ACh receptors

Question 1

nAch receptors are what kind of cation-conducting channels (selective/non-selective)?

Answer 1

non selective because they can conduct Na, Ca into cell/K out of cell

Question 2

In the context of nACh (and their ability to conduct different ions) what is the relevance of knowing its reversal potential (potential at which there is no current flow)?

Answer 2

acts as a fingerprint to identify which ions are being conducted through channel
- can be used to find out what proteins/subunits are implicated in cation conduction

Question 3

characteristic of bi-liganded nAcH kinetics

Answer 3

• prolonged channel opening with brief closures

Question 4

Characteristics of mono-liganded nAcH kinetics?

Answer 4

• brief channel openings

Question 5

nAch receptor subtypes found in skeletal muscle?

Answer 5

a1, b1,delta, gamma (embryonic), epsilon (adult muscle)

Question 6

nAch receptor subtypes in neurons

Answer 6

alpha2-9, beta2-4

Question 6

location of ach agonist binding on nAch receptors?

Answer 6

subunit interfaces

Question 6

GABA, glycine, nAch, 5HT3 receptors are part of which receptor family?

Answer 6

cys-loop receptor family

Question 6

effect of 5HT3b subunit on single channel conductance in 5HT3 heteromultimer
?

Answer 6

increased conductance due to presence of QDA residues in TM3-TM4 intracell. loop component

Question 6

what kind of conduction do following receptors facilitate (cation/anion)?
- 5HT3R
- GABAaR
- GlycineR

Answer 6

• cation conducting
• anion conducting (Cl-)
• anion conducting

Question 6

investigation on alpha7 (nACh)/ 5HT3a (5HT3) chimera

significance of a-bungarotoxin having no effect on 5HT3a

Answer 6

• no effect suggests binding site is most likely not in 5HT3a region

Question 6

what kind of structure is common in cys-loop receptors?

Answer 6

pentameric structure

Question 7

what properties of 5HT3B subunit caused increased conductance?

Answer 7

• Q,D,A residues

Question 8

how can one convert cationic nACh receptor alpha7 (with glutamate residue at TM2) to anionic?

Answer 8

• mutate E to arginine (R)

Question 9

how to convert anionic alpha1-gly receptor (arg residue at TM2) to cationic?

Answer 9

mutate R to glutamate (E)

Question 10

can the following isoforms form functional homomeric pentamers (yes/no)?
- 5HT3a (can traffic to cell surface)
- 5HT3b (cannot traffic to cell surface)

Answer 10

• yes
• no

Question 11

What did the study comparing 5HT3 (a,b isoforms) and homomeric a7 nACh receptor reveal about structures important in conductance of cys-loop receptors?

Answer 11

• Tm2 is not solely responsible for conductance
• the Tm3-4 loop is important to single channel conductance

Question 12

subunit makeup of adult skeletal muscle nACh receptor?

Answer 12

• 2alpha
• beta
  -delta
• EPSILON

Question 13

what is the effect of ACH binding protein (agonist, antagonist) on nAChr subunits (specifically their loop C in context of binding pocket?)

Answer 13

AGONIST
- stabilizes loop C contracted form– closure over binding pocket

ANTAGONIST
- induces loop C extended form– loop C is away from binding pocket