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BS3054 > 28th Oct - PI3K > Flashcards

28th Oct - PI3K Flashcards

1
Q

What is the most abundant phospholipid in the membrane?

A

Phosphatidylcholine

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2
Q

in the inositol ring in phosphatidylinositol which position is attached to the phosphate group?

A

1

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3
Q

What is the function of PI3Ks?

A

They phosphorylate the 3’H position of the inositol ring in phophatidylinositol

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4
Q

What are the 3 main classes of PI3K?

A

Classes I, II and III

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5
Q

What is the preferred substrate of PI3K 1a?

A

PIP2

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6
Q

Is PI3K class 1a dimeric?

A

Yes it’s heterodimeric - 1 catalytic subunit and 1 regulatory subunit

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7
Q

Outline the basic recruitment of PI3K by a growth factor receptor

A

GF receptor autophosphorylates reecruiting the p85 regulatory domain of PI3K aswell as Grb2 and SOS which recruit Ras which binds to the p110 catalytic domain of PI3K

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8
Q

List 5 downstream effectors of PI3K 1a

A 
Rac and Rho
TEC
ARF6
PLC gamma
PKB
PDK1
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9
Q

What is PKB?

A

A serine/threonine kinase

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10
Q

What are the mammalian isoforms of PKB?

A

alpha, beta and gamma

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11
Q

What are the 3 functionallly distinct regions of PKB?

A

PH domain
Kinase domain
Hydrophobic motif

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12
Q

Are most targets inhibited or activated by PKB phosphorylation?

A

Inhibited

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13
Q

How is PKB activated?

A
  1. PIP3 brings PKB to the membrane through its PH domain.
  2. PDK1 phosphorylates the catalytic subunit at T308 –> partial activation
  3. mTORC1 phosphorylates the regulatory subunit at S473 –> full activation
    • -mTORC1 is partially activated in a positive feedback loop by partially activated PKB
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14
Q

What are the targets of PKB?

A

(inhibits) Caspase 9
(inhibits) BAD
(inhibits) GSK3
(inhibits) FKHR-L1
(stimulates) mTORC1

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15
Q

What are the two main enzymes involved in PI3K signalling termination?

A

SHIP and PTEN

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16
Q

What is the function of the src-homology 2 containing phosphatases?

A

They convert PIP3–> PtdIns(3,4)P2 preventing PIP3 dependent proteins from docking to the membrane whilst still allowing PI3k recruitment to the membrane

17
Q

What is the function of the phosphatase and tensin homolog?

A

PTEN reduced PIP3 by converting it to PIP2, thus inhibiting PI3k

18
Q

What are the two classical PI3K inhibitors?

A

Wortmannin and LY294002

19
Q

Give an example of a second generation PI3K inhibitor?

A 
Oncothyreon
PWT-458
SF1126
GDC-0941
XL147
20
Q

Why would it be beneficial to inhibit PI3K?

A

PI3K is often OE in cancer

21
Q

What is Perifosine?

A

A PKB inhibitor

22
Q

Support the claim that PI3K is linked to cancer

A

Class 1a PI3K catalytic subunit was isolated as the transforming gene in v-P3K (chicken sarcoma virus)

Amplication of 3q26 occurs in 40% of ovarian cancers

PI3K presence is crucial for v-src cell transformation

BS3054 (25 decks)

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