12-RECEPTORS – Dr. Groseclose Flashcards Preview

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Flashcards in 12-RECEPTORS – Dr. Groseclose Deck (23):
1

What are the major types of receptors?

Acetylcholine
ATP (purine)
gamma-aminobutyrate (GABA)
glutamate
serotonin (5HT)

2

For Acetylcholine (type of nicotinic cholinergic) receptors, how many and what type of subunits make up acetylcholine? Where is it located? Name an example of an acetylcholine receptor

heterodimer (5 subunits - 2 alpha, one beta, 1 gamma, 1 delta)
Located spanning the cell membrane

ex. Na+/K+ channel

3

For G-Protein coupled receptors (GPCRs), how many and what type of subunits make up GPCR? Where is it located?
What does it bind to and what is the response time?

Has one or two subunits (one subunit spans the membrane with 7 domains)
Located inside the membrane
Receptor engages proteins that bind GUANINE (hence G-proteins). G-protein has 3 subunits.
Interact with effector molecule via G-protein

4

Describe the structure of PARs. What superfamily do PARs belong to? What activates each of the four PARs? Which PARs? Which two are found on human platelets?

β receptor has 7 span shape. It is activated by thrombin/trypsin.
Thrombin = Par 1,3,4.
Trypsin = Par 2.

PAR1 and PAR4 are found on human platelets.

5

Describe the Phototransduction pathway

Light activates Rhodopsin to undergo a conformational change that allows it to bind to an inner membrane G-protein. When the G-protein binds, the ALPHA subunit undergoes a conformational change and is released as alpha-GTP. Alpha-GTP binds and activates cyclic-GMP phosphodiesterase. Which can now convert CGMP to GMP. When consumed, alpha-GTP is converted to alpha-GDP.

6

What physical characteristics distinguish the groups of receptors from each other? (ie. Location within the cell, subunit structure, distinctive 2o structure such as 7-span)

Intracellular receptors are located within the nucleus of the cells. The other three types are located in the cell membrane.

- Ligand-gated ion channel has five similar subunits that open an ion passageway.
- Insulin-like receptors are able to phsophorylate themselves and attach phosphates to tyrosine residues.
- G-protein coupled receptors include a special PAR receptor that has a 7-span shape

7

Discuss the various ways in which activated receptors accomplish their cellular effects. (ie. Increasing or decreasing cyclic nucleotides, changing ionic permeability, altering transcription)

Ligand-gated ion channels open up ion passageways and therefore the receptors work based on their changed ionic permeability.

G-protein coupled receptors are activated after being bound by a hormone where they then affect cAMP and cGMP and cause an effect on an effector molecule (ie. Other kinases, β-adrenergic receptors).

PARs (protease activated receptors) are G-protein linked receptors that are activated by the proteolytic removal of a portion of the N-terminus of the 7 span shaped receptor by either thrombin or trypsin.

Insulin-like receptors are those that work by attaching phosphates to tyrosine residues (phosphorylation)

Intracellular receptors work after the ligand diffuses into the cell membrane and binds to the receptor. The ligand-receptor complex acts in the nucleus by altering transcription.

8

Discuss the different ways in which receptors can be characterized.

- Location: Surface of cell/Interior of cell {span the membrane?}
- Type of Interaction: Ligand (agonist vs. antagonist)
- # of subunits
- Mechanism of Action: Ionotropic vs. Metabotropic
- Response time

9

What is a ligand?

the substance that binds to a receptor

10

What is an agonist?

stimulating the receptor physiologically by acting as "native" ligand

11

What is an antagonist?

prevents activity, or inhibits the receptor's usual response

12

What is a receptor?

cellular proteins located on the cell surface or cell interior that interact with molecules like hormones, toxins, cytokines, drugs, and neurotransmitters

13

What characteristic of the protease activated receptors (PARs) is unique?

PARs (G-protein linked receptors) are unique in that their mechanism of Activation: they are activated by the proteolytic removal of a portion of the N-terminus of the receptor itself. Therefore the new N-terminus generated IS the ligand.

14

Discuss the gross structure of G-proteins.

G-proteins are comprised of 3 subunits (alpha-the largest, beta, and gamma)

15

EC_50 vs K_D: Which of these values describes binding of receptor and ligand? Which of these describes effectiveness in eliciting a cell response?

K_D = ligand concentration for half maximal occupancy of receptors

EC_50 = ligand concentration for half-maximal cellular response

16

What is the largest superfamily of receptors?

G-Protein Coupled Receptors (GPCRs)

17

Which family of receptors facilitates addiction to tobacco?

Acetylcholine receptors (aka. nicotinic receptors)

18

Discuss the structural and functional similarities of the families of internal receptors.

Internal receptors change the expression of genes, residing mostly in the nuceleus. Usually, gene expression is turned on by the receptor-ligand complex binding to the DNA, but not always.

19

Which receptor has been associated with protection against pancreatitis and acinar cells?

PAR2

20

How many subunits are in insulin receptors? Where is it located? What is the distinctive aspect of this group? What does this receptor attach to?

2 subunits each with α & β subunit
Located in the cell membrane.
Unique: the ability to phosphorylate itself.
Attaches phosphates to tyrosine.

21

What are Toll-like receptors (TLRs)? What type of immunity are TLRs related to? What kind of pathological conditions are TLRs associated with?

pattern-recognition receptors central to the inflammatory response found in hepatocytes, vascular smooth muscles and neurons.

TLRs are related to innate immunity.
Dysregulated activation of TLRs is related to overt inflammation like sepsis, autoimmune diseases, and cancer.

22

Which receptors are responsible for peridontitis?

Toll-like Receptor 2 and 4 mutations

23

Name some intracellular receptors

Retinoic Acid
Thyroid hormone
Steroids
Vitamin D