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Foundations of Medicine > FOM 7.2.2 > Flashcards

FOM 7.2.2 Flashcards

1
Q

What are the key characteristics of second messengers?

A

non-protein, rapidly prod/mobilized, diffusible, bind 2nd messenger effectors

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2
Q

What are the six prominent 2nd messengers?

A

cAMP, cGMP, Ca, diacylglycerol, IP3, NO

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3
Q

What are the four types of critical components of 2nd messenger signaling?

A

Activators (GPCR, kinase, 2nd messenger)
Produce/Mobilize 2nd messenger (cyclases, phospholipases, channels, NOS)
2nd messenger Targets (kinases, channels)
Downregulation (phosphodiesterases, channels, metabolic enzymes)

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4
Q

What two of the most common G protein effector molecules?

A

Adenylate cyclase (AC) and Phospholipase C (PLC)

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5
Q

When the G alpha s (GTP) subunit binds adenylate cyclase, what is rapidly produced by AC?

A

cAMP

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6
Q

What is the primary target of cAMP?

A

PKA, protein kinase A

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7
Q

Describe how cAMP activates PKA.

A

PKA actually consists of 2 regulatory subunits (R) bound to 2 catalytic subunits (C). Binding of cAMP to the regulatory subunits releases the catalytic subunits, which are now active.

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8
Q

What are the 4 phosphorylation targets of PKA?

A

1) phosphorylation of GPCRs leads to heterologous desensitization
2) phosphorylation of metabolic enzymes
3) cAMP response element-binding proteins (CREB) are transcription factors
4) conductance regulator channel (CFTR)

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9
Q

Describe how cholera toxin effects the second messenger pathway.

A

Individuals with cholera exhibit sustained production of cAMP (ADP ribosylation of GalphaS ) in intestinal cells. This leads to unregulated PKA activity. PKA phosphorylates and activates the CFTR channel, ultimately leading to secretion of salt into the intestinal lumen, followed by osmosis of water. This results in massive diarrhea and dehydration and can even lead to death.

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10
Q

What is the end result of the activating mutation in the Luteinizing hormone (LH) receptor? What is the end result of the deactivating mutation in the Luteinizing hormone (LH) receptor?

A

Activating: precocious testosterone prod -> precocious puberty (as early as age 3)
Deactivating: pseudohermaphroditism

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11
Q

What is the role G alpha protein?

A

After dissociation with it affects adenylate cyclase and phospholipase C

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12
Q

Upon activation what is the role of adenylate cyclase?

A

It converts ATP to cAMP

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13
Q

What is adenylate cyclase inactivated by?

A

G alpha i

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14
Q

What is the basic activation sequence of cAMP signaling?

A

After signaling through GPCR the G alpha subunit is activated. The alpha subunit then goes and activates adenylate cyclase. Which then turns ATP to cAMP. Increased intracellular cAMP leads to activation of PKA by dissociating it from its regulatory subunit. PKA will go and do a number of processes.

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15
Q

What are some effects of activated PKA?

A

Phosphorylation of GPCR leading to desensitization. Increased blood glucose levels. Activating CREB which can lead transcription of genes. Targeting CFTR to transport salt across the membrane of the intestine.

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16
Q

What is the affect of the cholera toxin on cAMP signaling?

A

GTP cannot be hydrolyzed so it sends out constant cAMP production. This leads to increased PKA activity leading to overactive CFTR which pours salt across the membrane leading to massive diarrhea.

17
Q

What is the role of leutenizing hormone and cAMP signaling mutations?

A

Mutations can lead to no need for a signal to produce a response that can produce a response that leads to early puberty or a mutation that inactivates it. The G alpha has no action, leading to no cAMP production, low testosterone and psuedohermaphrotism.

18
Q

Activation of phospholipase C leads to what?

A

lead to cleavage of membrane bound PIP2 into DAG (membrane bound) and IP3 (not).

19
Q

After cleavage of PIP2 what does IP3 do?

A

Binds to receptors on the ER and stimulates Ca2+ release.

20
Q

After cleavage of PIP2 what does DAG do?

A

DAG bind to PKC and partially activating it

21
Q

What role does IP3 have on PKC?

A

IP3 creates the intracellular calcium release that leads to calcium binding to PKC and becoming fully activated

22
Q

What is the role of PKC?

A

It has functions similar to PKA

23
Q

What is the role of calcium in cellular function?

A

PKC activation, regualtion of proteins, depolarization leads to muscle contraction, binds calmodulin, and activates inflammatory mediators

24
Q

What cells is eNOS synthesized in?

A

endothelial cells

25
Q

What reaction does eNOS catalyze?

A

It catalyzes that creation of nitric oxide

26
Q

After synthesis what does NO do?

A

It travels to smooth muscle cells and affects guanylate cyclase and converts GTP to cGMP leading to smooth muscle cell relaxation.

27
Q

What is eNOS regulated by?

A

Ca2+

28
Q

How is iNOS different than eNOS?

A

It isnt regulated by Ca2+

29
Q

What does phosphodiesterase do?

A

It cleaves cAMP to yield AMP which decreases cAMP levels and as they fall this causes the regulatory subunits to reassociate with PKA

30
Q

How are DAG and IP3 signal turned off?

A

They are recycled by various enzymes leading to decreased IP3 and decreased PKC activity

31
Q

What is calcium down regulated as a second messenger?

A

It is pumped back into the reticulum by the SERCA

32
Q

How is iNOS signaling down regulated?

A

mRNA is degraded

33
Q

What is wrong in Cushings Syndrome?

A

PKA doesn’t associate with regulatory sub-unit so there is constant activity leading to increased cortisol levels

34
Q

What does a calcium channel blocker do?

A

Block calcium channels duh! The calcium release that leads to contraction inhibited and the muscle doesnt contract

35
Q

What does nitroglycerine do?

A

It passes NOS and is converted into NO which increases cGMP levels and leads to muscle relaxation

36
Q

What does viagra do?

A

It mimics cGMP which blocks the binding of cGMP to PDE which means that the cGMP has a longer lasting effect

37
Q

What is crosstalk?

A

One pathway affects another

Foundations of Medicine (79 decks)

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