Plasma Membrane-Associated Restriction Factors and Their Counteraction by HIV-1 Accessory Proteins

Ramirez, Peter W; Sharma, Shilpi; Singh, Rajendra; Stoneham, Charlotte A.; Vollbrecht, Thomas

doi:10.3390/cells8091020

Cited by 25 publications

(21 citation statements)

References 169 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the role of Nef homodimers in SERINC5 antagonism has not been explored, the mechanistic similarity between Nef-mediated downregulation of CD4 and SERINC5 suggests a key role. Both processes involve clathrin-mediated endocytosis via the tetrameric trafficking adaptor protein AP-2, which interacts directly with Nef through a hemicomplex of its α and σ2 subunits (19,29). Alignment of the Nef 4U5W homodimer with the crystal structure of Nef bound to the AP-2 α/σ2 hemicomplex shows that the Nef homodimer interface residues do not contact AP-2 ( Figure 1C), suggesting that the dimer interface mutations described above will not affect AP-2 recruitment.…”

Section: Structural Basis Of Hiv-1 Nef Homodimerizationmentioning

confidence: 99%

“…Though Nef is present in HIV-1 virions and expressed early within the viral life cycle (29), previous analyses have examined the impact of mutations on Nef self-association 40-48 hours posttransfection (25,26) which corresponds to the end of the HIV-1 life cycle (30). We therefore explored the kinetics of wild-type Nef homodimer formation and membrane association at 12-hour intervals using a cell-based bimolecular fluorescence complementation (BiFC) assay (31).…”

Section: Structural Basis Of Hiv-1 Nef Homodimerizationmentioning

confidence: 99%

See 1 more Smart Citation

Nef homodimers down-regulate SERINC5 by AP-2–mediated endocytosis to promote HIV-1 infectivity

Staudt

Smithgall

2020

Journal of Biological Chemistry

View full text Add to dashboard Cite

SERINC5 is a multi-pass intrinsic membrane protein that suppresses HIV-1 infectivity when incorporated into budding virions. The HIV-1 Nef virulence factor prevents viral incorporation of SERINC5 by triggering its downregulation from the producer cell membrane through an AP-2-dependent endolysosomal pathway. However, the mechanistic basis for SERINC5 downregulation by Nef remains elusive. Here we demonstrate that Nef homodimers are important for SERINC5 downregulation, trafficking to late endosomes, and exclusion from newly synthesized viral particles. Based on previous X-ray crystal structures, we mutated three conserved residues in the Nef dimer interface (L112, Y115, F121) and demonstrated attenuated homodimer formation in a cell-based fluorescence complementation assay. Point mutations at each position reduced the infectivity of HIV-1 produced from transfected 293T cells, the Jurkat TAg T cell line, and donor mononuclear cells in a SERINC5-dependent manner. In SERINC5-transfected 293T cells, virion incorporation of SERINC5 was increased by dimerization-defective Nef mutants, while downregulation of SERINC5 from the membrane of transfected Jurkat cells by these mutants was significantly reduced. Nef dimer interface mutants also failed to trigger internalization of SERINC5 and localization to Rab7+ late endosomes in T cells. Importantly, fluorescence complementation assays demonstrated that dimerization-defective Nef mutants retained interaction with both SERINC5 and AP-2. These results show that downregulation of SERINC5 and subsequent enhancement of viral infectivity requires Nef homodimers and support a mechanism by which the Nef dimer bridges SERINC5 to AP-2 for endocytosis. Pharmacological disruption of Nef homodimers may control HIV-1 infectivity and viral spread by enhancing virion incorporation of SERINC5.

show abstract

Section: Structural Basis Of Hiv-1 Nef Homodimerizationmentioning

confidence: 99%

Section: Structural Basis Of Hiv-1 Nef Homodimerizationmentioning

confidence: 99%

Nef homodimers down-regulate SERINC5 by AP-2–mediated endocytosis to promote HIV-1 infectivity

Staudt

Smithgall

2020

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…CD4 binds virus through the D1 Ig domain, and CCR5 has two virus- binding domains in its N-terminus and in its second extracellular loop ( Figure 2 A) [ 7 ]. CD4 is downregulated in infected cells by the HIV-1 proteins Nef and Vpu ( Figure 2 B), and this prevents superinfection, thus avoiding apoptosis and production of infection-compromised virions, and also reduces sensitivity to inhibition by another restriction factor, SERINC5 [ 8 , 9 , 10 ]. While there are no known variants of CD4 in humans that affect the efficiency of HIV-1 infection, CD4 is highly variable in chimpanzees, and this variation is responsible for restricted susceptibility to SIV, the progenitor of HIV-1 ( Figure 2 B) [ 11 , 12 ].…”

Section: Retroviral Restriction Factorsmentioning

confidence: 99%

Retroviral Restriction Factors and Their Viral Targets: Restriction Strategies and Evolutionary Adaptations

Boso

Kozak

2020

Microorganisms

View full text Add to dashboard Cite

The evolutionary conflict between retroviruses and their vertebrate hosts over millions of years has led to the emergence of cellular innate immune proteins termed restriction factors as well as their viral antagonists. Evidence accumulated in the last two decades has substantially increased our understanding of the elaborate mechanisms utilized by these restriction factors to inhibit retroviral replication, mechanisms that either directly block viral proteins or interfere with the cellular pathways hijacked by the viruses. Analyses of these complex interactions describe patterns of accelerated evolution for these restriction factors as well as the acquisition and evolution of their virus-encoded antagonists. Evidence is also mounting that many restriction factors identified for their inhibition of specific retroviruses have broader antiviral activity against additional retroviruses as well as against other viruses, and that exposure to these multiple virus challenges has shaped their adaptive evolution. In this review, we provide an overview of the restriction factors that interfere with different steps of the retroviral life cycle, describing their mechanisms of action, adaptive evolution, viral targets and the viral antagonists that evolved to counter these factors.

show abstract

“…Motifs responsible for each of Nef’s functions have been identified in mutagenesis studies on laboratory-adapted HIV-1 strains 3 – 5 , 15 – 19 . For instance, the introduction of mutations to the highly conserved FPD motif (Phe121-Pro122-Asp123) in Nef was shown to result in disruption of Nef’s ability to counteract SERINC3/5, thus decreasing the infectivity of progeny virions 12 , 20 . However, it is unclear whether highly diverse naturally-occurring (patient-derived) Nef sequences also display differential abilities to counteract SERINC3/5; and if so, it remains elusive whether this ability of patient-derived Nef influences viral fitness in vivo.…”

Section: Introductionmentioning

confidence: 99%

Impaired ability of Nef to counteract SERINC5 is associated with reduced plasma viremia in HIV-infected individuals

Toyoda

Kamori

Tan

et al. 2020

Sci Rep

View full text Add to dashboard Cite

HIV-1 Nef plays an essential role in enhancing virion infectivity by antagonizing the host restriction molecule SERINC5. Because Nef is highly polymorphic due to the selective forces of host cellular immunity, we hypothesized that certain immune-escape polymorphisms may impair Nef’s ability to antagonize SERINC5 and thereby influence viral fitness in vivo. To test this hypothesis, we identified 58 Nef polymorphisms that were overrepresented in HIV-infected patients in Japan sharing the same HLA genotypes. The number of immune-associated Nef polymorphisms was inversely correlated with the plasma viral load. By breaking down the specific HLA allele-associated mutations, we found that a number of the HLA-B*51:01-associated Y120F and Q125H mutations were most significantly associated with a reduced plasma viral load. A series of biochemical experiments showed that the double mutations Y120F/Q125H, but not either single mutation, impaired Nef’s ability to antagonize SERINC5 and was associated with decreasing virion infectivity and viral replication in primary lymphocytes. In contrast, other Nef functions such as CD4, CCR5, CXCR4 and HLA class I downregulation and CD74 upregulation remained unchanged. Taken together, our results suggest that the differential ability of Nef to counteract SERINC5 by naturally occurring immune-associated mutations was associated with the plasma viral load in vivo.

show abstract

Plasma Membrane-Associated Restriction Factors and Their Counteraction by HIV-1 Accessory Proteins

Cited by 25 publications

References 169 publications

Nef homodimers down-regulate SERINC5 by AP-2–mediated endocytosis to promote HIV-1 infectivity

Nef homodimers down-regulate SERINC5 by AP-2–mediated endocytosis to promote HIV-1 infectivity

Retroviral Restriction Factors and Their Viral Targets: Restriction Strategies and Evolutionary Adaptations

Impaired ability of Nef to counteract SERINC5 is associated with reduced plasma viremia in HIV-infected individuals

Contact Info

Product

Resources

About