signal transduction

Question 1

What is “Signal Transduction”?

Answer 1

The process by which a cell converts an extracellular signal into a response.

Question 2

what is signal transduction used in?

Answer 2

Involved in:
Cell-cell communication
Cell’s response to environment
Intracellular homeostasis (internal communication)

Question 3

what are the chemical ways cells used to communicate

Answer 3

Autocrine & Paracrine: local signalling

Endocrine system: distant, diffuse target, transported via blood

Question 4

state the process of cell signalling

Answer 4

signal molecule binds to receptor protein

receptor protein activates intracellular signal molecules

intracellular signal molecules alters target proteins

target proteins create response

Question 5

what is external message to cell?

Answer 5

Signal

Question 6

example of a signalling system

Answer 6

ligand–receptor interaction:

Peptides/proteins, e.g. growth factors, vasoconstrictors

Amino acid derivatives - epinephrine, histamine

Other small biomolecules - ATP

Steroids, prostaglandins

Gases e.g. nitric oxide (NO)

Photons

Damaged DNA

Odorants, tastants

Question 7

example of cell membrane receptor?

Answer 7

growth factor receptor

Question 8

features of cell membrane receptor?

Answer 8

Lipophobic ligand can’t enter cell
Outer surface receptor
Fast response

Question 9

example of Cytosolic/nuclear recceptors?

Answer 9

steroid hormone receptor

Question 10

features of Cytosolic/nuclear recceptors?

Answer 10

Lipophilic ligand enters cell
Often regulates gene exprn
Slower response

Question 11

list the Membrane receptor classes

Answer 11

(1)ligand-gated ion channels

(2)G protein–coupled receptors (GPCRs)

(3)enzyme-linked receptors

(4)nuclear receptors

Question 12

describe ligand-gated ion channels

Answer 12

ligand binding opens of closes the channel

Question 13

describe G protein–coupled receptors (GPCRs)

Answer 13

ligand binding to a G protein-coupled receptor opens an ion channel or alters enzyme activity.

Question 14

describe enzyme-linked receptors

Answer 14

ligand binding to a receptor-enzyme activates the intracellular enzyme.

Question 15

describe nuclear receptors?

Answer 15

ligand binding to integrin receptors alters the cytoskeleton.

Question 16

describe cell signal initiation and transduction.

Answer 16

refer to slide 09

Question 17

what do pathways do to the signal?

Answer 17

Pathways amplify the signal

Question 18

what happens during enzyme cascade

Answer 18

signal amplification during relay

Question 19

what are proto-oncogenes

Answer 19

A gene involved in normal cell growth.

Question 20

what causes growth of cancer cells in reference to proto-oncogenes

Answer 20

Mutations (changes) in a proto-oncogene may cause it to become an oncogene, which can cause the growth of cancer cells

Question 21

list the different proto-oncogenes

Answer 21

Serine/Threonine Kinases
Raf
Akt

Non-receptor tyrosine kinases
Src (Avian/Rous sarcoma virus)
Abl (Abelson murine leukaemia virus)

GTP-binding proteins
Ras

Question 22

list 8 ligands which, via receptor binding, signal diverse cellular responses

Answer 22

KGF

PDGF

VEGF

EGF

FGF

IGF

TGF-B

CTGF

Question 23

DEFINE KGF

Answer 23

keratinocyte growth factor

growth and new keratinocyte generation

Question 24

DESCRIBE PDGF

Answer 24

Platelet derived growth factor

cell growth, new generation and repair of blood vessels, collagen production

Question 25

describe the VEGF

Answer 25

Vascular endothelial Growth factor promotion of angiogensis promotion wound healing.

Question 26

EGF

Answer 26

epidermal growth factor promotion of epithelial cell growth, angiogenesis, promotion of wound healing

Question 27

FGF

Answer 27

fibroablast growth factor growth factor present in the epithelialization phase of wound healing, keratinocytes cover wound forming.

Question 28

describe IGF

Answer 28

insulin like growth factor for cell growth regulation

Question 29

describe TGF-B

Answer 29

Transforming growth factor- beta growth and neogenesis of epithelial cells and vascular endothelial cells, promotion wound healing.

Question 30

CTGF

Answer 30

Connective tissue growth factor promotes angiogenesis, cartilage regeneration, and platelet adhesion.

Question 31

STOPPED AT THAT SLIDE

Question 32

List the signaling downstream effector domains and what they are bind to?

Answer 32

• SH2 and PTB domains : bind to tyrosine phosphorylated sites • SH3 and WW domains : bind to proline - rich sequences • PDZ domains : bind to hydrophobic residues at target protein C- termini • PH domains - bind to different phosphoinosites • FYVE domains : bind to phosphatidylinositol 3- phosphate (in membrane)

Question 33

Binding of docking proteins is sequence specific. True or false?

Answer 33

True

Question 34

State where Activated ( phosphorylated) PTKs is bind to in SH2 domains and what they do?

Answer 34

•Non-receptor TKs such as Src •Phospholipase Cg (PLCg) - catalyses the breakdown of the lipid, phosphatidylinositol (4,5) bisphosphate (PI4,5P2), into two second messengers: IP3 & DAG •Phosphatidylinositol 3’ kinase (PI 3-kinase) - Phosphorylates PI4,5P2 to generate the second messenger PI3,4,5P3 •SHP2 tyrosine phosphatase - dephosphorylates pY residues on RTKs •GTPase activating protein - inactivates p21Ras-GTP •Nck2 - regulates the cytoskeleton

Question 35

What are the mechanisms for attenuation & termination of RTK activation?

Answer 35

- ligand antagonists - receptor antagonists - phosphorylation and dephosphorylation - receptor endocytosis - receptor degradation by the ubiquitin- proteasome pathway

Question 36

How was tyrosine kinases attempted to be blocked?

Answer 36

•Late 1980 - low molecular weight tyrosine Kinase inhibitors (TKIs) was developed but not very good •it was difficult for low molecular wt compounds to interfere with ligand binding or protein substrate • failed to create non competitive kinase or allosteric inhibitors • ATP competitive inhibitors appeared as target choice

Question 37

Where does the ATP binding sites in TKs happens?

Answer 37

ATP binds within a deep cleft formed between the two lobes of the TK domain

Question 38

The ATP binding site regions in TKs are?

Answer 38

Adenine region – Two key H bonds formed by interaction of N-1 and N-6 amino group of the adenine ring. Many potent inhibitors target one of these H bonds. Sugar region – a hydrophilic region, except a few e.g. EGFR. Hydrophobic pocket –Important role in inhibitor selectivity. Hydrophobic channel – not used by ATP May be exploited for inhibitor specificity. Phosphate binding region – Used for improving inhibitor selectivity.

Question 39

what does Tyrosine kinase inhibitors (TKIs) do?

Answer 39

Bind specifically to kinase domain of TKs Block substrate phosphorylation Block subsequent downstream signalling

Question 40

Apart from the cancer cells, what other cells are targeted in TKIs?

Answer 40

Tumour cells Endothelial cells in tumour angiogenesis (VEGFRs) Stromal fibroblasts

Question 41

what are the development of TKIs in place?

Answer 41

Structure-based drug design Crystallographic structure information Combinatorial chemistry and high-throughput screening

Question 42

TKIs development aims to achieve what?

Answer 42

Greater potency Greater selectivity Higher efficacy Decreased toxicity ADMET