4.2

Question 1

What initiates intracellular RTK signalling?

Answer 1

Tyrosine phosphorylation of the receptor and recruitment of intracellular proteins.

Question 2

What are the major cellular processes influenced by RTK signalling?

Answer 2

Survival, proliferation, differentiation, metabolism, motility.

Question 3

What mechanism ensures signalling is switched off?

Answer 3

Negative feedback via phosphatases and receptor downregulation.

Question 4

How are extracellular signals propagated intracellularly?

Answer 4

Through protein–protein interactions mediated by modular binding domains.

Question 5

What are the types of intracellular signalling proteins?

Answer 5

Enzymes, adaptors/scaffold proteins, docking molecules, and small messengers.

Question 6

What role does phosphorylation play in these signalling pathways?

Answer 6

It recruits and activates proteins via domain–motif interactions.

Question 7

What is the function of SH2 domains?

Answer 7

Bind to phosphorylated tyrosine (pY) residues in specific motifs.

Question 8

What determines SH2 binding specificity?

Answer 8

The amino acid sequence surrounding the pY site, especially C-terminal residues.

Question 9

What is a PTB domain?

Answer 9

Phosphotyrosine-binding domain that binds to NPXpY motifs.

Question 10

How is PTB domain binding different from SH2?

Answer 10

PTB domains recognize N-terminal flanking residues (e.g., NPX).

Question 11

What do SH3 domains bind to?

Answer 11

Proline-rich motifs (PXXP), independent of phosphorylation.

Question 12

What do PH domains bind to?

Answer 12

Phosphorylated phosphoinositide lipids (PIP2, PIP3) in membranes.

Question 13

What proteins have SH2 domains?

Answer 13

Src, PI3K, PLCγ, Grb2.

Question 14

What proteins have PTB domains?

Answer 14

IRS1, Shc.

Question 15

What proteins have SH3 domains?

Answer 15

Nck, Src, Grb2.

Question 16

What proteins have PH domains?

Answer 16

Akt, PDK1, PLCγ.

Question 17

What are motifs in signalling proteins?

Answer 17

Short amino acid sequences that interact with modular domains.

Question 18

What do RTK pY residues recruit?

Answer 18

Proteins containing SH2 or PTB domains.

Question 19

What happens after proteins are recruited to pY sites?

Answer 19

They are phosphorylated and activated to propagate signals.

Question 20

How do modular domains contribute to signalling complexity?

Answer 20

Multiple modules in a protein allow diverse, multi-pathway interactions.

Question 21

What domains are found in c-Src?

Answer 21

SH3, SH2, kinase domain.

Question 22

What domains are found in SHP2?

Answer 22

Two SH2 domains and a phosphatase domain.

Question 23

What domains are found in IRS1?

Answer 23

PTB and PH domains.

Question 24

What domains are found in Nck?

Answer 24

One SH2 and three SH3 domains.

Question 25

What ensures signalling specificity?

Answer 25

The precise sequence context around pY residues and the modular domain involved.

Question 26

What is the typical range of phosphorylation sites on an RTK?

Answer 26

5 to 12 sites.

Question 27

What is the result of each pY recruiting a specific protein?

Answer 27

Signal diversification and amplification.

Question 28

How are signals turned off?

Answer 28

Via tyrosine phosphatases and receptor degradation (e.g., ubiquitylation).

Question 29

What does SH3 bind to?

Answer 29

PXXP motifs (proline-rich regions).

Question 30

What lipid products do PH domains recognize?

Answer 30

PIP2 and PIP3.

Question 31

What type of receptor triggers PIP3 production?

Answer 31

RTKs via activation of PI3K.

Question 32

What triggers IRS1 recruitment to the insulin receptor?

Answer 32

Tyrosine phosphorylation and PTB domain binding to pY-containing motifs.