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Akt/PKB signaling pathway - Quiz
Contributed by: Shields
  • 1. What is the primary function of the Akt signaling pathway?
A) Inhibiting protein synthesis
B) Reducing cellular metabolism
C) Promoting apoptosis
D) Promoting survival and growth
  • 2. Which enzyme acts as a second messenger after being phosphorylated by PI3K?
A) Ras
B) Grb2
C) PIP3
D) PTEN
  • 3. What type of kinase is Akt?
A) Serine/threonine kinase
B) Histidine kinase
C) Lipid kinase
D) Tyrosine kinase
  • 4. Which protein is a major antagonist of PI3K activity?
A) GAB
B) PTEN
C) IRS
D) Sos1
  • 5. What is the composition of Class I PI3Ks?
A) Regulatory p85 and catalytic p110 subunits
B) Two identical catalytic subunits
C) Single catalytic subunit only
D) Regulatory p110 and catalytic p85 subunits
  • 6. How does the p85 subunit bind to activated receptor tyrosine kinases?
A) Via its G protein-binding domain
B) Via its kinase domain
C) Via its lipid-binding domain
D) Via its SH2 domain
  • 7. Which molecule acts as an adaptor to recruit p85 via GAB scaffold proteins?
A) PTEN
B) Sos1
C) Ras
D) Grb2
  • 8. What can activate the p110 subunit independently of p85?
A) Akt
B) Ras-GTP
C) PIP3
D) PTEN
  • 9. Which diseases are linked to PI3K-Akt pathway deregulation?
A) Cancer and type 2 diabetes
B) Hypertension and arthritis
C) Cystic fibrosis and asthma
D) Anemia and malaria
  • 10. Approximately how many different substrates does Akt phosphorylate?
A) 1000
B) 100
C) 10
D) 500
  • 11. How are G protein-coupled receptors (GPCRs) able to activate PI3K?
A) Via recruitment of PTEN
B) Via inhibition of Grb2
C) Via direct phosphorylation of p85
D) Via G-protein beta-gamma dimers or Ras
  • 12. What triggers the initial activation of the receptor tyrosine kinase (RTK) pathway?
A) Binding of an extracellular ligand
B) Binding of intracellular PIP3
C) Loss of PTEN function
D) Dephosphorylation of p85
  • 13. What is the structural consequence of extracellular ligand binding to an RTK?
A) Receptor degradation
B) Receptor dimerization
C) Nuclear translocation
D) Lipid cleavage
  • 14. Where are the phosphoinositide docking sites located for Akt recruitment?
A) Mitochondrial matrix
B) Endoplasmic reticulum
C) Plasma membrane
D) Nuclear envelope
  • 15. Which enzyme catalyzes the addition of phosphate groups to the 3'-OH position of phosphoinositides?
A) PI3K
B) Akt
C) PDK1
D) mTORC2
  • 16. Which lipid product is produced from the phosphorylation of PI(4,5)P2?
A) PI(3)P
B) PI(3,4)P2
C) PI
D) PI(3,4,5)P3
  • 17. Where does Akt reside when in an inactive conformation?
A) Plasma membrane
B) Nucleus
C) Cytosol
D) Endoplasmic reticulum
  • 18. Which phosphorylation site in the kinase domain of Akt is required for partial activation?
A) Ser308
B) Thr473
C) Ser473
D) Thr308
  • 19. Which kinase is responsible for phosphorylating Akt at Thr308?
A) mTORC2
B) DNA-PK
C) ILK
D) PDK1
  • 20. How is Akt activity attenuated after stimulation?
A) Translocation to the nucleus
B) Binding to inhibitory proteins
C) Dephosphorylation by phosphatases
D) Degradation by proteasomes
  • 21. What happens to PIP3 levels after cell stimulation to help attenuate Akt activity?
A) They increase
B) They convert to PI
C) They remain stable
D) They decrease
  • 22. Which kinase is activated in response to increases in cellular Ca2+ to activate Akt?
A) CAMKK
B) ILK
C) mTORC2
D) PDK1
  • 23. What is required for Akt to move from the cytosol to the plasma membrane?
A) DNA damage
B) PI3K activity
C) Calcium depletion
D) Heat shock
  • 24. Which enzyme dephosphorylates PI(3,4,5)P3 at the 5' position?
A) PTEN
B) PP2A
C) SHIP
D) PHLPP
  • 25. Which E3 ligase is responsible for targeting PTEN for degradation?
A) NEDD4-1
B) IRS-1
C) FoxO
D) S6K1
  • 26. Which phosphatase dephosphorylates Akt at Thr308?
A) PTEN
B) PP2A
C) SHIP
D) PHLPP
  • 27. Which protein dephosphorylates Akt at Ser473?
A) CTMP
B) SHIP
C) PP2A
D) PHLPP
  • 28. How does Akt influence PTEN expression in a positive feedback loop?
A) It promotes the stability of PTEN mRNA
B) It up-regulates the E3 ligase NEDD4-1
C) It activates the transcription of PTEN
D) It directly phosphorylates PTEN to increase its activity
  • 29. Which complex is responsible for the negative feedback loop that down-regulates IRS-1 transcription?
A) PTEN
B) Akt
C) PP2A
D) mTORC1
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