Functional analysis of the relationship between Vpx and the restriction factor SAMHD1.
SAMHD1 is a newly identified restriction factor that targets lentiviruses in myeloid cells and is countered by the SIV(SM)/HIV-2 Vpx protein. By analyzing a large panel of Vpx mutants, we identify several residues throughout the 3-helix bundle predicted for Vpx that impair both its functionality and its ability to degrade SAMHD1. We determine that SAMHD1 is a strictly non-shuttling nuclear protein and that as expected WT Vpx localizes with it in the nucleus. However, we also identify a functional Vpx mutant with predominant cytoplasmic distribution that colocalizes with SAMHD1 in this location, suggesting that Vpx may also retain SAMHD1 in the cell cytoplasm, prior to its entry into the nucleus. Several mutations in Vpx were shown to affect the stability of Vpx, as well as Vpx:Vpx interactions. However, no strict correlation was observed between these parameters and the functionality of Vpx, implying that neither properties is absolutely required for this function and indicating that even unstable Vpx mutants may be very efficient in inducing SAMHD1 degradation. Overall, our analysis identifies several Vpx residues required for SAMHD1 degradation and points to a very efficient and plastic mechanism through which Vpx depletes this restriction factor.
Department of Human Virology, ENS-L, INSERM, U758, University of Lyon, Lyon I, F69364, France.
Gregory
G
Berger
Jocelyn
J
Turpin
Stéphanie
S
Cordeil
Kevin
K
Tartour
Xuan-Nhi
XN
Nguyen
Renaud
R
Mahieux
Andrea
A
Cimarelli
D000818:Animals; D000998:Antiviral Agents / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003713:Dendritic Cells / Q000821:virology; D057809:HEK293 Cells; D015498:HIV-2 / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008264:Macrophages / Q000821:virology; D051379:Mice; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D009154:Mutation; D041681:NIH 3T3 Cells; D011485:Protein Binding; D000076106:SAM Domain and HD Domain-Containing Protein 1; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism*; D037521:Virulence Factors / Q000378:metabolism
D000998:Antiviral Agents; C074286:VPX protein, Human immunodeficiency virus 2; D054334:Viral Regulatory and Accessory Proteins; D037521:Virulence Factors; D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; C484281:Samhd1 protein, mouse; D020559:Monomeric GTP-Binding Proteins