Receptors And Signal transduction

Question 1

What are the major modes of signaling?

Answer 1

• Direct Cell-cell (Gap junction)
• Membrane-bound molecules
• Receptor-mediated communication (surface receptors/nuclear receptors)
• Vesicular communication
• Inter-kingdom Comm

Question 2

Define Agonist

Answer 2

A Ligand which causes the receptor to activate a response in the cell.

Question 3

Define Antagonist

Answer 3

A ligand which causes the receptor to become inactive

Question 4

Differentiate EC50 with Kd.

Answer 4

EC50 - [Drug] at which 50% of drug effect is observed

Kd - Dissociation constant at which 50% of drug is bound to receptor

Question 5

What are the 3 main classifications of receptors?

Answer 5

1. Ion channel-linked
2. G-protein coupled
3. Enzyme-linked

Question 6

Differentiate Nicotinic and muscarinic receptors and their ligands in the PNS.

Answer 6

Nicotinic receptors are activate by sympathetic preganglionic Neurons which release Ach

Muscarinic receptors are activated by Ach in the parasympathetic nervous system by post-Ganglion is neurons

Question 7

Which type of receptor is primarily involved in skeletal muscle contraction?

A. Parasympathetic Nicotinic
B. Somatic Nicotinic
C. sympathetic Muscarinic
D. Somatic Muscarinic

Answer 7

B. Somatic Nicotinic

Question 8

What are two examples of Ach Nicotinic antagonist?

Answer 8

Cobra Toxin

Curare Plant

Question 9

What are the three types of GPCRs?

Answer 9

GI, Gs, Gq

Question 10

What are Beta-2 agonists used for?

Answer 10

Treatment of histamine-activated smooth muscle contraction (Asthma and allergies)

Question 11

How can receptors become desensitized?

Answer 11

• Occurs via phosphorylation
• Ex. Phosphorylation Beta-2 receptors affect the regulation of histamine GPCRs through heterologous regulation —> synergistic affect towards vasodilation

Question 12

Describe the pathway from receptor activation from insulin to uptake of glucose into the cell.

Answer 12

Insulin Binds -> Tyr Kinase autophosphorylates via ATP —> Mobilization of GLUT4 transporter to plasma membrane

Question 13

What is a PAR?

Answer 13

a unique family of GPCRs that are irreversibly activated following proteolytic cleavage of their extracellular N-terminus.

Question 14

What role do GPCRs play in the clotting cascade?

Answer 14

• Platelets express various GPCRs
• Activated platelets release coagulation factors which crease thrombin concentrations
• Thrombin activates PAR-1 on platelets and cleave amino terminals
• The remaining part is self-binding and activates intracellular events

Question 15

What type of receptor is activated by thyroid hormone?

Answer 15

Nuclear receptor

Question 16

What are the classifications of cell signals?

Answer 16

Endocrine - Ligand acts on far away signal

Paracrine - Ligand is secreted by one cella and acts on a nearby target

Autocrine - Ligand secreted acts on secreting cell and surrounding cells of the same type.

Question 17

How are JAK-STAT receptors involved in immune response?

Answer 17

• Interferon receptors are JAK/STAT receptors

- Interferons such as IFN-gamma are important for stress response and inflammatory response

Question 18

Differentiate Gq vs Gs responses in intracellular signal transduction.

Answer 18

Gq —> PLC —> PIP2 to IP3 + DAG —> IP3 opens Ca channels —> Ca + DAG bind PKC —>PKC phosphorylation and downstream affect

Gs —> Activate Adenylyl Cyclase —> Increase cAMP —> PKA —> Downstream affects

Question 19

Which receptors acitvate Gq and smooth muscle contraction?

Answer 19

H1 (histamine)
Alpha-1 (Adrenergic)
V1 - (ADH)
M1/3 (Muscarinic)

“HAVe 1 M&M”

Question 20

Which receptors are Gs and activate PKA resulting in increase Ca and inhibition of smooth muscle contraction?

Answer 20

Beta 1/2/3 Adrenergic
D1 (dopamine)
H2 (histamine)
V2 (ADH)

Question 21

Which receptors are Gi and Inhibit Gs activity?

Answer 21

M2 (muscarinic)
Alpha 2 Adrenergic
D2 (Dopamine)

“MAD 2s”

Question 22

Describe the pathology of Hyperhtyroidism and related diseases.

Answer 22

• Increase production of T#/T$
• T3 increase BMR
• Too much T# results in Tachcardia and Sympathetic response
• Weight loss, Heath intolerance, Sweating, Hyperactivity, anxiety, insomnia
• Graves’ disease, Goiter, and thyroid adenoma