FGF signalling

Question 1

Describe the extracellular domain of the FRFR

Answer 1

also called the ectodomain. binds ligands, 621 aa ling, has an Ig-I, II and III, which is nearest the membrane, which bind the ligands.

Question 2

How is cell growth rate control?

Answer 2

Via the length of the G1 phase, which dictates the lenght of the cycle. Hence rate is dependant on the decision to pass the G1-S check point.

Question 3

How many FGF proteins are there? and what are they?

Answer 3

22. 1-23 (mouse 15/human 19 homolog), small glygoproteins secreted by cells into the ECM where they are sequestered and kept near cells. Contain a single sugar molecule.

Question 4

What is paracrine?

Answer 4

effects near by cells.

Question 5

Autocrine?

Answer 5

effects the same cell which secretes it.

Question 6

Endocrine?

Answer 6

enters to blood stream to effect distant cells.

Question 7

What is the cellular function of FGFR signalling?

Answer 7

regulate cell proliferate, survival, differentiation and migration.

Question 8

What is the function of FGFR for the whole organism?

Answer 8

Development of various tissues and systems, homeostasis, angiogenesis and tissue repair.

Question 9

How many families of FGFRs are there and how do we know?

Answer 9

7, using phylogenic analyses i.e. looking at inherited molecular differences, mostly as a DNA level.

Question 10

How is a variety of specific FGFRs produced?

Answer 10

4 different genes and alternative slicing in the DNA which encoded the extracellular domain.

Question 11

What activated the FGFR and what happened to it?

Answer 11

A complex is formed: FGF2/herpin/FGFR1. This causes dimerisation (sometimes trimeriasation) which leads to a conformational change of the kinase domain. this leads to cross (auto) phophorylation.

Question 12

Whats is Frs2?

Answer 12

FGFR substrate 2, binds phophorylated FGFR by its photyrosine-binding domain. This is then phosphorylated and able to recurite Sos can Ras.

Question 13

What are the end points of FGF signalling?

Answer 13

Gene transcription and regulation of the cytoskeleton.

Question 14

What does Ras-GAP do?

Answer 14

This is one of the GTPase activating proteins which increases the activity of the GTPase domain of Ras, inactivating the protein up to 100,000 times faster. Does so my inserting a arginine finger into the domain.

Question 15

Which phosphorylations last longer? Ser/thr or Y?

Answer 15

Ser/thr

Question 16

What are the key downstream genes of MAPK signalling?

Answer 16

G1 cyclins

Question 17

How is PI3K activated?

Answer 17

Directly by FGFR via its SH2 domain or by Ras via its Ras binding domain.

Question 18

How are lipids involved in PI3K signalling?

Answer 18

PI3K phosphorylated the inositol head PIP2 to give PIP3 which is bound by pleckstrin homology (PH) domain containing proteins, this includes protein kinase B.

Question 19

How does Ras bind the plasma membrane?

Answer 19

Via the prenyl group.

Question 20

What happens when protein kinase B binds PIP3.

Answer 20

The kinase is now teathered to the membrane and is phosphylated (by PDK1 and 2) to became active. It then phophorylates multiple multiple cellular substrates to encourage cell survival.

Question 21

What is the function of PTEN?

Answer 21

Is a phosphatase with reverts PIP3 to PIP3 which can interact with PH domain containing proteins. Mutations of PTEN are frequently found in human tumours.

Question 22

How is FGF signalling negatively regulated?

Answer 22

FGFR intertnalization and degradation/recycling. Regulation of ligand binding. Regulation of MAPK signalling.

Question 23

What are Mpk1 and 3?

Answer 23

Mapk phosphatases that de-phosphorylate Erk1/2

Question 24

What does sprouty do?

Answer 24

completes with Grb2 to bind Sos and so stop the interaction and signalling via Ras activation. Also able to bind and inhibit Raf.

Question 25

What processes to FGFs play a role in?

Answer 25

Development of tissues, angiogenesis, wound healing and regeneration and homeostasis.

Question 26

Which FGFRs suppress bone growth and how?

Answer 26

2 and 3. by inhibiting cell proliferation and promoting premature differentiation.

Question 27

How may FGF signalling lead to proliferation? cell cycle arrest?

Answer 27

by inducing cyclin D, by inducing p21 which leads to cell cycle arrest in chrondrocyctes,

Question 28

What do activating mutations of a. FGFR1, b. 2 and c. 3 cause?

Answer 28

a. pfeifer syndrome b. various craniosynostosis and c. achondroplasia.

Question 29

How is the FGFR signalling context dependant?

Answer 29

differences in FGFR (kinase activity, adaptor proteins, internalization and degradatrion), cell-specific expression of FGF/FGFRs, TF, adaptors etc, affect of MAPK signalling (positive or negative) and cross talk with other signalling pathways (wnt).

Question 30

What can acitivating mutations of FGFR3 cause?

Answer 30

Somatic mutations in 50% of non-muscle invasive and 15% of muscle invasive bladder caners (aa substitutions). Not sure if this mutation is functional or not in bladder cancer

Question 31

What are the three layers of the bladder urothelium?

Answer 31

The basal cells, intermediate cells and umbrella cells (highly specialised).

Question 32

What is the evidence that FGFR3 mutations in bladder cancer are not function?

Answer 32

Mutations of the coding regions are from in skeletal disorders and there is no evidence that this (and in germ line) is a predisposition to bladder cancer.

Question 33

What is a possible chromosomal translocation involving FGFR3?

Answer 33

t(4;14) in 15% of multiple melanoma. moves next to promoter of ig heavy chain causing over expression. This is rarely a precusor to MM suggesting it promotes progression. In 5% of t(4;14) translocations FGFR3 is also mutated.

Question 34

What does amplification of FGFR1 cause?

Answer 34

10% of oestrogen receptor-positive cancers, 20% of smoking related lung cancers (NSCLC, squamous cell carcinoma). Caused by amplification of the 8p11-12 region.

Question 35

What does amplification of FGFR2 cause?

Answer 35

more than 10% of gastric cancers, associated with poor prognosis.

Question 36

What to SNPS in the FGFR2 loci indicate?

Answer 36

susceptibilities to cancer. Likely for breast cancer. SNPs in the introns correlate with increased rise.

Question 37

What cancer had a truncated FGFR2 been linked to?

Answer 37

in a gastric cancer cell line, C-terminal deletion. This inhibited the receptors internalisation, suggested to impair the signalling.

Question 38

What is the evidence that FGF signalling can act in a tumour supressive manor?

Answer 38

FGFR2 downregulation in progression on bladder , prostate cancers and salivary adinocarcinomas. Inactivating mutations of FGFR2 in melanoma. Expression of FGFR2IIIb blocks proliferation in bladder cancer cell line. Mice lacking FGF2IIIb inkeratinocytes develop skin cancer more easily. Likely due to context dependent signalling.

Question 39

Which FGFs are pro-angiogenic signallers? How less may FGF signalling influence angiogensis?

Answer 39

FGF1 FGF2 and FGF8b. Cross talk with PDGFR signalling.

Question 40

Give an example of autocrine FGF signalling and cancer.

Answer 40

Overexpression of FGFR1 and FGFR2 leading to autocrine signalling in melanoma and a NSCLC cell line.

Question 41

Give an example of paracrine FGF signalling in cancer.

Answer 41

Upregulation of FGFR2 and FGFR6 in prostate cancer, high levels of FGFR1, FGFR2 and FGFR7 in breast cancer.

Question 42

Give an example of endocrine FGF signalling and cancer.

Answer 42

transgenic mice expressing FGF19 in skeletal muscle developed hepatocellular carcinoma. FGF19 over expression is found in liver, colonicand lung squamous carcinoma.

Question 43

Name three approaches to inhibition of FGF signalling in cancer.

Answer 43

1. inhibiting PDGFR (platelet-derived growth factor receptor) together with small molecular TK inhibitors to surpress angiogenesis as well as proliferation. 2. antibody-bases approaches which provide specificity. 3. Ligand-trap arroaches which may inhibit multiple FGF signalling pathways.

Question 44

What problems have been encountered when trying to inhibit FGF signalling in cancer?

Answer 44

Inhibition of the normal function of FGFR3 in phosphate homeostasis (leads to abnormal calcification). Inhibition of FGFR1-IIIc in the hypothalamus has led to severe anorexia in animal models.