lecture 14 - protein activation & inhibition 2

Question 1

What is the term for relay molecules used in signal transduction?

Answer 1

Second messengers

Question 2

What are the 2 types of alpha G protein?

Answer 2

Gas (G alpha stimulatory) and Gai (G alpha inhibitory)

Question 3

What is the role of Gas (G alpha stimulatory) proteins?

Answer 3

A G protein that when activated by a GPCR will activate the adenylate cyclase enzyme

Question 4

What is the role of Gai (G alpha inhibitory) proteins?

Answer 4

A G protein that when activated by a GPCR will inhibit adenylate cyclase enzyme activity

Question 5

What is the process of GPCR signal transduction and second messenger pathway (activation via Gas)?

Answer 5

Agonist ligand activates GPCR, G protein activated, adenylate cyclase activated, cAMP (cyclic AMP) produced and diffused into cell, protein kinase A production, further signal transduction to generate cell response

Question 6

What does adenylate cyclase produce in signal transduction?

Answer 6

cAMP (cyclic AMP)

Question 7

In a GPCR signal transduction pathway, what does cAMP production lead to?

Answer 7

Protein kinase A production

Question 8

How do Receptor tyrosine-kinases (RTKs) start signal transduction?

Answer 8

They use phosphorylation of adaptor proteins to initiate transduction

Question 9

What turns activity on/off or up/down in RTK signal transduction?

Answer 9

Phosphorylation and dephosphorylation

Question 10

What is the basic mechanism of the phosphorylation cascade?

Answer 10

Protein activity is regulated when inactive protein kinases transfer phosphates from ATP to become activate protein kinases

Question 11

How are protein phosphotases involved in RTK signal transduction?

Answer 11

They rapidly remove phosphates from proteins (dephosphorylation) to carefully control signal transduction

Question 12

What is the mechanism for ligand-gated ion channel receptor signalling?

Answer 12

When agonist ligands bind them cause a conformational change that activates the channel allowing ions to flow through into the cell.

Question 13

What is the fasted type of receptor signalling?

Answer 13

Ligand-gated ion channels, as there is no second messenger pathway

Question 14

Why can the same ligand-receptor pair have a slightly different effect in different cells?

Answer 14

Signal transduction depends on the combinations of receptors found in a cell or location, because a different combination of relay molecules can change signal transduction

Question 15

What is pathway branching in terms of signal transduction regulation?

Answer 15

When a single signalling event leads to multiple second messengers being activated, creating several different responses

Question 16

What is crosstalk in terms of signal transduction regulation?

Answer 16

When two different receptors and relay molecules are needed to activate a single relay molecule and signal transduction pathway

Question 17

What is ligand dissociation in terms of signal transduction regulation?

Answer 17

When a ligand dissociated to end activation and cellular signalling via a receptor

Question 18

What is internalisation in terms of signal transduction regulation?

Answer 18

The removal of a receptor from a cell via endocytosis

Question 19

What chemical type of ligand are insulin and glucagon?

Answer 19

Peptide ligands

Question 20

What is the process of receptor signal transduction by insulin in muscle/adipose tissue?

Answer 20

Activation of an RTK insulin receptor causes phosphorylation of an adaptor protein and then further signal transduction that ultimately results in a a GLUT-4 translocation to the cell membrane, where it allows glucose to enter the cell

Question 21

What is the process of receptor signal transduction by insulin in liver cells?

Answer 21

RTK receptor activation causes phosphorylation of an adaptor protein, signal transduction and then glycogen synthesis

Question 22

What is the process of receptor signal transduction by glucagon in liver cells?

Answer 22

GPCR activation causes G protein (alpha s) activation and further signal transduction events, leading to glycogen breakdown

Question 23

What is the process of receptor signal transduction by GLP-1 in pancreatic beta cells?

Answer 23

A GLP-1 receptors (GPCR) is activated by the GLP-1 ligand. Causes G protein (alpha s) activation and further signal transduction events that ultimately result in insulin secretion.