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BIO 317 > 2 - An Adrenaline Rush through the Second Messenger cAMP > Flashcards

2 - An Adrenaline Rush through the Second Messenger cAMP Flashcards

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1
Q

What response does adrenaline mediate?

A

Fight or flight response

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2
Q

True or false: The stress system has many different responses

A

True: many different organs react in different ways

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3
Q

How can a hormone have different effects (3 ways) on different cell types?

A
  1. Different receptors for the hormone
  2. Different signal transduction pathways
  3. Different proteins for carrying out the response
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4
Q

Liver cells and smooth muscle cells have the same receptor for adrenaline, but have different responses. How is this possible?

A

Different intercellular proteins changes the response

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5
Q

Skeletal blood vessels and intestinal blood vessels have similar intercellular proteins, but respond different to adrenaline. How is this possible?

A

Different receptors for adrenaline

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6
Q

What is a high affinity / low affinity ligand?

A

Ligands that have strong binding / weak binding (respectively) to a particular receptor

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7
Q

What are the three basic logic circuits for signal transduction?

A

Additive (OR), more than additive (AND) (synergistic), and less than additive (NOT) (antagonistic)

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8
Q

What does an “additive” response correspond to (in boolean)?

A

OR

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9
Q

What does a “more than additive” response correspond to (in boolean)?

A

AND

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10
Q

What does a “less than additive” response correspond to (in boolean)?

A

NOT

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11
Q

What response does an OR boolean correspond to?

A

Additive

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12
Q

What response does an AND boolean correspond to?

A

More than additive

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13
Q

What response does a NOT boolean correspond to?

A

Less than additive

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14
Q

What are the responses of molecules A and B in an additive response?

A

A -> response
B -> response
A + B -> response

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15
Q

What are the responses of molecules A and B in a synergistic response?

A

A -> 0
B -> 0
A + B -> response

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16
Q

What are the responses of molecules A and B in an antagonistic response?

A

A -> response
B -> 0
A + B -> 0

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17
Q

What does the graph look like for an additional response?

A

Two individual curves add together to get the combined curve

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18
Q

What does the graph look like for a synergistic response?

A

The individual curves are very low, but the combined curve is very high

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19
Q

What does the graph look like for an antagonistic response

A

The combined curve is inbetween the two individual curves (one of them being very low)

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20
Q

In a ligand binding curve, what are the axes?

A

X: Concentration
Y: Binding %

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21
Q

What is the use of a radioligand?

A

Track binding on a receptor through radioactivity

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22
Q

What is Bmax?

A

The maximal number of binding sites

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23
Q

Where is Bmax on a saturation curve?

A

At 100% binding

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24
Q

What is Kd?

A

The affinity of ligand for the receptor

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25
Q

Where is Kd on a saturation curve?

A

At 50% binding

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26
Q

What are the two major types of receptors?

A

Direct receptors, and indirect receptors

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27
Q

What are some features of a direct receptor?

A

Fast signaling, and a highly correlated binding and response

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28
Q

What are some features of an indirect receptor?

A

Slow signaling, with binding and response not well correlated

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29
Q

For a direct receptor, what does the curve of % of maximal response look like?

A

Closely follows the binding curve

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30
Q

For an indirect receptor, what does the curve of % of maximal response look like?

A

Sharp increase in the beginning (fewer receptors to get a maximal response), does not closely follow binding curve

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31
Q

What is an example of a direct channel?

A

Acetylcholine ion channel (simple binding opens up ion channel)

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32
Q

How are the binding curves of a direct and indirect receptor different?

A

Nothing; they look the same

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33
Q

How are the % of maximal response curves of a direct and an indirect receptor different?

A

The direct receptor follows the binding curve, while the indirect receptor reaches maximum much sooner

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34
Q

Why is a direct receptor faster?

A

Linear relationship (one receptor leads to one intermediate protein)

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35
Q

Why is an indirect receptor slower?

A

Has an integrated response, where many intermediate proteins are integrated together for a response)

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36
Q

Why is an indirect receptor more efficient (takes fewer receptors to achieve a maximal response)?

A

The many intermediate proteins allow for more amplification, and thus a greater signal

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37
Q

Who is Earl Sutherland?

A

Scientist who studied cAMP and adrenaline response in the liver

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38
Q

Who studied cAMP and adrenaline response in the liver?

A

Earl Sutherland

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39
Q

What decade was Earl Sutherland’s research in?

A

1970s

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40
Q

How did Earl Sutherland prove that cAMP was a second messenger?

A

Knock out of cAMP, and adding adrenaline, produced no response

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41
Q

What was the conclusion of Earl Sutherland’s first experiments?

A

There must be something between adrenaline and cAMP to produce the fight/flight response

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42
Q

What does adenylyl cyclase do?

A

Converts ATP into cAMP

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43
Q

What enzyme converts ATP into cAMP?

A

Adenylyl cyclase

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44
Q

What structural changes are done by adenylyl cyclase to convert ATP into cAMP?

A
  1. Create a ring with the phosphate (connected twice to the ribose sugar)
  2. Release a pyrophosphate (P-P)
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45
Q

What does phosphodiesterase do?

A

Converts cAMP into AMP

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46
Q

What enzyme converts cAMP into AMP?

A

Phosphodiesterase

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47
Q

What structural changes are done by phosphodiesterase to convert cAMP into AMP?

A

Remove the ring by adding water

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48
Q

What enzyme does caffeine inhibit?

A

Phosphodiesterase

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49
Q

What process does caffeine inhibit in the body?

A

The breakdown of cAMP into AMP

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50
Q

How does caffeine affect the adrenaline response in the body?

A

Caffeine inhibits phosphodiesterase, keeping cAMP levels high, and thus prolonging the adrenaline response

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51
Q

What are the effects of caffeine in the body?

A

Increases heart rate, dilates blood vessels

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52
Q

How do blood vessels get affected by caffeine in the body, and why?

A

Blood vessels dilate, because it delivers more oxygen

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53
Q

What does adenosine do in the brain?

A

Binds to receptors to promote drowsiness

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54
Q

How does caffeine interact with adenosine receptors?

A

Caffeine blocks the receptors, and prevents the adenosine response

55
Q

Why does a person remain alert after having caffeine?

A

Caffeine blocks adenosine receptors, thus preventing drowsiness

56
Q

Why does adenosine build up during the day?

A

Byproduct of ATP consumption during the day (energy)

57
Q

What are the effects of caffeine in the brain?

A

Prevent drowsiness, blocks dilating blood vessels, elevating mood

58
Q

How do blood vessels get affected by caffeine in the brain, and why?

A

Blood vessels do not dilate, because dilating blood vessels occurs as a response to inhibitory sleep signals (sent by adenosine). Since caffeine blocks these responses, the blood vessels do not dilate

59
Q

What molecule inhibits neurons through adenosine receptors?

A

Adenosine (inhibits neurons to promote drowsiness)

60
Q

How does dopamine interact with dopamine receptors?

A

Binds to the receptors to improve mood

61
Q

How does adenosine interact with dopamine receptors?

A

Binds to adenosine receptors associated with dopamine receptors, and inhibits dopamine binding, thus decreasing alertness

62
Q

How does caffeine interact with dopamine receptors?

A

Binds to adenosine receptors associated with dopamine receptors, and prevents adenosine from binding. This allows dopamine to bind, thus elevating mood

63
Q

How does caffeine affect dopamine levels in the brain?

A

Caffeine increases dopamine levels by slowing down rate of dopamine resorption

64
Q

What does caffeine, amphetamines, cocaine, and heroin have in common?

A

All increase dopamine levels by slowing down rate of dopamine resorption (addictive properties)

65
Q

How does caffeine elevate mood?

A

Prevents adenosine from blocking dopamine binding, and increases dopamine levels. Dopamine binding elevates mood

66
Q

What is an agonist?

A

A molecule that binds to a receptor to produce a response

67
Q

What is an antagonist?

A

A molecule that binds to a receptor to block access to agonists

68
Q

For adenosine receptors, is adenosine an agonist or an antagonist?

A

Agonist

69
Q

For adenosine receptors, is caffeine an agonist or an antagonist?

A

Antagonist

70
Q

What was Earl Sutherland’s first model?

A

Adenylyl cyclase was the receptor (hormone binds to adenylyl cyclase)

71
Q

What is now known to be false about Earl Sutherland’s first model?

A

Adenylyl cyclase is not the receptor, it just converts ATP into cAMP

72
Q

What was Earl Sutherland’s second model?

A

Adenylyl cyclase is part of a receptor complex (adenylyl cyclase is associated with some receptor)

73
Q

How were Earl Sutherland’s models tested (general steps)?

A
  1. Purify adenylyl cyclase and receptor
  2. Show they don’t work individually
  3. Reconstitute components together to produce a response
74
Q

What does NEM (N-ethylmaleimide) do?

A

Blocks adenylyl cyclase (prevents ATP -> cAMP)

75
Q

What compound inhibits adenylyl cyclase?

A

NEM

76
Q

What does forskolin do?

A

Activates adenylyl cyclase (without hormone)

77
Q

What compounds activates adenylyl cyclase (without a hormone)?

A

Forskolin

78
Q

How were Earl Sutherland’s models tested (lab techniques)?

A
  1. Pharmacological manipulation of cAMP

2. Live cell reconstitution

79
Q

What was the purpose of Earl Sutherland’s second experiments?

A

Show that the adrenaline response needs the adrenaline receptor as a separate entity from adenylyl cyclase

80
Q

What protein(s) do turkey red blood cells (TRBCs) have (in the Sutherland experiments)?

A

Adrenaline receptors, and adenylyl cyclase

81
Q

What protein(s) do adrenal cortical cells (ACCs) have (in the Sutherland experiment)?

A

Adenylyl cyclase

82
Q

How come TRBCs and ACCs could not be fused together directly?

A

TRBCs have everything you need, so there would be no new information about the system

83
Q

What does TRBC stand for?

A

Turkey red blood cells

84
Q

What does ACC stand for?

A

Adrenal cortical cells

85
Q

What are the steps Sutherland took to combine the cells and create the system?

A
  1. Kill adenylyl cyclase in TRBCs
  2. Confirm adrenaline still binds to adrenaline receptors
  3. Confirms ACCs still respond to forskolin
  4. Do reconstruction, and test whether it responds
86
Q

What is the purpose of Sutherland killing adenylyl cyclase in TRBCs?

A

Prevent adrenaline response in TRBCs by removing adenylyl cyclase

87
Q

How did Sutherland kill adenylyl cyclase in TRBCs?

A

Through NEM

88
Q

What is the purpose of Sutherland confirming adrenaline still binds to adrenaline receptors?

A

Show that the adrenaline receptors can still bind to adrenaline

89
Q

How did Sutherland confirm adrenaline still binds to adrenaline receptors?

A

Radioactive ligand binding curves

90
Q

What is the purpose of Sutherland confirming that ACCs still respond to forskolin?

A

Show that adenylyl cyclase is still active

91
Q

How did Sutherland confirm that adenylyl cyclase was still working in ACCs?

A

Through forskolin

92
Q

What is a heterokayron?

A

Fused two cells

93
Q

What is the result of the Sutherland cell reconstitution?

A

The system was responsive to adrenaline, thus providing evidence for his second model (associated receptor and adenylyl cyclase)

94
Q

What are the limitations of the Sutherland studies?

A

Could not describe the mechanics of how the adrenal receptor worked

95
Q

What did Lefkowitz and Kobilka study?

A

How the adrenal receptor worked

96
Q

Who studied how the adrenal receptor worked?

A

Leftkowitz and Kobilka

97
Q

What decade did Leftkowitz and Kobilka study the adrenal receptor?

A

1980s

98
Q

What experiments did Leftkowitz and Kobilka perform?

A

Overexpression of adrenal receptors

99
Q

When adrenaline was added in Leftkowitz and Kobilka experiments, what was the general pattern between no AR, low AR, medium AR, and high AR?

A

There was a basal level of expression at no AR, and high / equal levels of expression at the other concentrations

100
Q

When adrenaline was added in Leftkowitz and Kobilka experiments, what conclusion could be made about the adrenaline receptor?

A

Indirect receptor (large response at a low amount of receptor)

101
Q

When adrenaline was not added in Leftkowitz and Kobilka experiments, what was the general pattern between no AR, low AR, medium AR, and high AR?

A

Increasing response from no -> low -> medium -> high

102
Q

When adrenaline was not added in Leftkowitz and Kobilka experiments, what conclusion could be made about the adrenaline receptor?

A

Response level was also driven by receptor density

103
Q

What is the reason that response level was driven by receptor density?

A

Receptors dimerize to produce a response

104
Q

How does adrenaline interact with receptor dimerization?

A

Adrenaline ligand stabilizes the dimerization, and thus produces the response

105
Q

What is required to activate adrenal receptors (besides adrenaline)?

A

Dimerization

106
Q

What is required to stabilize adrenal receptors?

A

Adrenaline (ligand)

107
Q

What happens in strong binding activity?

A

An extracellular and intercellular molecule both bind to the receptor to get a large response

108
Q

How many hydrophobic regions are found in the adrenaline receptor?

A

7

109
Q

What is the significance of the adrenaline receptor having 7 hydrophobic domains?

A

Must pass through the membrane 7 times (stitched)

110
Q

Where are transmembrane proteins made?

A

ER

111
Q

What environment does the ER lumen resemble?

A

Extracellular environment

112
Q

What environment does the cytosol resemble?

A

Intracellular environment

113
Q

What does a hydrophobic start-transfer sequence do?

A

Causes the protein to move to a translocation channel

114
Q

What does a translocation channel do?

A

Allows the protein to be made in the ER lumen (transmembrane proteins)

115
Q

What does a hydrophobic stop-transfer sequence do?

A

Causes the protein to move from the translocation channel to the ER membrane (transmembrane)

116
Q

What does a signal peptidase do?

A

Cleave the hydrophobic start-transfer sequence if it is found at the beginning of the protein

117
Q

True or false: A signal peptidase always cleaves the hydrophobic start-transfer sequence

A

False: If the hydrophobic start-transfer sequence is found in the middle of the protein, it is not cleaved

118
Q

What does SRP stand for?

A

Signal recognition particle

119
Q

What does the SRP do?

A

Recognize the hydrophobic start-transfer sequence, and directs the protein to the translocation channel on the ER

120
Q

How is a water soluble protein made in the ER (in terms of the hydrophobic sequences)

A

The sequences need to be at the beginning and the end; otherwise, there would be transmembrane regions

121
Q

True or false: transmembrane proteins are made with a defined orientation

A

True: there is a distinct extracellular and intercellular side, and thus a distinct direction

122
Q

How are multipass transmembrane proteins made (in terms of the hydrophobic sequences)?

A

Multiple pairs of these sequences are required, one for each pass

123
Q

What side of the membrane will the protein sequence between a hydrophobic start sequence and a hydrophobic stop sequence (or the ends of the protein) be in?

A

Extracellular side

124
Q

What side of the membrane will the protein sequence between a hydrophobic stop sequence and a hydrophobic start sequence (or the ends of the protein) be in?

A

Intercellular side

125
Q

How are signaling events reversible (in terms of energy and delta G)?

A

There is a low delta G because they are small changes (conformational changes, etc.)

126
Q

How come there is a basal level of cAMP expression?

A

Lots of processes use cAMP, which depend on the context

127
Q

How come adrenal receptors don’t dimerize under physiological conditions without adrenaline?

A

There is not enough density to drive dimerization

128
Q

How does chronic caffeine affect adrenal receptors?

A

Alters the density of adrenal receptors (and other mood receptors), and makes them higher affinity

129
Q

What determines whether caffeine or adensoine will bind first to the adenosine receptors?

A

Concentration

130
Q

Which has the bigger physiological response: caffeine inhibiting phosophodiesterase, or caffeine blocking adenosine receptors?

A

Caffeine blocking adenosine receptors (20 fold difference)

131
Q

Why is AMPA (an ion gated channel) either direct or indirect?

A

Direct, because a binding of the ligand leads to an immediate change in the confirmation to allow calcium to flow into the cell

132
Q

What is divergent signaling?

A

Different ligands change the conformation of the receptor differently, and thus goes down different pathways

133
Q

True or false: when creating a synthetic drug, you must decide whether to have a direct or indirect response

A

False: the native signaling pathway is already there, and thus it is predetermined whether your pathway is direct or indirect

BIO 317 (27 decks)

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