Extracellular Matrix Biology II Flashcards

1
Q

Give two examples of multi-adhesive glycoproteins.

A

Fibronectin, Laminin

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2
Q

Where are Laminins found?

A

Basement Membrane

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3
Q

Describe, in full, the structure of Laminin.

A

It is a cross shaped molecule consisting of an alpha, beta and gamma chain
It has different parts that have different binding capabilities
The N terminus of all the chains there are globular regions
There is a coiled-coil region, which is the region in which the three chains are wrapped around each other

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4
Q

What causes congenital muscular dystrophy?

A

Absence of alpha 2 chain in laminin 2

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5
Q

Why is fibronectin considered essential for life?

A

There are no known mutations of fibronectin in humans

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6
Q

Describe three roles of fibronectin.

A

Binding to integrin and linking ECM to the actin cytoskeleton – cell binding Self-association
Binding to other ECM components

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7
Q

What is the general structure of fibronectin?

A

It is a dimer that is joined by disulphide bonds – it has various domains that can bind to different things

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8
Q

Describe the link between fibronectin and the intracellular compartment.

A

Fibronectin associated with an integrin which associates with actin – forms a mechanical continuum with the actin cytoskeleton
The fibronectin is also bound to collagen

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9
Q

What part of fibronectin do integrins bind to?

A

RGD motif

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10
Q

Describe the general structure of proteoglycans.

A

Consists of a core protein with one or more GAG chains covalently attached

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11
Q

What is the basic structure of GAG chains and what is a characteristic feature of GAG chains?

A

It is a long, unbranched chain consisting of a repeating disaccharide It has a large volume
Can form hydrated gels

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12
Q

What are the four families of GAG chains?

A

Hyaluronan
Heparan Sulfate
Chondroitin Sulfate/Dermatan sulphate
Keratan sulfate

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13
Q

What is unique about hyaluronan?

A

It doesn’t have a core protein – it is just a massive polysaccharide
It is synthesised on the cell membrane rather than by the ER

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14
Q

How are GAG chains linked to the core protein?

A

It is connected via a link tetrasaccharide

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15
Q

What does Decorin do?

A

Regulates collagen fibre size and arrangement

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16
Q

What does hyaline cartilage consist of?

A

Aggrecan aggregates – consists of aggrecan (GAG chains = keratan sulphate and chondroitin sulphate) associated with hyaluronan and a link protein

17
Q

Describe how hyaline cartilage resists compressive force.

A

The GAG chains in aggrecan are heavily sulphated and carboxylated so it is very negatively charged
This means that it can attract osmotically active cations such as Na+ and Ca2+, which attracts water forming a gel like substance
When it experiences a compressive force, the water is squeezed out and the water returns when the compressive force is removed

18
Q

What causes osteoarthritis?

A

Loss of extracellular matrix

19
Q

What happens in fibrotic disorders?

A

Excess deposition of collagen – normal tissue gets replaced by collagen