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Drugs and Disease > Receptor Transduction Systems > Flashcards

Receptor Transduction Systems Flashcards

1
Q

what is signal transduction?

A

a process by which a cell converts a signal or stimulus into a response

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2
Q

what does signal transduction involve?

A

a sequence of biochemical reactions carried out by enzymes and linked through intracellular signalling molecules

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3
Q

what is a second messenger?

A

intracellular signalling molecules

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4
Q

what does the signalling cascade allow?

A

a single stimulus to be amplified, and/or expanded to produce multiple different responses

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5
Q

examples of responses produced by signal transduction

A

modulation of gene translation, hormone secretion, energy production, cell division and cell motion

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6
Q

why does gene translation effects lead to further longer term changes?

A

because genes are expressed as proteins, many of which are enzymes, transcription factors or other regulators of cellular activity

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7
Q

examples of intracellular second messenger signalling molecules

A
  • cyclic nucleotides (cAMP, cGMP)
  • calcium ions
  • derivatives of phosphatidylinositoltriphosphate (PIP3): IP3 and DAG
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8
Q

what do second messengers regulate?

A

the function of specific cellular effectors commonly kinase or phosphatase enzymes

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9
Q

how do extracellular stimuli engage signal transduction pathways?

A

they engage it through 4 primary types of receptor

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10
Q

what are the two types of receptors?

A

cell surface transmembrane receptors and nuclear receptors

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11
Q

what are the cell surface transmembrane receptors?

A
  • receptors linked to ion channels
  • receptors couples to G proteins
  • receptors couples to enzymes
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12
Q

what are nuclear receptors?

A

receptors that affect gene transcription

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13
Q

what do ligand-gated ion channels do?

A

they, upon ligand binding, open a pore in the membrane increasing permeability to specific ions

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14
Q

what kind of responses are consequence of this increase in the membrane permeability?

A

postsynaptic excitatory or inhibitory responses

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15
Q

what do voltage-gated ion channels respond to?

A

changes in membrane potential - underlies the action potential impulses that travel along nerves

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16
Q

how are ligand-gated ion channels?

A

multimeric transmembrane receptors

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17
Q

what does multimeric mean?

A

A multiprotein complex is a group of two or more associated polypeptide chains

18
Q

are ligand-gated ion channels specific?

A

they open pores for specific ions; commonly for cations (Na+ and K+)

19
Q

what type of transport do ions undergo with ligand-gated ion channels?

A

passive transport (down the concentration or electrical gradient) - very rapid

20
Q

how does the nicotinic acetylcholine receptors work?

A
  1. receptor with 2 binding sites for ACh
  2. agonist (ACh) binds
  3. channel opens, ions pass through
  4. antagonist inhibits binding of agonist (channel shut down)
21
Q

other examples of ligand-gated ion channels

A
  • GABAa receptor: a ligand-gated Cl- channel
  • ionotropic glutamate receptor: a cation channel
  • 5-HT3 receptor: a ligand-gated cation channel
22
Q

common functions of ligand-gated ion channels

A
  1. cation channels - influx of positive ions: Na+ –> depolarisation - cell activation
  2. anion channels - influx of negative ions: Cl- –> hyperpolarisation - inhibition of the cell
  3. receptors found in fast responding cells - nerves and muscles
23
Q

what is tubocurarine?

A

competitive reversible antagonist of ACh at nicotinic receptors

24
Q

what is tubocurarine used for?

A

to relax skeletal muscle in surgery

25
Q

how are the effects of tubocurarine reversed?

A

by increasing ACh concentration through inhibition of the enzyme acetylcholinesterase

26
Q

what does GABAa receptor do?

A

it opens a Cl- ion channel leading to hyperpolarisation and cell inhibition

27
Q

what are the GABAa receptors used for?

A

drugs activating the GABAa receptor, e.g. diazepam, are used as tranquillisers and anticonvulsants

28
Q

what are the G-protein receptors (GPCRs) involved in?

A

in all types of stimulus-response pathway including hormones, neurotransmitters, sensory stimuli, etc.

29
Q

what are GPCRs?

A

integral membrane proteins that possess seven transmembrane domains - 7TM receptors

30
Q

how are the extracellular parts of GPCRs?

A

are often glycosylated

31
Q

what do GPCRs contain?

A

two highly conserved cysteine residues in extracellular loops that form an intramolecular disulphide bond to stabilise the receptor structure

32
Q

how do GPCRs work?

A
  1. receptor agonist binds to GPCR
  2. forms G-protein attached to membrane
  3. effector gives a response
33
Q

what are G-proteins consisted of?

A

3 subunits: alpha, beta and gamma

34
Q

what do the G-protein subunit determine?

A

which targets are activated - the alpha subunit and beta-gamma complex can each activate intracellular targets

35
Q

what are the physiological roles of GPCRs?

A
  1. sensation
  2. behaviour
  3. immune system and inflammation
  4. metabolism
  5. autonomic nervous system
36
Q

what does the sensational role of GPCRs consist of?

A

GPCRs respond to light (opsins), taste and smell (olfactory receptors)

37
Q

what does the behavioural role of GPCRs consist of?

A

GPCRs in brain bind several neurotransmitters, ex serotonin and dopamine

38
Q

what does the immune role of GPCRs consist of?

A

chemokine GPCRs meidate recruitment of immune cells to their needed location; while histamine receptors generate immune responses

39
Q

what does the metabolic role of GPCRs consist of?

A

GPCRs in the pancreas respond to gut hormones or dietary components in order to regulate insulin and glucagon secretion

40
Q

what does the autonomic nervous system role consist of?

A

both the sympathetic (adrenoceptors) and parasympathetic (muscarinic receptors) nervous systems use GPCRs to mediate their effects

41
Q

what is the autonomic nervous system responsible for?

A

responsible for the control of many autonomic functions of the body such as blood pressure, heart rate and digestive processes

Drugs and Disease (25 decks)

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