Lecture 11 part 3

Question 1

G protein-coupled receptors include (ligands, receptors and signal transduction)?

Answer 1

Ligands:
epinephrine, glucagon, serotonin etc.

Receptors:
seven transmembrane alpha helices; cytosolic domain associated with a membrane-coupled trimeric G protein.

Signal transduction:
(1) Second-messenger pathways involving cAMP or others; (2) linked ion channels; (3)
MAP kinase pathway.

Question 2

Receptor tyrosine kinases (RTKs) includes (ligands, receptors and signal transduction)?

Answer 2

Ligands:
insulin, epidermal growth factor (EGF), fibroblast growth factor (FGF) etc.

Receptors:
single transmembrane alpha helix; protein
tyrosine kinase activity in cytosolic domain.

Signal transduction:
(1) Ras–MAP kinase pathway; (2) IP3/DAG pathway; (3) PIP3 kinase pathway.

Question 3

Ligand-gated ion channels includes (ligands, receptors and signal transduction?

Answer 3

Ligands:
neurotransmitters (e.g., acetylcholine, glutamate), cGMP, physical factors (e.g., touch, stretching), IP3 (receptor in ER membrane).

Receptors:
four or five subunits with a homologous segment in each subunit lining the ion channel.

Signal transduction:
(1) localized change in membrane potential due to ion influx, (2) elevation of cytosolic Ca2+.

Question 4

Intracellular receptors are for?

Answer 4

Receptors for steroid hormones, thyroid hormones, retinoids and vitamin D.

Question 5

What domain intracellular receptors include?

Answer 5

A transcription-activating domain, a DNA-binding domain and a ligand-binding domain;

Question 6

What does hormone response element means?

Answer 6

The receptor–ligand complex binds a promoter region of the target genes; in the case of hormones

Question 7

GPCR’s can regulate what functions?

Answer 7

Immune system, growth, sensen like smell or taste, visual, behaviour etc.

Question 8

What GPCR’s are able to bind?

Answer 8

GTP and CDP. Guanosine triphospohate and guanosine diphosphate.

Question 9

What are G-protein subunits?

Answer 9

Alpha- bete and gamma subunits. Alpha- and gamme subunits are attached to the cell membrane via lipid anchors.

Question 10

What does G-protein bind when inactive?

Answer 10

GDP, to the alpha subunit.

Question 11

What happens when a ligand binds to, for example, to a GPCR?

Answer 11

A conformational change. In a case of GPCR the G-protein will look different. Alpha unit separates it self from others (dissociates).
AND it exchanges GDP to GTP!

Question 12

What happens after a GPCR has gone over a conformational change and the subunits are separated+

Answer 12

They will find a protein in the membrane. The subunit is going to alter and regulate the function of that protein found.

Question 13

What can the target proteins be?

Answer 13

Enzymes that produce a second messengers or ion channels that also lets ions be second messengers

Question 14

How can we make GPCR go back to normal?

Answer 14

GTP can be hydrolized to GDP. Loses a phosphate.

Question 15

What is special about enzyme linked receptors?

Answer 15

In addition to just receiving signals; they also function as enzymes.

Question 16

What is the most common enzyme linked receptor?

Answer 16

Receptor tyrosine kinases

Question 17

What does receptor tyrosine kinases regulate?

Answer 17

Cell growth, growth factors

Question 18

What does kinase mean?

Answer 18

Ability to transfer phosphorus molecules. Usually from a high energy substance like ATP

Question 19

Receptor tyrosine kinases have the ability to?

Answer 19

To transfer phosphorus from ATP to intracellular proteins which activates them.

Question 20

What is a gross-linked dimer?

Answer 20

When a signalling molecule binds to RTK, it causes the other RTK to associate with each other.

Question 21

Why does RTK’s need to act in pairs?

Answer 21

Cross-linking activates the tyrosine kinase activity in RTK’s thorugh phosphorylation. So they phosphorylates the tyrosines with crossing each others.

Question 22

Ones we have phosphorus’s on the tyrosines what can be done?

Answer 22

Different proteins can come by and attach themselves to them. The proteins need to have a SH2 domain.

Question 23

What are ligand-gated ion channels?

Answer 23

Transmembrane ion channels that are open or closed in response to binding of a ligand.

Question 24

When a ligand binds to a receptor for a ligand-gated ion channel?

Answer 24

The channel opens. Allosteric binding -> away from the ion channel.

Question 25

When ions pass through the ligand-gated channel, what happens inside the cell?

Answer 25

It will cause a change in the electrical properties of a cell.

Question 26

Ligands that can go through membrane binds to?

Answer 26

Intracellular receptors, hydrophobic.

Question 27

What can act as a hydrophobic signalling molecule?

Answer 27

Vitamin D or steroid hormones!