Copper Homeostasis And Disease

Question 1

What are the 3 targets of copper in a human cell

Answer 1

The Tgn, sod1 in cytosol and mt, COX in mt

Question 2

What is the chaperone at the tgn and what does it deliver cu to

Answer 2

Atox1
Atp7a (in all but liver cells) and atp7b

Question 3

The chaperone in mt is unknown. What is the one delivering sod1

Answer 3

Ccs

Question 4

What does excess cu bind

Answer 4

Metallothiopeines (regulated by mtf)

Question 5

What importer is major for copper and where is it

Answer 5

Ctr1
Found in vesicles and plasma membrane

The apical side of eneterocutes for absorption
Baso lateral for liver from the blood

Question 6

What 2 ways is ctr1 regulation (down reg in how cu)

Answer 6

Sp1 transcription factor

Internalisation through methionine residues

Question 7

What does the sp1 do in high cu

Answer 7

Zinc displaced by copper. This stops it binding dna for ctr1 txn

Question 8

How does sp1 bind dna

Answer 8

Zinc finger so when zinc displaced conformation isn’t corrrct

Question 9

Where is ccs located

Answer 9

Intermembrane space next to sod1

Question 10

What does the unknown copper chaperone in mt deliver cu to first which transfers to next chaperone till it gets to COX

Answer 10

Cox17 chaperone

Question 11

What does cox17 transfer cu to which make up the 2 copper sites in cox enzyme

Answer 11

Sco1 and cox11

Question 12

What is needed for ccs to fully transfer cu to sod1

Answer 12

Form a disulfide bond in the sod1

Question 13

Is the copper sensing mechanism known

Answer 13

No. Unlike fe system

Question 14

How do we know regulation exists then

Answer 14

When ctr1 was deleted in heart heart starved of cu

Found high cu levels in serum showing enterocytes increased export
And also reduced cu in liver showing increased export out of liver

Question 15

How was this increased export achieved

Answer 15

Increased atp7a levels (even when normally not expressed in liver as much)

Question 16

Why is cu needed during hypoxia

Answer 16

It is used as a cofactor for fe oxidases, so to make heme you need the ferrous fe form and so cu needed

Question 17

What’s the difference between atp7a and b transporters action

Answer 17

Atp7a needed in cells like enterocytes to in excess deliver cu from tgn to the membrane into bloodstream

Atp7b needed more in liver, when cu received from blood stream, excess exported from tgn to canicular membrane (bile excretion)

Question 18

What do they do in the tgn

Answer 18

Incorporate cu into the enzymes/proteins

Question 19

What do they use to transport cu

Answer 19

Atp

They are p type ATPases

Question 20

Explain the structure

Answer 20

Channel forming helices
Activation domain
Phosphorylation domain
Nucleotide binding domain

Question 21

What do they have on their n terminus

Answer 21

6 metal binding domains (cysteine rich) - binds cu

Question 22

Where does atox deliver cu to

Answer 22

The 6 mbd sites

Question 23

What happens when mbd are full

Answer 23

A cu will be transferred to the cpc motif opening the pore

Question 24

What happens before conformational change so channel entrance closes but exit opens

Answer 24

Phosphorylation - N domain binds atp and phosphate transferred to the P domain

Question 25

What dephosphorylates p domain allowing channel back to basal state

Answer 25

A domain

Question 26

What happens when cu levels drop again

Answer 26

Recycled back to the tgn

Question 27

Which residues on the c terminus allow retrieval back

Answer 27

Leucine

Question 28

Where does atp7b transfer cu post Golgi

Answer 28

Sub apical vesicles associated with the bile duct membrane

Question 29

What in the atp7b is there not in 7A which specifically allows this apical targeting and also retention back to tgn (other than leucine sites)

Answer 29

The 9 aa within The 63 aa sequence on amino terminal

Question 30

What happens when there’s a mutation in the 9 aa n terminal

Answer 30

Baso lateral localisation instead of apical, and scattered through cytosol not tgn

Question 31

Why are kinases speculated to play a regulation role in these atpases

Answer 31

They are commonly phos on their serine residues. ESP when cu is low at the tgn stopping exit

Question 32

What is menkes diseased

Answer 32

X linked recessive mutations in the atp7a (over 400 mutations)

Question 33

What does severity depend on

Answer 33

If the mutation causes complete loss of action

Question 34

Give some symptoms

Answer 34

Neurone degeneration, kinky hair

Question 35

Explain the pathogenesis

Answer 35

Firstly, a lot of cu lost in diet as no export of it out of enterocytes into blood Starves cells

Question 36

Where else does cu accumulate other than intestines

Answer 36

Brain because has a lot of atp7a dependant movement

Question 37

Where does cu from vlood enter brain

Answer 37

Endothelial cells of the BBB

Question 38

What does atp7a move cu to from the BbB cells in normal conditions

Answer 38

Astrocyte cells which then transfer to neurones

Question 39

Which cells hve atp7a to pump excess cu out of brain to blood via csf-b barrier

Answer 39

The choroid plexus (blocked movement back to blood 6

Question 40

Why is normal movement of cu to synaptic gap needed via atp7a

Answer 40

Binds nmda receptor to block it needed for synaptic plasticity and neurone development

Question 41

What does it mean when nmda is active constantly in Menkes

Answer 41

Neurone degen and seizures

Question 42

What sort of enzymes are starved due to no action of atp7a at the tgn

Answer 42

Cox Sod Ceruloplasmin (fe oxidase) Lox- collagen cross linking

Question 43

Why would blocking sulhydryl oxidase cause kinked hair

Answer 43

Causes keratin cross linking

Question 44

Classical menkes is severe loss of function mutations even deletions. What is the name for milder menkes

Answer 44

Occipital horn syndrome

Question 45

Is there treatment for classical menkes

Answer 45

No they die early due to ceased development and neurone degen

Question 46

How could you diagnose

Answer 46

Genotyping Serum cu levels or ceruloplasmin (low) By clinical features eg kinky haur

Question 47

What are the treatments for OHS

Answer 47

Cu administration Symptomatic treatment

Question 48

What is Wilson’s

Answer 48

Autosomal recessive of atp7b

Question 49

What does this cause

Answer 49

Build up of cu in liver as bile duct excretion is impaired Also then spreads via blood to brain, kidney, eyes and deposits of cu

Question 50

How does excess copper cause damage

Answer 50

Fenton chemistry Radicals cause lipid peroxidation, protein and dna damage

Question 51

What would be severe liver symptoms after a lot of radical build up

Answer 51

Cirrhosis and fibrosis (hard to treat£

Question 52

Why would waste build up in blood eg ammonia

Answer 52

Hepatocytes usually filter blood eg turn ammonia to urea

Question 53

What is build up in eyes called

Answer 53

Kayser fisher rings

Question 54

What sort of brain problems does Wilson’s cause and why

Answer 54

Builds up in basal ganglia Cognitive, psychiatric and nervous

Question 55

Why would there be low xeruloplasmin levels in diagnosis

Answer 55

Bc atp7b allows tgn incorporation into enzymes like ceruloplasmin

Question 56

How could you treat it

Answer 56

Cu Chelators - excrete in urine Low cu diet Liver transplant Zinc acetate- increases MTs

Question 57

Give the most common mutation in atp7b Wilson’s

Answer 57

H1069Q

Question 58

What does it do

Answer 58

Causes faster degradation in the er so it can’t traffic post Golgi Due to the mutant binding hsp70

Question 59

Which mutation in the 9aa n terminus causes no apical/bile movement

Answer 59

N41A