3D mesh, providing toughness and resilience

BM: 2D mesh

Connective tissue consists mostly of ____ with embedded ____ and immune cells.

ECM

embedded fibroblasts

What synthesizes and secretes the ECM molecules of connective tissue?

Fibroblast

What clear out the proteins of the ECM? What about the cells of the ECM?

Proteins: proteases

Cells: immune cells (macrophages, neutrophils, etc)

Matrix metalloproteases (MMPs)

A type of protease that degrades the ECM and releases GFs

Cancer is associated with (increased/decreased) ECM clearance

increased

Lysosomal storage diseases are associated with _______ ECM clearance.

decreased

Colllagen are ______ proteins of the ECM

major fibrous proteins

How does collagen bundle?

Triple helix → triple helix dimer → interwound dimers (tetramer)

Collagens contain what AA sequence?

Gly-X-Y-Gly-X-Y etc

Where Y is often hydroxyproline

Which types of collagen are found in bone, skin, and tendon?

Type I and II

Which type of collagen is found in the BM?

Type IV

Fibrous vs mesh collagen - location and function

Fibrous: type I and II, tensile strength

Mesh: type IV, flexibility

Collagen synthesis:

1. Protein undergoes 2 post-translational modifs: ________ and _______

2. Protein disulfide isomerases then rearrange ______ bonds to allow for ________ formation.

3. _______ out of cell

4. N and C proteases remove ________ to allow for ______ of collagens.

5. Lysyl oxidase creates lysine ______ for strength.

Collagen synthesis:

1. Protein undergoes 2 post-translational modifs: hydroxylation and glycosylation

2. Protein disulfide isomerases then rearrange disulfide bonds to allow for triple helix formation.

3. Exocytosis out of cell

4. N and C proteases remove N and C terminal peptides to allow for self-bundling of collagens.

5. Lysyl oxidase creates lysine crosslinks for strength.

Hydroxylation of collagen occurs at which AAs?

Lysine and proline

Lysyl hydroxylase

What does this allow for?

Hydroxylates lysines on newly formed collagen

Allows for glycosylation

Prolyl hydroxylase

What does this allow for?

Hydroxylates prolines on newly formed collagen

Triple helix formation

Gal and Glc transferases

What does this allow for?

Glycosylate newly formed collagen

Increased tensile strength

Protein disulfide isomerase

Rearranges disulfide bonds for triple helix formation

N and C proteases

What does this allow for?

Cleaves N and C terminal peptides of collagen

Allows them to self-assemble into multimers

Lysyl oxidase

What does this allow for?

Crosslinks collagens

Permanent linkage for strength

Protoprocollagen → protocollagen → collagen

After post-translational modifs: protoprocollagen

After triple helix formation: procollagen

After exocytosis: collagen

Which cells are collagen made in?

Fibroblasts

Proline and lysine hydroxylation require which 2 molecules?

Vitamin c, iron (Fe2+)

Scurvy is caused by a lack of ______.

vitamin C

A vitamin C deficiency leads to what collagen effects?

Less hydroxylation → inefficient collagen synthesis → weak collagen effects

In the ECM, collagen can be non-enzymatically glycated. Why does this occur? What can it lead to?

If there is exposure to too much glucose

Leads to uncontrolled crosslinking → stiffness in tissues

How does non-enzymatic glycosylation of collagen lead to CVD?

Too much glycosylation → too much crosslinking and hardening in BVs

Which tissues would elastin be found abundantly in?

Those that have to repeatedly stretch and change shape

Smooth muscle, vasculature, lungs, ligaments

Elastase

Degrades elastin in the ECM

What are the 2 forms that fibrilin can take and what are their functions?

1. Microfibrils (elasin free): binds GFs like TGFB

2. Elastic fiber (with elasin): mediates elasticity

Elastic fiber vs microfibril characteristics

Elastic fiber: stretchy, mechanical elasticity

Microfibril: more tough

TGFB

Growth hormone that binds microfibrils

a1-antitrypsin

Inhibits elastase

Low a1-antitrypsin = (low/high) elastase = (low/high) = (low/high) elastin breakdown = (no/yes) emphysema

Low a1-antitrypsin = high elastase = high elastin breakdown = yes emphysema

Emphysema

Low elastin leading to loss of lung elasticity and decreased surface area

2 main causes of emphysema

1. Mutation in a1-antitrypsin gene (low levels)

2. Smoking

Glycosaminoglycans (GAGS) are which type of molecule?

Polysaccharides (carbs)

GAGs have a (+/-) charge and bind large amounts of ____

negative

water

Proteoglycans are which type of molecule? How are they composed

Glycoproteins

A core protein with GAG extensions

Hyaluronan and aggregan are examples of what?

Proteoglycans

Hyaluronan

Most abundant proteoglycan that is involved in pressure resistance and joint lubrication

Aggregan

Most abundant proteoglycan in cartilage

Binds to hylaronan to form huge aggregates

T/F: proteoglycans can form massive aggregates

T

The 3 important fibrous proteins in the ECM are

1. Collagen

2. Elastin

3. Fibrilin

The 2 important carbs in the ECM are what?

1. GAGs

2. Proteoglycans (hyaluronan, aggregan)

The 2 important multi-adhesive proteins in the ECM are what?

1. Fibronectin

2. Integrin

Fibronectin is a ____ protein that functions to ____

multiadhesive protein

bridge molecules together

Fibronectin contains a _____ motif that binds ____

RGD (arginine, glycine, aspartate)

Integrin

Plasma fibronectin

Involved in blood clotting by trapping platelets

Fibronectin composition

2 polypeptide chains that are disulfide-linked

Integrins are ______ glycoproteins that link the _____ to the _____ of cells

transmembrane

ECM to cytoskeleton

What allows integrins to recognize and bind fibronectin?

The RGD motif on fibronectin

Integrins composition

Heterodimeric - a and b chains

T/F: individual integrins are strong

F - many of them together form a strong bond

Along with clearing the ECM, MMPs are responsible for what?

Releasing growth factors in the ECM to convert ECM molecules to their active form

MMPs are ____-dependent proteases

Zn2+

TIMPs vs a2-macroglobulins

Both inhibit MMPs

TIMP: in solid tissues

a2-macrogolbulin: in blood

Where are lipids and GAG components sent to after they are broken down?

Lysosomes in macrophages

Osteogenesis imperfecta

What inheritance does it have?

Defects in type I collagen

Autosomal dominant

Ehlers-Dahnlos syndrome

Disorders in collagen

Hyperflexible joints, extensible skin, mitral valve prolapse are characteristics of which disease?

Ehlers-Dahnlos

Marfan syndrome cause

Defects in fibrilin-1 that cause it to be cleared too quickly

Causes free floating TGFB → rapid growth

Marfan syndrome characteristics

Tall, thin physique

Long fingers

CV symptoms need to be monitored

Integrin binds to ______ in the connective tissue ECM and ______ in the BM to connect cells to the matrix.

fibronectin in connective tissue

laminin in BM

Laminin in the BM binds _____ to ______

type IV collagen to integrin

Alport syndrome is caused by disorders in ______

Disorder in type IV collagen

Alport syndrome characteristics

Impaired kidney function

Eyes and ears defects

Goodpasture syndrome causes

Autoimmune reaction where pt develops antibodies against their own type IV collagen

Goodpasture syndrome affects what organs?

Kidneys, lungs