Cell signalling 4

Question 1

What are guanylyl cyclases activated by and in what homeostasis are they involved in ?

Answer 1

Guanylyl cyclases are activated by atrial/brain natriuretic peptides
They are involved in sodium homeostasis

Question 2

How does cGMP activate Protein kinase G ( PKG)

Answer 2

Like cAMP - cGMP binds to the regulatory domains of protein kinase G which results in the catalytic domain becoming active - allowing the enzyme to phosphorylate substrates

Question 3

What enzyme breaks down cGMP?

Answer 3

Phosphodiesterase converts cGMP into its linear form

Question 4

What is the overall effect of cGMP on smooth muscle cells - mention effects on ion levels

Answer 4

cGMP results in the decrease of Ca2+ ions in the muscle cell resulting in rapid relaxation of smooth muscle cell

Question 5

What are serine/threonine kinases activated by and what proteins do they recruit ?

Answer 5

Ser/ thr kinases are activated by TGF-Beta ligands and they recruit smad proteins as transcription factors

Question 6

At what part of early development is TGF-Beta signalling important for ?

Answer 6

TGF-Beta signalling is important for mesoderm induction in early development
+ FGF signalling

Question 7

Describe Wnt signalling when it is activated ? ( what does it prevent when active )
Mention stimulus, receptor, effector and transcription factor

Answer 7

Wnt binds to LRP5/6 and frizzled receptor- this causes Dishevelled protein to recruit actin
Actin comes from the complex which degraded Beta catenin
The transcription factor Beta-catenin is then not degraded and therefore can diffuse through the nuclear membrane for transcription of genes

Question 8

As well as the constant degradation of Beta-catenin how is this TF prevented from binding to LEF and TCF

Answer 8

Groucho binds to LEF and TCF instead of Beta-Catenin

Question 9

What is the function of Wnt signalling ?

Answer 9

Wnt signalling is used during embryonic development as well as nerve circuit patterning

Question 10

What are the 3 ligands involved in hedgehog signalling?

Answer 10

Sonic, Indian and Desert

Question 11

Hedgehog signallling is similar to Wnt signalling- Name the stimulus , receptor effector and transcription factor involved

Answer 11

Hedgehog - stimulus
Patched - Receptor
Effector - smoothened
Cubitus/ Gli (mammalian )
Like wnt signalling hedgehog signalling involves the effector from recruiting proteins which prevents the degradation of the TF , in this case Cubitus/ Gli