Cell Receptor/Signaling

Question 1

What is a ligand?

Answer 1

a water or lipid soluble molecule that participates in cell signaling by binding to a receptor from the cell and eliciting a certain response.

Question 2

What is endocrine signaling?

Answer 2

The signaling molecule is transmitted through the blood

Question 3

What is autocrine signaling?

Answer 3

The signaling molecule is secreted by the cells that express the receptor protein

Question 4

What is paracrine signaling?

Answer 4

The signaling molecule is secreted to neighboring cells by a different cell type

Question 5

What is juxacrine signaling?

Answer 5

The signaling molecule will be secreted and bind to the signaling cell. The molecule will then bind to target cell, creating a linkage between the two cells

Question 6

Hydrophilic signaling

Answer 6

The signal cannot penetrate cell membrane. Uses secondary messenger system to elicit response. Signal tends to have a short half life

Question 7

Lipophilic signaling

Answer 7

This signal is able to penetrate the cell membrane. The receptors can be in the cytoplasm or in the nucleus. These type of signals will generally interact directly in gene expression or repression. Signal has a long half life

Question 8

What is the process of the GPCR?

Answer 8

Signal binds to GPCR inducing confirmational change. GEF will then exchange GDP bound to the alpha subunit of the trimeric G protein with GTP causing the alpha unit to disassociate with the beta and gamma unit. The activated alpha unit then interacts with an effector protein and produces secondary molecules.

Question 9

What is the process of Gs in GPCR?

Answer 9

Activated alpha G protein will stimulate adenylate cyclase. This protein then converts ATP to cAMP. PKA is then stimulated by cAMP which will phosphorylate many other proteins in signal pathway.

Question 10

What is the process of Gi in GPCR?

Answer 10

Activated alpha G protein will inhibit adenylate cyclase function. No cAMP will be produced.

Question 11

What is the process of Gt in GPCR?

Answer 11

Activated alpha G protein will stimulate cGMP phosphodiesterase. This will then convert cGMP to 5’GMP

Question 12

What is the process of Gq in GPCR?

Answer 12

Activated G protein will stimulate phospholipase C. This protein catalyzes a reaction that makes PIP2 into IP3 and DAG. IP3 will then go bind to a receptor on the ER releasing Ca2+ into the cytoplasm. The Ca2+ will then stimulate the Ca2+ calmodulin complex or DAG in the PM. DAG will then activate PKC to phosphorylate other proteins.

Question 13

What is the effector enzyme and secondary molecules for the Gs in GPCR?

Answer 13

Effector - Adenylate Cyclase

Secondary- cAMP

Question 14

What is the effector enzyme and secondary molecules for the Gi in GPCR?

Answer 14

Effector- Adenylate Cyclase

secondary- none

Question 15

What is the effector enzyme and secondary molecules for the Gt in GPCR?

Answer 15

Effector- cGMP phosphodiesterase

secondary- 5’GMP

Question 16

What is the effector enzyme and secondary molecules for the Gq in GPCR?

Answer 16

Effector- phospholipase C

secondary- PIP2 which disassociates to IP3 and DAG

Question 17

How is epinephrine so diverse?

Answer 17

The same signal can result in differing physiological responses in cells with the same receptor. It depends on the tissue it interacts with.

Question 18

What does cholera toxin do to the g protein pathway?

Answer 18

It inhibits the GTPase activity. There will be increased levels of cAMP since Gs alpha will not be inactivated. This increase will mean that Cl- channels will remain open and the cells will lose water. Results in severe diarrhea.

Question 19

What is the function of GTPase?

Answer 19

It will dephosphorylate the GTP on the alpha subunit to GDP. This inactivates the protein

Question 20

What does the pertussis toxin do to the g protein pathway?

Answer 20

It prevents the activation of the alpha subunit in Gi which means that adenylate cyclase will remain active. There will be higher levels of cAMP. This leads to fluid loss.

Question 21

Signal desensitizing

Answer 21

The cell will begin to ignore certain signaling molecules- it achieves this by decreased hormone levels, removing secondary molecules or removing signal receptors

Question 22

GRKs and arrestin

Answer 22

G protein receptor kinases will phosphorylate the GPCR and arrestin will come bind to the third intracellular loop, resulting in deactivation of the complex.

Question 23

How do Receptor Tyrosine Kinases work?

Answer 23

A signaling molecule binds to the protein causing dimerization of the two complexes. Tyrosine residues are then phosphorylated and various docking protein recognize this signal. This will then activate down stream processes.

Question 24

What are the recognition domains of the RTKs?

Answer 24

adapter proteins GRB-2 and IRS-1 have SH2 or PTB domains that recognize phosphorylated regions on tyrosine residues.

Question 25

How is RTK signaling terminated?

Answer 25

degradation of signaling molecules, ligand-induced endocytosis, accelerated RAS inactivation and dephosphorylation

Question 26

How is GPCR signaling terminated?

Answer 26

GTPase will dephosphorylate the alpha unit on the g-protein