The Biology Of Ageing 6

Front 1

What is a protein?

Back 1

Is a complex, high MW organic compound that consists of amino acids joined by peptide bonds.

Front 2

What is homeostasis?

Back 2

The property of an open system.

Regulation of its internal environment to maintain a stable, constant condition by means of multiple feedback controls, regardless of the external conditions.

Front 3

How is negative feedback carried out?

Back 3

If the bodies conditions change from the set point and this is detected, corrective mechanisms are activated to return the conditions back to the set point.

Front 4

Why do we need protein homeostasis?

Back 4

To maintain the correct number of each type of protein in the cell - synthesis and degradation.

Front 5

What is p53?

Back 5

A TF and a tumour suppressor

Front 6

What is p53 involved in?

Back 6

Cell cycle arrest, DNA repair and apoptosis

Front 7

Is p53 usually at high or low levels in normal body?

Back 7

Low

Front 8

What is p53 normally bound to?

Back 8

Its inhibitor - mdm2

Front 9

What is mdm2?

Back 9

An E3 ligase

Front 10

What does mdm2 cause?

Back 10

Ubquitination and degradation by the proteasome

Front 11

What is p53 a TF for?

Back 11

mdm2 - high levels of p53 lead to an increase in mdm2.

Front 12

Is p53 invloed in a negative feedback loop?

Back 12

Yes, a negative feedback loop where it provides its own negative feedback.

Front 13

What causes p53 to be released from mdm2?

Back 13

Phosphorylation following DNA damage

Front 14

What protein are p53 and mdm2 phosphorylated by?

Back 14

ATM

Front 15

What protein does p53 transcribe that causes cell cycle arrest?

Back 15

p21

Front 16

What is homeostasis a balance between?

Back 16

Protein synthesis and degradation

Available chaperones and misfiled proteins

Front 17

What are the 6 stages of the life cycle of a protein?

Back 17

1) Synthesis

2) Folding

3) Transport

4) Modifications

5) Function

6) Degradation

Front 18

If DNA damage happens in the non-coding region of a protein what will be the effect on synthesis?

Back 18

No effect on synthesis

Front 19

If DNA damage occurs in the promotor region of a protein what will be the effect on synthesis?

Back 19

Could be more or less synthesis happening

Front 20

If DNA damage occurs in the coding region of a protein what will the effect be on synthesis?

Back 20

Incorrect protein will be synthesised

Front 21

What are the 3 different types of folding?

Back 21

1) Chaperone-independent

2) Hsp70-assisted protein folding

3) Assisted by Hsp70 and chaperonin complexes

Front 22

What type of folding happens automatically as the protein is synthesised on the ribosome?

Back 22

Chaperone-independent

Front 23

What is the human chaperonin (GroES in yeast) that assists folding in 15% of proteins?

Back 23

Hsp60

Front 24

What organelle sorts and packages proteins ready for transportation?

Back 24

Golgi apparatus

Front 25

What are 4 modifications that can affect a proteins function?

Back 25

1) Phosphorylation

2) Acetylation

3) Glycosylation

4) Ubiquitination

(can also get undesirable modifications due to ROS)

Front 26

What are the 2 major classes of protein damage?

Back 26

1) Conformational

2) Covalent

Front 27

What is conformational damage?

Back 27

Unfolding of the protein caused by heating, attack by free radicals, chemicals, pH changes etc

Front 28

What is covalent damage?

Back 28

Chemical damage in the amino acid make up of the protein e.g./// oxidation, isomerisation

Front 29

What is an example of covalent damage?

Back 29

AGEs

Front 30

What are AGEs?

Back 30

Advanced glycation end-products

Front 31

What is glycation?

Back 31

(Sometimes called non-enzymatic glycosylation)

It is the result of covalent bonding of a protein or lipid molecule with a sugar molecule, without the controlling action of an enzyme.

Front 32

What does the cross-linking of AGE products prevent from happening?

Back 32

Degradation (can't be degraded)

Front 33

Which is the most difficult type of damage to repair?

Back 33

Covalent as conformational just involves refolding by chaperones

Front 34

What happens to proteins that cannot be repaired?

Back 34

They are degraded

Front 35

What are molecular chaperones also known as?

Back 35

Heat shock proteins

Front 36

When are chaperones unregulated?

Back 36

After stress

Front 37

What do chaperones prevent from happening?

Back 37

Protein aggregation - becauseof the macromolecular crowding within the cell which can easily lead toincorrect interactions between proteins.

Front 38

What does HSF1 regulate?

Back 38

= Heat Shock Factor 1

Regulates the transcription of heat shock genes

Front 39

How is HSF1 normally present?

Back 39

As inactive monomers (by binding of Hsp90 to the monomers)

Front 40

In stressed cells, what does HSF1 form?

Back 40

Homotrimers

Front 41

How does HSF1 form homotrimers?

Back 41

By proteins denaturing

Front 42

How are the trimers activated?

Back 42

By phosphorylation

Front 43

What part of proteins do chaperones bind to?

Back 43

They bind to exposed hypdrophobic regions of proteins and assist in the assembly or disassembly of other protein structures.

Front 44

When the trimers translocate to the nucleus, what do they bind to?

Back 44

The heat shock element (HSE)

Front 45

What does activation of the HSE cause?

Back 45

Synthesis of heat shock proteins (the heat shock response)

Front 46

How is the heat shock response switched off?

Back 46

Hsp70 up regulates a phosphatase to dephosphorylate the homotrimers.

Front 47

What do misfolded proteins expose?

Back 47

Hydrophobic surfaces

Front 48

What causes aggregation in the cell?

Back 48

Hydrophobic surfaces sticking together

Front 49

How do chaperones prevent aggregation?

Back 49

They bind to the hydrophobic region to prevent misfolded proteins sticking together.

Front 50

How are chaperones involved with signal transduction?

Back 50

Hsp70 and Hsp90 interact with many different signalling pathways

Front 51

How does Hsp90 regulate glucocorticoid receptor signalling?

Back 51

1) GR is bound to Hsp90, which is bound to FKBP51.

2) if a hormone binds to GR, FKBP51 is exchanged for FKBP52.

3) the motor protein dynein also binds to the complex.

4) Dynein attaches to the cytoskeleton and transports the whole complex into the nucleus.

5) Once in the nucleus, Hsp90 dissociates so GR can form homodimers on DNA.

Front 52

What is the link between chaperones and ageing?

Back 52

There is a decline in the HSR with age, possibly due to a decline in HSF1 transcriptional response with age.

Front 53

Over expression of ..... has been shown to extend lifespan?

Back 53

Over expression of HSF1 and HSPs or an upregulation of HSP's during stress (centenarians).

Front 54

What are the 2 protein degradation pathways?

Back 54

1) Lysosomal

2) Proteasomal

Front 55

What do lysosomes contain?

Back 55

Digestive enzymes

Front 56

Which is the more rapid type of protein degradation?

Back 56

Proteasomal pathways

Front 57

What are the 2 types of proteasomal pathways?

Back 57

1) Non-specific

2) Specific

Front 58

What type of proteasome is the non-specific pathway via?

Back 58

20S

Front 59

What type of proteasome is the specific pathway via?

Back 59

26S

Front 60

What acts as a molecular tag in the specific proteasomal pathway?

Back 60

Ubiquitin

Front 61

What are the 3 types of lysosomal degradation?

Back 61

1) Macroautophagy

2) Microautophagy

3) Chaperone-mediated autophagy

Front 62

What is macroautophagy unregulated by?

Back 62

Stress such as oxidative damage or starvation

Front 63

How are the 3 methods of lysosomal degradation carried out?

Back 63

Look at diagram

Front 64

Where are proteasome located?

Back 64

In the nucleus and cytoplasm

Front 65

What is proteolysis?

Back 65

A chemical reaction that breaks peptide bonds

Front 66

What is the function of the alpha-subunit of a 20S proteasome?

Back 66

Maintain a gate that substrates enter through

Front 67

What is the function of the beta-subunit of a 20S proteasome?

Back 67

Contain the protease active sites on interior

Front 68

What are the 3 parts of the 26S proteasome?

Back 68

19S, 20S, 19S

Front 69

What binds to the 19S regulatory cap of the 26S proteasome?

Back 69

Alpha-subunits of the 20S proteasome

Front 70

What doe the 19S contain?

Back 70

ATPase active sites and ubiquitin binding sites

Front 71

What is E1 enzyme?

Back 71

An ubiquitin-activating enzyme

Front 72

What is E2 enzyme?

Back 72

An ubiquitin-conjugating enzyme

Front 73

What is E3 enzyme?

Back 73

An ubiquitin ligase

Front 74

What is DUB?

Back 74

De-ubiquitinating enzyme

Front 75

What will failure of any part of the quality control system lead to?

Back 75

An increase in aggregation

Front 76

What is ubiquitin?

Back 76

A small regulatory protein

Front 77

Which ubiquitin enzyme only has one type in mammals?

Back 77

E1

Front 78

What are DUB's?

Back 78

A large group of proteases that cleave ubiquitin molecules

Front 79

What type of proteases are the majority of DUBs?

Back 79

Cysteine proteases

Front 80

What is the correlation with ubiquitin with age?

Back 80

There is no change in the levels of ubiquitin or ubiquitin enzymes with age, but there is an increase in ubiquitinated proteins with age (suggesting impaired degradation).

Front 81

Are proteasomes turned over by lysosomes?

Back 81

Yes

Front 82

What is the main thing that can inhibit protein degradation and chaperones?

Back 82

Protein aggregation (chaperones get trapped inside aggregates)

Front 83

What are prion diseases?

Back 83

(transmissible spongiform encephalopathies)

Diseases affecting the nervous system and brain

Front 84

What does a prion protein undergo a change in?

Back 84

Structure - causing aggregation

Front 85

Does a protein aggregate have a good or poor solubility?

Back 85

Poor

Front 86

What does the propensity of a protein to aggregate depend on? (3)

Back 86

The secondary structure - beta-pleated sheet

Stability of the tertiary structure

Charge

Front 87

What is an inclusion body?

Back 87

When an aggregate (small clump of protein) is formed (after hydrophobic regions are internalised), monomers bind to the protein causing the formation of an inclusion body.

Front 88

What are aggresomes?

Back 88

The formation of inclusion bodies by active retrograde transport of misfiled proteins along microtubules.

Front 89

What is present in aggregates apart from misfiled proteins? (4)

Back 89

Ubiquitin

Chaperones

Proteasomal sub-units

E3 ligases

Front 90

What (eventually) does a loss of protein homeostasis cause?

Back 90

Age-related diseases