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The Expression of Functional Vpx during Pathogenic SIVmac Infections of Rhesus Macaques Suppresses SAMHD1 in CD4+ Memory T Cells.

Shingai M, Welbourn S, Brenchley JM, Acharya P, Miyagi E, Plishka RJ, Buckler-White A, Kwong PD, Nishimura Y, Strebel K, Martin MA - PLoS Pathog. (2015)

Bottom Line: Mechanistically, this Vpx activity was recently reported to involve the degradation of Sterile Alpha Motif and HD domain-containing protein 1 (SAMHD1) in this cell lineage.Here we show that when macaques were inoculated with either the T cell tropic SIVmac239 or the macrophage tropic SIVmac316 carrying a Vpx point mutation that abrogates the recruitment of DCAF1 and the ensuing degradation of endogenous SAMHD1 in cultured CD4+ T cells, virus acquisition, progeny virion production in memory CD4+ T cells during acute infection, and the maintenance of set-point viremia were greatly attenuated.These results indicate that a critical role of Vpx in vivo is to promote the degradation of SAMHD1 in memory CD4+ T lymphocytes, thereby generating high levels of plasma viremia and the induction of immunodeficiency.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.

ABSTRACT
For nearly 20 years, the principal biological function of the HIV-2/SIV Vpx gene has been thought to be required for optimal virus replication in myeloid cells. Mechanistically, this Vpx activity was recently reported to involve the degradation of Sterile Alpha Motif and HD domain-containing protein 1 (SAMHD1) in this cell lineage. Here we show that when macaques were inoculated with either the T cell tropic SIVmac239 or the macrophage tropic SIVmac316 carrying a Vpx point mutation that abrogates the recruitment of DCAF1 and the ensuing degradation of endogenous SAMHD1 in cultured CD4+ T cells, virus acquisition, progeny virion production in memory CD4+ T cells during acute infection, and the maintenance of set-point viremia were greatly attenuated. Revertant viruses emerging in two animals exhibited an augmented replication phenotype in memory CD4+ T lymphocytes both in vitro and in vivo, which was associated with reduced levels of endogenous SAMHD1. These results indicate that a critical role of Vpx in vivo is to promote the degradation of SAMHD1 in memory CD4+ T lymphocytes, thereby generating high levels of plasma viremia and the induction of immunodeficiency.

No MeSH data available.


Related in: MedlinePlus

Mapping of Vpx mutations at the Vpx-DCAF1-SAMHD1 interface.(A) Crystal structure (PDB ID 4CC9) of the c-terminal domain of SAMHD1 (green) in complex with WT Vpx (blue) and DCAF1 (salmon). (B) Zoomed-in view displaying the interactions of Gln 76Vpx at the Vpx-DCAF1 interface. Models of the Q76A Vpx mutation (C), the Q76S Vpx substitution (D) in the revertant recovered from macaque K42, and the Q76A/I32T Vpx double substitution in the revertant recovered from macaque JAX4 (E). Hydrogen bonds are indicated by dashed lines and the red spheres denote a crystallographic water molecule observed the structure.
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ppat.1004928.g008: Mapping of Vpx mutations at the Vpx-DCAF1-SAMHD1 interface.(A) Crystal structure (PDB ID 4CC9) of the c-terminal domain of SAMHD1 (green) in complex with WT Vpx (blue) and DCAF1 (salmon). (B) Zoomed-in view displaying the interactions of Gln 76Vpx at the Vpx-DCAF1 interface. Models of the Q76A Vpx mutation (C), the Q76S Vpx substitution (D) in the revertant recovered from macaque K42, and the Q76A/I32T Vpx double substitution in the revertant recovered from macaque JAX4 (E). Hydrogen bonds are indicated by dashed lines and the red spheres denote a crystallographic water molecule observed the structure.

Mentions: A recent structural study of Vpx and DCAF1 reported that residues Ile32 and Gln76 of Vpxsm both make contact with Trp1156 of the DCAF1 cytoplasmic domain [17]. Vpx residues Ile32 and Gln76 are in close physical proximity within the SAMHD1- DCAF1-Vpx ternary complex with Ile32 making hydrophobic interactions with the aliphatic base of the Gln76 side chain. The carbonyl side chain of Vpx residue Gln76 makes H-bond interactions with DCAF1 Trp1156 and the NH2 side chain of Vpx Gln76 bonds with the main chain carbonyl of DCAF1 Asn1135 (Fig 8A and 8B). In addition, the main chain carbonyl of Vpx Gln76 hydrogen bonds with a water molecule (W1) that mediates extensive contacts between Vpx and DCAF1. Thus Gln76 appears to play a critical role at the Vpx-DCAF1 interface. Modeling the Gln76Ala disabling mutation in Vpx used in this study on the Vpx-DCAF1-SAMHD1 crystal structure places DCAF1 Trp1156 in a predominantly unfavorable hydrophobic environment and creates a potentially destabilizing void at the interface, and also results in loss of interactions mediated by Gln76 in WT (Fig 8C). Substituting the Vpx Ala mutation at position 76 with Ser, as is present in the K42 revertant virus, is predicted to partially fill the cavity created by the original Gln76Ala change and to restore some of the interactions with DCAF1 (Fig 8D). Similarly, the Ile32Thr change, in the presence of the original Vpx Ala mutation, is predicted to restore a hydrogen bond interaction between Vpx and DCAF1 and also stabilizes the interface providing a complementary polar site for DCAF1 Trp1156 to interact with (Fig 8E). Thus by recreating a shared surface to which SAMHD1 binds, Vpx substitutions that are predicted to facilitate interaction with DCAF1 augment SIV replicative capacity in vivo.


The Expression of Functional Vpx during Pathogenic SIVmac Infections of Rhesus Macaques Suppresses SAMHD1 in CD4+ Memory T Cells.

Shingai M, Welbourn S, Brenchley JM, Acharya P, Miyagi E, Plishka RJ, Buckler-White A, Kwong PD, Nishimura Y, Strebel K, Martin MA - PLoS Pathog. (2015)

Mapping of Vpx mutations at the Vpx-DCAF1-SAMHD1 interface.(A) Crystal structure (PDB ID 4CC9) of the c-terminal domain of SAMHD1 (green) in complex with WT Vpx (blue) and DCAF1 (salmon). (B) Zoomed-in view displaying the interactions of Gln 76Vpx at the Vpx-DCAF1 interface. Models of the Q76A Vpx mutation (C), the Q76S Vpx substitution (D) in the revertant recovered from macaque K42, and the Q76A/I32T Vpx double substitution in the revertant recovered from macaque JAX4 (E). Hydrogen bonds are indicated by dashed lines and the red spheres denote a crystallographic water molecule observed the structure.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440783&req=5

ppat.1004928.g008: Mapping of Vpx mutations at the Vpx-DCAF1-SAMHD1 interface.(A) Crystal structure (PDB ID 4CC9) of the c-terminal domain of SAMHD1 (green) in complex with WT Vpx (blue) and DCAF1 (salmon). (B) Zoomed-in view displaying the interactions of Gln 76Vpx at the Vpx-DCAF1 interface. Models of the Q76A Vpx mutation (C), the Q76S Vpx substitution (D) in the revertant recovered from macaque K42, and the Q76A/I32T Vpx double substitution in the revertant recovered from macaque JAX4 (E). Hydrogen bonds are indicated by dashed lines and the red spheres denote a crystallographic water molecule observed the structure.
Mentions: A recent structural study of Vpx and DCAF1 reported that residues Ile32 and Gln76 of Vpxsm both make contact with Trp1156 of the DCAF1 cytoplasmic domain [17]. Vpx residues Ile32 and Gln76 are in close physical proximity within the SAMHD1- DCAF1-Vpx ternary complex with Ile32 making hydrophobic interactions with the aliphatic base of the Gln76 side chain. The carbonyl side chain of Vpx residue Gln76 makes H-bond interactions with DCAF1 Trp1156 and the NH2 side chain of Vpx Gln76 bonds with the main chain carbonyl of DCAF1 Asn1135 (Fig 8A and 8B). In addition, the main chain carbonyl of Vpx Gln76 hydrogen bonds with a water molecule (W1) that mediates extensive contacts between Vpx and DCAF1. Thus Gln76 appears to play a critical role at the Vpx-DCAF1 interface. Modeling the Gln76Ala disabling mutation in Vpx used in this study on the Vpx-DCAF1-SAMHD1 crystal structure places DCAF1 Trp1156 in a predominantly unfavorable hydrophobic environment and creates a potentially destabilizing void at the interface, and also results in loss of interactions mediated by Gln76 in WT (Fig 8C). Substituting the Vpx Ala mutation at position 76 with Ser, as is present in the K42 revertant virus, is predicted to partially fill the cavity created by the original Gln76Ala change and to restore some of the interactions with DCAF1 (Fig 8D). Similarly, the Ile32Thr change, in the presence of the original Vpx Ala mutation, is predicted to restore a hydrogen bond interaction between Vpx and DCAF1 and also stabilizes the interface providing a complementary polar site for DCAF1 Trp1156 to interact with (Fig 8E). Thus by recreating a shared surface to which SAMHD1 binds, Vpx substitutions that are predicted to facilitate interaction with DCAF1 augment SIV replicative capacity in vivo.

Bottom Line: Mechanistically, this Vpx activity was recently reported to involve the degradation of Sterile Alpha Motif and HD domain-containing protein 1 (SAMHD1) in this cell lineage.Here we show that when macaques were inoculated with either the T cell tropic SIVmac239 or the macrophage tropic SIVmac316 carrying a Vpx point mutation that abrogates the recruitment of DCAF1 and the ensuing degradation of endogenous SAMHD1 in cultured CD4+ T cells, virus acquisition, progeny virion production in memory CD4+ T cells during acute infection, and the maintenance of set-point viremia were greatly attenuated.These results indicate that a critical role of Vpx in vivo is to promote the degradation of SAMHD1 in memory CD4+ T lymphocytes, thereby generating high levels of plasma viremia and the induction of immunodeficiency.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.

ABSTRACT
For nearly 20 years, the principal biological function of the HIV-2/SIV Vpx gene has been thought to be required for optimal virus replication in myeloid cells. Mechanistically, this Vpx activity was recently reported to involve the degradation of Sterile Alpha Motif and HD domain-containing protein 1 (SAMHD1) in this cell lineage. Here we show that when macaques were inoculated with either the T cell tropic SIVmac239 or the macrophage tropic SIVmac316 carrying a Vpx point mutation that abrogates the recruitment of DCAF1 and the ensuing degradation of endogenous SAMHD1 in cultured CD4+ T cells, virus acquisition, progeny virion production in memory CD4+ T cells during acute infection, and the maintenance of set-point viremia were greatly attenuated. Revertant viruses emerging in two animals exhibited an augmented replication phenotype in memory CD4+ T lymphocytes both in vitro and in vivo, which was associated with reduced levels of endogenous SAMHD1. These results indicate that a critical role of Vpx in vivo is to promote the degradation of SAMHD1 in memory CD4+ T lymphocytes, thereby generating high levels of plasma viremia and the induction of immunodeficiency.

No MeSH data available.


Related in: MedlinePlus