CellSig11 - 31 Flashcards Preview

Y2S2 - Cell Signalling > CellSig11 - 31 > Flashcards

Flashcards in CellSig11 - 31 Deck (31):
1

How was notch identified?

Forward genetic screens in Drosophila - notch wing phenotype - by Thomas Hunt Morgan - 1866-1945

2

How many notch receptors does Drosophila have?

1

3

How many delta ligands do Drosophila have?

2 - delta and serrate

4

How many delta ligands do vertebrates have?

At least 9 members of this family

5

How many notch receptors do humans have?

4 (Notch 1-4)

6

What are delta ligands collectively known as?

DSL family

7

Characterise delta/notch structures and function

1TM domains, with many EC EGF repeats, juxtacrine in function, notch also has many IC ankyrin repeats

8

What is important about EC EGF repeats?

Made up of repeated cysteines in regular intervals that form sulphide bridges, adding structure

9

What regulates EGF cysteine pairing?

Protein disulphide isomerase in the ER

10

Outline the delta-notch pathway

Notch activation > Notch-intra translocates to the nucleus > activation of CSL > transcription

11

What constitutes CSL?

CBF1/SuH/LAG1

12

What is furin's role in notch activation?

Cuts the receptor to produce a heterodimer, S1, which then implants into the PM

13

What is furin?

Serine protease - controls first cleavage of notch

14

How is notch cleaved for a second time?

Ligand dependent, TACE cuts off EC domain, but notch remains in membrane because TM domain still attached

15

What is TACE?

Metalloprotease

16

What is presenilin?

Gamma-secretase - controls third cleavage, and release of notch from the PM

17

What releases notch from the PM?

Presenilin

18

Outline notch degradation

E1 - ubiquitin activating enzyme > E2 - ubiquitin conjugating enzyme > E3 ubiquitin ligase (notch specific) > proteasome

19

Characterise Su(dx)/Itch

3 major domains - WW binds notch, HECT mediates ubiquitination, C2 localises to the PM

20

Characterise Sel-10

Recognises Notch-intra, but lacks ubiquitin ligase activity, so recruits one via its F box

21

Characterise Neur/Mib

Binds delta, RING domain ligases, required to activate endocytic pathway

22

What domains are present in notch-intra?

NLS - nuclear localisation sequence, RAM and ANK domains - protein/protein interaction domains, activation domain - transcriptional activator

23

Outline transcriptional activity without Notch present

CBF1 anchors HDAC via SMRT and SKIP near the promoter, reducing DNA acetylation

24

Outline transcriptional activity with Notch present

Notch-intra displaces SMRT and HDAC and acts as a transcriptional activator

25

How is Alzheimers related to Notch activation?

Similar mechanism - amyloid precursor protein (APP) cleaved by alpha or beta-secretase, then by presenilin in one of two places (40 or 42 a/a). The 42 a/a version is a major component of the amyloid plaques

26

How was the first human notch cloned?

From T-cell acute lymphoblastic leukemia patients - Truncated Allele of Notch (TAN1)

27

What is TAN1?

Translocation of TCR-beta gene fused to Notch-intra

28

How does TAN1 cause leukemia?

TCR-beta strongly expressed in immature T-cells, therefore Notch is made consituently active

29

What does CADSIL stand for?

Cerebral AD ateriopathy with subcortical infarcts and leukoencephalopathy

30

What is CADSIL?

Recurrent strokes leading to dementia, due to build of granular material in smooth muscle of blood vessels

31

What causes CADSIL?

Mis-sense mutations in Notch3 - usually the first 5 EGF repeats