PP2A1 binding, cell transducing and apoptotic properties of Vpr(77-92): a new functional domain of HIV-1 Vpr proteins.
BACKGROUND
The hallmark of HIV-1 pathogenesis is the progressive CD4(+) T cell depletion and high propensity of CD4(+) T cells to apoptosis. HIV-1 viral protein R (Vpr) is a major pro-apoptotic gene product. A first Vpr-mediated apoptotic mechanism that requires a physical interaction of HIV-1 Vpr(71-82) mitochondriotoxic domain containing the conserved sequence (71-)HFRIGCRHSRIG(-82) with the Adenine Nucleotide Translocator (ANT) has been characterized. The family of Ser/Thr protein phosphatase PP2A interacts with several viral proteins to regulate cell growth and apoptotic pathways. Previous studies based on yeast two hybrid assays and mutational experiments indicated that PP2A(1) is involved in the induction of G2 arrest by HIV-1 Vpr.


RESULTS
Experiments combining pull-down, cell penetration and apoptosis analyses in distinct human cells indicate that the PP2A(1) binding sequence from Vpr(77-92) is a new cell penetrating apoptotic sequence. We also found that the I84P mutation or the IIQ/VTR(83-85) and T89A substitutions in the Vpr(77-92) sequence prevent PP2A(1) binding, cell penetration and apoptosis. In addition the double R77A and R80A mutation known to inactivate the mitochondriotoxic Vpr(71-82) domain, has no effect on the biological properties of the Vpr(77-92) domain.


CONCLUSIONS
Together our data provide evidence for the first time that the Vpr(77-92) sequence delineates a biological active domain of Vpr with PP2A(1) binding and pro-apoptotic capacities and, it is conceivable that this cell penetrating sequence may account for the Vpr internalization in uninfected cells. Finally, our data also implicate the existence of two partially overlapping pro-apoptotic domains in the Vpr C-terminal part, a redundancy that represents a new approach to address the question of biological relevance of HIV-1 Vpr. In this context, future studies will be required to determine the functional relevance of the Vpr(77-92) domain in full length Vpr protein and also in entire HIV provirus.
Laboratoire E3 Phosphatases, Unité Signalisation Moléculaire et Activation Cellulaire, Institut Pasteur, Paris, France.
Angélique N
AN
Godet
Julien
J
Guergnon
Amélie
A
Croset
Xavier
X
Cayla
Pierre Barthélemy
PB
Falanga
Jean-Hervé
JH
Colle
Alphonse
A
Garcia
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects*; D001665:Binding Sites / Q000235:genetics; D019921:Biotinylation; D045744:Cell Line, Tumor; D006367:HeLa Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D019169:Jurkat Cells; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D011485:Protein Binding; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D054325:vpr Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000235:genetics
D010446:Peptide Fragments; D054325:vpr Gene Products, Human Immunodeficiency Virus; C514912:vpr protein, Human immunodeficiency virus 1; C517189:PPP2CA protein, human; D054648:Protein Phosphatase 2