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Pharmacology #1 > #3 > Flashcards

#3 Flashcards

1
Q

What are the 4 types of signaling receptors?

A
  1. Ligand activated ion channels
  2. G protein coupled receptors
  3. Tyrosine kinase receptors
  4. Ligand activated transcription factors
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2
Q

About 40% of all drugs are directed agonists or antagonists of one which type of receptor?

A

G protein coupled receptor

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3
Q

_______ produce graded potential (local effects).

A

Ligand activated ion channels in the plasma membrane.

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4
Q

How does depolarization occur?

A

Ligand activated ion channels let sodium in to cell.

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5
Q

How does Hyperpolarization occur?

A

Ligand activated ion channels let Cl- in to cell.

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6
Q

What is considered the basis of synaptic transmission of nerve impulses?

A

The activating and inhibiting ligand activated plasma membrane ion channels. (Hence many drugs target here)

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7
Q

How do drugs act on synaptic transmission? (4 main ways)

A
  1. Mimic or block the actions of NT’s to affect synaptic transmission.
  2. Some drugs might block the channel to affect synaptic transmission.
  3. Some drugs might affect transmitter reuptake. (Block it so effect of NT is prolonged)
  4. Some drugs might affect transmitter metabolism.
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8
Q

What are Ligand activated channels in the Organelles?

A

IP3-mediated Ca+ release from the ER.

*This receptor mediates Ca++ release from the ER internal store.

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9
Q

What is MOST signaling by Ca++ mediated by?

A

Ca++/Calmodulin complex

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10
Q

What occurs during an increase in Ca++?

A

Increases binding of Ca++ to Calmodulin, altering the structure of the Ca ++/calmodulin complex

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11
Q

What does the Ca++/Calmodulin complex do?

A

Activates numerous effector proteins such as:

  • Calcium/calmodulin dependent protein kinase
  • Nitric oxide synthase
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12
Q

How do Agonists activate G-protein coupled receptors?

A

Agonists bind to the GPCR’s, alter the proteins conformation, leading to the activation of a trimeric G protein.

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13
Q

What are the 4 steps of the G- Protein Cycle?

A
  1. Ligand bound GCPR stimulates GDP-GTP exchange.
  2. This causes the complex to fall apart into two pieces; G-alpha and G-betaG-Gamma.
  3. The G-alpha has an intrinsic GTPase activity Eventually the GTP is hydrolyzed to GDP and Pi. RGS proteins accelerate this process.
  4. After GTP hydrolysis the complex reassembles.
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14
Q

Does G-alpha or G-BetaG-Gamma participate in signaling events?

A

Both!

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15
Q

What is the major signaler in cells?

A

The liberated G-alpha protein.

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16
Q

What is the Minor signaler in cells?

A

The liberated G-betaG-gamma protein

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17
Q

There are ____ different classes of G-alpha proteins based on _____.

A

5 different types

Based on what they activate.

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18
Q

Most important class of G alpha proteins is….

A

G-alpha S

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19
Q

What is the most important function of cAMP?

A

Binds to regulatory substances releasing and activating protein kinase A (Active catalytic subunit)

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20
Q

What occurs when PKA (or other protein kinases) phosphorylate transcription factors?

A

Changes in gene expression

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21
Q

What are the Major effectors of G-alpha’s?

A

Signaling molecules embedded within phospholipids in the membrane. G protein coupled receptors liberate them by activating phospholipases.

  • Phospholipase C beta
22
Q

_______ is the source of eicosinoid signaling molecules.

A

Arachidonic acid

23
Q

What are the products of Phospholipase C-beta mediated hydrolysis? What is the importance of them?

A
  • Diacyl glycerol (DAG)
  • Inositol (3,4,5)-Triphosphate (IP3)

*Both are important signaling molecules

24
Q

________ serves as the substrate for phospholipase C.

A

Phosphatidylinositol-4,5 bis phosphate (PIP2)

25
Q

Cleavage of PIP2 by phospholipase C yields ________ and _________.

A
  • DAG

- IP3

26
Q

What are 2 examples of proteins activated by the Ca/calmodulin complex?

A
  1. Calcium/Calmodulin dependent protein kinase

2. Nitric oxide synthase

27
Q

__________ Activates protein kinase C.

A

DAG

*DAG allows the enzyme to bind Ca++ tighter therefore enzyme can function at lower Ca++ concentrations.

28
Q

______ plays a critical role in turning off the GPCR.

A

G-beta/G-gamma complex.

*Helps localize the trimeric G protein to the membrane

29
Q

The trimeric G protein gets turned on by _______.

A

agonist-GPCR complex.

*Trimeric G protein then turns itself off and Agonist-GCPR complex is free to activate other trimeric G-proteins.

30
Q

What does IP3 do?

A

Activates Ca++ release from ER…Which ends up activating PKC?

31
Q

What Does DAG do?

A

Activates PKC

32
Q

After trimeric G protein gets turned on by agonist-GPCR complex, does the signal stay around?

A

No! The receptor gets turned off by a process called desensitization!

33
Q

What is desensitization and how does it take place?

A

Desensitization is where GPCR’s are endocytosed.

34
Q

Endocytosed receptors (during desensitization have 2 fates, what are they?

A
  1. Recycled

2. Degradation

35
Q

Why is receptor desensitization important in pharmacology?

A

B/C sometimes drugs are administered chronically and this can lead to loss of responsiveness to the drug and results that would seem paradoxical if one failed to consider desensitization.

36
Q

Describe the process of signaling by receptor tyrosine kinases….(

A
  1. Receptors either contain an intrinsic tyrosine kinase enzyme or an extrinsic tyrosine kinase enzyme.
  2. Binding of the ligand leads to dimerization of the receptor.
  3. Some receptors form homodimers, some from heterodimers, some form both.
  4. Dimerization leads to transphosphorylation of receptors.
  5. Tyrosine phosphorylation of receptor leads to docking of signaling molecules.
  6. the positioning of proteins near the membrane leads to different cascades of signaling.
    * MAP kinase cascade is an example of this signaling cascade
37
Q

What does Akt signaling do?

A

Pushes cell toward growth and expansion phase.

38
Q

Describe JAK-STAT signaling (signaling cascade) 5 steps…

A
  1. Binding of ligand (cytokine) leads to phosphorylation of receptor by JAK kinase.
  2. This leads to binding of STAT protein (one of six) to the phosphorylated receptor.
  3. This leads to phosphorylation of STAT protein by JAK kinase.
  4. This leads to dimerization of STAT protein.
  5. This leads to translocation of STAT dimer to nucleus and transcriptional activation of panels of genes.
39
Q

When does a STAT become active?

A

After forming a dimer with another STAT.

*STAT’s are phosphorylated at their SH2 domain.

40
Q

What does JAK-STAT signaling cause?

A

Transcriptional activation of panels of genes.

41
Q

What is the importance of JAK-STAT signaling?

A

It is the single most important pathway in which cytokines work!

42
Q

How many STAT proteins are there?

A

6

43
Q

Why are STAT proteins important? What do they do?

A

STAT proteins form different dimers which bind to different receptors which activates different panels of genes which mediate the biological responses to cytokines.

44
Q

Phosphorylation of transcription factors by PKA and other kinases can lead to ____________.

A

changes in gene expression!

45
Q

What is Cross talk?

A

The ability amongst some pathways to create complex signaling possibilities.

46
Q

What are Nuclear Hormone receptors?

A 
Receptors for steroids such as:
Glucocorticoids
Mineralocorticoids
Testosterone 
Estrogens and Progesterones 
and other molecules ...
47
Q

What is a class 1 nuclear receptor?

A

Exist as a complex with heat shock proteins in the absence of ligand.

48
Q

What do Class 1 Nuclear receptors do?

A

Ligand binding to the complex induces it to fall apart and from a homodimer and bind to specific DNA Response element. Once bound, it binds coactivators to stimulate transcription.

*Ligands for receptor are glucocorticoids, progesterones estrogens and androgens.

49
Q

What is a class 2 Nuclear receptor?

A

A receptor that binds to DNA at its specific response element in the ABSENCE of a ligand.

50
Q

What do class 2 nuclear receptors do?

A

Bind corepressors in the absence of a ligand to repress transcription.

*Form homo and heterodimers

51
Q

_______ acts as a switch to change from binding corepressors to coactivators and so changing from inhibiting transcription to activating it.

A

Ligand binding

Pharmacology #1 (6 decks)

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