receptor basics and gpcr

Question 1

describe paracrine signalling

Answer 1

signalling cell release local mediator

Question 2

describe endocrine signalling

Answer 2

signalling cell releases hormone to blood stream the travels target cell

Question 3

describe nervous system signalling.

Answer 3

pre synaptic membrane releases neurotransmitter which acts on post synaptic membrane target cell.

Question 4

define what a receptor is

Answer 4

molecule that recognises a specific ligand and which in response to ligand brings about regulation of cellular processes

Question 5

define what a ligand is. what type of ligands are there?

Answer 5

any molecule that binds at a receptor site
activate receptor agonist
inhibit receptor antagonist

Question 6

What is kD? What is it like compared to Km of enzymes?

Answer 6

kD binding affinity of ligand is normally much higher that enzyme affinity

Question 7

What are the 4 main types of receptor?

Answer 7

membrane bound r’s with integral ion channels
membrane bound r’s with integral enzyme activity
membrane bound r’s that are couple to effector through transducing proteins
intracellular receptors

Question 8

Name a receptor with an integral ion channel.

Answer 8

nicotinic ACh receptor

Question 9

How many subunits are in a nAChR?

Answer 9

5

Question 10

How do tyrosine kinases work? What type of receptor are they?

Answer 10

integral enzyme activity
work in as dimer
ligand binds tyrosine activated by autophosphorylation
enzymes and proteins with SH2 domain recognise and are then phosphorylated (enzyme itself or transducer proteins)

Question 11

Name a receptor that is coupled to a transducing protein

Answer 11

7 tm receptors or g protein coupled receptors

Question 12

Name a receptor that is intracellular. What are the main components of this kind of receptor?

Answer 12

oestrogen receptor 
DNA binding domain 
hinge region 
hormone bindingdomain 
transcription activating domain 
inhibitory protein complex

Question 13

What are the superfamilies of cell surface receptors?

Answer 13

GPCR’s
ligand gated ion channels
R’s with intrinsic enzyme activity

Question 14

Name a agonist of gpcr?

Answer 14

salbutamol on beta2 adrenorecptors for anti asthma

Question 15

Name antagonist of gpcr?

Answer 15

propanolol on beta adrenoreceptor for hypertension

Question 16

Where is the ligand binding domain of a gpcr?

Answer 16

between 2/3 tm domains

n-terminal region

Question 17

What is a g protein?

Answer 17

guanine nucleotide binding protein

Question 18

What subunits make up g proteins?

Answer 18

heterotrimeric
alpha
beta gamma

Question 19

What does a ligand binding to a gpcr cause?

Answer 19

GTP exchange GDP on alpha subunit

alpha and beta gamma complexes dissociate and act on effectors

Question 20

What allows the termination of a g protein signal?

Answer 20

alpha subunit GTPase activity converts GTP to GDP

inactive heterotrimeric complex forms again

Question 21

What provides g protein diversity?

Answer 21

many different isoforms of subunit

Question 22

What decides which gpcr the g protein interacts with?

Answer 22

alpha subunit

Question 23

What receptor interacts with the alpha s subunit and what effectors does it act on?

Answer 23

beta adreno receptor

up-regulate adenylyl cyclase

Question 24

What receptor interacts with the alpha i subunit and what effectors does it act on?

Answer 24

alpha 2 adrenoreceptor
M2/M4 Muscarinic r
down regulate adenylyl cyclase

Question 25

What receptor interacts with the alpha q subunit and what effectors does it act on?

Answer 25

alpha 1 adrenorecetor
M1/M3 muscarinic receptor
upregulate phospholipase C

Question 26

What does the pertussis toxin do?

Answer 26

modify alpha i subunit to stop gdp being release

Question 27

What does the cholera toxin do?

Answer 27

modify alpha s subunit prevent GTPase activity so signalling is maintained
lots electrolytes to lumen attracting water
causes diarrhoea