Intracellular Signalling - Protein Kinases Flashcards

1
Q

What are the 3 main groups of protein kinases?

A
  1. Serine/Threonine kinases
  2. Tyrosine kinases
  3. Dual-specificity kinases
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2
Q

What is function of protein kinases?

A

Enzymes that facilitate the transfer of a phosphate group from ATP to a specific amino acid reside (Set, Thr or Tyr) on a specific protein

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3
Q

What is result of phosphorylation of a protein?

A

Changes the function of the protein (may activate or inhibit)

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4
Q

Where is the phosphate group from ATP added?

A

Onto the hydroxyl group (OH) on the side group of the amino acids

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5
Q

What do serine/threonine kinases do?

A

Phosphorylate Ser and/or Thr residues

PKA, PKC, PKG

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6
Q

What do tyrosine kinases do?

A

Phosphorylate only Tyr residues

Receptor TKs (insulin receptor)
Non-receptor TKs (Src)
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7
Q

What do dual-specificity kinases do?

A

Phosphorylate Ser/Thr and Tyr residues

MAP kinase kinases

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8
Q

What are phosphatases?

A

Remove phosphate groups from amino acid residues to oppose the effects of kinases

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9
Q

What are the 2 major groups of phosphatases?

A
  1. Ser/Thr-directed phosphoprotein phosphatases (PPPs)

2. Tyr-directed phosphotyrosine phosphatases (PTPs)

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10
Q

Why are there not as many different phosphatases as kinases?

A

Due to the broad specificity of phosphatases

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11
Q

How can kinases modulate protein function?

A
  1. Phosphorylation of a protein leading to a conformational change that directly alters the function of that particular protein
  2. Phosphorylation of a transcription factor that alters gene transcription and protein expression levels
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12
Q

What occurs during MAP kinase cascades?

A
  1. An MAP kinase kinase kinase (MAPKKK) phosphorylates and activates an MAP kinase kinase (MAPKK)
  2. MAPKK phosphorylates and activates an MAP kinase (MAPK)
  3. MAPK phosphorylates a downstream substrate (a phosphoprotein or eve another kinase)
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13
Q

What are the 3 main MAP kinase cascades?

A
  1. ERK pathway
  2. p38 pathway
  3. JRK pathway
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14
Q

What is the ERK pathway activated by?

A

Growth factors and GPCR ligands

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15
Q

What are the p38 and JRK pathways activated by?

A

Stresses and inflammatory cytokines

p38 and JRK sometimes known as the stress-activated protein kinases (SAP kinases)

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16
Q

What is the NF-kB pathway activated by?

A

Mostly by pro-inflammatory molecules (interleukin-1 and TNF-alpha)

17
Q

What is ‘Gleevec’?

A

Protein kinase inhibitor - drug was initially developed to treat chronic myelogenous leukaemia (CML)

18
Q

How does Gleevec work?

A

Inhibits activity of the non-receptor tyrosine kinase BCR-Abl and the receptor tyrosine kinases c-KIT and PDGF Receptor A

Inhibits cancerous WBC proliferation

19
Q

In the NF-kB pathway, what are the receptors coupled to?

A

The activation of the MAP kinase kinase kinase MEKK3

20
Q

Describe NF-kB pathway

A
  1. Receptors are coupled to the activation of the MAP kinase kinase kinase MEKK3
  2. This phosphorylates IkB kinase (IKK)
  3. This phosphorylates IkB (the inhibitory binding partner of NF-kB –> a transcription factor)
21
Q

What does phosphorylation of IkB result in?

A

Targets it to an intracellular protein degradation pathway (‘the proteasome’)

This frees NF-kB to translocate to the nucleus

22
Q

What is effect of free NF-kB in nucleus?

A

Acts as transcription factor to promote the transcription of inflammatory genes

23
Q

What is dysregulation of kinases linked to?

A

Cancer development

24
Q

How does phosphorylation differ to G-proteins?

A

In contrast to G-proteins (always switched on by GTP), phosphorylation may activate or inhibit protein function

25
How are MAP kinases and glycogen synthase kinase (GSK)-3 affected by phosphorylation?
- MAP kinases --> activated by phosphorylation | - Glycogen synthase kinase (GSK)-3 --> inhibited by phosphorylation
26
What do kinase cascades allow?
The signal to be amplified
27
How do the MAP kinase cascades work?
1. A MAP kinase kinase kinase (MAPKKK) phosphorylates and activates a MAP kinase kinase (MAPKK) 2. In turn phosphorylates and activates a MAP kinase (MAPK) 3. Then phosphorylates a downstream substrate (a phosphoprotein or even another kinase).
28
Describe effect when adrenaline binds to B1-AR
1. G protein is Gs 2. Stimulates adenyl cyclase 3. Stimulates cAMP 4. Activates protein kinase A 5. Activates phosphorylase kinase which continues the pathway for the breakdown of glycogen
29
What is protein kinase A involved in?
'fight or flight' response in mammals
30
Describe effect when ACh binds to Muscarinic M2
1. G protein is Gi 2. Inhibits adenyl cyclase 3. Reduces cAMP levels 4. Reduced activation of protein kinase A
31
Describe effect when angiotensin II binds to AT1R
1. G protein is Gq 2. Activates phospholipase C 3. Produces DAG and IP3 4. DAG activates protein kinase C 5. IP3 increase Ca2+ which activates protein kinase C and Ca/CaM kinase
32
Describe effect of neuropeptide or NO
1. Activates guanylate cyclase (no receptor/G protein) 2. Increases cGMP 3. Actives protein kinase G
33
What is dysregulation of many kinases linked to?
Cancer development