Progression of the Epstein-Barr Virus

1
Progression of the Epstein-Barr Virus

• Role of the Latent Membrane Protein 1 (LMP1) in
  activating the PI3K/Akt Pathway
• Presented by Mitchell Cadet

Dawson D.W., G. Tramountanis, A.G. Eliopoulos,
and L.S. Young. 2002. Epstein-Barr Virus Latent
Membrane Protein 1(LMP1)Activates the
Phosphatidylinositol 3-Kinase/Akt Pathway to
Promote Cell Survival and Induce Actin Filament
Remodeling. Journal of Biological Chemistry.
2783694-3704
2
Brief History

• 1958 Michael Burkitt discovers malignant tumor in
  African Children
• Michael Epstein Yvonne Barr cultures a virus
  with typical herpesvirus morphology
• A lab technician acquires mononucleosis while
  working with Burkitts lymphoma virus

3
Description

• Ubiquitous herpesvirus associated with the
  development of tumors
• Circular form of DNA which becomes spliced into
  the host cell DNA
• Exploits the process of B cell development

4
Epidemiology

• Direct oral contact contamination with saliva
• Entry site is the oropharynx
• Moves to the parotid gland
• Remains latent in the throat and blood

5
Two Key Proteins

• LMP1
• LMP2
• Colonizes memory B cells, provides essential
  survival signals

6
LMP1

• Integral membrane protein
• Major transforming protein of EBV
• Drives resting B cells out of their resting state
• Activates the PI3K/Akt Pathway

7
PI3K Akt

• Phosphatidylinositol 3-Kinase (PI3K), activates
  cellular processes in response to extracellular
  stimuli
• Regulates actin cytoskeletal organization and
  cell shape remodeling

• A downstream target of PI3K responsible for
  promoting cell survival

8
Purpose

• Is LMP1 Sufficient to Activate the PI3K/Akt
  Pathway?

9
Methods/Resources

• LMP1 Chimeric Protein in Rat-1 Cells
• Immunostaining of Microinjected Cells for LMP1
  and Actin
• Western Blotting
• Determination of Cell Viability

10
Expression of LMP1 Activation of PI3K/Akt
Pathway
11
Findings

• Levels of PI3K activity significantly greater in
  LMP1-expressing cells
• Elevated PI3K activity correlated with activation
  of Akt
• Greater levels of Akt activity in LMP1-expressing
  cells

12
LMP1-induced Cells Level of PI3K Activity
13
Findings

• Hours after LMP1 is induced, the level of PI3K
  activity climbs 2-3 fold

14
Exposure of LMP1-expressing Rat1 Cells and Cell
Viability
15
Findings

• As the dosage of LMP1 positive cells increases,
  the percent of viable cells decrease dramatically

16
Discussion

• LMP1 has been shown to activate the PI3K/Akt
  pathway
• Evidenced by increased activity in cells
  expressing LMP1 and the ability of inducible LMP1
  expression to also stimulate PI3K activity

17
Significance

• Consequence the ability of LMP1 to induce
  morphological transformation in Rat-1 cells
• Ability to induce actin reorganization likely to
  contribute to the establishment of EBV
  persistence in memory B cell pool

18
Conclusion

• Because of the effects of PI3K on cell survival
  and proliferation EBV is able to target and
  manipulate this pathway for efficient promotion
  of infection and replication

19
Time!