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FUN F > F6 Receptors and signalling > Flashcards

F6 Receptors and signalling Flashcards

1
Q

examples of chemical messengers

A
  • hormones
  • growth factors
  • neurotransmitters
  • paracrine agents
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2
Q

simply describe hormones. site of secretion and effects

A
  • secreted from site of synthesis in circulating blood (for long range communication)
  • has short and long term effects
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3
Q

effect of growth factors

A

long term control of cell growth and differentiation

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4
Q

effect of neurotransmitters

A

fast chemical transmission at neuronal synapses

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5
Q

effect of paracrine agents

A

local control of cell behaviour in the immediate environment

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6
Q

explain relationship between adrenaline and noradrenaline

A
  • adrenaline is a hormone and noradrenaline is neurotransmitter
  • they work on the same set of adrenoceptors
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7
Q

common characteristics of receptors

A
  • selective binding site for native hormone / transmitter
  • act as molecular switches (inactive and active states)
  • signal is amplified
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8
Q

common types of signal amplification

A
  • second messenger (many molecules produced eg. cAMP)
  • enzyme activity (catalytic: many molecules of substrate converted)
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9
Q

what are the 4 types of receptors?

A
  • ligand-gated ion channels
  • G protein coupled receptors
  • catalytic receptors
  • nuclear receptors
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10
Q

order the 4 types of receptors from fast to slow

A
  • ligand-gated ion channels
  • G protein coupled receptors
  • catalytic receptors
  • nuclear receptors
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11
Q

what are ligand-gated ion channels primarily responsible for?

A
  • fast synaptic transmission
  • eg. nicotinic receptors
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12
Q

describe signal amplification in terms of ligand-gated ion channels

A
  • opening a single ion channel lets thousands of ions flow through
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13
Q

describe amplification in terms of G protein coupled receptors

A
  • 1 receptor can activate many G proteins
  • activated ‘effector’ proteins are often enzymes or ion channels
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14
Q

describe catalytic receptors and what happens when activated. give an example

A
  • activated by hormone binding
  • causes enzyme activity
  • Tyrosine Kinase receptors for growth factors eg. EGF
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15
Q

give an example of a nuclear receptor

A
  • transcription factors
  • eg. steroid hormones (oestrogen receptor (ER))
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16
Q

describe the process of transcription factor action

A
  • ligands diffuse across membranes to intracellular receptors
  • when receptors (transcription factors) are activated, they can translocate to the nucleus and bind to DNA to promote transcription
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17
Q

why can ligands diffuse across membranes to activate transcription factors?

A

they are lipophilic

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18
Q

how does the G protein coupled receptor system cause amplification?

A
  • one receptor can activate many G proteins
  • activated ‘effector’ proteins are often enzymes or ion channels
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19
Q

why does the G protein coupled receptor system have flexibility?

A

it’s a 3 stage system that offers variety in messengers recognised and cellular responses generated

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20
Q

what do GPCRs look like?

A
  • 7 transmembrane domain helices
  • 7 transmembrane receptors
  • extracellular N terminus
  • intercellular C terminus
  • 3 extracellular loops (ECL), 3 intracellular loops (ICL)
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21
Q

how do GPCRs exhibit a wide diversity?

A
  • 800 different GPCR proteins
  • 7 transmembrane domain ‘template’ allows many types of binding site (receptors can be adapted for different binding sites)
22
Q

NA action on arterioles in GIT

A
  • bind to alpha 1 adrenoceptor
  • cause contraction
23
Q

NA action on arterioles in skeletal muscle

A
  • bind to beta 2 adrenoceptor
  • cause relaxation
24
Q

NA action on airway smooth muscle in bronchioles

A
  • bind to beta 2 adrenoceptor
  • cause relaxation
25
Q

what are the 3 main types of G protein?

A

Gs, Gi, Gq
(a particular receptor will normally activate just one type of G protein)

26
Q

name 2 effectors of G proteins

A
  • adenylyl cyclase
  • phospholipase C (PL C)
27
Q

what G proteins are adenylyl cyclase regulated by?

A
  • regulated by Gs, Gi
  • catalyses production of cAMP
28
Q

what can phospholipase C be activated by?

A
  • Gq receptor
29
Q

what subunits are there of G proteins?

A

G alpha and G beta

30
Q

what do the G alpha subunits bind to?

A
  • binds guanine nucleotides (GDP/GTP)
  • part of the activation process
31
Q

what is cAMP synthesised by?

A

adenylyl cyclase

32
Q

what does cAMP trigger and how?

A
  • cellular responses
  • bind and activate protein kinase A (PK A)
33
Q

after being triggered by cAMP, what does PK A do?

A
  • phosphorylates target proteins to change their function
34
Q

what is a ‘kinase’?

A

phosphorylates proteins to change their function

35
Q

what do Gs-coupled receptors do to adenylyl cyclase? describe the events that this allows for afterwards

A
  • stimulate adenylyl cyclase
  • adenylyl cyclase can then make cAMP from ATP
  • cAMP activates PK A which activates target protein
36
Q

what do Gi-coupled receptors do to adenylyl cyclase? describe the events afterwards

A
  • inhibit adenylyl cyclase
  • cAMP levels and PK A activity decreases
37
Q

what do Gq-coupled receptors do?

A
  • activate a membrane enzyme (phospholipase C / PL C)
38
Q

after activation by Gq-coupled receptors, what does phospholipase C (PL C) do?

A
  • hydrolyses a plasma membrane lipid (PIP2)
  • 2 intracellular messengers are produced (IP3 and DAG)
39
Q

after hydrolysis of PIP2, what does one of the products, IP3, do?

A
  • activates ion channels and calcium ions influx into the cytoplasm resulting in smooth muscle contraction
40
Q

describe the alpha 1 adrenoceptor in terms of G protein coupling and its effects

A
  • Gq coupled
  • increases intracellular calcium ions
41
Q

describe the alpha 2 adrenoceptor in terms of G protein coupling and its effects

A
  • Gi coupled
  • decreases intracellular cAMP
42
Q

describe the beta adrenoceptors in terms of G protein coupling and their effects

A
  • Gs coupled
  • increases intracellular cAMP
43
Q

effect of noradrenaline on the arterioles in the GIT in terms of the receptor and response in smooth muscle

A
  • alpha 1 adrenoceptor
  • Gq coupled
  • increases intracellular calcium ions
  • contraction
44
Q

effect of noradrenaline on the arterioles in the skeletal muscle in terms of the receptor and response in smooth muscle

A
  • beta 2 adrenoceptor
  • Gs coupled
  • increases intracellular cAMP
  • relaxation
45
Q

effect of noradrenaline on the airway in terms of the receptor and response in smooth muscle

A
  • beta 2 adrenoceptor
  • Gs coupled
  • increases intracellular cAMP
  • relaxation
46
Q

second messengers of Gq-coupled GPCR

A
  • increased IP3
  • DAG
  • intracellular calcium ions
47
Q

second messengers of Gs-coupled GPCR

A
  • increased cAMP
48
Q

second messengers of Gi-coupled GPCR

A

decreased cAMP

49
Q

effect of Gq-coupled receptors on neurons, smooth muscle, epithelial cells and endocrine cells

A
  • neurons: increased NT release
  • smooth muscle: contraction
  • epithelial cells: increased fluid secretion
  • endocrine cells: increased hormone secretion
50
Q

effect of Gs-coupled receptors on neurons, smooth muscle, epithelial cells and endocrine cells

A
  • neurons: increased NT release
  • smooth muscle: relaxation
  • epithelial cells: increased fluid secretion
  • endocrine cells: increased hormone secretion
51
Q

effect of Gi-coupled receptors on neurons, smooth muscle, epithelial cells and endocrine cells

A
  • neurons: decreased NT release
  • smooth muscle: contraction
  • epithelial cells: decreased fluid secretion
  • secretory cells: decreased hormone secretion
52
Q

what are the 4 main receptor superfamilies?

A
  • ligand-gated ion channels
  • GPCRs
  • catalytic receptors
  • nuclear receptors

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