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Drugs - new Flashcards

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1
Q

Name the 6 drug types of interest that interact with GPCRs

A
  1. Mescalin
  2. Psilocybin
  3. Opiates (enkephalins)
  4. Muscarin (Acetylcholine)
  5. Caffeine (Adenosine)
  6. Cannabis (THC)
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2
Q

Describe the 6 steps of the G-protein activation/deactivation cycle (can be a drawing if you want)

A
  1. Binding of hormone induces a conformational change in receptor
  2. Activated receptor binds Gα subunit
  3. Activated receptor causes conformational change in Gα’ triggering dissociation of GDP
  4. Binding of GTP to Gα triggers dissociation of Gα both from the receptor and from Gβγ
  5. Hormone dissociates from receptor; Gα binds to effector, activating it
  6. Hydrolysis of GTP to GDP causes Gα to dissociate from effector and re-associate with Gβγ
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3
Q

What is a GPCR?

A
  • G-protein-coupled-receptor
  • 7TM receptor protein
  • Upon ligand binding, it sets off a G-protein activation/deactivation cycle that can set off signaling pathways
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4
Q

Describe a heterotrimeric G-protein

A
  • Made up of 3 subunits:
  • GTPases that hydrolyze GTP
  • Molecular switches
  • Gβ and Gγ = Gα must dissociate from these two to work
  • Gα = The really important one
    • when GTP bound (on form) will bind effector protein, leading to stimulation or inhibition of target enzyme
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5
Q

Name 4 ways in which G-proteins may be modified by lipids

A
  1. G αS Palmitoylation at N-terminus: Palmitic acid on cysteine thioester linkage – reversible – Palmitic acid (Palm oil)
  2. G αi Myristoylation and Palmitoylation – Mysteric acid (nutmeg)
  3. G γ Prenylation – prenyl group
  4. Farnesylation or geranylageranylation to CAAX-Box at C-terminus
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6
Q

Name 2 ways in which G-proteins may be modifed via pathogenic ADP-ribosylation

A
  1. Vibrio cholera: produces ADP-ribosyltransferase specific for Gsα
  2. Bordella pertussis produces ADP-ribosyltransferase specific for Gi
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7
Q

What is the purpose of adenylate cyclase?

also known as adenylyl cyclase

A

Catalyzes the conversion of ATP to cAMP + pyrophosphate

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8
Q

Name 3 major pathways of cAMP signaling

A
  1. protein Kinase A (PKA) activation
  2. -Regulation of ion channels
  3. -Cross Talk with growth factor receptor signalling
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9
Q

What role does PKA play in glycogen breakdown?

A

targets enzymes, leading to glycogen breakdown

  1. PKA phosphorylates Glycogen synthase - deacctivates it
  2. PKA phosphorylates Phosphorylase kinase - activates it, leading to breakdown of glycogen
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10
Q

What role does PKA play in activation of CREB?

A
  • PKA phosphorylates KID box
  • CBP (CREB binding protein) - CREB coactivator
    • CBP recognizes and binds to CREB after KID box is phosphorylated.
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11
Q

What molecule is:

  • Is a transcription factor
  • immediate early genes are targets
  • Activates genes very quickly (within minutes)
  • Neuronal rapid response genes - plays a major role in stabilizing memory (especially long term memory)
A
  • Role of CREB (cAMP response element binding protein)
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12
Q

Name the 3 classes of phosphlipid modification enzymes

A
  1. Phospholipases
  2. lipid kinases
  3. lipid phosphatases
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13
Q

What 2 secondary messengers are created by phospholipase C, and where are they localized?

A
  1. DAG: remains in membrane
  2. IP3: moves to ER to open Ca2+ channels
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14
Q

What are the 3 steps to Phospholipase C (PLC) activation?

A
  1. -GSα activates AC (adenylyl Cyclase)
  2. -Giα inactivates AC
  3. Gq activates PLC (phospholipase C)
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15
Q

Name 3 tools in the Ca2+ signaling toolkit

A
  1. ATP driven Ca2+ pumps: remove Ca2+ from cytoplasm
  2. Ca2+ release channels: release Ca2+ in response to stimuli
    1. -Voltage gated channels
    2. -Receptor operated channels
    3. -Second messenger operated channels (IP3)
  3. Buffers: bind free Ca2+ in cytoplasm and ER
    1. -Calmodulin
    2. -Careticulin
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16
Q

Group of terpeno-phenolic compounds produced by plants of the genus Cannabis, such as Cannabis indica or Cannabis sativa

A

Phytocannabinoids

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17
Q

What are teh 2 main cannabinoids?

A
  1. Tetrahydrocannabinol (THC): anti-nociception and psychoactivity (hallcinations and other unwanted effects)
  2. Cannabidiol (CBD): anti-anxiety, anti-epileptic, anti-bactterial, anti-inflammatory. Little or no psychoactivity. Can potentially treat neuropathic pain.
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18
Q

Why can cannabinoids persist in the body for a long time?

A

Are highly lipid soluble

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19
Q

Where are cannabinoids concentrated in the plant?

A

Glandular trichomes of female plant

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20
Q

Why do plants synthesize cannabinoids?

A
  • THC is assumed to be involved in self defense, potentially against herbivores
  • THC posseses high UV-B absorption properties
    • protects plants from UV radiation?
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21
Q

CB1 receptor:

What is its ligand?

where is it localized?

Where is it coupled to?

What is its action?

A
  • What is its ligand?
    • cannabinoids
  • where is it localized?
    • presynapses
  • Where is it coupled to?
    • mainly Gi
  • What is its action?
    • inhibition of adenylate cyclase
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22
Q

CB2

What is its ligand?

where is it localized?

Where is it coupled to?

What is its action?

A
  • What is its ligand?
    • Cannabinoids
  • where is it localized?
    • outside CNS (Spleen)
  • Where is it coupled to?
    • mainly coupled to Gi
  • What is its action?
    • can be upregulated in response to injury and inflammation
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23
Q

Name 4 functions of both CB1 and CB2 upon activation

A
  1. Mediate inhibition of neurotransmitter release
  2. Block Ca2+ channels
  3. Activate K+ channels
  4. Activate MAP kinase
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24
Q

AT which two synapses is neurotransmission inhibited upon activation of CB1?

A

Inhibition of synaptic neurotransmission at both:

  1. -inhibitory synapses (GABA)
  2. -Excitatory synapses (glutamate)
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25
Q

Describe retrograde signaling in the context of cannabinoid receptor CB1

A
  1. Post synaptic neuron sends out endogenous cannabinoids that bind to CB1
  2. This alters the release of neurotransmitters (GABA, Glutamate)
  3. Causes potent and long lasting changes in presynaptic neurotransmitter release
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26
Q

Name 2 endocannabinoids

A
  1. Arachidonylglycerol (2-AG)
  2. Arachinidolethanolamide (AEA) Anandamide
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27
Q

What are 4 roles of Ach in the peripheral nervous system?

A
  • -muscle activation
  • -released from all pre- and postganglionic parasympathetic neurons
  • -preganglionic sympathetic neurons
  • -leads to release of adrenaline and noradrenaline from adrenal gland
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28
Q

What are 6 roles of Ach in the Central nervous system?

A
  1. -Cholinergic neurotransmitter system (inhibition)
  2. -neuromodulator for plasticity
  3. -sensory perceptions upon waking up
  4. -sustaining attention
  5. -promotion of REM sleep
  6. -memory
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29
Q

What are the 5 Ach receptors, where are they located and what is their receptor type?

A
  • M1/M3/M5
    • location: Atonomic ganglia, CNS
    • receptor type: Gq/11 - Phospholipase C
  • M2
    • Location: heart
    • Receptor type: Gi - Adenylate cyclase
  • M4
    • location: frontal brain
    • Receptor type: Gi - adenylate cyclase
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30
Q

3 points about muscarinic Ach receptors

A
  1. Are GPCRs
  2. Are Metabotropic (acts through secondary messenger)
  3. Have a lasting effect on neurons
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31
Q

Name an agonist of muscarinic Ach receptor

A

•Receptor agonists: Muscarine

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32
Q

name 3 antagonists of muscarinic Ach receptor

A
  1. Atropine,
  2. Hyoscamine,
  3. Scopolamine
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33
Q

Name 2 other types of drugs besides agonists or antagonists that act on the Muscarinic Ach Receptors (don’t need examples, but feel free to name them)

A
  • •Acetylcholine esterase inhibitors:
    • Examples:
      • •Drugs to treat alyheimers
      • •Naturally occuring: Venoms and Toxins
      • •Pesticides, chemincal warfare (Tabun – a nerve agent)
  • •Release inhibitors:
    • ​Examples:
      • Black widow venom (first contraction, then paralysis), Botulinus
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34
Q

Why do plants synthesize caffeine? (3 reasons)

A
  • 1)used for defense againt insects
    • –showsn to kill larvae of tobacco hornworm by competetively inhibiting phosphodiesterase (PDE)
  • 2) Used as an attractant for pollinators
    • –enhances reward memory of honeybees, improving reproductive success of plant
  • 3) Used against competing plants
    • –is released from decaying seeds and leaves, and accumulates in soil, possibly wards off competition by other plants
    • –this is a limiting problem in intercropped coffee plantations
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35
Q

What kind of molecule is caffeine and where in plant found?

A
  • Xanthine = Purine alkaloid (1,3,7-Trimethylpurine-2,6-dione)
  • Mostly found in leaves and seeds of coffee plants (but also 60 other plants, e.g. Tea, Kola nut, yerba mate
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36
Q

What is the effect of caffeine in animals and how does its structure matter

A
  • caffeine has similar structure to adenosine,
  • binds to adenosine receptors (without activating them)
  • Antagonizes adenosine by preventing adenosine from binding to these same receptors
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37
Q

A1 adenosine receptor:

Location

What happens upon activation?

What effect does adenosine have upon it in relation to sleepiness?

A
  • Location: brain cortex, hypothalamus, hippocampus, basal ganglia
  • Upon activation:
    • -AC-inhibition,
    • activation of inwardly rectifying K+ channels,
    • activates PLC,
    • blocks neurotransmitter release
  • Sleepiness:
    • -these are found on neurons responsible for keeping us awake
    • -if bound by adenosine, these neurons become less active, making us sleepy
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38
Q

A2 adenosine receptor:

Location

What happens upon activation?

What effect does adenosine have upon it in relation to sleepiness?

A
  • Location:
    • Striatum, nucleus accumbens, olfactory bulb
    • Co-localizes with dopamine receptors in regions for motor control
  • upon activation:
    • -AC-activation, brain, heart, inflammation
  • Sleepiness
    • -These are found on neurons that promote sleep
    • -If bound, these neurons become more active, making us sleepy
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39
Q

Describe the cycle of adenosine formation and breakdown

A
  1. Cells breakdown ATP for energy, producing adenosine
  2. Adenosine exported from cell via transporters
  3. Builds up in extracellular space (e.g. synaptic cleft)
  4. Adenosine binds adenosine receptors, making us sleepy
  5. during sleep, brain replenishes ATP using adenosine, reducing adenosine levels
  6. When not enough adenosine remaining to activate adenosine receptors, we wake up feeling nice and refreshed.
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40
Q

What is adenylate cyclase superactivity and how may it occur?

A
  • AC superactivity is where the AC enzyme needs less signaling to make cAMP
  • Can occur upon repeated opioid receptor stimulation
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41
Q

How do opioids control pain?

A
  • There are 2 pathways of pain control
  • The ascending pathway: recieves pain signal, makes its way to somatosensory cortex
  • The descending pathway: triggered by ascending pathway.
    • releases enkephalins (endogenous opioids) that inhibit ascending pain transmission
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42
Q

Physcological effects of opioids

A
  • -opioid signalling also occurs in certain areas of the brain and induces psychological effects such as euphoria and feelins of pleasure and reward.
  • -caused by excessive release of dopamine
  • -opitate receptors are also located in respiratory center of the brainstem, where they are involved in controlling the breathing rate.
  • -overdoes of heroin or morphine can arrest breathing altogether, causing death.
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43
Q

Opioid receptor effects

A
  • Are GPCRs
  • Can either inhibit or activate Adenylate cyclase depending on receptor and ligand.
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44
Q

What molecule is:

  • -Monoamine neurotransmitter controlling: cognition, mood, and reward
  • -implicated in depression, bipolar disorder, ADHD
  • -is important for neurostimulation
A
  • Dopamine
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45
Q

What are two Dopamine Receptors and what do they regulate?

A
  • D1: Golf-stimulation of AC on pathway facilitating motor activity
  • D2: Gi-inhibition of AC on pathway inhibiting motor activity
    • Overall effect: motorstimulation
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46
Q

How does cocaine work?

A
  • Cocaine binds DAT dopamine transporter
    • -prevents re-uptake of dopamine (also seratonin and norepinephrine-triple uptake inhibitor)
    • -this causes a dopamine overflow
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47
Q

What is the DAT transporter?

A
  • Dopamine transporter – DAT
    • -is the target for cocaine
    • -regulates availability of dopamine in the brain
      • –Actively translocates released dopamine back into the presynaptic neuron
    • -is an SLC transporter(solute carrier transporter) – Na+/dopamine transporter
  • DAT Structure:
    • -12 TM helices
    • -inwardly facing and outwardly facing conformations control direction of dopamine movement
    • -N and C- terminal tails in the cytoplasm are the sites for regulation
    • -Arg60 stabilises outward conformation
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48
Q

What are 5HT2A receptors?

A
  • Seratonin receptors
  • High concentration in pyramidal neuron cells
  • Expressed throughout CNS, neocortex
  • Upon activation, enhance glutamate release by interaction with other receptors
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49
Q

Why do 5HT2A agonists cause a psychodelic effect?

A
  • Cause robust increase in activity of pyramidal neurons
  • pyramidal cells are hyperexcitatory
  • leads to excess glutamate from multiple thalamic afferents
  • Sensory and cognative overload leads to psychodelic effects.
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50
Q

Name 4 drugs that interact with 5HT2A receptors

A
  1. Mescalin = peyote
  2. Psilocybin = magic mushrooms
  3. Ketamine
  4. Phencyclidin = angel dust
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51
Q

Name and either draw or describe 4 types of ion channels

A
  1. Voltage gated
  2. Ligand gated (extracellular ligand)
  3. Ligand gated (intracellular ligand)
  4. Mechanically gated
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52
Q

Give a basic description of voltage gated ion channels including:

How they respond to membrane potential

How is membrane potential measured

A
  • Ion channels open or close in response to membrane potential
  • Membrane potential is measured by concentration of ions outside and inside membrane
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53
Q

What is the membrane potential of a membrane if there is an excess positive charge outside the membrane?

A

It is negative, because the membrane potential is always listed as inside –> outside

Calculation would be: (Charge inside membrane) - (charge outside membrane)

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54
Q

What are the natural ion concentrations at resting potential?

A
  • Higher outside cell:
    • Na+
    • Ca2+
  • Higher inside cell:
    • K+
  • Ca2+ is also stored in the ER
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55
Q

List steps of opening of voltage gated ion channel

A
  1. Resting potential is always negative
  2. Na+ channels open in response to a signal
  3. Na+ ions go inside (down concentration gradient)
  4. this leads to depolarization of membrane
  5. Voltage gated ion channels open once voltage threshold is reached
56
Q

What is Patch-clamp tracing and what is it used to measure?

A
  • -used to measure change in mombrane potential

Method:

  1. -take a small section of membrane of cell
  2. -apply voltage
  3. -measure if this voltage that you apply changes the membrane potential
  4. -check which channels open
  5. -can then measure a current if channels open
57
Q

Describe or draw the structure of voltage gated ion channels

A
  • transmembrane structure with central pore
    • -aqueous channel
  • voltage sensing helix
    • -moves according to voltage, allowing channel to open
  • blockage after opening
    • -after channel opens, needs to block opening otherwise things would equalize again
58
Q

Name the two important channel types at the neuromuscular junction

A
  • L-type Ca2+ channels:
    • On plasma membrane of muscle fibers
    • creates a long lasting Ca2+ currents, and interacts directly with ryanodine receptors in SR
  • Ryanodine receptor:
    • intracellular Ca2+ channel
    • Ca2+ induced Ca2+ release from ER or SR
    • RYR1 - Skeletal muscle
    • RYR2 - Myocardium
    • RYR3 - widely expressed, especially in brain
59
Q

How does Ca2+ enter into the presynaptic neuron?

A

Vesicle Fusion P/Q type channel:

  • synprint site binds SNAREs:
    • anchoring to exocytosis machinery syntaxin (t-SNARE)
    • and SNAP25 (v-SNARE) mutations in human genetic disorders (e.g. Episodic ataxia, familial hemiplegic migrane)
60
Q

Name 3 toxins that act on the neuromuscular junction and the channels the interact with

A
  1. Ω-agatoxin: P/Q type channels
  2. Ω-conotoxin: N-type channels
  3. Tarantula venom: R-type channels
61
Q

Describe the structure of a nicotinic Ach receptor

A
  • -5 subunits arranged around central pore α α β γ δ
  • -Each subunit has 4 TM domains
  • -Pentameric organisation: wide range of different channels
  • 2 types:
    • Muscle
    • Neuronal
  • -rotation of α-subunit upon ligand binding
  • -Flexible glycine linkers
  • -conformational change by acetylcholine – twisting of helices
62
Q

Function of Acetylcholine (Ach) at neuromuscular junction

A
  • -Acetylcholine is neurotransmitter at neuromuscular junction
    • -binds to acetylcholine gated cation channels (nicotinergic acetylcholine receptor)
  • Expressed in muscle cells:
    • -activation-contraction coupling
  • Expressed in brain:
    • -learning, memory
    • -Loss: schitzophrenia, epilepsy, drug addiction, autoantibodies, usage dependant muscle weakness
63
Q

Nicotine.

What is it?

How quickly does it work?

On what does it act?

A
  • -competeative AchR-agonist
  • -Crosses blood-brain barrier and reaches brain in 10-20 seconds. Elimation half life = 2 hours
  • -Acts on:
    • nicotinic acetylcholine receptors α3β4 receptor (autonomic ganglia and adrenal medulla)
    • and α4β2 receptor (CNS).
64
Q

What happens upon Ach binding Nicotinic Ach receptors?

A
  • -Acetylcholine binding activates channel; Na+/K+
    • Na+/Ca2+ - influx; K+ - efflux (very small)
    • Net flow: positive charge inward
  • -Sum: resting potential -85 mV in muscle cell membrane is changed to -60 mV
  • -Opening of voltage dependent Na+ channels – voltage dependent Ca2+-channels re activated and cause Ca2+-efflux from SR
65
Q

List 6 AchR toxins:

A
  1. Nicotine: Competative AchR agonist
  2. Curare: competative AchR antagonist
  3. Snake alpha-toxins: antagonize AchR
  4. Coniine (poison hemlock): competative AchR-antagonist
  5. Cytisin: Competative AchR agonist
  6. Anatoxin A: AchR agonist
66
Q

Which ion channels are excitatory and which are inhibitory? Give an example for each

A
  • Cation Channels: Excitatory receptors
    • -nicotine/acetylcholine (5HT3 – serotonin)
  • Anion channels: Inhibitory receptors
    • -glycine: bind glycine
    • -GABA
67
Q

Why are inhibitory and excitatory ion channels named as such?

A
  • Inhibitory: anion channels.
    • allow negative ions in, reducing voltage of membrane.
    • restin potential is negative, so these take it further from depolarization voltage
  • Excitatory: cation channels
    • allow positive ions in, bringing up membrane potential, taking it closer to depolarization voltage
68
Q

describe the 5HT3 receptor

How does the selectivity filter work

A
  • Seratonin receptor
  • cys-loop receptor (in contrast to other 5HT receptors which are GPCRs)
  • Na+/k+ channel: excitatory
  • Pore size selectivity filter
    • allows hydrated ions to pass
    • removal of hydrated shell needs energy
69
Q

Describe GABA receptors

Type of receptor

What happens upon activation

Localization

A
  • Cys loop receptors
  • Cl- channels
  • Activation causes hyperpolarization –> Neuronal inhibition
  • Localization:
    • Brain, spinal chord, basal ganglia, cerebellum –> motor control
    • Thalamus –> sleep
70
Q

On what sort of receptor do these drugs have an effect, and what is the effect?

  1. Benzodiazepines
  2. Barbiturates
  3. ibotenic acid
  4. Muscimol

Plant derived:

  1. Thujone
  2. Bicuculline
  3. Picrotoxin
  4. Badrian
A

GABA receptors

  1. Benzodiazepines = enhance GABA action
  2. Barbiturates = enhance GABA action
  3. ibotenic acid = pro-drug for Muscimol
  4. Muscimol = Agonist

Plant derived:

  1. Thujone = antagonist
  2. Bicuculline = competative antagonist
  3. Picrotoxin = Competative antagonist
  4. Badrian = GABA carrier
71
Q

What molecule is:

  • A crystalline alkaloid
  • deathly to humans: 30-120 mg
  • Antagonist for inhibitory glycine receptor
  • Also binds Ach receptors on motor nerves in spinal cord and Seratonin-3-receptor
A

Strychnine

72
Q

Glutamate receptors

Type of receptor

Localization

Agonist drug example:

types: (3 types)

A
  • Type: ligand gated Na+/Ca2+ channel
  • Localization:
    • -primarily located in the brain, bund glutamate
  • Drug: ibotenic acid is an agonist-excitation, agitation, neuronal death
  • Types:
    1. AMPA receptors (α‐Amino‐3‐hydroxy‐5‐methylisooxazole-4‐propionic acid)
      1. -Synthetic agonist
      2. -ethanol is an antagonist!
    2. Kainate receptors (kainic acid) (sea weed, neuronal death induces exitotoxic lesions)
      1. -used against parasitic worms
    3. NMDA receptors (N-methyl-D-aspartate)
      1. -overactive during alcohol withdrawal
      2. -also exitotoxic lesions
      3. -correlation with schizophrenia
73
Q

Name 3 glutamate amino acids found to be excitatory on neurons

A
  1. N-methyl-D-Aspartate (NMDA)
  2. Aminomethylphosphonsaure (AMPA)
  3. Kainate (from red algae)
74
Q

What process is described by the following?

  • -Post synaptic neuronal cell death
  • -Glutamate overload on receptor, excess Ca2+ influx
  • -Involved in spinal cord injury, alzheimers, neurodegenerative diseases, alcoholism, alcohol withdrawal and over-rapid benzodiazepine withdrawal
A

Excitocytoxicity:

75
Q

AMPA-receptor

receptor type:

subunits

Regulation

A
  • -Glutamate receptor
  • -four subunits: GluA1-GluA4: all receptors are heteromers with varying subunit composition
  • Regulation:
    • -regulation by auxiliary subunits
    • -RNA-editing of GluA2: Adenosine deaminase acting on RNA
76
Q

NMDA-receptor

Processes involved in:

Structure:

In what situation does it open?

It is a silent receptor, what does this mean?

A
  • -Learning and memory long term potentiation (LTR), synaptic plasticity
  • -Heterotetramer
  • -Does not open after glutamate binding, only after depolarization through AMPA-receptors! This releases Mg2+ block
  • -Silent receptors! Will become active when AMPA-receptors are co-expressed-role in learning: LTR
77
Q

Interaction of NMDA with AMPA-receptor

A
  • NMDA receptor activated by depolarization caused by AMPA receptor opening
  • not by glutamate binding!
  • NMDA has a Mg2+ block that is only removed upon AMPA activation
78
Q

Name 2 drugs that interact with NMDA receptors

A
  1. Ketamine:
    1. -non-competative antagonists
  2. PCP-angel dust
    1. -Open Channel blocker
79
Q

Give a potential explanation for the symptoms of schizophrenia

A

Aberrant signaling between interacting dopaminergic, GABAergic and Glutamergic circuits in the brain

80
Q

Structure of TRPs

A
  • -6 TM domains, channel between 5 and 6
  • -Ca2+ or Na+ flow into cell
  • -have TRP box at C-terminal
  • 3 families:
    • 1-TRPC family
      • –4 A at N-terminal
    • 2-TRPV family
      • –3 A at N-terminal
    • 3-TRPM family
      • –extra long N- and C- terminals
81
Q

Rod and cone cells:

What is ligand

what is result of ligand binding

A
  • cGMP binding to receptor allows flow of ions such as Na+ and Ca2+ through channel
    • –in rod photoreceptor, Ca2+ binding to Calmodulin (CaM) helps activate it
82
Q

What is ligand bound to receptor in olfactory neuron and result of this

A
  • binding of cAMP allows flow of Ca2+ through channel.
    • –Ca2+ binds to calmodulin as well
83
Q

What receptor is this?

  • -Peripheral sensory neurons and brain and spinal cord
  • -responds to chemicals
    • -Capsaicin – spicy food
      • —Heat (>43 C)
      • —Inflammation
    • -also tarantula toxins
A

TRPV1​

84
Q

What receptor is this?

  • -voltage dependent Cold-sensitive channel
  • -high Permeability for Ca2+
  • Activation
    • -Activated at 15-22 C
    • -Allosteric modulator: menthol shifts activation threshold to less cold temperature
      • -menthol at high does induces heart arrhythmy
A

TRPM8

85
Q

How are hormone receptors activated?

A
  • -hormone binds to ligand (hormone) binding domain in cytosol
  • -inhibitor releases
  • -protein can move into nucleus and bind to response element, activate gene transcription with DNA binding domain binding to response element
86
Q

What are the 2 Nuclear receptor response elements

A
  1. Inverted repeats
    1. -receptors bind as homodimers (C4 zinc finger, 4 cysteine residues)
  2. Direct Repeats:
    1. -Receptors bind as heterodimers with common nuclear receptor monomer named RXR
87
Q

What molecule does this describe?

  • Small hydrophobic molecules that can diffsue into cells and activate intracellular targets directly
  • bound by carriers in blood
    • -Sex hormone binding globulin
    • -Corticosteroid binding globulin
    • -Retinal binding globulin
    • -Thyroid hormine binding globulin
    • -All hormones bind to serum albumin with low affinity.
A

Steroid Hormones

88
Q

Ligand dependent and ligand independent mechanisms of estrogen receptors

A
  • Ligand Dependent:
    • -Ligand must bind to estrogen receptor for it to go into nucleus and bind to response element
  • Ligand independent:
    • -Growth factor (GF) binds to receptor on plasma membrane, leading to phosphorylation of ER (estrogen receptor), allowing it to enter nucleus and bind response element
89
Q

What are some examples of phytoestrogens, and how were they discovered in 1940?

A
  • -flavonoids (soybean, chickpea, parsley, onions, blueberries, Ginkgo)
  • -Isoflavins, Coumestans: Phytoestrogens

Discovery

  • -Observation in 1940: red clover has an effect on the reproductive rate of grazing sheep!
  • -No clear effects on human infants and adults (non ruminants-digestion is different from sheep)
  • Flavanoids have structural similarity to estrogen
90
Q

Give a basic description of nuclear receptor ligands

A
  • -Small Hydrophobic molecules can diffuse into cells and activate their intracellular targets directly
  • -This is true for steroid hormones, thyroid hormones, retinoids
  • -They regulate gene transcription
91
Q

Describe the TGFβ signaling pathway including:

The ligand

The Receptor

The transcription factor

The location of these things

A
  1. Ligand: TGFß is proteolytically released from a precursor and stored in the extracellular matrix
  2. TGF-pathway receptors: 3 receptors are cooperating:
    1. -RI: Dimer of transmembrane proteins; serine/Threonine-kinase intracellular domain; activated by RII after binding of TGFß
    2. -RII: Dimer of transmembrane proteins; Serine/Threonine-kinase; Constitutively active
    3. -RIII: ß-Glycan; binds and concentrates TGFß-molecules at cell surface
  3. Transcription factor: Smad
    1. -SMAD: SMA/Mad related
    2. -MH: Mad homology
    3. 3 domains:
      1. -MH1: nuclear import/DNA binding
      2. -Linker domain
      3. -MH2: Receptor/SMAD binding
    4. Process:
      1. -smads are phosphorylated at the receptor. This exposes the nuclear localization signal (NLS)
      2. -phosphorylated Smads and Co-Smads move into the nucleus
      3. -Activate transcription
    5. Types:
      1. -R-Smads: Receptor regulated
      2. -Co-Smads: (recruited by R-Smads)
      3. -Inhibiting Smads
92
Q

Name Eight representative signalling pathways with nuclear receptors

A
  1. 1-TGFß
  2. 2-Cytokine
  3. 3-RTK
  4. 4-GPCR
  5. 5-Wngless
  6. 6-Hedgehog
  7. 7-TNFα
  8. 8-Notch
93
Q

Briefly describe Wnt-Signalling

A
  • -Axis determination in embryonic development
  • -Embryonic patterning („Wingless“)
  • -Stem cell differentiation and maintanance (e.g. Hemopoietic stem cells, ES-cells)
  • -Colon cancer and others
  • -Highly conserved in animals
94
Q

At which points in the cell cycle do different drugs target?

A
  1. Drugs targeting tubulin = M-phase
  2. DNA damaging drugs, and topoisomerase inhibitors = S-phase
  3. Drugs interfering with growth factor signaling = G1 phase
  4. Drugs inhibiting cdc25 = G2-M phase checkpoint
95
Q

How do the drugs that bind tubulin work, and what are 3 of them.

A
  • -Drugs inhibit microtubule polymerization or stabilize microtubules
  • -All inhibit microtubule dynamics
  • -All inhibit mitosis

Drugs:

  • -Vinblastine
  • -Colchicine: not used as anti-cancer drug – too toxic, gout
  • -Taxol: ovarian, breast, lung cancer
96
Q

Topoisomerase I role and drug

A

relaxation of supercoiling (no ATP required)

  • 1-Nicking: single strand cut (only for relaxing of supercoiling)
  • 2-Controlled rotation
  • 3-Relegation: (This step can be inhibited by Camptothecin)
97
Q

Topoisomerase II process and drugs

A
  • Double strand cut (ATP required)
  • 1-DNA binding
    • -Aclarubicin, Doxorubicin can inhibit this
  • 2-ATP binding
  • 3-Cleavage
    • -Quinolones, Ellipticines, Azatoxins supercharge this
  • 4-Strand Passage
  • 5-Relegation
    • -Etoposide, Doxorubicin inhibit this
  • 6-Product release
    • -ICRF-187 inhibits this
98
Q

Describe the JAK/STAT pathway

A
  1. Ligands: Cytokines:
    1. E.g.: Prolaktin, Interferone, Interleukin, Lymphokines, Erythropeitin
  2. Process:
    1. Ligand binds receptor
    2. Activated receptor recruits JAK kinase
    3. 2 parts of receptor come together
    4. STAT transcription factor is recruited and phosphorylated
    5. STAT dimerizes and translocates to nucleus where it activates transcription.
99
Q

What do interferons cause?

A
  • Interfere with virus infection
  • activate immune cells
  • enhance antigen presentation
  • produce fever
100
Q

Describe TNF signaling

A
  1. Ligands: TNFα
  2. Pathway:
    1. Ligand binds receptor
    2. Receptors come together to forma trimer
    3. Conformational change leads to dissociation of inhibitory protein SODD from intracellular death domain
    4. Dissociation enables adaptor protein TRADD to bind to death domain, serving as a platform for subsequent protein binding
    5. After TRADD binding, 3 pathways can happen:
      1. Activation of NFκB via release from cytoplasmic complex, which is then translocated to nucleus, leading to:
        1. Activation of inflammatory cytokines
        2. Prostaglandin E
        3. Survival genes
      2. Activation of MAPK pathways
      3. Induction of death signaling:
        1. TRADD binds FADD, recruiting caspase 8
        2. Is often masked by antiapoptotic effects of NFκB
101
Q

What do the Anti-inflammatory phytochemical drugs target?

A

NFkB?

102
Q

Name an example of a very important RTK

A

Insulin receptor

103
Q

How can the signal be propogated by a flexible protein with one transmembrane domain?:

A
  • Answer: ligand induced receptor dimerization
    • -receptor is not connected/complete until ligand(growth factor) binds, creating a dimer
    • -This allows for autophosphorylatin of the C-terminal of the protein
104
Q

Describe RTK signaling

A
  • Ligands: Growth and survival factors
    • e.g. Wortmannin, NGF

Pathway:

  1. Ligand binds to receptor, dimerizing it.
    1. e.g. TyrP binding SH2 domain
  2. After dimerization, downstream proteins are recruited
    1. Target proteins:
      1. 1-Enzymes:
        1. -PI(3) Kinase à PI(3,4,5)P
        2. -PhospholipaseCγ à DAG+IP3
      2. 2-Adaptor Proteins: Grb2 (ras-MAP kinase)
  3. Proteins are phosphorylated and translocated to the plasma membrane
105
Q

Describe MVA pathway–

A
  • Isoprenoid synthesis pathway
  • Mevalonate pathway or HMG-CoA reductase pathway
  • -Takes place in cytosol
  • -generates: Sesquiterpenes, Triterpenes (sterols)
  • -Exists in: eukaryotes (including humans), Archaebacteria, Plants
106
Q

Describe the MEP pathway

A
  • Isoprenoid synthesis pathway
  • MEP – 2-C-methyl-D-erythritol 4-phosphate/1-deoxy-D-xylulose 5-Phosphate pathway (MEP/DOXP pathway)
  • -in plastid
  • -Generates: Monoterpenes, Carotenoids (tetraterpenes), Diterpenes
  • -Exists in: eubacteria, plants
107
Q

Why plants produce isoprenoids:

A
  • -photosynthesis, photoprotection
  • -Plant-environment interactions such as defense mechanisms, allelopathy, pollination, and attracting
  • -membrane integrity
  • -Cleavage products: Ubiquinone, phytol chain of chlorophylls, plastiquinone (electron transport chains) Hormones
  • -signalling
108
Q

DXR in MEP pathway: Significance?

A
  • -DXP reductoisomerase: enzyme that interconverts DXP and MEP
109
Q

Isoprenoid pathway steps:

A
  1. Primary metabolites are converted via Isomerase (IPPàDMAPP)
  2. Prenyltransferase converts to next precursor (GPP, FPP, or GGPP)
  3. Terpene synthase converts precursor to terpenes (Limonene, Amorphadiene, Taxadiene)
  4. Tailoring enzymes further process (Menthol, Artemisinin, Taxol)
110
Q

When are the MEP and MVA pathways upregulated in light and dark?

A
  • MEP pathway becomes upregulated in light
  • MVA pathway downregulated in light
111
Q

Name 2 Tailoring enzymes:

A
  1. Tailoring Enzyme: Cytochrome P450
    1. Hydoxylation, isomerization, epoxydation, N-dealkylation, cyclization, cytosolic site of ER.
  2. -Tailoring Enzyme: 2-oxoglutarate-dependent dioxygenases (2OGDs)
    1. Non-heme proteins that localíze in cytosol as soluble proteins
    2. Fe(II) as cofactor, require 2-Oxoglutarate (2OG) and Molecular oxygen (R + 2OG + O2 à R-OH + succinate + O2)
112
Q

How does Taxol work as an anticancer drug?

A

-Chemotherapy: Binds to tubulin, stabilizes microtubules and as a result interferes with normal breakdown of microtubules during cell division, inhibition of cell division, induces apoptosis

113
Q

How does Etoposide work as a anti-cancer drug?

A
  1. Inhibits topoisomerase II by inhibiting relegation
    1. Leads to DNA damage, apoptosis
114
Q

What molecule is this?

  • -similar to capsaicin, but 1000 x hotter on scoville scale
  • -Relieves pain by making plasma membrane of sensory neurons permeable to cations, especially calcium
  • -helps with chronic pain by binding to calcium channels found on C-fiber (and some A delta nerve fibers). With their calcium channel gates blocked open, substantial amounts of calcium ions enter the cell body, naturally triggering cellular programmed death (apoptosis)
A

resiniferatoxin

115
Q

What molecule is this?

  • -Yellow, orange or red pigments
  • -Contribute to photosynthesis
  • -Protect plants from too much light
  • -Regulators of developmental responses in plants
A

Carotenoids

116
Q

What molecule is this?

  • -present in many essential oils (citronella, cyclamen, lemon grass, rose…)
  • -Perfumery to emphasize odors of sweet floral perfumes (co-solvent that regulates the volatility of the odorants)
  • -Natural pesticide for mites and is a pheramone for several other insects
A

Farnesol

117
Q

What molecule is this?

  • one or more sugary residues are added to triterpene
  • -saponins are secondary metabolites that allow plants to cope with environmental conditions (storing and conserving water, resisting predators, surviving severe weather)
A

Saponins

118
Q

5 Functions of phenylpropanoids:

A
  1. Light Protection (flavonoids)
    1. -Passive: UV- and Blue light absorption
    2. -Active: Quenching of radicals
  2. Attraction of pollinators (anthocyanines)
    1. -colors of flowers
  3. Defence (Lignane, silbene, cumarine, Flavonoide, tannine)
    1. -against: fungi, bacteria, virus
    2. -Feeding
    3. -Bad taste
    4. -Phototoxic
  4. Stabilization (lignin)
  5. Water and gas-impermeability (suberin, cutin)
119
Q

What molecule is this?

  • -can be present in all parts of plant
  • -defense against insects and bacteria
  • -UV-protection
  • -protection against early germination
A

Cumarines:

120
Q

What molecule is this?

  • -Formation of wood
  • -defence against bacteria
  • -pharmaceutical purpose
    • –Rhaponticin, a phytoestrogene from rhubarb
  • -Resveratrol – red wine
    • –anti-tumor
    • –also in skin of red grapes
A

Stilbenoids

121
Q

What toxins cause this?

  • Internal bleeding of animals:
    • -sweet clover disease
      • –spoiled sweet clover/hay (molding)
      • –during the process of spoiling, the harmless natural coumarins are converted to toxic dicumarol
      • –dicumarol combines with proenzyme required for synthesis of prothrombin (by preventing formation of active enzyme)
      • –probably also interferes with synthesis of factor VII and other coagulation factors
    • -Warfarin for rat poisoning
    • -protection against heart attack (oral anticoagulants)
    • -melilotus to treat vein problems (superficial)
A

Cumarines

122
Q

What molecule is this?

  • -Belong to flavanoid class
  • -(red – blue) depending on pH
  • -Cyanide, Delphinium
A

Anthocyans

123
Q

What molecule is this?

  • -(yellow, UV)
  • -Have 3-hydroxyflavone backbobe
  • -Diversity comes from positions of phenolic –OH groups
  • -Kaempferol, Quercitin
  • -In a wide variety of fruits and vegetables
  • -Have duel florescence, and might contribute to UV protection and flower color
  • -Might also play a role in health benefits of cranberry juice
A

Flavonols

124
Q

Name 2 ways that Flavonoids can be good for health

A
  1. -Can be ROS scavengers
  2. -Can be chelators (binding of metal ions)
125
Q

What molecule is this describing?

  • biosynthesis similar to fatty acids: Starting point is Acyl-CoA
  • In the Cannabis variety used for textiles, the cannabinoids CBDA and CBCA occur at high concentrations instead of THCA
A

Polyketides

126
Q

Odorant Receptors:

A
  • -Metabotropic GPCRs in vertebrates
  • -Ionotropic 7TM receptors in insects
    • –act as ligand gated channels
127
Q

Volatiles:

A
  • -are organic chemicals that have a high vapor pressure at ordinary room temperature
  • -Main Volatile Organic Chemical (VOC) is isoprene
128
Q

Volatiles role in plants:

A
  • Protection against:
    • -Abiotic stress (Thermotolerance and photoprotection), Herbivores, Pathogens, Competitors
  • Attraction of:
    • -Beneficial: pollinators, Mutualistic microbes, Seed dispensers, Predators of parasitoids
    • -Detrimental: Herbivores, Parasitoids, Pathogens
  • Signaling: Within plant, and between plant, Allelopathy
129
Q

name the 4 biosynthetic classes that volatiles originate from

A
  • -Terpenoids,
  • fatty acid catabolites,
  • aromatics,
  • amino-derived products
130
Q

2 Categories of Volatiles:

A
  • Terpenoids:
    • -monoterpenes (fenchane, camphane, thujone, pinane)
    • -Sesquiterpenes
  • Phenylpropanoids (dillapiole, carvacrol, cuminaldehyde)
    • -Phenylalanine to phenylacetaldehyde – a volatile found in the floral scent of rose, petunia
131
Q

Essential oils in insect control:

A
  • Essential oils are neurotoxic for insects
    • -Thymol binds GABA receptors
    • -Eugenol activates octopamine receptors
132
Q

Sour taste process:

A
  • -Acidic food contains H+ ions
  • -Blocks potassium ion channel and prevents leakage of the hyperpolarizing potassium
  • -Depolarization occurs in the receptor cell, results in sour sensation
  • -Also taste sensors for carbonation
133
Q

Salty taste process:

A
  • -Entry of Na+ ion into ion channel or receptor cells
  • -As a result, depolarization occurs.
134
Q

Sweet taste process

A
  • -Sugar molecule (both natural and artificial) binds to sweet receptors
  • -This binding activates secondary messenger pathway GPCRs
  • cAMP levels increase
  • activates a protein kinase
  • K+ channels phosphorylated and close
  • depolarization occurs
  • Ca2+ channels open
  • Neurotransmitter release
135
Q

Umami taste process

A
  • -GPCR second messenger pathway also causes umami sensation
  • -similar to sweet pathway
  • -only stimulated by L-glutamate and L-aspartate
136
Q

Bitter taste process:

A
  • Bitter substance binds receptor
  • GPCR activated
  • PLC activated
  • PLC catalyzes PIP2 –> IP3
  • IP3 causes release of Ca2+
  • Ca2+ influx causes neurotransmitter release
137
Q

Taste Interactions:

A
  • -salt-sour interaction and sour-bitter interaction enhance each taste
  • -Saltiness suppresses bitterness
  • -Umami suppresses bitterness by inhibiting binding of bitter ligand to bitter taste receptors
  • -Suppressing bitter taste is important, since bitterness has a negative hedonic (regarding senstations) impact on food intake

Cell Bio Exam (17 decks)

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