17645544_McDonald_Vpr

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17645544_McDonald_Vpr

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  1. Vpr protein of HIV-1

    Slide 1 - Vpr protein of HIV-1

    • http://www.rkm.com.au/VIRUS/HIV/HIV-images/VIRUS-HIV-life-cycle.jpg
    • https://www.aids.gov/images/aids-infographics/global-aids-overview-1.jpg
  2. Viral protein of regulation (Vpr) of HIV-1

    Slide 2 - Viral protein of regulation (Vpr) of HIV-1

    • Accessory protein made up of 96 Amino acids (Morellet et al., 2003)
    • Found in the serum and cerebrospinal fluid of AIDS patients (Piller et al., 1999), and associated with the virion (Deniaud et al., 2004)
    • Vpr is able to form a cation selective ion channel across lipid bilayers (Piller et al., 1999)
    • http://www.slideshare.net/ShumezHameedullah/hiv-pathogenesis-staging-and-cutaneous-manifestations
  3. Structure of protein

    Slide 3 - Structure of protein

    • 3 α-helical regions
    • 96 amino acid residue protein
    • N-terminal; associated with ability to form ion channels in membranes.
    • C-terminal; alterations in cell cycle. Cytotoxic, but not required for production of ion channels.
    • hydrophobic region
    • (Morellet et al., 2003, Piller et al.,1999)
    • http://www.rcsb.org/pdb/explore/explore.do?structureId=1M8L
  4. Functions and effects of Vpr

    Slide 4 - Functions and effects of Vpr

    • increase the viral replication of HIV and transactivation
    • suppression of immune activation
    • induction of G2 arrest
    • induction of apoptosis
    • (Piller et al., 1998, Morellet et al., 2003, Boya et al., 2004)
    • http://www.retrovirology.com/content/figures/1742-4690-8-25-1.jpg
  5. Slide 5

    • G2 Arrest
    • Inhibition of phosphatase Cdc25C, which normally activates cyclin B1–p34Cdc2
    • Disrupts cell cycle (Morellet, et al., 2003)
    • Induction of apoptosis
    • Vpr binds to permeability transition pore complex (PTPC)
    • cytochrome c is released from mitochondria, resulting in apoptosis
    • (piller et al., 1999)
    • Disruption of the cell cycle and induction of apoptosis
    • http://www.retrovirology.com/content/figures/1742-4690-8-25-1.jpg
  6. Ion channels formed by Vpr

    Slide 6 - Ion channels formed by Vpr

    • Amino-terminal domain is the area of Vpr primarily responsible for channel activity
    • Channels formed by the Vpr protein result in a large inward current of cations, causing depolarization and cell death.
    • Mutations in the amphipathic N-terminal region change ion selectivity
    • Ion channels from Vpr have been shown to kill intact neurons.
    • (piller et al., 1999)
  7. C-terminal

    Slide 7 - C-terminal

    • Currents generated in planer lipid bilayers using C-terminal mutants at different holding potentials.(Piller et al., 1999)
    • A and B show channel activity following the deletion of 8 to amino acids from the C-terminus.
    • The currents generation is similar to that of wild type Vpr, but no rectification occurs at positive potentials.
    • C and D show point distribution between a proposed salt bridge between the N-terminus and R95 of the C-terminal region.
    • Ion channel activity is shown to be similar to that of wild type Vpr.
    • (Piller et al., 1999)
  8. Hydrophobic region

    Slide 8 - Hydrophobic region

    • Currents generated in planer lipid bilayers using mutations at the hydrophobic region at different holding potentials.(Piller et al., 1999)
    • A and B show channel activity following the deletion of Amino acids 63-73 and point mutation G75R
    • C and D show channel activity following point mutation that disrupts the proposed salt bridge between E58 and R62
    • Both mutations show channel activity similar to that of wild type Vpr, indicating that the hydrophobic region of Vpr is unlikely to play a role in ion channel formation.
    • (Piller et al., 1999)
  9. N-terminal

    Slide 9 - N-terminal

    • Currents generated in planer lipid bilayers using N-terminal mutants at different holding potentials.(Piller et al., 1999)
    • A and B represent channel activity following point mutation at glutamate N21
    • C and D represent channel activity following a point mutation at glutamate N24.
    • Both mutations formed less cation selective ion channels than wild type Vpr.
    • Sodium to chloride ion permeability was 4 times lower than wild type Vpr
    • N 21 did not rectify at positive potentials
    • These effects indicate that mutation resulted in changes in ion selectivity
    • (Piller et al., 1999)
  10. Synthetic C-terminal and N-terminal peptides

    Slide 10 - Synthetic C-terminal and N-terminal peptides

    • Currents generated in planer lipid bilayers using synthetic peptides at different holding potentials.(Piller et al., 1999)
    • This figure shows the average currents of synthetic peptides representing regions of Vpr plotted vs. the holding potential.
    • N21 showed no channel activity, indicating it was insufficient to form ion channels.
    • N40 showed channel activity consistent with wild type Vpr.
    • C21 showed channel activity only at highly negative potentials, or in the presence of negatively charged ions, indicating cytotoxic effects only in negative conditions.
    • The N terminal region, N40, is therefore most likely responsible for damage to neurons.
    • These cytotoxic effects long term may lead to AIDS dementia during infection.
    • (Piller et al., 1999)
  11. Reasons to study Vpr

    Slide 11 - Reasons to study Vpr

    • Vpr is a possible virulence factor of HIV-1 infection. It therefore has a possible use in the development of new treatments to slow the progression to AIDS (Boya et al., 2004).
    • There is no cure for HIV. Treatment is a lifelong commitment, and many treatments involve side effects. Development of new treatments allow for more options for patients to minimise side effects.
    • A better understanding of the virus increases the likelihood of finding a cure.
    • https://www.aids.gov/hiv-aids-basics/just-diagnosed-with-hiv-aids/treatment-options/side-effects/
  12. Conclusion

    Slide 12 - Conclusion

    • Cation-selective channels formed by the Vpr protein result in a large inward current of cations, causing depolarization and cell death.
    • C-terminal region and hydrophobic region appear to be non-essential to ion channel formation.
    • Amino-terminal domain is the area of Vpr primarily responsible for channel activity and damage to hippocampal neurons (Piller et al., 1999).
    • The Vpr ion channel has potential as a target for AIDS treatments aimed at treating neurological symptoms.
  13. References

    Slide 13 - References

    • BOYA, P., PAULEAU, A.-L., PONCET, D., GONZALEZ-POLO, R.-A., ZAMZAMI, N. & KROEMER, G. 2004. Viral proteins targeting mitochondria: controlling cell death. Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1659, 178-189.
    • CHIN-PEI, C., KREMER, C., HENKLEIN, P., SCHUBERT, U., FINK, R. H. A. & FISCHER, W. B. 2010. Modulating the activity of the channel-forming segment of Vpr protein from HIV-1. European Biophysics Journal, 39, 1089-1095.
    • DENIAUD, A., BRENNER, C. & KROEMER, G. 2004. Mitochondrial membrane permeabilization by HIV-1 Vpr. Mitochondrion, 4, 223-233.
    • EMERMAN, M. HIV-1, Vpr and the cell cycle. Current Biology, 6, 1096-1103.
    • KOGAN, M., & RAPPAPORT, J. (2011). HIV-1 Accessory Protein Vpr: Relevance in the pathogenesis of HIV and potential for therapeutic intervention.Retrovirology, 8, 25. doi:10.1186/1742-4690-8-25
    • MORELLET, N., BOUAZIZ, S., PETITJEAN, P. & ROQUES, B. P. 2003. NMR structure of the HIV-1 regulatory protein VPR. J Mol Biol, 327, 215-27.
    • PILLER, S. C., EWART, G. D., JANS, D. A., GAGE, P. W. & COX, G. B. 1999. The Amino-Terminal Region of Vpr from Human Immunodeficiency Virus Type 1 Forms Ion Channels and Kills Neurons. Journal of Virology, 73, 4230-4238.
    • PILLER, S. C., EWART, G. D., PREMKUMAR, A., COX, G. B. & GAGE, P. W. 1996. Vpr Protein of Human Immunodeficiency Virus Type 1 Forms Cation-Selective Channels in Planar Lipid Bilayers. Proceedings of the National Academy of Sciences of the United States of America, 93, 111-115.
    • ROMANI, B. & ENGELBRECHT, S. 2009. Human immunodeficiency virus type 1 Vpr: functions and molecular interactions. Journal of General Virology, 90, 1795-1805.