Elsie and freek

Question 1

TGF beta Superfamily

Answer 1

TGF beta like and BMP like

Question 2

TGF beta like family transduction molecules

Answer 2

SMAD 2/3 and 4

Question 3

BMP like family transduction molecules

Answer 3

SMAD 1/5/8 and 4

Question 4

SMAD signalling pathway

Answer 4

TGF beta binds to type 2 receptor
joins type 1 and type 2 receptors together
type 1 has kinase activity and is activated
SMAD proteins are then phosphorylated together
together they act as TF or move to where they are needed

Question 5

how are BMP pathways regulated

Answer 5

through inhibition.
ligand traps like chordin/noggin bind to BMP signalling ligands and stop BMP bind to type 2 receptor

can be visualised through SMAD detection

Question 6

how can expression of TGF beta signalling pathways be experimented with

Answer 6

Genetic engineering of receptors to be
always on - gain of function
dead - loss of function

Question 7

How have model organisms been used regarding TGF betas

Answer 7

Xenopus and Zebrafish showed SMAD 2/3 is required for mesoderm formation. also showed oep is equivalent to type 1 receptor

Question 8

Receptor tyrosine kinase

Answer 8

Cell surface signalling receptor
58 types
mostly exist as monomers except insulin

Question 9

RTK structure

Answer 9

extracellular - ligand binding domain
intracellular - tyrosine kinase domain

Question 10

RTK activation

Answer 10

ligand dimerises -> receptor dimerises
when correct alignment kinase domains cross phosphorylate each other which
- stabilises receptor in active state
- phosphorylates other kinases in intracellular domain which creates more docking sites

Question 11

what recognises open docking ports

Answer 11

SH2 domains

Question 12

RAS switch

Answer 12

inactive ras has GDP, its is activated by a GEF that phosphorylases it to have a GTP. This is then removed by GAP proteins in the cytoplasm.

Question 13

RTK use of RAS switch

Answer 13

GRB2 binds to docking site, joins with SOS which is a GEF. RAS activated and phosphorylates Raf then Mek and then MapK which is the final phosphorylated in cascade.

Question 14

FGF ligands overview

Answer 14

22 members
signal through 4 receptors
Type of RTK receptor

Question 15

FGF receptor structure

Answer 15

D1 D2 D3 and acid box in extracellular domain
ligands bind to D2 and D3
D2 has a HSPG domain
Kinase domain in the intracellular domain

Question 16

How are FGFRs activated

Answer 16

transmembrane HSPGs use modifications in sulphur to create specific binding sites for paracrine FGF ligands
This causes proximity of FGFs to each other allowing for facilitated dimerization of FGFRs and therefore activation

Question 17

which type of FGF ligands go into the blood

Answer 17

endocrine FGFs as they have low affinity for HSPGs

Question 18

what does activation of FGFRs lead to

Answer 18

MapK activation - cell proliferation
Akt - cell survival
Calcineurin - cell motility

Question 19

Human diseases that result from FGFR mutations

Answer 19

apart syndrome
achondroplasia
Pfeiffer syndrome
—All affect skeletal formation—

Question 20

areas where Hh and Wnt signalling are used

Answer 20

Tissue patterning and development in organs
Regulation of stem cell fate / division and maintenance
initiation of cancer

Question 21

History of Hh and Wnt

Answer 21

discovered in drosophilla
Hh = segment polarity gene
Wnt name = wingless phenotype (Wg) + Int1 in mice were found to be the same gene
Highly conserved in most organisms

Question 22

Hh signal production

Answer 22

AA N terminal make it go into secretary pathway
C terminal chopped off (autoproteolysis) and cholesterol added to new C terminal
Palmitoylation to N terminal
Protein targeted to membrane where dispatched allows it to exit the cell

Question 23

Hh movement outside the cell

Answer 23

Cholesterol and Palmitate are highly hydrophobic
Scube allows movement outside the cell using HSPGs and cytonemes

Question 24

Wnt signal production

Answer 24

AA N terminal make it go into secretary pathway
Palmitoylation to cys77
palmitoleic acid added to ser209
Wntless helps transport to membrane and leave the cell

Question 25

Wnt movement using HSPG

Answer 25

binds to chain, rolls onto DLP protein on HSPG, then rolls onto chain again. HSPG mesh around cell allows it to roll across membrane Handover mechanism

Question 26

Wnt movement using cytoneme

Answer 26

Wntless located in specific areas of cell membrane. cytoneme forms when Wnt is on membrane and extends to touch neighbouring cells

Question 27

Overall main points about Wnt and Hh signals

Answer 27

Very hydrophobic Transported by handover using HSPGs or cytonemes

Question 28

Hh signal transduction

Answer 28

Patched stops pumping cholesterol out of inner leaflet Cholesterol allowed to build up in inner leaflet of cell membrane Smoothened is active Ci to CiR by Costal2, CKI and SUFU complex is blocked Ci enters nucleus and activates Hh genes

Question 29

What happens in absence of Hh ligand

Answer 29

Patched pumps cholesterol out of inner leaflet Costal2 complex and SUFU complexes with kinase activity ubiquitate Ci converted to CiR constantly by SLIMB

Question 30

What processes does Smoothened undergo

Answer 30

relocation, accumulation, phosphorylation

Question 31

Where in mammalian cells does Hh signalling occur?

Answer 31

In the cillia of cells

Question 32

what happens to patched when Hh binds to it

Answer 32

it is internalised and degraded

Question 33

How does Hh signalling self regulate

Answer 33

Ci represses expression of patched - negative feedback Ci activated Gli1 transcription (homologue of Ci that cannot be repressed) - positive feedback

Question 34

Where do we see Hh signalling

Answer 34

Drosophila wing disk - AP axis patterning Neural tube development- Tube formation and patterning from notochord Vertebrate limb development - limb bud outgrowth and proximal distal patterning of bones

Question 35

What diseases arise from Hh signalling defects

Answer 35

holoprosencephaly Cancers- Basal cell carcinoma - MOST COMMON CANCER

Question 36

How do Hh mutations lead to cancer

Answer 36

Overexpression of Hh genes from inactivation of patched or sufu activation of smoothened

Question 37

How does cyclopamine act

Answer 37

Inhibits smoothened

Question 38

Wnt signalling pathway

Answer 38

Wnt binds to arrow and frizzled surface membrane proteins Dsh is recruited to Frizzled allowing destruction complex to bind to Arrow and Frizzled. This phosphorylates the destruction complex, stopping Slimb from binding. This stops B-catenine from being degraded B-catenine levels buildup and enter the nucleus and removes groucho

Question 39

How is B-catenine expressed

Answer 39

Continuously however it is degraded when Wnt is not present

Question 40

What is the destruction complex made of and how does it act

Answer 40

APC Axin CKI GSKI Recruits Slimb which targets B-catenine for degredation

Question 41

What blocks Wnt expression on the genome

Answer 41

Groucho, which is removed by B-catenine

Question 42

Is Wnt expressed all the time if groucho didn't repress it

Answer 42

YES

Question 43

Examples of Wnt signalling

Answer 43

Dorsal Ventral patterning and folding of the wing disk in drosophila nerve fate and guidance in C.Elegans Maintenance of stem cells in the gut

Question 44

How can Wnt mutations lead to cancer and what types of cancer are common as a result

Answer 44

Loss of APC gene in destruction complex causes ectopic expression of Wnt in the gut. This creates inactive polyps in the gut, colon and rectum Also leads to breast, ovarian and uterine cancers

Question 45

Function of Wnt in Bone diseases

Answer 45

Wnt3 causes limb formation LRP5 causes increased wnt signalling causing increased bone density Axin2 loss causes loss of teeth

Question 46

Are these the only pathways that Wnt and Hh use?

Answer 46

No