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BS3054 > 21st Nov - Signalling to the nucleus > Flashcards

21st Nov - Signalling to the nucleus Flashcards

1
Q

Give an example of how a proteins cellular localisation is altered by regulating the NLS/NES

A

NFAT
Dephosphorylation by cacineurin exposes the NLS –> nucleus

Phosphorylation by NK masks the NLS –> cytoplasm

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2
Q

What are the two main ways in which TF level can be modulated?

A

Alteration in expression levels

Alteration in TF stability

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3
Q

Give an example of how TFs are regulated through their expression levels

A

JNK and ERK5 regulation of the c-jun promoter via phosphorylation of it’s TF MEF2C

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4
Q

Give an example of how TFs are regulated through altering their stability

A

Phosphorylation can affect covalent attachment of ubiqutin to lysine residues e.g. activated JNK phosphorylates c-Jun, JunB, ATF-2 and p53 protecting them from ubuquitination

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5
Q

Give an example of how TF binding to DNA can be regulated by phosphorylation

A

JNK phosporylates the n-terminal transactivation domain of c-Jun. This enhances DNA binding by promoting the dephosphorylation of sites on c-Jun that inhibit its binding to DNA

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6
Q

Give an example of how TF phosphorylation can alter their ability to interact with other proteins

A

Phosphorylated CREB’s recruitment of CBP

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7
Q

What are the two major routes from cell surface receptor proteins to genes?

A

Phosphorylation cascades

Cytoplasmic TFs

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8
Q

Briefly outline the MAPK cascade

A

MAPKKK phosphorylate two serine residues on MAPKKs. MAPKKs phosphorylate MAPK on threonine and tyrosine residues causing MAPK activation, where they translocate to the nucleus to phosphorylate a number of TFs

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9
Q

Outline the ERK pathway

A

Ras/Rac/Cdc 42/Rho –> Raf –> MEK1/MEK2 –> ERK –> SRF and TCF

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10
Q

Outline the JNK pathway

A

Ras/Rac/Cdc 42/Rho –> MEKK –> MKK4/MKK7 –> JNK –> API/ SRF and TCF/ ATF2

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11
Q

Outline the p38 pathway

A

Ras/Rac/Cdc 42/Rho –> TAK –> MKK3/6 –> p38 –> ATF2

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12
Q

How can TF phosphorylation by MAPK affect their properties?

A

Regulatory protein interaction
Intracellular localisation
Protein level
DNA binding

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13
Q

Outline the pathway to CREB activation in neurones

A

AMPAR/NMDAR/L-type calcium channels/Gq –> Ca –> CaM –> CamKIVM –> CWREB phosphorylation

Gs –> AC –> cAMP –> PKA –> CREB phosphorylation

TRK –> Raf –> MEK –> ERK –> RSK1-3 –> CREB phosphorylation

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14
Q

What are the physiological effects of the Wnt pathway?

A

Cell proliferation, differentiation, motility and survival
Embryonic development
Homeostasis maintenance in mature tissue

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15
Q

What are the three different Wnt signalling pathways?

A

Canonical
Serine phosphorylation in the SMAD signalling pathway
Phosphoinositide dependent release of Tubby

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16
Q

Outline the canonical Wnt signalling pathway

A

When Wnt is absent, beta catenin is phosphorylated and sequestered in the multiprotein destruction complex of GSK-3, Axin, APC and CKI alpha

When Wnt binds to the frizzled receptor it recruits disheveled. Activated disheveled disrupts the Axin/APC/CK1alpja/GSK3 complex by inhibiting GSK-3. This means that beta catenin can accumulate in the cytoplasm and translocate to the nucleus where it displaces Grouche and binds to TCF/LEF to transcriptionally activate genes

17
Q

Outline the Serine phosphorylation in the SMAD signalling pathway Wnt signalling pathway

A

TGFbeta activates the TGF beta receptor, which causes SMAD 2/3 activation by serine phosphorylation.
SMAD4 binds to SMAD 2/3.
SMAD complex goes to the nucleus to act as a TF

18
Q

What are Smad proteins?

A

The only known latent cytoplasmic TFs that become directly activated by serine phosphorylation at their cognate receptor, they transduce signals on behalf of the TGF-beta superfamily of ligands

19
Q

What are the functional regions of the Tubby protein?

A

C-term binds strongly to DNA
N-term contains the transcriptional activation domain
A domain Binds to PIP2 in plasma membrane

20
Q

Outline the Wnt signalling pathway: Phosphoinositide dependent release of Tubby

A 
Agonist binds to Gq receptor
Activates PLC-beta
Converts PIP2 --> DAG +IP£
Tubby binds to PIP2 in the membrane, so when PIP2 is depleted Tubby is released.
Tubby translocates the nucleus

BS3054 (25 decks)

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