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BIOM 3090 > Lec 2 > Flashcards

Lec 2 Flashcards

1
Q

What are major functions of physiological receptors? (2) VIA what domains?

A
  • Ligand binding (VIA ligand binding domain)
  • Message propagation (VIA effector domain)
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2
Q

How do drugs modify cellular function after binding to receptors? (4)

A
  • Initiate
  • Enhance
  • Diminish
  • Terminate (Block)
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3
Q

What is the signal transduction pathway? (AKA receptor- effector coupling mechanism) (3)

A

the receptor, its cellular target, and any intermediary molecules

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4
Q

What are the major types of drug receptors? (4)

A
  • transmembrane ion channels
  • transmembran G-protein coupled
  • transmembrane enzymatic cytosolic domain coupled
  • intracellular
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5
Q

What is the membrane lipid bilayer impermeable to?

A

Polar (charged) anions and cations (Na+, K+, Ca2+, Cl-)

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6
Q

What do ion channels have key roles in?(4)

A
  • neurotransmission
  • cardiac conduction
  • smooth and skeletal muscle contraction
  • secretion
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7
Q

How are ion channels classified? (3)

A
  • Architecture (subunits)
  • Ions conducted through the channel
  • mechanism of activation (Ligand and voltage activated channels are major drug targets)
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8
Q

Where are ligand activated (gated) channels found?

A

In the CNS
- Excitatory NTs (ACh or glutamate)
- inhibitory NTs (glycine or GABA)

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9
Q

What are characteristics of nicotinic acetylcholine receptor ()

A
  • ligand gated channel
  • isoforms found in skeletal muscle and neurons
  • has 5 subunits in skeletal muscle
  • closed state is occluded by bulky amino acids side chains
  • open is when ACh binds to alpha unit
  • Na+ is major electrolyte passed K+ also passed
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10
Q

How many subunits do ligand gated channels have?

A

5

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11
Q

What causes for ligand gated channel to be closed?

A

bulky amino acid side chains

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12
Q

How does ligand gated channel open?

A

Binding of 2 molecules of ACh to alpha subunit

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13
Q

What is the major electrolyte passed in ligand gated channels? what else is passed?

A

Na+, K+

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14
Q

What are voltage-activated channel types? (4)

A

Na+, K+, Ca2+, Cl-

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15
Q

Where do voltage activated Na+ channels initiate action potentials?

A

Axons of nerves and muscles

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16
Q

Can drugs have greater affinity for certain conformations?

A

Yes, like state-dependent (local anaesthetics and antiarrythmics)

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17
Q

What is a local anesthetic example and how it works?

A

Lidocaine binds to the channel to prolong the refractory period

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18
Q

What is the refractory period?

A

Inactive channel

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19
Q

What is the polarized period?

A

Reset and opening of channel

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20
Q

What are some intracellular molecule activated ion channel characteristics?

A

Sulfonylurea receptor (SUR1)
- regulated ATP dependent K+ channel in pancreatic beta cells
- sulfonylurea class oral hypoglycemics

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21
Q

What is the most abundant class of receptors in the body?

A

G-protein coupled receptors (GPCRs)

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22
Q

How many GPCRs do humans express?

A

over 800

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23
Q

What are GPCRs for? (~2)

A
  • over half are dedicated to sensory perception (sight, smell, taste)
  • the rest are for nerve activity tension in smooth muscle, metabolism, force and rate of cardiac contraction and secretion of most glands.
24
Q

How are GPCRs activated?

A

By neurotransmitters (ACh, NE), eicosanoids (PGs), peptide hormones, opioids and others

25
Q

What receptors do over half of all non antibiotic drugs act?

A

GPCRs

26
Q

What do GPCRs bind to?

A

G proteins

27
Q

How are signals from G proteins terminated?

A

Hydrolysis of GTP to GDP by inherent GTP-ase activity on alpha subunit

28
Q

Major role for G proteins

A

Activate effector molecules that produce second messengers

29
Q

How are effectors characterized (4)

A
  • Adenylyl cyclase
  • gyanylyl cyclase
  • phospholipase C
  • various ion channels
30
Q

What are the best known G proteins

A

G alpha

31
Q

What is the lesser known G protein?

A

Beta gamma subunit isoforms role
- can regulate K+ and Ca2+ channels

32
Q

What are beta adrenergic receptor group characteristics

A

Important
- catecholamines (EPI NOREPI)- endogenous ligands- stimulate cAMP and cellular effects

33
Q

What are key G protein mediated second messengers? (4)

A

-cGMP
-IP3
-cAMP
-DAG

34
Q

What are some transmembrane receptors with intracellular linked enzymatic domain characteristics? (SHORTEN THIS)

A
  • important in metabolism, growth and differentiation, tonic activation can cause tumours
  • have single membrane spanning proteins compared to seven (G-protein receptors)
  • receptors form dimers or multi subunit complexes for transduction of signals
  • activity if receptors = adding/removing phosphate groups from specific aa’s (phosphorylation can cause change in energy and shape)
35
Q

What are receptor tyrosine kinase characteristics? (SHORTEN THIS)

A
  • largest group of this receptor class
  • endogenous ligands (insulin)
  • effectors include SH2 domains on other signalling molecules like Grb2
  • drugs (Imatinib - TK inhibitor)
  • anticancer agent
36
Q

What modifies nuclear hormone events?

A

circulating steroid hormones are lipophilic diffusing through the plasma membrane to bind transcription factors

37
Q

What do receptors process? (2)

A

ligand binding domain and a DNA binding domain

38
Q

What do nuclear events depend on?

A

which co-activators or co-repressors of gene transcription are recruited

39
Q

Is gene transcription fast or slow? are they long lasting?

A

SLOW - min to hrs but they’re long lasting

40
Q

What is lag on in gene transcription?

A

Slow onset of cellular effects

41
Q

What is lag off in gene transcription?

A

slow onset of cellular effects

42
Q

What is an example of gene transcription in nuclear hormone receptors?

A

Glucocorticoids

43
Q

What is NO gas?

A

Labile gas produced locally
- important in the CV system
- binds to N-terminal domain of soluble GC and enhances activation of cGMP

44
Q

What is the endothelial NO?

A

eNOS

45
Q

What is the inducible NO?

A

iNOS

46
Q

What is the neuronal NO

A

nNOS

47
Q

what are vascular smooth muscle effects of cGMP?

A

cGMP acting on PKG
- vasodilation from reduced intracellular calcium levels (Angina pectoris and nitrovasodilators)

48
Q

Can drug receptors exist outside of the plasma? why?

A

yes, for communication purposes

49
Q

Examples of drug receptors found outside of the plasma are… (2)

A
  • vasoconstriction (ACE inhibitors)
  • Neurotransmitters (Acetylcholinesterase inhibitors)
50
Q

Why do some drug receptors have a cell surface adhesion function ?

A

to allow cell-cell interaction for various functions (inflammation, coagulation) (eptifibatide an antagonist of the platelet GPIIb-IIIa receptor)

51
Q

What is an example of a drug receptor that provides a structural role for the cell?

A

Antineoplastics - Microtubule inhibitors (paclitaxel for cancer therapy)

52
Q

How do cells integrate multiple signals to produce a coherent cellular response?

A

Signalling convergence by second messengers can generate coordinated net cellular effects

53
Q

Is the magnitude of a cellular response to a ligand lesser than the initiating stimulus?

A

No, greater than

54
Q

Can cells amplify the effects of receptor binding by ligands (Epinephrine / adrenaline)

A

YES !

55
Q

Why can drug-induced activation or inhibition of a receptor have long lasting effects on subsequent responsiveness to drug binding?

A

It prevents overstimulating of the pathway and cellular damage

BIOM 3090 (5 decks)

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