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Jacopo Biomembranes > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

In what tissue is ClC-1 found?

A

Skeletal muscle

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2
Q

What is the function of ClC-1?

A

Recover resting membrane potential.

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3
Q

What human disease is ClC one responsable for?

A

Myotonia congenita

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4
Q

What does the ClC-1 KO mice show?

A

It is affected by myotonia congenita.

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5
Q

Where is ClC-2/(GlialCam) normally found?

A

Brain, Kidney, liver, heart, pancreas, skeletal muscles, lungs, GI tract.

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6
Q

What is ClC-2/(GlialCam) and ClC-KA/Barttin function?

A

Transepithelial transport

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7
Q

What human disease is ClC-2/(GlialCam) responsible for?

A

Leukodistrophy, azoospermia.

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8
Q

What does the ClC-2/(GlialCam) KO mice show?

A

Retinal and testes degeneration, leukodistrophy.

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9
Q

Where is ClC-Ka/Barttin normally found?

A

In inner ear, kidney.

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10
Q

What human diseas is associtated with ClC-Ka/Barttin?

A

Loss of Barttin or both ClC-Ks: Bartter IV (renal and salt loss and deafness).

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11
Q

What do ClC-Ka/Barrtin KO mice show?

A

Diabetes insipidus.

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12
Q

What human disease is usually associated with ClC-Kb/Barrtin?

A

Loss of ClC-Kb: Bartter III (renal salt loss).

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13
Q

Where is ClC-3 usually found?

A

Its expression is broad.

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14
Q

What function does ClC-3 perform?

A

Ion homeostasis of intracellular vesicles.

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15
Q

What do ClC-3 KO mice show?

A

Retinal and brain degeneration

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16
Q

Where is ClC-4 normally found?

A

Skeletal muscle, brain and heart.

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17
Q

What is the thought function of ClC-4?

A

Ion homeostasis of endosomes.

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18
Q

What is the human disease that is thought to be associated with ClC-4?

A

Intellectual disabilities.

19
Q

Where is ClC-5 normally found?

A

In kidney and intestine.

20
Q

What is the function performed by ClC-5?

A

Ion homeostasis of early endosomes.

21
Q

Which human disease seems to be associated with ClC-5?

A

Dent’s disease.

22
Q

What do ClC-5 KO mice show?

A

Impaired renal endocytosis.

23
Q

Where is ClC-6 normally found?

A

Neurons.

24
Q

What is the function performed by ClC-6?

A

Ion homeostasis of late endosomes.

25
Q

What do ClC-6 KO mice show?

A

Lysosomal storage disease.

26
Q

Where is ClC-7/Ostm1 found?

A

Brain, kidney, liver and bone.

27
Q

What is the function performed by ClC-7?

A

Acidification of resorption lacuna in osteoclasts, ion homeostasis of lysosomes.

28
Q

What human disease is associated with ClC-7?

A

Osteoporosis, retinal degeneration, lysosomal storage disease.

29
Q

What do ClC-7 KO mice show?

A

Osteoporosis, retinal degeneration, lysosomal storage disease.

30
Q

Briefly describe the structure of ClC proteins?

A

They are homodimers, each with a separate Cl- conduction pathway.

31
Q

What does each protomer consist of?

A

18 helical domains (A-R) most of which do not cross the membrane and are remarkably tilted.
2 intracellular cystathionine-β-synthase (CBS) domains.

32
Q

What does appear in the 3D structure of protomers of ClC proteins?

A

Helices D, F, N and R contribute to the Cl- conduction pathway.
Helices H, I, P, Q are part of the interface between the two protomers
Helix R connects the transmembrane element of the structure to the intracellular domain

33
Q

What are the three anionin binding site that are formed on each protomer?

A

Sex
Scen
Sin

34
Q

Describe Sex, Scen and Sin:

A

They are exposed to extra and intracellular solutions, respectively but Scen is cut off from water below by a costriction provided by the side chains of Sercen and Tyrcen and above by a conserved glutamate residue Gluex.

35
Q

Describe the deprotonated side chain of Gluex.

A

Can alternatively occupy Sex, Scen and competes with a Cl- ion for binding.

36
Q

What happens when Gluex occupies Sex?

A

The channel is non-conducting.

37
Q

What happens when Gluex mutate to glutamine?

A

It mimick protonation of the Gluex side chain and this allow the binding of a Cl- ion, the channel is conducting.

38
Q

What happens when Gluex occupies Scen?

A

The channel is non conducting.

39
Q

What are the conditions that make ClC-1 conducting?

A

1) All Cl- binding (co-ordination) sites must be occupied by Cl- ions.
2) When protonated (i.e neutral) Gluex moves out the condution pathway allowing Cl- ions to bindi simulataneously to all three binding (co-ordination) sites.

40
Q

What are the conditions that make ClC-2 non-conducting?

A

When deprotonated (i.e negatively charged) Gluex occupies either Sex or Scen, preventing binding (co-ordination) of a Cl- ion at these sites.

41
Q

What facilitates the opening of fast gates of ClC-1?

A
  • extracellular Cl- (competes with Gluex for binding)

- low extracellular pH (promotes the protonated species of Gluex)

42
Q

How do mutations of ClC-1 give rise to myotonia?

A

1) inverting the voltage sensitivity of the channel
2) affecting the ion selectivity of the pore
3) reducing expression of the channel at the sarcolemma.

43
Q

What normally happens during repetitive firing of AP in skeletal muscle?

A

K+ ions accumulate in the narrow confines of the T-tubule system. The potential depolarizing influence of elevated K+ is normally prevented by ClC-1.

44
Q

What happens during repetitive firing of AP in skeletal muscle in individuals affected by myotonia?

A

Defects in ClC-1 expression or function allow muscle depolarization and the firing of autonomous action potentials.

Jacopo Biomembranes (16 decks)

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