Voltage-Gated Ion Channels

Question 1

2 subunit types of VG Na channels

Answer 1

alpha and beta

Question 2

Alpha subunit of VG Na channel

Answer 2

Modeled as 4 internal repeats

Question 3

Voltage sensor of VG Na channel

Answer 3

TM4 (S4)

Question 4

What part forms the channel of VG Na channel?

Answer 4

P loop, H5 or SS1-SS2

Question 5

VG Na channel inactivation gate is located between?

Answer 5

Repeat III and IV

Question 6

Activation of VG Na channel is dependent on?

Answer 6

Voltage (requires adequate depolarization)

Question 7

Open probability of VG Na channel is dependent on?

Answer 7

Time (rapid inactivation)

Question 8

How long does it take for VG Na channel to go from active to inactive?

Answer 8

1 ms

Question 9

Inactivated state of VG Na channel is dependent on?

Answer 9

Time and voltage → requires time at negative (hyperpolarized) potential to de-inactivate

Question 10

VG Na channel is blocked by?

Answer 10

1. Local anesthetics (ex: lidocaine)

2. Tetrodotoxin

Question 11

If the membrane does not repolarize, what happens to VG Na channel?

Answer 11

Remains inactivated for extended time

Question 12

Mechanism of VG Na channel inactivation gate is called?

Answer 12

Hinged lid

Question 13

Cytoplasm loop of VG Na channel (hinged lid) is made of?

Answer 13

1. Isoleucine
2. Phenylalanine
3. Methionine

Question 14

In a cell with mutated VG Na channel which remains open, what happens to membrane potential?

Answer 14

Stays near E(Na)

Question 15

HYPP stands for?

Answer 15

Hyperkalemic Periodic Paralysis

Question 16

Hyperkalemia means?

Answer 16

High blood potassium

Question 17

HYPP is caused by?

Answer 17

Defect in sodium channels → high blood K is secondary

Question 18

What is the defect in Na channels in HYPP?

Answer 18

Rapid deactivation → no refractory period

Question 19

K channels are sensitive to?

Answer 19

Voltage and Calcium

Question 20

T of VG K channels determines?

Answer 20

Tetramerization → family specific

Has phosphorylation sites

Question 21

Inactivation latch of VG K channels is located?

Answer 21

Between loops 4 and 5

Question 22

Functional characteristics (activation, open probability and inactivation) of VG K channel are the same as?

Answer 22

VG Na channel

Question 23

VG K channels are blocked by?

Answer 23

1. Antiarrhythmics
2. Toxins
3. Dendrotoxin
4. Charybdotoxin
5. Agitoxin

Question 24

VG K channel inactivation latch is called?

Answer 24

Ball and chain

Question 25

Which inactivation method is more rapid, hinged lid or ball and chain?

Answer 25

Hinged lid

Question 26

Why is ball and chain inactivation slower than hinged lid?

Answer 26

Longer chain (chain length varies among K channels)

Question 27

Activated K channel has what effect on membrane potential?

Answer 27

Decreases membrane potential

Question 28

If drug blocks K channel, what happens to cell?

Answer 28

Will depolarize and have decreased ability to repolarize

Question 29

Action potential comes from?

Answer 29

Changing conductances over time

Question 30

Resting membrane potential is regulated by?

Answer 30

Basal conductances

Question 31

What induces depolarization to threshold?

Answer 31

Agonist

Question 32

Agonist-induced anion channels do what?

Answer 32

Reduce depolarizing impact of stimulating neurotransmitters (prevents reaching threshold)

Question 33

V-sensitive Ca channels are important for action potential in what cels?

Answer 33

Cardiac and nerve

Question 34

What type of channel is important for excitation-secretion coupling?

Answer 34

V-sensitive Ca channels

Question 35

V-sensitive Ca channels have intracellular regulation by?

Answer 35

1. Kinases 2. Ca 3. G-proteins

Question 36

Inactivation timer of V-sensitive Ca channels

Answer 36

TM6 of repeat I

Question 37

Voltage sensor of V-sensitive Ca channels

Answer 37

TM4

Question 38

Subunit types of Ca(V) channels

Answer 38

1. Alpba 2. Beta 3. Gamma 4. Delta

Question 39

Ca(V) channel functional characteristics

Answer 39

same as others

Question 40

Ca(v)1.x is what type?

Answer 40

L-type (long)

Question 41

Ca(V)1.x modulated by?

Answer 41

Dihydropyridines

Question 42

Dihydropyridines are a target for?

Answer 42

Drug interference with cardiac modulation

Question 43

Ca(V)2.x is what type?

Answer 43

P/N/R-type (neither)

Question 44

Ca(V)2.x is found in?

Answer 44

Dorsal root ganglion (pain interaction)

Question 45

Ca(V)2.x is blocked by?

Answer 45

1. Agatoxin 2. Conotoxins 3. SNX-482

Question 46

Ca(V)3.x is what type?

Answer 46

T-type (transient)

Question 47

Ca(V)3.x is found in?

Answer 47

CNS (anticonvulsant target)

Question 48

Ca(V)3.x is blocked by?

Answer 48

Kurtoxin (from scorpion)

Question 49

Antiarrhythmic drugs target?

Answer 49

Rapidly activating cardiac K channels